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063339617 | summary | FIELD OF THE INVENTION This invention relates to microlithography (transfer of a pattern, defined by a reticle or mask, to a sensitive substrate). Microlithography is a key technology used in the manufacture of semiconductor integrated circuits, displays, and the like. More specifically, the invention pertains to reflection masks, to microlithography apparatus employing such masks, and to methods for manufacturing integrated circuits and the like using such masks and microlithography apparatus. BACKGROUND OF THE INVENTION In recent years the progressive miniaturization of active elements in semiconductor integrated circuits has generated a critical need for microlithography technology that can achieve correspondingly finer resolution. This need has led to the development of projection microlithography in which, instead of using ultraviolet light as an energy beam, even shorter wavelengths are used such as soft X-rays having a wavelength in the range of approximately 10 to 15 nm. This new type of microlithography also is termed "EUV" (extreme ultraviolet) microlithography. In the EUV microlithography wavelength range, the refractive indices of materials tend to be very close to 1. As a result, conventional refractive and reflective optical elements cannot be used. Rather, grazing incidence optical components or multilayer mirrors typically are used. A grazing incidence mirror exploits total reflection resulting from its refractive index being slightly less than 1, and a multilayer mirror exploits a multilayer film ("multilayer") that superimposes and phase-aligns weakly reflected light to produce a net high reflectance of the light. A conventional EUV microlithography apparatus mainly comprises an X-ray source, an illumination-optical system, a mask, an imaging-optical system, a mask stage, and a wafer (substrate) stage. The apparatus "transfers" an image of a circuit pattern, as defined on the mask, to the wafer. So as to be imprinted with the image, the wafer is coated with an appropriate resist. The image is transferred to (projected onto) the resist by the imaging-optical system. The imaging-optical system typically comprises multiple multilayer mirrors. The mask typically is a reflection-type mask as disclosed in, for example, Murakami,Hyomen Gijutsu (Surface Technology) 49:849, 1998; and Murakami et al., Jpn. J. Appl. Phys. 34:6696-6700, 1995. In such a mask, an absorber layer (comprising a substance highly absorptive to soft X-ray radiation) is formed, in a prescribed circuit pattern, on or in a multilayer that reflects soft X-rays. As noted above, an EUV microlithography optical system typically comprises multiple multilayer mirrors and grazing-incidence mirrors. Thus, a soft X-ray beam is reflected multiple times as the beam passes through the optical system. Unfortunately, as the number of multilayer mirrors in the optical system increases, the full-width at half maximum (FWHM) of the reflectance spectrum of EUV light passing through the optical system correspondingly decreases. Whenever there is a significant difference between the center wavelength of EUV light passing (by reflection) through an optical system consisting of multiple multilayer mirrors and the center wavelength of the EUV light reflected from the multilayer of the reflection mask, a decrease is observed in the combined reflectance of the optical system and the mask. As a result, the quantity of EUV light passing through the optical system and actually reaching the wafer is decreased undesirably. If, over the plane of the reflection mask, there is a non-uniformity of the thickness period of the multilayer, then the reflectance of the reflection mask at the wavelength used in the microlithography apparatus will vary correspondingly according to position on the mask. This reflectance non-uniformity of the reflection mask is manifest as a non-uniformity in illumination of the wafer (located at an optically conjugate position relative to the reflection mask). As a result, exposure undesirably will vary at different locations on the wafer. Also, whenever the exposure (i.e., total amount of light energy projected onto the resist on the wafer) exceeds a certain desired range, the linewidth of the circuit pattern transferred onto the wafer exhibits an excessive change that tends to degrade resolution. SUMMARY OF THE INVENTION In view of the shortcomings of conventional systems as summarized above, an object of the invention is to provide apparatus and methods that perform microlithographic exposures in which the linewidth of the circuit pattern transferred onto the wafer is substantially unaffected by reflectance non-uniformities of the reflection mask. To such end, and according to a first aspect of the invention, reflection masks are provided for use especially in microlithography using soft X-rays (i.e., extreme ultraviolet or "EUV" microlithography). A representative embodiment of such a reflection mask comprises a multilayer mirror and an absorptive layer. The multilayer mirror reflects incident electromagnetic radiation (e.g., soft X-rays of a prescribed wavelength). The absorptive layer, superposed on the multilayer mirror, defines elements of a pattern defined by the mask. Through the thickness dimension of the multilayer mirror, the laminations have a thickness period that varies with distance through the thickness dimension. With such a reflection mask, the full-width at half-maximum (FWHM) (in a reflectance spectrum of the electromagnetic radiation from the multilayer mirror) is larger than in conventional reflection masks. As a result, reflectance of the electromagnetic radiation from respective positions on the multilayer mirror exhibits less change with changes in respective center wavelengths of reflected radiation than in conventional reflection masks. This, in turn, produces less change in wafer illumination over the pattern as transferred to the wafer. (As used herein, a "center wavelength" is a wavelength at which a reflective surface exhibits maximum reflectivity.) In another representative embodiment of a reflection mask according to the invention, the multilayer mirror is formed by laminating, in a first "block," multiple layers having a first thickness period and, in a second "block" superposed on the first block, multiple layers having a second thickness period different from the first thickness period. A "block" in this context is a group of superposed laminated individual layers. More generally, the multilayer mirror can be formed of multiple (two or more) blocks each having a respective thickness period. With such a configuration, the FWHM in the reflectance spectrum of the multilayer mirror is larger than in conventional reflection masks. Such a configuration is especially effective whenever differences in the distribution of thicknesses of layers comprising the multilayer mirror vary substantially, such as resulting from the formation of the multilayer mirror. Desirably, for use in reflecting soft X-rays, each block comprises alternating layers of molybdenum and silicon. In another representative embodiment, the reflection mask comprises a multilayer mirror is formed by laminating multiple layers superposedly such that the multilayer mirror has a thickness period that progressively varies with distance through the thickness dimension of the multilayer mirror. Again, for reflecting X-rays, the multilayer mirror desirably comprises alternating layers of molybdenum and silicon. This configuration is especially useful whenever differences in the distribution of layer thicknesses in the multilayer mirror are relatively small. According to another aspect of the invention, methods (to be used in microlithography) are provided for reducing adverse effects on the linewidth of the pattern, as transferred to the substrate, caused by a non-uniformity of reflection of illumination light from the reflection mask. In a first step of a representative embodiment of such a method, a reflection mask according to any of the embodiments summarized above is provided. The reflection mask is illuminated with the illumination light, and the reflected illumination light is passed through an optical system to as to form an image of the pattern on the substrate. The illumination light desirably is of a type with which a reflection mask can be used, such as soft X-rays. With such methods, it is possible to prevent substantial drops in reflectance from the mask even if the center wavelength of light reflected from the mask is shifted. Also, because the FWHM in the spectrum of light reflected from the multilayer mirror is large compared to conventional masks, even if the center wavelength of reflected light varies according to respective positions on the mask, the ratio of the change in reflectance to a difference between the center wavelength and the actual wavelength is small. This correspondingly reduces illumination non-uniformities on the wafer. According to another aspect of the invention, microlithography apparatus are provided. A representative embodiment of such an apparatus comprises an illumination optical system situated and configured to irradiate electromagnetic radiation from a source onto a reflection mask (that defines a pattern to be projected onto a substrate). The apparatus also comprises an imaging-optical system situated and configured to direct portions of the electromagnetic radiation reflected from the reflection mask to the substrate so as to form an image of the pattern on the substrate. The reflection mask comprises a multilayer mirror (that reflects a prescribed wavelength of the electromagnetic radiation) and an absorber layer, superposed on the multilayer mirror, that absorbs the electromagnetic radiation and defines elements of the pattern. The multilayer mirror has a thickness period, through the thickness dimension of the multilayer mirror, that varies through the thickness dimension. With such apparatus, even if the center wavelength reflected by the mask is shifted, the exposure dose on the wafer exhibits less change than with a conventional reflection mask exhibiting a similar shift in center wavelength. This makes it possible to manufacture integrated circuits with good throughput. In addition, since the FWHM of the reflectance spectrum of light from the multilayer mirror is relatively large, illumination non-uniformity on the wafer is relatively small (compared to conventional apparatus), even if the center wavelength of light reflected from the mask varies significantly with position on the mask. This allows patterns to be transferred with better control of pattern linewidth, thereby increasing the yield of acceptable integrated circuit product. The foregoing and additional features and advantages of the invention will be more readily apparent from the following detailed description, which proceeds with reference to the accompanying drawings. |
claims | 1. An ion acceleration device, comprising:an inner electrode formed of a plasma;an outer electrode surrounding the inner plasma electrode;a vacuum chamber surrounding the inner electrode;a source for supplying ions between the inner plasma electrode and the outer electrode; anda means for creating a potential between the inner plasma electrode and the outer electrode to accelerate ions towards the inner plasma electrode;wherein the plasma is created by forming a high voltage potential between a first electrode and a second electrode positioned within the outer electrode or by focusing a radio frequency source within the vacuum. 2. The ion acceleration device of claim 1, wherein the inner electrode is formed by a high voltage potential created between a first electrode and a second electrode. 3. The ion acceleration device of claim 1, wherein the outer electrode forms at least part of the vacuum chamber. 4. The ion acceleration device of claim 1 wherein the source for supplying ions is a gas source which supplies a gas between the inner electrode and the outer electrode which is ionized in situ when the potential is created between the inner plasma electrode and the outer electrode. 5. The ion acceleration device as in either claim 1 wherein the inner electrode is formed by focusing a radio frequency emission on an ionizable gas. 6. The ion acceleration device of claim 1, wherein the source for supplying ions is an ion gun. 7. An inertial electrostatic confinement fusion device, comprising:an inner electrode formed of a plasma;an outer electrode surrounding the inner plasma electrode;a vacuum chamber surrounding the inner plasma electrode;a source for supplying ions into the vacuum chamber; anda means for creating a potential between the inner plasma electrode and the outer electrode to accelerate ions towards the inner plasma electrode;wherein the plasma is created by forming a high voltage potential between a first electrode and a second electrode positioned within the outer electrode or by focusing a radio frequency source within the vacuum. 8. The inertial electrostatic confinement fusion device of claim 7, wherein the inner plasma electrode is formed by a high voltage potential created between a first electrode and a second electrode. 9. The inertial electrostatic confinement fusion device of claim 7, wherein the outer electrode forms at least part of the vacuum chamber. 10. The inertial electrostatic confinement fusion device of claim 7, wherein the source for supplying ions is a gas source which supplies a gas between the inner electrode and the outer electrode which is ionized in situ when a potential is created between the inner plasma electrode and the outer electrode. 11. The inertial electrostatic confinement fusion device of claim 7, wherein inner electrode is formed by focusing a radio frequency emission on an ionizable gas. 12. The inertial electrostatic confinement fusion device of claim 7, wherein the gas source is a deuterium gas source. 13. The inertial electrostatic confinement fusion device of claim 7, wherein the source for supplying ions is an ion gun. 14. A method of accelerating ions comprising:forming a vacuum;creating a plasma within the vacuum;surrounding the plasma with an outer electrode;providing an ion source between the plasma and the outer electrode; andforming a potential between the plasma and the outer electrode to accelerate ions from the ion source towards the plasma;wherein the plasma is created by forming a high voltage potential between a first electrode and a second electrode positioned within the outer electrode or by focusing a radio frequency source within the vacuum. 15. A method of producing a nuclear reaction comprising:forming a vacuum;creating a plasma within the vacuum;surrounding the plasma with an outer electrode;forming a potential between the inner and outer electrodes; and providing ions that are effected by the potential between the inner and outer electrodes so as to accelerate the ions towards the inner electrode resulting in collisions of the ions with other particles creating a nuclear fusion reaction;wherein the plasma is created by forming a high voltage potential between a first electrode and a second electrode positioned within the outer electrode or by focusing a radio frequency source within the vacuum. 16. The method of claim 14, wherein the ions are provided by providing a supplied gas between the plasma and the outer electrode. 17. The method of claim 15, wherein the ions are provided by supplying a deuterium gas. |
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abstract | A direct vessel injection (DVI) nozzle for minimum emergency core coolant (ECC) bypass is disclosed. The DVI nozzle is used in a pressurized light water reactor (PLWR) having a reactor vessel with a reactor coolant system in which a coolant flows into the reactor vessel through a cold leg and passes through a reactor core prior to being discharged to the outside of the reactor vessel through a hot leg. The DVI nozzle, provided to directly inject ECC into the reactor vessel to cool the reactor core during a break in the reactor coolant system, such as a cold leg break (CLB) that may occur in the PLWR, is placed on the reactor vessel at a position horizontally offset from the central axis of the hot leg at an angle of 10° to 30° and is involved within a region defined above the central axis of the hot leg by a distance of 1.5 times the sum of diameters of the hot leg and the DVI nozzle. Thus, the DVI nozzle efficiently injects ECC, and remarkably reduces the direct ECC bypass fraction to a broken cold leg and minimizes the amount of direct ECC bypass. |
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040424545 | summary | BACKGROUND OF THE INVENTION 1. Field of the Invention The invention relates to a method of producing homogeneously doped n-type Si monocrystals and somewhat more particularly to a method of producing homogeneously doped n-type Si monocrystals having a specific resistivity greater than about 30 ohm .times. cm by thermal neutron radiation. 2. Prior Art Si crystal bodies, such as rods, are generally doped after the precipitation or deposition of solid Si onto a heated mandrel or rod-shaped carrier member with the aid of thermal and/or pyrolytic decomposition of gaseous Si compounds. In such a process, dopants are intermixed with a gaseous Si compound and decompose at the carrier member so as to be dispersed within the forming Si body. The Si rods or bodies so produced are polycrystalline and must be converted into a monocrystalline state by subsequent zone melting processes. During such zone melting, the concentration of the dopant within the Si rod often changes in an uncontrollable manner and considerably higher dopant concentrations must be provided in the polycrystalline rods in order to attain a desired dopant concentration in the final monocrystalline rods, especially in instances where a plurality of zone melting processes are utilized. However, such processes are time-consuming and inexact. Further, the devices available for carrying out such processes are only marginally satisfactory and are extremely expensive. Other methods of producing doped Si crystal bodies are also known, for example, from German Offenlegungsschrift Nos. 1,544,276 and 2,020,182. These prior art references suggest that select dopants be converted to a gaseous state and fed, with the aid of a carrier gas flux, to a molten Si material positioned within an evacuated reaction chamber so that the gaseous dopant is directly blown or carried, for example, into the molten zone of a Si rod undergoing crucible-free zone melt processing. Boron and/or phosphorous compounds which are easily handleable and easily vaporized are generally the dopants utilized with this method. The dosage or concentration of dopants supplied to the molten Si is regulated via valves. However, a great drawback to such methods is that the valves used to control the dopant dosage do not operate in the necessarily exact manner to provide reproducible results. In addition, these methods provide a more or less non-homogeneous distribution of dopants within the finished rod after zone melting. The semiconductor components produced from such inexactly doped Si rods cannot obtain their optimum characteristic properties since the fluctuation of dopants during the growth process of the monocrystalline rods becomes noticeable during the zone melting processes by forming facets and uneven temperature distributions in the melt; in other words, the fluctuations of dopant cause noticeable radial and axial inhomogeneities in the specific resistivity of such a rod; for example, during the occurrence of "striations" which are inhomogeneities of material concentration, fluctuations occur nearly periodically in the crystal. M. Tanenbaum et al., "Preparation of Uniform Resistivity n-Type Silicon by Nuclear Transmutation", 108 Journal of Electrochemical Society, No. 2, pages 171-176 (February 1961) suggests that Si crystals having n-type conductivity may be produced by radiation of thermal neutrons on pure Si crystals. In this process, the natural isotope Si.sup.30, which is present in pure Si crystals is transmuted into the unstable isotope Si.sup.31 by the capture of a thermal neutron and emission of .gamma. radiation. The unstable Si.sup.31 isotope decays by .beta..sup.- emission with a 2.62 hr. half-life into the stable P.sup.31 isotope. However, pure starting crystals which are required for this process are costly. SUMMARY OF THE INVENTION The invention provides a method of homogeneously doping Si monocrystals so that an n-type conductivity (having a specific resistivity > 30 .OMEGA. cm) is achieved by causing a nuclear reaction within the Si crystals by radiating thermal neutrons thereon in accordance with the reaction: EQU Si.sup.30 (n, .gamma.) Si.sup.31 .sup..beta..sup.- P.sup.31. the invention allows the production of a homogeneous striation-free doping over an entire length and cross-section of a Si crystal body in a simple, rational and reproducible manner independent of body diameter. The invention produces n-type Si bodies having a resistance greater than 30 ohm .times. cm with an exact and homogeneous dopant distribution therein. Heretofore available prior art methods are practically useless in achieving narrow radial and axial resistivity tolerances in n-type Si bodies. The prior art methods are particularly useless in providing tolerance ranges narrower than .+-.5% for resistivity (.rho.) values of 90 through 180 ohm .times. cm. In accordance with the principles of the invention, polycrystalline Si rods are first freed from any donor material therein by crucible-free zone melting in a vacuum or a protective gas environment and then converted or transformed into a monocrystalline state by prior art methods. Thereafter, the specific electrical resistivity of the rods, which are highly ohmic and n- or p-conductive, is measured and the rods are then subjected to a controlled (time, intensity and target area) radiation of thermal neutrons in accordance with the measured conductivity so that the desired n-conductivity is produced in such rods. |
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description | The present invention generally relates to charged particle beam imaging, and more particularly, to a method for forming a plurality of images of substantially the same area on a sample for defect inspection within the area. In the manufacture of semiconductor devices, patterned substrates are inspected for defects so that the production of acceptable devices can be achieved. Inspection of a patterned substrate can be carried out through various technologies, one of which is charged particle beam inspection. A common example of charged particle beam inspection is electron beam (EB) inspection. EB inspection is performed by scanning an electron beam over surface patterns of devices formed on a substrate, and collecting the secondary electrons emanated from the surface patterns of scanned devices as inspection signals. The signals are processed and represented in grey levels to produce images of surface patterns of the scanned devices. The patterned surface contains pattern features which either form the electrical devices or direct/indirect electrical connect to the buried devices. The obtained image shown in grey level contrast represents the difference in electrical charging voltages associated with the devices, connections, as well as the materials. The image is thus also known as a voltage contrast (VC) image. Abnormal grey levels, or abnormal VCs, are detected to identify defective devices or connections. For example, if a bright grey level shows up where a darker grey level should have been observed, it is deemed there exists a bright voltage contrast (BVC) defect. On the other hand, if a dark grey level shows up where a brighter grey level should have been observed, it is deemed there exists a dark voltage contrast (DVC) defect. When the electron beam is scanned over the surface pattern of a device, charging may be induced and accumulate on the device. The resulting charging can be negative or positive, depending on the electron beam conditions (landing energy, beam current, etc.) used, as well as surface pattern materials in exposure to electron beam scanning. In this specification, for a given surface layer of a device, an electron beam condition leading to accumulation of positive charging on the scanned device will be referred to as “positive imaging mode.” On the other hand, an electron beam condition leading to accumulation of negative charging on the scanned device will be referred to as “negative imaging mode.” The positive imaging mode or negative imaging mode may lead to different voltage contrast images for a given surface layer of devices. For example, for the positive imaging mode, an open circuit defect may appear relatively dark in the image due to excessive positive charging accumulated if a normal feature is expected to be well grounded, and display a DVC. On the other hand, a short circuit defect may appear relatively bright due to the formed release path of charging if a normal feature is expected to be floated, and display a BVC in the image. When a semiconductor device is being scanned in a particular imaging mode, its electrical characteristics give rise to a default VC for this device. For instance, metal contact plugs coupled to the same PN junction device may display different VCs in the positive and negative imaging mode, respectively. Taking the positive imaging mode as an example, PN junctions in a normal NMOS device, such as an n-doped region or a plug connected thereto, are typically reverse biased when being scanned in the positive imaging mode, whereas PN junctions in a normal PMOS device, such as a p-doped region or a plug connected thereto, are typically forward biased when being scanned in the positive imaging mode. The biasing condition of these devices affects their VC behaviors, as will be illustrated below. Referring to the drawings, FIG. 1 is a schematic illustration of MOSFET devices after the process step of metal CMP (Chemical Mechanical Planarization) in the positive imaging mode. FIG. 1A is a schematic illustration of a PMOS transistor being imaged in the positive imaging mode in accordance with the conventional art, and FIG. 1B is a schematic illustration of an NMOS transistor being imaged in the positive imaging mode in accordance with the conventional art. As shown in FIG. 1A, PMOS transistor 100A comprises a gate plug 101A, a normal P+/N-well plug 102A, an open P+/N-well plug 103A, and a shorted P+/N-well plug 104A. Image 110A illustrates VC behaviors of the respective above components. As the surface is positively charged, normal P+/N-well junction associated to plug 102A is forward biased, thus is in the “ON” state whereby excessive positive charges can be released to N-well via the junction. A normal P+/N-well plug 102A is therefore, to some extent, equivalent to being shorted/leaking to substrate, and appears bright in the voltage contrast image 110A. P+/N-well plug 104A can be shorted to the substrate or gate plug (for example, short/leakage to the substrate is illustrated in the figure as a black strip 107A connecting plug 104A and N-well). Charges on plug 104A can thus be easily released to N-well or substrate regardless of the ON/OFF state of the P+/N-well junction associated to plug 104A. As a result, plug 104A appears brighter in the VC image 110A. Another typical defect is open P+/N-well plug 103A, i.e. the plug does not contact to the buried device as expected. As a result, positive charges on the surface of P+/N-well plug 103A accumulate to a significant level, and deliver a voltage contrast much darker than the normal plugs 102A. The gate plug 101A is equivalent to an open circuit as it is electrically isolated from the substrate (N-well) by a gate dielectric layer 105A, so it appears similar to the open P+/N-well plug 103A. As one can perceive from the image 110A, for inspection of PMOS plugs at a given positive mode imaging condition, it will be easy to identify the defective open P+/N-well plugs 103A from normal P+/N-well plugs 102A with high sensitivity, but difficult or insensitive to identify the P+/N-well short/leakage defects 104A from normal P+/N-well plugs 102A. Similar inspection of the NMOS transistor is illustrated in FIG. 1B. As shown, NMOS transistor 100B comprises a gate electrode 101B, a normal N+/P-well plug 102B, an open N+/P-well plug 103B, and a shorted N+/P-well plug 104B. Image 110B illustrates the VC behaviors of respective above components. As the surface is positively charged, the N+/P-well junction associated to plug 102B is reverse biased. Therefore, the junction is in the “OFF” state and to some extent equivalent to being an open circuit. As a result, positive charging accumulates on N+/P-well plug 102B, making it appear dark in image 110B. Though the open plug 103B differs from the normal plug 102B in that it is a real open-circuit to the associated buried N+/P-well junction, no significant difference in image contrast is observed between plugs 102B and 103B as they hold the positive charging to a similar level. In real cases, minor junction leakage may exit on the reverse biased N+/P-well junction, thus a normal N+/P-well plug 102B may appear slightly brighter than an open plug 103B as shown in image 110B. Another defect type is junction short or leakage in which the N+/P-well plug 104B may be either leaking a current or directly shorted to the substrate (illustrated in the figure as a black strip 107B connecting plug 104B and P-well). A plug of this defect type releases charges effectively even with its associated junction reverse biased to the OFF state. As a result, shorted plug 104B appears much brighter in image contrast. Gate plug 101B is equivalent to an open circuit as it is electrically isolated from the substrate (P-well) by a gate dielectric layer 105B. Therefore, it appears similar to the open N+/P-well plug 103B in the VC image 110B (darker VC). Hence, it can be perceived from FIG. 1B that for inspection of NMOS plugs at a given positive mode imaging condition, it is difficult or insensitive to identify the defective open N+/P-well plugs 103B from the normal N+/P-well plugs 102B, but it is sensitive to identify the P+/N-well short or leakage defects 104B from normal N+/P-well plugs 102B. Therefore, a conclusion can be drawn that the positive mode EBI has high sensitivity to capture P+/N-well plug open defects, but suffers low sensitivity in detecting N+/P-well plug open. Different approaches have been proposed to improve the situation, for example, by applying strong extraction field to reversely breakdown the N+/P-well junction, or by charging the sample surface negatively to forward bias the N+/P-well junction (the negative mode scanning). These techniques either suffer high risk of wafer arcing damage as extremely high electrical field is created in the vicinity of wafer, or need at least two separate inspections to detect both the P+/N-well plug open and the N+/P-well plug open, which is time costly. Another approach to boost the detection sensitivity of, for example, the open N+/P-well plug at the positive imaging mode was proposed by Larry (U.S. Pat. No. 4,902,967). The proposed method uses an optical beam which has energy higher than the band gap to illuminate the device under inspection. Photo-current will be induced while the surface of the device is being scanned, which either induces photocurrent across the N+/P-well junction, or stimulates leakage current across the thin gate oxide. Ground or substrate electrons are able to come up and neutralize the positive charging accumulated on the scanned surface of the device, and the N+/P-well junctions in the scanned device become, to some extent, leaking or shorted regardless of its actual biasing condition (forward or reverse biased) in the normal positive imaging mode. This helps to drain off the accumulated positive charges on the scanned device, especially the reverse biased N+/P-well junctions as illustrated in FIG. 1B. Referring to FIG. 1C, an NMOS transistor 100C is illustrated being imaged in the positive imaging mode with optical beam illumination in accordance with the conventional art. The NMOS transistor 100C comprises a gate electrode 101C, a normal N+/P-well plug 102C, an open N+/P-well plug 103C, and a shorted N+/P-well plug 104C. Image 110C illustrates the VC behaviors of respective above components. As shown, optical beam illumination stimulates photo-currents. In the presence of the photo-currents, ground or substrate electrons are able to come up and neutralize the positive charging accumulated on the scanned device surface. This helps to drain off the charging accumulated on normal N+/P-well plug 102C. As a result, plug 102C turns bright in image 110C, and thus the contrast between a normal N+/P-well plug 102C and an open N+/P-well plug 103C which appears dark is greatly enhanced whereby detection sensitivity of open N+/P-well plug 103C is improved. It is noted that gate plug 101C also turns relatively brighter as compared to the gate plug 101B of FIG. 1B (inspection without optical illumination). This is due to the stimulated leakage in gate oxide 105C. This phenomenon can be used to separate the normal gate plug and the open gate contact which does not physically land on gate electrode. One disadvantage of the above approach is that the optical beam will stimulate the normal N+/P-well plug 102C to leak, thus the N+/P-well leakage or short defects such as plug 104C may become difficult to detect. As a result, at least two inspection actions are still needed to accomplish the detection of both the of-interest open and short/leakage defects. Referring to FIG. 2A, not admitted art, a positive imaging mode VC image is captured, without optical illumination, of a sample containing both NMOS and PMOS transistors. The sample device can be, for example, an SRAM device. Herein, defect 200 A is a P+/N-well open defect displaying a DVC (visually distinguishable), defect 200B is an N+/P-well leakage/short defect displaying a BVC (visually distinguishable), defect 200C is an open N+/P-well plug defect displaying a DVC (less distinguishable). Defect 200D is an open gate contact displaying a DVC (less distinguishable); as shown it is immersed in the normal gate plugs as there are no substantial electrical differences between them. Furthermore, defect 200E is a gate short/leakage defect displaying a BVC (visually distinguishable). No P+/N-well leakage or short defect (BVC) is present in FIG. 2A. In the schematic of FIG. 2B, not admitted art, a positive imaging mode VC image is captured, with optical beam illumination, of the sample device of FIG. 2A. As with the FIG. 2A schematic, the image is captured in positive imaging mode. It can be seen from FIG. 2B that with optical beam illumination all normal N+/P-well plugs turn bright. As a result, the N+/P-well leakage/short defect 200B becomes hidden (less distinguishable) in the normal bright plugs, and the open N+/P-well plug defect 200C stands out (visually distinguishable) as a high contrast dark plug. It is noted that the P+/N-well plug open defect 200A is almost unaffected by the optical beam illumination (visually distinguishable). Also, the optical beam illumination, by stimulating certain level of leakage through the thin gate oxide, turns the gate plug relatively bright. The gate plug defect 200E thus becomes less distinguishable. The open gate plug defect 200D, however, is not affected by this induced gate oxide leakage, thus standing out (visually distinguishable) as a darker plug. In general processes of semiconductor device manufacture, it is common to see both NMOS and PMOS plugs in a layer from the surface. FIGS. 2A and 2B illustrate complementary images, or complementary imaging approaches, for detecting different types of defects present on a single sample. These complementary approaches may be implemented in the negative imaging mode and applied to other types of devices as well. Since these complementary approaches only require changes in optical beam illumination condition (on/off), there will be a great benefit to combine the above two imaging steps (one with optical beam illumination, the other without) into one imaging sequence for improved throughput without sacrificing the detection sensitivity to different types of defects. One embodiment of the present invention discloses an imaging method for forming a plurality of images of substantially the same area on a sample for defect inspection within the area. The images preferably have a size of X*Y pixels with a predefined pixel size p. The images are formed by charged particle beam imaging where a charged particle beam is repeatedly line-scanned over the area with a line-to-line advancement direction perpendicular to the line scan direction. The disclosed method comprises line-scanning the charged particle beam over the area to form a plurality of n*Y scan lines by repeatedly forming a group of n scan lines for Y times. During the formation of each group of n scan lines, an optical beam is, from one line scan to another, selectively illuminated on the area prior to or simultaneously with scanning of the charged particle beam. In addition, during the formation of each group of n scan lines, a condition of illumination of the optical beam selectively changes from one line scan to another. The conditions at which the individual n scan line is formed are applied to the formation of all groups of n scan lines. In another embodiment of the present invention, a charged particle beam inspection system is disclosed. The disclosed charged particle beam inspection system comprises a charged particle beam imaging apparatus, an optical beam apparatus, and a defect determination apparatus. The charged particle beam imaging apparatus is for forming voltage contrast images of a sample by scanning a charged particle beam over the sample surface. The images preferably have a size of X*Y pixels with a predefined pixel size p. The optical beam apparatus is for illuminating an optical beam on the sample. The defect determination apparatus comprises a control module and an image analysis module, wherein the control module is coupled to the charged particle beam imaging apparatus and the optical beam apparatus for controlling these elements, such that the charged particle beam is line-scanned over the sample surface to form a plurality of n*Y scan lines by repeatedly forming a group of n scan lines for Y times, and during the formation of each group of n scan lines, the optical beam is, from one line scan to another, selectively illuminated on the sample surface prior to or simultaneously with scanning of the charged particle beam, and during the formation of each group of n scan lines, a condition of illumination of the optical beam selectively changes from one line scan to another. The condition at which the individual n scan line is formed may be applied to the formation of all groups of n scan lines. The image analysis module is coupled with the charged particle beam imaging apparatus for receiving and analyzing the voltage contrast images from the charged particle beam imaging apparatus, thereby determining the presence of certain types of defects on the sample. Although the present invention will be described in accordance with the embodiments shown below, one of ordinary skill in the art will readily recognize that there could be variations to the embodiments and those variations would be within the spirit and scope of the present invention. Accordingly, many modifications may be made by one of ordinary skill in the art without departing from the spirit and scope of the appended claims. As mentioned earlier, when being scanned in a particular mode, a semiconductor device may display a default voltage contrast (VC) which is a result of change in the device's electrical characteristics. Further, this default VC could lead to confusion in identifying the presence of certain types of defects on the semiconductor device. For example, in the positive imaging mode, all PN-junctions of a normal NMOS device are reverse biased; therefore, the normal N+/P-well plugs may appear similar to a defective open plug in the grey level image (e.g. they both display a darker VC). On the other hand, all PN-junctions in a normal PMOS device are forward biased in the positive imaging mode and therefore may appear similar to a junction short/leakage defect in the grey level image (e.g. they both display a brighter VC). Table 1 lists these and other possible cases (in the positive imaging mode). TABLE 1ElectricalElectricalCharacteristic ofCharacteristic ofDevicenormal devicepossible defectN+/P-well plug~openOpen; Short,(OFF at reverse bias)Junction leakageP+/N-well plug~shortOpen; Short,(ON at forward bias)Junction leakageGate plug~openOpen; Short/leakage(isolated from substrateby gate dielectric) It can be seen from Table 1 that the identification of an open defect on an N+/P-well plug may be confused by the normal N+/P-well plugs from the obtained voltage contrast image as both are equivalent to an open circuit, and present in DVC at positive mode. On the other hand, the identification of a short/leakage defect on a P+/N-well plug may be confused by the normal P+/N-well plugs from the obtained voltage contrast images as both plugs are equivalent to short-circuit, and present in BVC at positive mode. As mentioned earlier, illumination of the optical beam is able to enhance the detection sensitivity of certain types of defects on a specific semiconductor device. Reference is made to Table 2 to indicate a number of general cases: TABLE 2Defect types (on specificplugs) with enhanceddetection sensitivity\OpticalIllumination ONIllumination OFFbeam illumination condition(Condition 1)(Condition 2)N+/P-well plugOpenShort/leakageP+/N-well plugOpenOpenGate plugOpenShort/leakage It can be seen from Table 2, in conjunction with FIGS. 2A and 2B, that the positive imaging mode without optical beam illumination (Condition 2) is sensitive to defects 200A (P+/N-well plug open), 200B (N+/P-well plug short/leakage), and 200E (Gate plug short/leakage), but insensitive to defects 200C (N+/P-well plug open) and 200D (gate plug open). On the other hand, the positive imaging mode with optical beam illumination (Condition 1) is insensitive to defects 200B and 200E, but sensitive to defects 200A, 200C and 200D. In other words, as an open defect on the P+/N-well plug, defect 200A corresponds to a high detection sensitivity with the optical beam illumination either ON or OFF. As a short or leakage defect on the N+/P-well plug, defect 200B corresponds to a high detection sensitivity with the optical beam illumination OFF. As an open defect on the N+/P-well plug, defect 200C corresponds to a high detection sensitivity with the optical beam illumination ON. Moreover, as an open defect on the gate plug, defect 200D corresponds to a high detection sensitivity with the optical beam illumination ON. Further, as a short or leakage defect on the gate plug, defect 200E corresponds to a high detection sensitivity with the optical beam illumination OFF. As shown in the examples of FIGS. 2A and 2B, to implement the above approach of optical illumination-assisted inspection, two images can be formed for the same area of interest 20 on a sample, with one of the two images being formed without optical beam illumination and the other formed with optical beam illumination. Such implementation can be performed in a step-and-scan mode and a continuously moving stage mode. For example, in the step-and-scan mode, two images of substantially the same area of interest may be formed and analyzed to carry out inspection of the area of interest, and then the imaging system, or the sample stage, can move one step to another area of interest on the sample. In the continuously moving stage mode, two images of substantially the same area of interest can be formed by repeating the stage motion, whereby the stage moves forward during one imaging action, then moves back to a designated starting point, and then moves forward again for another imaging action to be performed at substantially the same position on the sample. This algorithm may suffer from (1) the position of scan on the sample being different between the two imaging actions due to mechanical positioning errors; and (2) throughput loss as the stage must move back and forth for the two imaging actions to be performed. Despite these problems, for currently available EBI systems, the continuously moving stage mode imaging will still generally have a higher throughput than the step-and-scan mode imaging method. Therefore, according to an aspect of the invention, it is necessary to integrate the two (or more) complementary imaging approaches into one scan sequence without sacrificing throughput and sensitivity. In one embodiment, a method of charged particle beam inspection of a semiconductor device is disclosed. The disclosed method scans the sample, such as a patterned surface of a semiconductor device, line by line with a charged particle beam; meanwhile, an optical beam is modulated on/off or to different power levels or selected from different sources of wavelength, in synchronization with the line scans and in a preferred (but not the only) implementation, is kept constant during each line scan. This forms multiple line scans at different optical beam conditions. Formation of such a group of line scans is repeated to complete the whole imaging process. One objective of the disclosed method is to form one or a plurality of images by a unique scanning sequence over substantially the same area on the sample at different optical beam illumination conditions, which will be referred to as the “imaging condition” hereinafter for simplicity of explanation. The disclosed method applies to both the continuously moving stage mode and the step-and-scan mode. Conventionally, with either of these two types of modes, a charged particle beam may be repeatedly raster scanned over an area of interest on the sample. Specifically, the charged particle beam is repeatedly line-scanned over the area of interest with a line-to-line advancement direction perpendicular to the line scan direction. In the continuously moving stage mode, the line-to-line advancement is achieved by continuously moving a sample stage whereupon the sample is secured for imaging. In the step-and-scan mode, the line-to-line advancement is achieved by offsetting the charged particle beam by means of, for example, a beam deflection device. Referring to FIG. 3A, a schematic illustration of a raster scan may be likened to that of the conventional art. It is first noted that the continuously moving stage mode is used as an example here to describe the conventional raster scan. This is merely for simplicity of explanation and should not limit the scope of the present invention. As shown, sample 300 is held on a stage moving at a predefined constant speed in a stage moving direction 301. Electron beam, for example, meanwhile is scanned over the surface of sample 300 in two directions such as, typically, a line scan direction 302 and a line-to-line advancement direction 303. In this example, the line scan direction 302 is selected to be substantially perpendicular to the stage moving direction 301 for covering the width of the obtained image while the line-to-line advancement direction 303 is selected to be substantially perpendicular to the line scan direction 302. The net effect of electron beam scan components in line-to-line advancement direction 303 and stage moving direction 301 defines the line-to-line scan offset. A two-dimensional array of scan lines 320 is, thus, accordingly formed on the surface of sample 300. It is noted that the dotted line in scan line array 320 indicates the trace of the scanning beam's flying back from the end of the previous scan line to the start of the next scan line. The distance between each scan line is called the pixel size and is denoted “P.” If the stage moving speed 301 is equal to zero, i.e. sample 300 is held on a stationary stage, then this example is equivalent to a raster scan implemented in the step-and-repeat mode. If the line-to-line advancement component 303 is equal to zero, i.e. the stage is in motion with a constant speed, then this example is equivalent to the typical continuously moving stage mode. In one embodiment of the present invention, neither the stage moving direction 301 nor the line-to-line advancement direction 303 is equal to none, i.e. the sample stage is moving one-dimensionally and the charged particle beam is being raster scanned two-dimensionally during imaging. As distinguished from the traditional repeated single line scans of FIG. 3A forming a single condition image, the embodiment of FIG. 3B shows a group of n line scans being repeated such that “m” groups of n scan lines are formed on the sample, whereby image(s), each formed at a different imaging condition synchronized with the formation of individual scan lines, are thus obtained. Image signals from collections of m scan lines with each from a corresponding group of n scan lines are used to form at most n images, with each being formed at a different imaging condition. In one example, m is selected as a specific number, n is selected to be an integer greater than or equal to 2, and X and Y are both selected to be an integer greater than 2. If an image size of X*Y pixels with a predefined pixel size p (as shown in FIG. 3B) is desired for an image of a single condition, m can be selected to be Y, and the image size of the newly obtained images is X*Y*n pixels regardless of the number of images ultimately obtained. It is noted that for such a case, the total n*Y scan lines formed may be spaced apart by a fixed distance d (as shown in FIG. 3B) such that the product of n and d is equal to the specified pixel size p, i.e. n*d=p. Alternatively, the product of n and d may be greater than the specified pixel size p (n*d>p) or less than the specified pixel size p (n*d<p). The later cases, however, may render deformed images. As shown in FIG. 3B, a sample 350 travels along a sample moving direction indicated as 351. In one example, sample 350 is secured on a stage for imaging, and the sample moving direction 351 is selected to be along the stage moving direction. A charged particle beam is repeatedly line-scanned over an area of interest 360 on sample 350 with a line scan direction 352 and line-to-line advancement direction 353. In one example, sample moving direction 351 is selected to be in the direction identical to line-to-line advancement direction 353. In one example, line-to-line advancement direction 353 is selected to be perpendicular to line scan direction 352. Scanning of the charged particle beam forms a plurality of n*Y scan lines 370 on sample 350 through repeatedly forming a group of n scan lines 370 for Y times on the moving sample 350. It is noted that in this embodiment, the above mentioned “Y” dimension of pixels is measured along the line-to-line advancement direction 353. The imaging condition at which each scan line 370 is formed may be the same or different. Moreover, the change in imaging conditions is synchronized with each line scan and kept unchanged during the line scan. As shown in FIG. 3B, different line characters of scan line 370 indicate a different imaging condition. In other words, the imaging conditions for the 1st scan line (bold solid line), 2nd scan line (bold dotted line), and the 3rd scan line (thin dotted line), etc. are different from each other. In one embodiment, the imaging condition change is realized by varying the power of the optical beam(s) (from one or more sources). During the formation of each scan line 370, the optical beam(s) illuminate the area 360 to be scanned by the charged particle beam. The power of the optical beam(s) is modulated to a fixed level prior to or simultaneously with scanning of the charged particle beam on the sample, and kept unchanged during each line scan. In another embodiment, the imaging condition change is realized by varying the wavelength of optical beam(s) (from one or more sources). During the formation of each scan line 370, the optical beam(s) illuminate the area 360 to be scanned by the charged particle beam. The wavelength of the optical beam(s) is varied prior to or simultaneously with scanning of the charged particle beam on the sample, and kept unchanged during each line scan. In a more general embodiment, the imaging condition change is realized by varying the wavelength, power or combination thereof for the optical beam(s) (from one or more sources). In one embodiment, the optical beam may be illuminated on the sample in synchronization with (for example, simultaneously with or prior to) scanning of the charged particle beam with a varying or constant beam intensity, wavelength, beam energy, duration of illumination, or any combination thereof. In this embodiment, n images are obtained from the n*Y scan lines. The obtained n images are formed at n different imaging conditions, each synchronizing with individual line scans. FIGS. 3C, 3D and 3E, illustrative of such situation, are images of a sample formed in accordance with embodiments of the present invention. As shown, each of the n images is formed from image signals collected from selected Y line scans out of the total n*Y line scans. In other words, scan lines correspondingly selected from each of the Y groups of scan lines are used to form one of the (at most) n images. For example, as shown in FIG. 3C, the 1st scan line (bold solid line) within each of the Y groups of scan lines is selected to provide the image signals for forming a 1st image of area 360. As shown in FIG. 3D, the 2nd scan line (bold dotted line) within each of the Y groups of scan lines is selected to provide the image signals for forming a 2nd image of area 360. As shown in FIG. 3E, the 3rd scan line (thin dotted line) within each of the Y groups of scan lines is selected to provide the image signals for forming a 3rd image of area 360, and so on and so forth. It is noted from FIGS. 3C, 3D and 3E that each formed image has Y pixels with a pixel size p along the line-to-line advancement direction. Further, each formed image covers substantially the same physical area 360 on sample 350. However, as mentioned earlier, the image signals from the n*Y scan lines (in Y groups of n scan lines) may be used for forming “at most” n images. This is because not each scan line needs to be set to be formed at a different imaging condition. For example, multiple scan lines may be set to be formed at the same imaging condition, and then the image signals from these scan lines are averaged to give an enhanced image quality. In such case, the total number of images that may be obtained from the n*Y scan lines must be less than n. FIG. 3F is a schematic illustration of a charged particle beam inspection method in accordance with an embodiment of the present invention. As this embodiment is similar to that of FIG. 3B, descriptions of similar elements and associated notations will not be repeated here. As shown, the 1st and 2nd scan lines in each of the Y groups of scan lines are represented in an identical bold line. This means that the 1st and 2nd scan lines are formed at the same imaging condition. Therefore, image signals from these two scan lines can be averaged to form one image with enhanced quality. As a result, the total images that will be obtained from n*Y scan lines is (n-1) in this embodiment. In accordance with one exemplary implementation, image signals from scan lines formed at different imaging conditions may be averaged as well. It is noted that the embodiment of FIG. 3B, by changing the imaging condition in a substantially line-by-line manner, allows for the optical illumination-assisted charged particle beam inspection to be realized in one inspection action. In other words, the need to repeat imaging at different imaging conditions (e.g. illumination ON vs. OFF) is eliminated. For example, for such inspection to be performed in the continuously moving stage mode, the stage does not need to move back and forth. Multiple images targeting at the inspection of different types of defects can be produced as the stage moves along. This greatly improves the inspection throughput. As mentioned earlier, the patterns in the imaged area of interest may be represented in grey level profiles in the obtained images. Defects existing in the imaged patterns may be identified from these grey level images as abnormal grey levels or abnormal VCs. In one example, individual obtained images may be inspected independently. For instance, if the patterns in the area of interest are formed in repetition, defect identification can be performed by analyzing the grey level profiles displayed by the repeating patterns in the concerned image. Alternatively, cross-image comparison may be used. FIG. 3G is a schematic illustration of a prolonged version of the disclosed imaging method illustrated in FIG. 3B in accordance with an embodiment of the present invention. It is noted first that similar elements and notations which have been described in conjunction with FIG. 3B will not be repeated here. In this embodiment, the disclosed imaging method is performed to image a moving sample 350 which has multiple areas 360 thereon. In one example, these areas 360 have identical patterns and layouts, and may be located at a corresponding location(s) on different dies and/or sides. As shown in FIG. 3G, when sample 350 continues to move forward along direction 351, the disclosed imaging method is repeatedly performed such that two or more separate areas 360 are imaged at identical imaging conditions. Assume n images are produced per imaging of area 360, then two or more sets of n images (each representing one area 360) will be obtained. Next, images formed at the same imaging condition, i.e. images formed from image signals generated by line scans performed at the same imaging condition, can be compared against each other to detect the presence of defects in the concerned image. For example, in FIG. 3G, images formed by image signals collected from 1st scan lines for each of the two imaging areas 360 may be compared. In another example, some or all of the obtained images can first be combined through mathematical operation such as linear addition, subtraction, etc., such that noises and/or grey levels of normal patterns are canceled or suppressed, and/or the grey level contrast between the normal and defective patterns are enhanced, making the inspection easier. Examples of the mathematical operations are linear addition, subtraction, etc. These operations are common image processing techniques, and details thereof will not be repeated here. In a further example, the individual images are compared against each other. As would be understood by those skilled in the art, combinations of the above image inspection methods are also possible for the ultimate purpose of identifying defects from the obtained grey level images. In one embodiment, the disclosed method is applied for the inspection of a sample having both NMOS and PMOS devices thereon, such as an SRAM. In another embodiment, the disclosed method can be applied for the inspection of photo diodes, CMOS sensors, and/or other devices that are sensitive to optical beam illumination. With reference to FIG. 4A, a schematic is provided of a positive imaging mode VC image of an SRAM device captured without laser beam illumination in accordance with an embodiment of the present invention. Plugs connected to N+/P-wells appear relatively dark as associated junctions are reverse biased, while plugs connected to P+/N-wells appear bright as forward biasing occurring thereto helps in the release of positive charging on the device surface. As shown in FIG. 4A, two abnormal contacts are indicated as A and B, respectively. Contact A is an open plug landing on an N+/P-well, appearing slightly darker than normal ones, while contact B is an open plug landing on a P+/N-well, appearing dark in contrast with the bright normal ones. It may be difficult to maintain balanced detection sensitivity for these two types of open plugs. Referring to FIG. 4B, another schematic is provided this time of a positive imaging mode VC image captured with laser beam illumination of the SRAM device of FIG. 4A in accordance with an embodiment of the present invention. In one example, the laser beam is selected to have a power of 5mW and a wavelength of 650nm. Alternatively, or additionally, power and wavelength may be used according to other examples. If the area is illuminated by an optical beam when being imaged with an EBI apparatus, normal N+plugs will gradually turn from dark to bright as the illumination power increases, finally reaching a state where all N+plugs appear as bright as that of P+plugs. The abnormal plugs coupled to the open contact, however, are not affected by illumination of the laser beam. This may make the two abnormal plugs A and B drop in the grey level up to 50% when compared to their normal counterparts. As a result, balanced detection sensitivity for open defects on both P+/N-well (defect B) and N+/P-well (defect A) can be achieved, as shown in FIG. 4B. Another example effect of laser beam illumination is that it boosts gate leakage thus revealing gate contact open conditions. Referring to FIG. 5A, which is a schematic illustration of a positive imaging mode VC image of an SRAM device captured without laser illumination in accordance with an embodiment of the present invention, normal gate plugs appear dark due to positive charging accumulation which is difficult to be released to the substrate via the gate oxide. The abnormal open gate contact shows up slightly darker, as indicated by arrow C. The difference in grey level due to the contact open condition may be about 30% as compared to the normal. Referring to FIG. 5B, which is a schematic illustration of a positive imaging mode VC image captured with laser beam illumination of the SRAM device of FIG. 5A in accordance with an embodiment of the present invention, when the laser is on, the laser light more or less stimulates gate oxide leakage and draws away excess positive charges on the normal gate. The normal gate plugs are thus lit up. On the contrary, the open gate plug is almost not affected by illumination of the laser beam. A measurement shows that the open gate plug grey level may drop in grey level up to 50% from the normal. In one embodiment, a charged particle beam inspection system is disclosed. Referring to FIG. 6, which is a schematic illustration of a charged particle beam inspection system in accordance with an embodiment of the present invention, a charged particle beam inspection system 600 comprises a charged particle beam imaging apparatus 610, an optical beam apparatus 620, and a defect determination apparatus 630. Charged particle beam imaging apparatus 610 is for forming a grey level or voltage contrast image of a sample of interest. Optical beam apparatus 620 is for illuminating an optical beam on the sample. Defect determination apparatus 630 comprises a control module 631 and an image analysis module 632. Charged particle beam imaging apparatus 610 may be a conventional charged particle beam microscope, such as a scanning electron microscope (SEM). As shown in FIG. 6, in charged particle beam imaging apparatus 610, a charged particle beam generator 611 generates a charged particle beam, and then the charged particle beam is condensed and focused by a condenser lens module 612 and an objective lens module 613, respectively, to form a charged particle beam probe 6111. The formed charged particle beam probe 6111 then bombards the surface of a sample 614 secured on a sample stage 615. Charged particle beam probe 6111 is controlled by a deflection module 616 to scan the surface of sample 614. After charged particle beam probe 6111 bombards the surface of sample 614, secondary charged particles 6112 are induced to be emitted from the sample surface along with other charged particles of beam probe 6111 reflected by sample 614. These particles are then detected and collected by a detector module 617. Then, detector module 617 generates a detection signal 6113 accordingly. An image forming module 618 coupled to detector module 617 receives detection signal 6113 and accordingly forms a charged particle microscopic image (grey level image) of sample 614. Control module 631 is coupled to charged particle beam imaging apparatus 610 and optical beam apparatus 620 for controlling these elements such that when sample 614 is being imaged, an optical beam 621 is selectively illuminated on sample 614 in coordination with the scanning of the imaging charged particle beam probe 6111. In particular, charged particle beam probe 6111 is line-scanned over the surface of sample 614 to form a plurality of n*Y scan lines by repeatedly forming a group of n scan lines for Y times. In addition, during the formation of each group of n scan lines, optical beam 621 is, from one line scan to another, selectively illuminated on the surface of sample 614 prior to or simultaneously with scanning of the charged particle beam probe 6111. Moreover, during the formation of each group of n scan lines, a condition of illumination of optical beam 621 selectively changes from one line scan to another. The conditions at which individual n scan lines are formed may be repeated for the formation of all Y groups of scan lines. In one example, control module 631 is coupled to deflection module 616 to control the scanning of charged particle beam probe 6111 over sample 614. In another example, control module 631 is coupled to deflection module 616 and/or sample stage 615 to control the relative motion of charged particle beam probe 6111 and sample 614, so as to carry out the line-to-line advancement of the scanning charged particle beam probe 6111. In a further example, sample stage 615 is controlled by control module 631 to move sample 614 continuously along the line-to-line advancement direction of the scanning charged particle beam probe 6111, such that the charged particle beam imaging is performed in the continuous scan mode. Image analysis module 632 is coupled to charged particle beam imaging apparatus 610 for receiving the grey level/voltage contrast image of sample 614 therefrom. In one example, image analysis module 632 is coupled to image forming module 618. With optical beam illumination controlled to be selectively performed in coordination with scanning of charged particle beam probe 6111, charged particle beam inspection system 600 is able to carry out the defect inspection method for the sample 614 as disclosed in embodiments of FIGS. 3 to 5. For example, defects identified from images formed with and without illumination of optical beam 621 on sample 614 are compared against each other so as to determine the presence of certain types of defects on sample 614. Although the present invention has been explained in relation to its preferred embodiment, it is to be understood that other modifications and variation can be made without departing from the spirit and scope of the invention as hereafter claimed. |
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claims | 1. A product of a process comprising the steps of:(a) Preparing a precursor solution comprising 2β-Carbomethoxy-3β-(4-fluorophenyl)-N-(3-tributyltin-E-allyl) nortropane), ethanol, hydrogen peroxide, and a phosphate buffer;(b) Preparing a sodium [1231]-iodide solution comprising sodium [1231]-iodide and trifluoroacetic acid having a pH of less than about 2;(c) Heating a mixture of said precursor solution and said sodium [123l]-iodide solution at a temperature of about 80° C. for about 15 minutes;(d) Eluting said resulting product [1231]-2β-carbomethoxy-3β-(4-flurophenyl)-N-(3-iodo-E-allyl) nortropane through a C18 preparative HPLC column with an eluent, wherein the eluent comprises about 15% (v/v) ethanol; and(e) Collecting product peak in a mixture of sodium chloride and an acetic acid buffer wherein said nortropane product is stable for at least 48 hours. |
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060211695 | summary | BACKGROUND OF THE INVENTION The current System 80+ Feedwater Control System (FWCS) automatically controls the feedwater flow to the steam generators between 5% and 100% power. However, feedwater control below 5% power is a manual operation. The current FWCS uses input signals of steam flow rate, feedwater flow rate, and steam generator level to develop output signals that control the position of the feedwater valves and the speed of the feedwater pumps. There is a large economizer feedwater valve, a small downcomer feedwater valve and a very small startup feedwater valves. The startup feedwater control valve is located in parallel with the downcomer feedwater valves. The large economizer feedwater valve is automatically controlled by the above three signals of the FWCS between 20% and 100% power. Also, the small downcomer feedwater valve is automatically controlled by the steam generator level signal of the FWCS between 5% and 20% power. Furthermore, the very small startup feedwater valve is manually controlled by an operator when the power level is between 0% and 5%. It is an object of the present invention to simplify the FWCS design, which previously had two automatically functioning systems, and one manually functioning system, according to the existing power levels. It is another object of the present invention to provide a more reliable feedwater system than is currently provided, especially with the System 80+ Feedwater Control System, by using additional input signals when the power level is between 5% and 20%, and by increasing the automatic feedwater control operating range, thereby relieving operators of monitoring and operating of the FWCS at operation power levels below 5%. SUMMARY OF THE INVENTION The above-described needs and others are met by a feedwater control system for a pressurized water reactor steam generating system, which includes a first input signal, which is determined by a downcomer feedwater flow differential pressure, a second input signal, which is determined by a reactor power level, a first output signal, which is determined by the first and second input signals, and, when combined with a third input signal which is determined by a steam generator level, which automatically controls at least one feedwater pump and designated valves which regulate water flow from the one or more feedwater pumps, to a steam generator, when a steam generator steam load and a reactor are operating at a first predetermined power level, and a second output signal, determined by a steam generator water level, which automatically controls at least one startup feedwater control valve when the steam generator steam load and the reactor are operating at a second predetermined power level. In a preferred embodiment of the invention, the first predetermined power level is between about 5 and about 20 percent, and the second predetermined power level is between zero and about 5 percent. Also in a preferred embodiment of the invention, the first designated valves include at least one economizer feedwater control valve, and at least one downcomer feedwater control valve. Furthermore, in a preferred embodiment of the invention, the startup feedwater control valve stops controlling feedwater at the first predetermined power level, and the feedwater control system includes a delay device, in series with the second output signal. The delay device ensures that the startup feedwater control valve does not reach a closed state until the downcomer valve reaches an opened state, thereby ensuring continuous feedwater supply to the steam generators. The above objects and others are also provided by a method of controlling a feedwater supply to a steam generator in a pressurized water reactor, which includes the steps of providing a first input signal which is determined by a downcomer feedwater flow differential pressure, and providing a second input signal which is determined by a reactor power level. The method also includes the steps of automatically controlling at least one feedwater pump and a designated set of valves which regulate water flow from the one or more feedwater pumps to a steam generator, using a first output signal which is determined by the first and second input signals and combined with a third input signal which is determined by a steam generator level, when a steam generator steam load and a reactor are operating at a first predetermined power level, and automatically controlling at least one startup feedwater control valve, using a second output signal which is determined by a steam generator water level, when the steam generator steam load and the reactor are operating at a second predetermined power level. As noted before, in a preferred embodiment of the invention, the first predetermined power level is between about 5 and about 20 percent, and the second predetermined power level is between zero and about 5 percent. Also in a preferred embodiment of the invention, the first designated valves include at least one economizer feedwater control valve, and at least one downcomer feedwater control valve. The method can also include the steps of providing a signal to close the startup feedwater control valve at the first predetermined power level, providing a delay device to the second output signal, and automatically operating the delayer to ensure that the startup feedwater control valve does not reach a closed state until the downcomer valve reaches an opened state. |
042186226 | description | In FIG. 1 there is illustrated neutron absorbing article 11, shown as a thin, flat, elongated, normally vertically positioned composite coated article, with individual larger particles of boron carbide, represented by numeral 13, shown in a matrix 15 of a mixture of polymeric material and finer boron carbide particles. A preferred final coat of polymeric material over the surface article is not identified in this figure but is shown in FIG. 2. In FIG. 2 fiberglass or other suitable inorganic, synthetic organic polymeric or natural fibrous material, in cloth form is shown (17) with fine boron carbide particle-phenolic polymer matrices 15 and 19 on sides of it, with matrix 15 having larger boron carbide particles 13 embedded in it, yet extending distances beyond the surface plane thereof. Outer coating 21 covers with phenolic or other suitable polymer the coarser boron carbide particles and the matrix in which they are embedded. Optionally, the outer sizing, sealing or additionally binding coating may also be applied to article side 19. Because the filling coat of polymer essentially penetrates into the fibers or into interstices in the base cloth or backing member between the fibers and does not add appreciably to the thickness thereof, this filling, which is "between" the cloth and the boron carbide-polymer matrices, is not illustrated in FIG. 2. In FIG. 3 a preferred manufacturing process is diagrammatically illustrated. In it the basic backing member, preferably a fiberglass cloth, is resin filled, after which the resin is partially cured, to an easy-to-handle, yet flexible solid. To one side of the cloth there is subsequently applied a mixture of curable resin and relatively fine boron carbide particles, after which the resin is partially cured, as previously described. Another such mixture of resin and boron carbide particles, sometimes of a slightly different composition or of slightly different proportions, is applied to the other side of the backing member and subsequently coarser boron carbide particles are adhered to such side and pressed into the resin thereof, after which such resin is partially cured, as previously described. A size coat is next applied over the adhered coarse particles and is partially cured. Then the article, often previously in web or sheet form of indeterminate length or of length greater than that desired, is cut to size and the sheets are stacked and finally, preferably completely cured (to C-stage) under a shape-controlling load. Numerals are applied to the various components and processing steps in FIG. 3 but will not be referred to further at this point because they are primarily to assist in identification of particular components and processing operations and their relations to such are self-evident. In FIG. 4 a continuous belt 61 of a backing member material, such as fiberglass cloth, coated with uncured liquid resin-boron carbide mix, moves in the direction of arrow 63 beneath distributor 65, from which coarser boron carbide particles 67, in a regular stream, drop onto it. The belt, sheet or web passes under roller 77 which presses the coarser particles into the resin-particles mix (without the roller contacting the resin) and then travels over roller 69 so that boron carbide particles 71, not held to the web by the resin, fall off it into collecting bin or trough 73. The backing member, coated with partially cured boron carbide-polymer mix on one side thereof (the roll side) and with uncured boron carbide-polymer mix with coarser boron carbide particles adhering thereto on the other side, passes under roll 75 and is taken off for further treatment, e.g., partial curing, coating, partial curing, final curing, etc. As described in FIG. 3 the final cure is preferably effected while the article is being held in shape. FIG. 5 illustrates a bundle of spent nuclear fuel rods or other nuclear material 90, only some of which is shown, located inside a casing 88 and in an aqueous (or other) medium (not specifically identified) inside a portion 83 of a storage rack (or other container) for such nuclear material. Storage rack portion 83 includes outer wall 85 and inner wall 87, held apart by vertical rods 89, to which they may be welded or otherwise affixed, with neutron absorbing articles 11 of this invention within such walls and surrounding the neutron emitting spent nuclear fuel rods 90, thereby absorbing neutrons emanating from the rods and protecting the external environment against the effects of the storage of the spent nuclear fuel. In the drawing the thickness of articles 11 has been exaggerated. The boron carbide particles, employed for their neutron absorbing capability, will normally be in rather finely divided particulate form. Thus, such particles will generally be within the No. 10 to No. 400 sieve range, U.S. Sieve Series, signifying that they will pass through a No. 10 sieve and rest on a No. 400 sieve. Usually the finer particles, utilized in forming matrices with polymeric materials, to be described later, will be of particle sizes in the No. 170 to No. 400 sieve range, preferably passing through a No. 200 sieve. The coarser boron carbide particles employed to form a heavier coating on one side of the article, are normally in the No. 10 to No. 200 sieve size range, preferably being from 35 to 200, more preferably 60 to 200 and sometimes most preferably in the 60 to 120 range. It is important that fairly finely divided boron carbide particles be employed, as described, to produce effective bonds to the polymeric material to be cured about such particles and to obtain a uniformly distributed boron carbide content in the polymeric matrix. Boron carbide often contains impurities, of which iron (including iron compounds) and B.sub.2 O.sub.3 (or impurities which can readily decompose to B.sub.2 O.sub.3 on heating) are among the more common. Both of such materials, especially B.sub.2 O.sub.3, have been found to have deleterious effects on neutron absorbing products in certain environments and therefore contents thereof are desirably limited. For example, although as much as 3% of iron or its compounds may be tolerable in the boron carbide particles of the boron carbide absorbers, preferably the iron content is held to 2%, more preferably to 1% and most preferably is less than 0.5%. Similarly, to obtain best absorbing articles, especially when they are of long, thin flat form, it is useful to limit the B.sub.2 O.sub.3 content (including boric acid, etc., as B.sub.2 O.sub.3), usually to no more than 2%, preferably to less than 1%, more preferably to less than 0.5% and most preferably to less than 0.2%. Of course, the lower the iron and B.sub.2 O.sub.3 contents the better. The boron carbide particles utilized will usually contain the normal isotopic ratio of B.sup.10 but may also contain more than such proportion to make even more effective neutron absorbers. Of course, it is also possible to use boron carbide with a lower than normal percentage of B.sup.10 (the normal percentage being about 18.3%, weight basis, of the boron present) but such products are rarely encountered and are less advantageous with respect to neutron absorbing activities. Other than the mentioned impurities, normally boron carbide should not contain significant amounts of components other than B.sub.4 C (boron and carbon in ideal combination) and minor variants of such formula unless the B.sub.4 C is intentionally diminished in concentration by use of a diluent or filler material, such as silicon carbide and others, various of which are mentioned in the Naum, Owens and Dooher application, previously cited. For satisfactory absorbing effectiveness at least 90% of the boron carbide particles should be boron carbide, preferably at least 94% and more preferably at least 97% and the B.sup.10 content of the particles (from the boron carbide) for best absorption characteristics will be at least 12%, preferably at least 14% (14.3% B.sup.10 is theoretically present in pure B.sub.4 C). To maintain the stability of the boron carbide-phenolic polymer article made under severe operating conditions it is often considered to be important to limit the contents of halogen, mercury, lead and sulfur and compounds thereof, such as halides, in the final product and so of course, such materials, sometimes found present in impure phenolic resins, solvents, fillers and plasticizers, will be omitted from those and will also be omitted from the composition of the boron carbide particles to the extent this is feasible. At the most, such materials will contain no more of such impurities than would result in the final product just meeting the upper limits of contents allowed, which will be mentioned in more detail in a subsequent discussion with respect to the phenolic polymer and the resins from which it is made. Although it is important and highly desirable that the boron carbide and other components employed in the making of the present articles should, for best results, contain little or no halogen, mercury, lead, sulfur and other objectionable materials, it is considered that for some applications wherein the presence of such materials is not considered to be harmful the specification limits set for contents thereof may be increased and in some instances no such limits will be imposed. Thus, in various applications, as when resistance to storage pool media, such as water and boric acid solutions, is not required, halogens, mercury, etc., may often be present without adversely affecting characteristics of the present articles. The solid, irreversibly cured polymeric material, cured to a continuous matrix about the finer boron carbide particles and cured so as to hold the coarser boron carbide particles in place, which polymer may also be employed as a preliminary filling coating on the backing member and as an overcoat for one side of the article, is preferably made from a phenolic resin which is in liquid form at normal temperatures, e.g., room temperature, 20.degree.-25.degree. C., but also may be from a resin which becomes liquid at an elevated temperature at which application of the resin may be effected in the present processes. The phenolic resins constitute a class of well-known thermosetting resins. Those most useful in the practice of the present invention are condensation products of phenolic compounds and aldehydes. Of the phenolic compounds phenols and lower alkyl- and hydroxy-lower alkyl-substituted phenols are preferred. Thus, the lower alkyl-substituted phenols may be of 1 to 3 substituents on the benzene ring, usually in ortho and/or para positions and may be of 1 to 3 carbon atoms, preferably methyl, and the hydroxy-lower alkyls present will similarly be 1 to 3 in number and of 1 to 3 carbon atoms each, preferably methylol. Mixed lower alkyls and hydroxy-lower alkyls may also be employed but the total of substituent groups, not counting the phenolic hydroxyl, is preferably no more than 3. Although it is possible to make a useful product with the phenol of the phenol aldehyde type resin essentially all substituted phenol, some phenol may also be present with it, e.g., 5 to 50%. For ease of expression the terms "phenolic type resins", "phenol aldehyde type resins" and "phenol formaldehyde type resins" may be employed in this specification to denote more broadly than "phenol formaldehyde resins" the acceptable types of materials described which have properties equivalent to or similar to those of phenol formaldehyde resins and trimethylol phenol formaldehyde resins when employed to produce thermosetting polymers in conjunction with boron carbide particles (or boron carbide plus diluent particles, e.g., silicon carbide and other particles, as described herein). Specific examples of useful "phenols" which may be employed in the practice of this invention, other than phenol, include cresol, xylenol and mesitol and the hydroxylower alkyl compounds preferred include mono-, di- and trimethylol phenols, preferably with substitution at the positions previously mentioned. Of course, ethyl and ethylol substitution instead of methyl and methylol substitution and mixed substitutions wherein the lower alkyls are both ethyl and methyl, the alkylols are both methylol and ethylol and wherein the alkyl and alkylol substituents are also mixed, are also useful. In short, with the guidance of this specification and the teaching herein that the presently preferred phenols are phenol and trimethylol phenol, other compounds, such as those previously described, may also be utilized providing that the effects obtained are similarly acceptable. This also applies to the selection of aldehydes and sources of aldehyde moieties employed but generally the only aldehyde utilized will be formaldehyde (compounds which decompose to produce formaldehyde may be substituted). The phenolic or phenol formaldehyde type resins utilized are employed as either resols, novolaks or mixes. The former are generally called one-stage or single-stage resins and the latter, with hexamethylenetetramine or equivalent present, are two-stage resins. The major difference is that the single-stage resins include sufficient aldehyde or alkylol moieties in the partially polymerized lower molecular weight resin to completely cure the polymer to cross-linked and thermoset state upon application of sufficient heat for a sufficient curing time. The two-stage resins or novolaks plus curing agent are initially partially polymerized to a lower molecular weight resin without sufficient aldehyde or equivalent present for irreversible cross-linking so that a source of such material, such as hexamethylenetetramine, is added to them in order for a complete cure to be obtained by subsequent heating. Either type of resin or mixtures thereof may be employed to make phenolic polymers such as those described herein. When the polymerization reaction in which the resin is formed is acid catalyzed HCl will usually be avoided (to minimize chloride content in the resin) and formic acid or other suitable chlorine-free acid may be used. Preferably the resin utilized is one which is normally liquid, even without the need for employment of solvents, although some water will often be present with it, e.g., 3 to 15% or preferably 6 to 12%. Preferably such resin will be a resol and the molecular weight of the resin will be in the range of 200 to 1,000, preferably 200 to 750 and most preferably 200 to 500. Thus, it is noted that the resin will usually be a monomer, dimer or trimer and preferably is a mixture of monomer and dimer. Generally the resin content of the liquid state resin preparation employed will be from 50 to 90%, preferably being about 55 to 85%. The solvent content, usually principally water, may be from 3 to 30% but is normally within the ranges previously given. Other components of the liquid resin include the aldehyde and phenolic compound from which it is made. Thus, for example, in a liquid unmodified phenolic resin of the single-stage type based principally on the condensation product of trimethylol phenol and formaldehyde, there may be present about 82% of dimer, about 4% of monomer, about 2% of trimethylol phenol, about 4% of formaldehyde and about 8% of water. Among the useful liquid products that may be employed are Arotap 352-W-70, which is of the description previously given for the trimethylol phenol formaldehyde and is especially low in halogen content; Arotap 352-W-71; Arotap 358-W-70 (also called Arofene 358-W-70), a formic acid catalyzed phenol formaldehyde resin of properties like that of Arotap 352 -W-70; Arotap 8082-Me-56; Arotap 8095-W-50; Arofene 744-W-55; Arofene 986-Al-50; Arofene 536-E-56; and Arofene 72155, all manufactured by Ashland Chemical Company; PA-149, manufactured by Polymer Applications, Inc. and B-178; R3; and R3A, all manufactured by The Carborundum Company. All such resins will be modified when desirable (when contents of the following impurities are too high) to omit halides, especially chloride, halogens, mercury, lead and sulfur and compounds thereof or to reduce proportions thereof present to acceptable limits. In some cases the procedure for manufacture of the resin will be changed accordingly. Generally the viscosity of such resin at 25.degree. C. will be in the range of 200 to 700 centipoises, preferably 200 or 250 to 500 centipoises. Usually the resin will have a comparatively high water tolerance, which will generally be from 200 to 2,000 or more percent and preferably will be at least 300%, e.g., at least 1,000%. Typical properties of a preferred resin, Arofene 358-W-70, are viscosity at 25.degree. C. in the range of 250 to 500 centipoises, gel time of 14 to 19 minutes, solids content of 69 to 73% and pH of 7.9. Although the phenolic resins and particularly the phenol formaldehyde type resins are highly preferred in the present applications other thermosettable resins may also be employed instead. These will not be described in the same detail as that given for the phenolic resins but the properties thereof will be similar. In some instances, it may be possible to utilize high softening point thermoplastic resins but generally this will not be preferred. Among the useful thermosetting polymers there may be mentioned the polyesters, epoxies, alkyds, diallyl phthalate, melamine and urea formaldehydes, polyurethanes and polyimides. More detailed descriptions of such materials and properties thereof may be found in the 1975-1976 Modern Plastics Encyclopedia, published by McGraw-Hill Inc., New York, N.Y., at pages 6-158 and 465-490 and in the Encyclopedia of Chemistry, 3rd Edition, by Hampel and Hawley, published by Van Nostrand Reinhold Company, New York, N.Y. In selecting other thermosetting (or thermoplastic , in certain circumstances) polymers consideration should be given to stability and strength retention upon radiation and resistance to softening or creeping at elevated temperatures within the range to which the present articles are normally exposed. The backing member utilized is preferably a woven fiberglass cloth but it is also within this invention to employ other materials instead, providing that they have processing and product characteristics which enable them to be made according to the present method and utilized in the manner described. Thus, instead of using fiberglass cloth, it is within the invention to employ fibers and cloths of synthetic organic polymeric materials, carbon, graphite, boron carbide, silicon carbide, boron nitride, ceramics, aluminum silicate, alumina, silica, quartz, zirconia, basalt, various combinations thereof, e.g., fiberglass and polyester, carbon and fiberglass, and even natural polymers, such as cellulose, cotton, linen, jute and hemp, providing that they are sufficiently strong and resistant to radiation. Also, it is within the invention to employ these materials in sheet or film form or as perforated sheets, insofar as such can be made. Furthermore, such sheet materials and cloths, including non-woven cloths and felts, may be reinforced with strengthening materials such as glass fibers, carbon fibers, silicon carbide fibers, boron carbide fibers, graphite fibers and other equivalent fibrous reinforcements. The important determining factors for successful products are flexibility, for processing and final use, and radiation resistance, so that the backing member will not deteriorate unacceptably upon exposure to radiation, e.g., 1.times.10.sup.11 rads. The particular use to which the product is to be put is important and various materials which might not stand up under excessive radiation can be used where the expected exposure is lower. Also, even for those materials which are unstable under radiation (and this applies to both the backing member and the coating[s] thereon), in some applications, like those wherein after manufacture the article is encased in a protective enclosure (which may be vented) some decomposition may be tolerable and in some cases even significant decomposition may not adversely affect the neutron absorbing capability of the product. For example, although polyester cloth is not preferred backing member material because of a lowering of tensile strength when it is exposed to massive radiation, leading to lower tensile strengths in products in which such cloth is used as a backing member, it may be acceptable in various applications, including those wherein it is held firmly in place, as between sandwiching metal walls, so that the B.sub.4 C particle distribution is maintained regular. Among other plastics or polymeric materials which may be employed as backing members there may be mentioned polyethylene, polypropylene, nylons, polyesters, polyethers, polyurethanes, polyacrylates and various other suitable thermoplastic and thermosetting materials, such as those described in the Modern Plastics Encyclopedia and the Encyclopedia of Chemistry publications cited above. Additionally, in some cases cotton and various other natural textile materials may be employed, alone or in mixtures. The backing member, whether of a film or sheet, woven or non-woven, should normally be of a thickness in the range of 0.1 to 2 mm., preferably 0.1 to 1 mm. and most preferably 0.2 to 0.3 mm. The weight of such material, preferably cloth, will normally be from 50 or 100 to 1,000 or 2,000 g./sq. m. The denier may be varied as desired and the weaves of cloths may be any such found to be suitable but preferably will be such as to result in a flexible backing. Various thread counts may be employed but preferably they are in the range of from 20 to 100 for both warp and fill, usually from 30 to 80. The cloth may be pretreated with known non-halogenated adhesion promoting chemicals to promote adherence of resin to it. For example, fiberglass is normally treated with a known aminosilane treatment which increases the adhesion of phenolic resin to the glass. Also, usually before use any coatings on the cloth, fibers or sheet, such as starch sizes, oils, waxes, etc., will be removed. The final neutron absorbing article is preferably 1 to 7 mm thick., more preferably about 1 to 4 mm. thick and most preferably about 1 to 2 or 3 mm. thick. The B.sup.10 loading is from 0.001 to 0.1 g./sq. cm., with the higher loadings being more feasible when an additional coating of "coarse" B.sub.4 C particles is laid on the "smooth" side of the present article so that coarse particles are on both sides thereof, or when two (or more) of the present articles are joined together, as by resin coating and polymerization, preferably at the "smooth" sides thereof. Usually the B.sup.10 concentration is from 0.001 to 0.05 g./sq. cm., preferably 0.005 to 0.03 g./sq. cm. (for example 0.01 to 0.02 g./sq. cm.) and the weight of the final article is in the range of 100 to 5,000 g./sq. m., preferably 500 to 3,000 g./sq. m. Preferably the boron carbide particles in the finished article are so distributed that 3 to 25%, preferably 10 to 20% to the total boron carbide and B.sup.10 is on one side of the backing member and the balance is on the other side, said balance being divided between 10 and 35%, preferably 15 to 30% of fairly finely divided boron carbide particles (mixed in with polymer) and 40 to 80%, preferably 55 to 75% in larger particle form (adhered to said polymer layer). Thus, the particles on one side are of particle sizes in the No. 10 to No. 400 sieve range, preferably 60 to 400 sieve range and on the other side are of particles in the 170 to 400 sieve range, preferably through a No. 200 sieve and sometimes more preferably through a No. 230 sieve. The most preferred embodiment of the invention is illustrated and has been described herein and will be that made by the preferred process to be described in detail, but in variations of the present invention the particles of boron carbide may be adhered to a suitable backing member by means of a preliminary uncured liquid resin coating without the utilization of filler coatings of polymer and of prior coats on the backing member of finely divided boron carbide particles-resin mixes. However, it is preferred to have both sides coated with at least some boron carbide particles in polymeric matrix for several reasons. The boron carbide particles help to increase the strength of the polymer and the ease of application thereof and furnish support for subsequent application(s) of resin, etc. Of course, when utilizing both sides of the backing member a greater total quantity of neutron absorbing B.sup.10 can be included in the present particles. Also, with boron carbide particles on both sides of the backing member the backing member material is better protected against radiation effects, at least with respect to neutron emissions. Furthermore, by employing a greater concentration of boron carbide particles on one side than the other, that with the heavier concentration may be located facing the probable source of neutron emissions and thereby may better protect the material of the backing member. The articles made will preferably include the same or closely related polymeric materials in the various layers and mixes and even when such are not employed it will be preferable to utilize polymers with similar curing properties so that a final, preferably complete cure of all the previously only partially cured resins may be effected at the end of the manufacturing procedure. The products made are form-retaining, yet possess a sufficiently flexibity so that they do not break apart and do not have pieces and boron carbide particles disconnected from them when they are subjected to flexural stresses of moderate degrees. They can be broken apart intentionally but are often resistant to separation, even when bent over 90.degree., and are resistant to cracking when bent up to 30 or 45.degree.. Also, they are light in weight and are of sufficient tensile strength so that they may be hung or "stood" in place. When free standing, with large sideward movements prevented by enclosing walls, as in a spent fuel storage rack, the product may take a sinuous shape but will still be effective as a satisfactory neutron absorber over the length of the container in which it is positioned. If subjected to stresses sufficient to crack a surface layer of boron carbide particles and polymer, the backing member will normally maintain the integrity of the product and prevent chipping off of pieces thereof. It has been found that even after radiation with as much as 10.sup.11 rads or more the products made, especially if based on a fiberglass backing, often have tensile strengths in excess of 400 kg./sq. cm. Normally the present articles have tensile strengths over 15 kg./sq. cm., preferably over 100 kg./sq. cm. and more preferably over 350 kg./sq. cm. In fact, with phenol formaldehyde type polymers being employed, although the tensile strength of the product diminishes somewhat over lengthy periods of exposure to radiation, up to as much as 10.sup.11 rads, during initial exposure it may even increase slightly, apparently due to the effect of radiation in promoting even more complete cross-linking of the product, beyond the extent readily obtainable with the usual heat cures. Although the products of this invention are useful in various applications wherein it is desirable to absorb neutrons from nuclear materials, such as nuclear wastes and nuclear fuels, most preferably they are employed in storage racks for spent nuclear fuel. In any such application it is important that a continuous layer of B.sup.10 be present so that there is a statistical distribution of boron carbide particles and B.sup.10 atoms that is uniform and homogeneous so that neutrons emitted from stored nuclear material will pass near enough to B.sup.10 atoms so as to be "absorbed" by them. It is also important that the B.sup.10 concentration is capable of being accurately designed into the article and that such is producible commercially so that nuclear power installations may have racks for spent fuel positively protected against releases of neutrons to the environment. When the present neutron absorbers are utilized in a spent fuel storage rack for storage of fuel from either a BWR or PWR installation or when they are used in other nuclear shielding applications, single articles having a length from 100 to 2,000 times the thickness and a width from 50 to 500 times the thickness may be employed. For example, when the product is about 1 to 2 mm. thick the length may be about 50 to 200 cm., with the width being about 10 to 30 cm. and with preferred dimensions being about 80 to 100 cm. and 20 to 25 cm. The absorbers may be mounted singly in the storage rack enclosure, one at each wall thereof, as illustrated in FIG. 5, or a plurality of such articles may be utilized face to back or back to back to obtain the desired extent of neutron absorption. In both cases, it is within the invention to mount one or a plurality of such articles vertically atop other article(s) so as to obtain the desired height of protection. A preferred method of making the composite neutron absorbers of this invention comprises applying to a first side of a backing member a mixture of thermosettable normally liquid synthetic organic polymeric material and finely divided boron carbide particles mixed therewith, partially curing the thermosettable polymeric material of the mix so that it no longer runs (is solid), coating the other side of the backing member with a thermosettable, normally liquid synthetic organic polymeric material, which may or may not be pre-mixed with finely divided boron carbide particles, applying boron carbide particles of generally larger particle size than those applied to the first side to the polymeric material on said other side of the backing member, pressing the particles into the resin, partially curing the resin and finally curing the polymer to cross-linked permanently set or "stage C" form. Preferably, before beginning the process the backing member is filled with a normally liquid polymeric material, which is partially cured to solid form. Also, it is preferred that the coarser boron carbide particles be adhered to a mix of finer boron carbide particles and thermosettable polymer rather than to the polymer only. Additionally, at the end of the process it is desirable for the side of the product with the coarser boron carbide particles on it to be coated with a protective layer of thermosettable resin and for such layer and the other only partially cross-linked polymer(s) present to be completely or as nearly as feasible completely cross-linked together. For ease of handling and to prevent sticking of pressing means to the product, when being cured to flat or other desired shape, such external coating should first be partially cured so as to make a solid product. The initial sizing of both sides of the backing member is partially cured after an effective add-on of resin of about 20 to 150 g./m., which is usually about 0.1 to 0.5 times the weight of the backing member. The resin applied will normally be of a viscosity of about 200 to 1,000 centipoises, preferably 250 to 500 centipoises at room temperature and will be of a solids content between 50 or 60 and 90%. After curing, which will be at a temperature in the range of 95.degree. to 125.degree. C. and will take place over a period of 20 minutes to three hours, the coated backing member is then back filled with a mixture of phenolic resin and fine boron carbide particles well dispersed therein, as by mixing in a high shear mixer, such as a Cowles mixer, over a period of from about 10 minutes to one hour. The initial polymer coating may be made by dipping and passing through squeeze rolls and the back filling may be effected by means of knives, rollers, doctor blades, etc., using standard equipment employed in making similar coatings, such as in making coated abrasive products. Preferably the various operations are conducted continuously. The proportion of boron carbide particles and phenolic resin in the back fill is preferably about 50:50 but may vary from 25:75 to 75:25. In this operation it is desirable for the mix to have a viscosity at 32.degree. C. of 3,000 to 10,000 centipoises, preferably 6,000 to 8,000 centipoises and such viscosity may be adjusted by the addition of solvent, preferably water, with the amount of such addition usually being from 1/2 to 5% of the weight of the resin applied. After back filling, which deposits about 20 to 100% of the weight of the original backing member of boron carbide particles, together with approximately the same weight of polymer, a partial cure like that previously described for the fill coat is effected. The back fill strengthens the backing member and fills it to support the make coat to be applied next. Then, a make coat is applied, comprising about the same proportion of the resin and finely divided boron carbide particles (mixed the same way) and with the addition of enough water so that the resulting viscosity is about 700 to 2,000 centipoises, preferably 1,000 to 1,500 centipoises, at 32.degree. C. A sufficient quantity of the polymer-boron carbide particles mix is applied to the previously uncoated (with boron carbide) side of the backing member to result in about 25 to 125%, preferably 50 to 100% of boron carbide deposited thereon (on an original backing member weight basis). Such making coat, while it is still wet and uncured, has coarser boron carbide grains applied to it, as illustrated in FIG. 4, in an even distribution over the entire surface thereof to the extent that about 150% to 350%, on an original backing member weight basis, of coarser boron carbide grains is applied onto and is pressed into the resin. Uniform distribution is obtained because the polymer holds the particles where they fall into contact with it and they are applied evenly. The product resulting is then partially cured, preferably over a period of 1 to 5 hours at a temperature of about 95.degree. to 125.degree. C., more preferably over about two hours at a temperature of about 107.degree. C. Finally, a clear size coat of resin is applied to the product on the coarse boron carbide side to deposit about 25 to 75% by weight thereof, on an original backing member weight basis. Such material is again partially cured and/or dried to make it sufficiently hard so that it can be rolled and/or cut to desired lengths. Up to this time preferably the entire operation takes place utilizing a continuous web of backing member but this may be modified to employ pieces thereof at any desirable stage. However, normally after partial curing of the final size coating or overcoat the web is cut to desired lengths, if not previously cut, and pieces thereof are positioned one atop another between flat plates located every 3 to ten articles high. Such plates may be of aluminum or stainless steel, which may be multiply stacked with the articles to be cured, placed in an oven and cured sufficiently to finally and completely or nearly completely cross-link the resin(s). The temperature employed for such cure may be in the range of 95.degree. to 320.degree. C., preferably 95.degree. to 200.degree. C. and more preferably 95.degree. to 125.degree. C. The curing time may be from 2 to 50 hours, preferably from 20 to 40 hours, with longer curing times being employed for lower temperature cures. The cure effected will normally be to over 90% of complete cross-linking of the polymer, preferably over 95% thereof and more preferably 99 to 100% thereof, to the final C-stage. Although in the above description the resinous material employed is normally liquid at room temperature or under the conditions of application it is also within this invention to utilize a mixture of particulate resin and normally liquid resin, such as mixtures thereof described in the Owens patent application previously referred to and incorporated by reference. However, use of normally liquid resin is preferred. The following examples illustrate but do not limit the invention. Unless otherwise indicated, all parts are by weight and all temperatures are in .degree. C. in the examples, the rest of this specification and in the claims. EXAMPLE 1 A fiberglass cloth backing member of the type known as 8 harness satin having 57 threads in the warp and 54 in the fill and of a thickness of 0.23 mm. and weighing about 300 g./m., which has been heat cleaned to remove any sizing thereon, such as oils and starches and which has previously been treated by an aminosilane treatment to enhance adhesion of phenolic resin to fiberglass, is dipped into Ashland Chemical Company phenol formaldehyde resin identified as Arotap 358-W-70, the characteristics of which have been previously described in this specification, and the coated cloth is passed through squeeze rolls to remove any excess resin. The resin viscosity is suitable for dip application but if too high it may be lowered by use of solvent(s) and/or heat (but if heat is used the temperature-time combination will be insufficient to effect curing). The backing employed is one wherein the weave has a 7 by 1 interlacing, in which the filling threads float over 7 warp threads and under 1 warp thread. The resin is dried or partially cured onto the backing member cloth at a temperature of 107.degree. C. for about one hour. The weight of the cloth indicates a pickup of about 17% (on the original cloth weight) or resin. The dip coated cloth is then back filled on its weave side with a 50:50 mix of the normally liquid phenolic resin and boron carbide particles which pass through a No. 200 sieve and most of which fail to pass a No. 400 sieve. The mix, made by mixing for about 20 minutes in a Cowles or equivalent high energy mixer, is of 5,000 parts of the resin and 5,000 parts of the fine boron carbide particles, with 100 parts of water added to result in a product of a viscosity of about 7,000 centipoises at 32.degree. C. The back fill weight, as applied, is about 100% of that of the original cloth and when dried adds 45% (original cloth weight basis) of boron carbide. The back filled cloth is then partially cured, in the way described earlier for the initial resin application to the cloth. The back fill mix formula is then modified by the addition of resin to produce a 55:45 resin:boron carbide particles mix and a small amount of water is added so as to reduce the viscosity to 1,275 centipoises at 32.degree. C. This mix is then applied to the other side of the previously dipped and back filled backing member so that a total weight of 175% of such material (original cloth weight basis) is applied as a make, which gives an addition of 75% (same basis) of boron carbide particles. The make coat, while it is still wet, has gravity-fed onto it from a distributor hopper boron carbide particles of sizes in the No. 60 to No. 200 sieve range to the extent that such cover the wet resin and excess particles are atop the covering layer. The coarse boron carbide grain is applied evenly, rolled so that it penetrates the resin-finer particles layer and excess is removed by turning the cloth from horizontal to vertical and further positions and letting unadhered particles fall off. A total of 225% (same basis) of "coarse" boron carbide grain is applied in this manner. The product, now with a total of about 345% of boron carbide (same basis) thereon, is then dried and/or partially cured so that it can be handled, which takes about two hours at 107.degree. C. A final clear size coat of resin is then applied (about 50% on a wet basis and about 40-45% on a dry basis) to the "coarse" side and the coated product is then dried and/or partially cured to such a state that it can be rolled and cut into desired lengths. The loading of boron carbide at such stage is about 1.035 kg./sq. m. or about 0.1 g./sq. cm. This corresponds to about 0.014 g./sq. cm. of B.sup.10. The partially cured material is then cut into pieces approximately 25 cm. by 75 cm. (it is about 1 mm. thick) and the pieces are fully cured by drying under weight (flat aluminum plates plus other articles are used to hold the materials flat) in an oven over a period of 30 hours at a temperature of 107.degree. C. The articles made, when tested for radiation exposure properties, are found to average about 450 kg./sq. cm. in tensile strength after exposure to 10.sup.11 rads whereas initial tensile strength, without exposure to radiation, is about 700 kg./sq. cm. After exposure the products look normal and can be flexed 20.degree. without breaking and can be bent 110.degree. without coming apart. When installed in a storage rack for spent nuclear fuel, a part of which is of the design illustrated in FIG. 5, the present neutron absorbing articles will be effective neutron absorbers. In a similar manner, various other of previously described backing members and polymers may be used and different size boron carbide particles may be employed. Also, some of the steps described in this example may be omitted, (such as the filling, back filling and final sizing) as previously taught and the adhering resin for holding the coarse B.sub.4 C particles may be used without additional fine B.sub.4 C with it. The products resulting will be satisfactory neutron absorbers in applications like those described herein and in various other applications in which neutron absorption from nuclear fuels, etc., is desirable. EXAMPLE 2 A continuous web, 30.5 cm. wide and 4.5 m. long, made of Deering-Milliken 76 by 36 heat set polyester drill, with a weight of 21 g./m., which has been heat set to reduce elongation, and which has a tensile strength of 53.7 kg./cm. width in warp and about 1/3 of that in fill, is fill coated with Ashland Chemical Company Arotap-358-W-70 resin by dipping into the resin and the excess resin is removed by passing the cloth between pressure rollers. The resin is cured in the manner described in Example 1 and the add-on thereof is about 60 g./sq. m. Next, a cloth filling mix is made from a minus No. 230 sieve fraction of a boron carbide powder and resin, with the proportion of boron carbide powder being equal to that of the resin. The boron carbide employed is a 60 mesh and finer product of The Carborundum Company and the proportion of such material under 230 mesh is about 25%, with a proportion over 120 mesh being about 50%. The resin-boron carbide mix is made with 1/80th thereof of water being added to make a 7800 centipoise viscosity mix at 32.degree. C. This cloth filling mix is applied to the polyester drill with knife application at a speed of about 3 m./minute. The weight of the mix applied is about 400 g./sq. m. and there was only very slight penetration of the web by the mix. The filled polyester drill is dried at 66.degree. C. for 1/2 hour and is subsequently dried and partially cured for two hours at 93.degree. C., hanging open in a festoon rack. A make coating mix of 50 parts of the resin, 40 parts of the boron carbide particles (through 230 mesh) and 4 parts of water is made, having a viscosity of 850 centipoises at 32.degree. C. and is applied to the reverse side of the filled polyester drill at the rate of about 450 g./sq. m. The plus 120 mesh fraction of the boron carbide particles is then gravity coated onto the uncured make coating mix, using apparatus such as illustrated in FIG. 4 and the grains of boron carbide are pressed into the resin, etc. without the pressing roll contacting the resin. The excess resin is removed, as shown in FIG. 4, and the article is cured partially in the manner previously described. About 600 g./sq. cm. of boron carbide particles are thusly adhered to the cloth. After partial cure is effected the material is roll coated with straight resin on the coarse grain surface thereof, having a viscosity of 285 centipoises at 32.degree. C., with the wet coating applied being at the rate of about 190 g./sq. m. The same partial curing heating cycle is used as was previously described. The material is then removed from the festoon rack, cut to pieces about 89 cm. long (and 30.5 cm. wide) and these are finally cured to cross-linked resin state in flattened and weighed down form (using aluminum plates on stacks of the articles) over a period of 30 hours at a temperature of about 107.degree. C. The final sheets made have a thickness of about 1.3 mm. and contain about 0.125 g. B.sup.10 /sq. cm. When subjected to intense test radiation of 1.times.10.sup.11 rads of electron radiation over 25 hours the material remains in its original form and possesses sufficient tensile strength to make it useful as a neutron absorber in spent fuel rack applications. However, it is much stronger in tension prior to radiation testing. Thus, initial tensile strengths may be in excess of 5,000 kg./sq. cm. but even after radiation the strength, although diminished, will be in excess of 15 or 20 kg./sq. cm. Instead of using the polyester drill mentioned in this example other cloths of other materials previously described in this specification may be substituted, as may be other resins and boron carbide particle fractions. Also, mixtures of each of such components may be employed. The products resulting will be useful neutron absorbers. The various advantages of the present invention have already been described but one additional advantage, which may be self-evident from the foregoing description, should be mentioned. By the present method of application of the coarser boron carbide particles to the backing member greater concentrations of boron carbide particles can be obtained in the article because there is no need to blend the adhering particles into the resin, which might make a mix of excessive viscosity. Also, a lesser quantity of resin may be employed. The invention has been described with respect to examples and various illustrations thereof but is not to be limited to these because it will be evident that one of skill in the art, with the present disclosure before him, will be able to utilize equivalents and substitutes for parts of the invention without departing from it. |
summary | ||
abstract | A charged particle beam system for performing precession diffraction includes a lens 11 for focusing a beam 5 in an object plane 9, and an objective lens 13 having a diffraction plane 27. A doublet 53 of lenses 35, 63 images the diffraction plane 27 into an intermediate diffraction plane 69 where a multipole 55 is located. A doublet 57 of lenses 65, 93 images the intermediate diffraction plane 69 into an intermediate diffraction plane 71 where a multipole 59 is located. A first deflection system 15 upstream of the object plane 9 can tilt to change an angle of incidence of the beam on the object plane. A second deflection system 37 between lenses 35 and 63 tilts the beam such that the change of the angle of incidence of the charged particle beam on the object plane is compensated. |
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abstract | A method of preparing magnetite particles may include providing a first solution of substantially ferrous sulphate. The first solution may be converted by replacing sulphate ions with chloride ions to produce a second solution of substantially ferrous chloride. The second solution may be oxidized to produce a third solution of substantially iron oxide. A system for purifying a solution of substantially iron oxide may include a solution reservoir, at least one membrane unit, and at least one pump for circulating the solution between the solution reservoir and the membrane unit. The solution may be delivered from the solution reservoir to an inlet of the membrane unit, and/or the solution may be returned from an outlet of the membrane unit to the solution reservoir. |
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abstract | To prevent reflective optical elements (2) for EUV lithography from becoming electrically charged as they are irradiated with EUV radiation (4), an optical system for EUV lithography is proposed, having a reflective optical element (2), including a substrate (21) with a highly reflective coating (22) emitting secondary electrons when irradiated with EUV radiation (4), and a source (3) of electrically charged particles, which is arranged in such a manner that electrically charged particles are applied to the reflective optical element (2), wherein the source (3) for the charge carrier compensation is exclusively a flood gun applying electrons to the reflective optical element (2). |
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claims | 1. An electron beam apparatus, comprising: a vacuum chamber; a large-area cathode disposed in the vacuum chamber; a first power supply connected to the cathode, wherein the first power supply is configured to apply a negative voltage to the cathode sufficient to cause the cathode to emit electrons toward a substrate disposed in the vacuum chamber; an aluminum anode positioned between the large-area cathode and the substrate, the anode being positioned on an upper surface of an electrically isolated shelf that projects inwardly from an interior portion of the vacuum chamber; and a second power supply connected to the anode, wherein the second power supply is configured to apply a voltage to the anode that is positive relative to the voltage applied to the cathode. 2. The apparatus of claim 1 , wherein the interior portion of the vacuum chamber is one of bead blasted, roughened, anodized or darkened. claim 1 3. The apparatus of claim 1 , wherein the interior portion of the vacuum chamber has an absorptivity of greater than about 0.5. claim 1 4. The apparatus of claim 1 , wherein the first power supply is configured to apply a voltage ranging from about xe2x88x921000 volts to about xe2x88x9230,000 volts. claim 1 5. The apparatus of claim 1 , wherein the second power supply is to apply a voltage ranging from about 0 volts to about xe2x88x92250 volts. claim 1 6. The apparatus of claim 1 , wherein the large-area cathode emits the electrons when the large-area cathode is struck with positive ions. claim 1 7. The apparatus of claim 1 , wherein the negative voltage applied to the large-area cathode is configured to attract positive ions to the large-area cathode; and wherein the electrons are emitted in response to the positive ions striking the large-area cathode. claim 1 8. The apparatus of claim 1 , wherein an interior portion of the vacuum chamber has an absorptivity of greater than about 0.5; and wherein the anode is freely positioned on the shelf. claim 1 9. The apparatus of claim 1 , wherein the shelf for laying the anode defines a space around a perimeter of the anode; and wherein an interior portion of the vacuum chamber is one of bead blasted, roughened, anodized or darkened. claim 1 10. The apparatus of claim 1 , wherein the anode defines a plurality of holes disposed therethrough; and wherein an interior portion of the vacuum chamber is one of bead blasted, roughened, anodized or darkened. claim 1 11. The apparatus of claim 1 , wherein the anode is placed on the shelf that defines a space around a perimeter of the anode and above the anode to allow the anode to expand and contract without bowing in response to varying temperatures during operation of the electron beam apparatus; and wherein an interior portion of the vacuum chamber is one of bead blasted, roughened, anodized or darkened. claim 1 12. The apparatus of claim 11 , wherein the interior portion of the vacuum chamber has an absorptivity of greater than about 0.5. claim 11 13. The apparatus of claim 1 , wherein the anode defines a plurality of holes disposed therethrough. claim 1 14. The apparatus of claim 13 , wherein the plurality of holes have a diameter that gradually decreases from a center of the anode to an edge of the anode. claim 13 15. The apparatus of claim 13 , wherein the plurality of holes have a diameter that gradually increases from a center of the anode to an edge of the anode. claim 13 16. The apparatus of claim 1 , wherein the anode and shelf are configured to allow both vertical and horizontal expansion of the anode, while maintaining a substantially planar upper surface of the anode, under varying thermal conditions. claim 1 17. The apparatus of claim 16 , wherein the shelf defines a space around a perimeter of the anode. claim 16 18. The apparatus of claim 16 , wherein at least one of the vacuum chamber, the large-area cathode or the shelf is made from aluminum. claim 16 19. The apparatus of claim 16 , wherein the shelf defines a space above the anode. claim 16 20. The apparatus of claim 19 , wherein the shelf further defines a space around a perimeter of the anode. claim 19 21. The apparatus of claim 20 , wherein each space allows the anode to expand and contract without bowing in response to varying temperatures during operation of the electron beam apparatus. claim 20 22. An electron beam apparatus, comprising: a vacuum chamber, wherein an interior portion of the vacuum chamber is one of bead blasted, roughened, anodized or darkened; a large-area cathode disposed in the vacuum chamber; a first power supply connected to the cathode, wherein the first power supply is configured to apply a negative voltage to the cathode sufficient to cause the cathode to emit electrons toward a substrate disposed in the vacuum chamber; an anode freely positioned between the large-area cathode and the substrate on an inwardly projecting shelf; and a second power supply connected to the anode, wherein the second power supply is configured to apply a voltage to the anode that is positive relative to the voltage applied to the cathode. 23. The apparatus of claim 22 , wherein an interior portion of the vacuum chamber has an absorptivity of greater than about 0.5. claim 22 24. The apparatus of claim 22 , wherein the first power supply is configured to apply a voltage ranging from about xe2x88x921000 volts to about xe2x88x9230,000 volts. claim 22 25. The apparatus of claim 22 , wherein the second power supply is configured to apply a voltage ranging from about 0 volts to about xe2x88x92250 volts. claim 22 26. The apparatus of claim 22 , wherein the anode defines a plurality of holes disposed therethrough. claim 22 27. The apparatus of claim 26 , wherein the plurality of holes has a diameter that gradually decreases from a center of the anode to an edge of the anode. claim 26 28. The apparatus of claim 26 , wherein the plurality of holes has a diameter that gradually increases from a center of the anode to an edge of the anode. claim 26 29. The apparatus of claim 22 , wherein the shelf is electrically isolated from the anode and the vacuum chamber. claim 22 30. The apparatus of claim 29 , wherein the shelf defines a space around a perimeter of the anode. claim 29 31. The apparatus of claim 29 , wherein at least one of the vacuum chamber, the large-area cathode or the shelf is made from aluminum. claim 29 32. The apparatus of claim 29 , wherein the shelf defines a space above the anode. claim 29 33. The apparatus of claim 32 , wherein the shelf further defines a space around a perimeter of the anode. claim 32 34. The apparatus of claim 33 , wherein each space allows the anode to expand and contract without bowing in response to varying temperatures during operation of the electron beam apparatus. claim 33 35. An electron beam apparatus, comprising: a vacuum chamber; a large-area cathode disposed in the vacuum chamber; a first power supply connected to the cathode, wherein the first power supply is configured to apply a negative voltage to the cathode sufficient to cause the cathode to emit electrons toward a substrate disposed in the vacuum chamber; an anode placed between the large-area cathode and the substrate; an electrically isolated shelf disposed in the vacuum chamber, wherein the shelf defines a surface on which the anode is placed is inwardly projecting and; and a second power supply connected to the anode, wherein the second power supply is configured to apply a voltage to the anode that is positive relative to the voltage applied to the cathode. 36. The apparatus of claim 35 , wherein the shelf defines a space around a perimeter of the anode. claim 35 37. The apparatus of claim 35 , wherein at least one of the vacuum chamber, the large-area cathode or the shelf is made from aluminum. claim 35 38. The apparatus of claim 35 , wherein an interior portion of the vacuum chamber is one of bead blasted, roughened, anodized or darkened. claim 35 39. The apparatus of claim 35 , wherein an interior portion of the vacuum chamber has an absorptivity of greater than about 0.5. claim 35 40. The apparatus of claim 35 , wherein the first power supply is configured to apply a voltage ranging from about xe2x88x921000 volts to about xe2x88x9230,000 volts. claim 35 41. The apparatus of claim 35 , wherein the second power supply is configured to apply a voltage ranging from about 0 volts to about xe2x88x92250 volts. claim 35 42. The apparatus of claim 35 , wherein the anode defines a plurality of holes disposed therethrough. claim 35 43. The apparatus of claim 42 , wherein the plurality of holes has a diameter that gradually decreases from a center of the anode to an edge of the anode. claim 42 44. The apparatus of claim 42 , wherein the plurality of holes has a diameter that gradually increases from a center of the anode to an edge of the anode. claim 42 45. The apparatus of claim 35 , wherein the shelf defines a space above the anode. claim 35 46. The apparatus of claim 45 , wherein the shelf further defines a space around a perimeter of the anode. claim 45 47. The apparatus of claim 46 , wherein each space allows the anode to expand and contract in response to varying temperatures during operation of the electron beam apparatus. claim 46 |
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047284862 | description | DETAILED DESCRIPTION The improved pressure control system of the present invention provides for quick replacement of a water seal for the power operated relief valves and safety valves of a pressurizer to protect the valve seats and prolong the life of the same. In FIG. 1, there is schematically illustrated an improved pressure control system for a pressurized water nuclear reactor which incorporates the loop seal water charging system of the present invention. The pressure control system 1, contains a pressurizer 3, normally formed as a vertical, cylindrical vessel, composed of carbon steel with austenitic stainless steel cladding on all surfaces exposed to primary reactor coolant. Electrical heaters 5 are provided in the bottom portion of the pressurizer 3 and spray nozzles 7 are provided in the upper portion thereof. The pressurizer is designed to accommodate positive and negative surges caused by load transients on the system. A surge line 9, attached to the bottom of the pressurizer 3, connects the pressurizer with the hot leg of a reactor coolant loop. During an insurge, the spray nozzles 7, which are fed from the cold leg of the reactor coolant loop through line or sprayer conduit 11, containing a regulating valve means 13, spray water into the upper portion of the pressurizer 3 to condense steam in the pressurizer 3 to prevent the pressure in the pressurizer from reaching the setpoint of power operated relief valves 15 in lines 17, which are normally fed from an off take line 18 connected to the pressurizer 3. During an outsurge, flashing of water to steam and generation of steam by actuation of heaters 5 keep the pressure above the low pressure reactor trip setpoint. The pressurizer 3 is also provided with safety relief valves 19, normally three such valves, as illustrated. The safety relief valves 19, in lines 21, are spring loaded and self-activated with back pressure compensation. Loop seals 23 are provided adjacently upstream in lines 17 and 21 of each of the power operated relief valves 15 and safety valves 19 for the protection of the valve seats of each of the valves. The loop seals 23 are in the form of a U-bend in the line below the valves, wherein condensed water accumulates as a loss of heat to the ambient occurs. This accumulated water prevents leakage of hydrogen or steam through the valve seat, and serves to keep the valve cool and protect the valve seat from wear. The power operated relief valves 15 and safety valves 19 discharge into a common line 25 which leads to a pressurizer relief tank 27. A conduit 29 is provided which communicates with each of the loop seals 23 and to a drain conduit 31 containing a valve 33 for draining the accumulated water from the loop seals, to common line 25, during maintenance or repair of the valves. The system as aforedescribed, is conventional, with the provision of loop seals to protect the power operated relief valves and safety valves. Once the accumulated water has been discharged from the loop seals by steam released by the pressurizer, however, closure of the valves completely is delayed so long as steam continues to pass over the valve seat and until further condensed steam has been accumulated to once again form the water seal. According to the present invention, means are provided to more quickly form the water seal in the loop seal of the valves to improve response time, and enhance valve life and reliability by reducing degradation of the valve seat. Means are provided for charging water to each of the loop seals, with means responsive to a rise of temperature therein, and with activation of the feeding of water being responsive to such rise in temperature. As illustrated, a common water supply comprises a conduit 35 communicating with the line 11, which feeds water to the sprayers 7 of the pressurizer 3. The conduit 35 has a flow restriction orifice 37 therein to control the rate of flow of water therethrough. The common water supply conduit 35 supplies water to branch conduits or fill lines 39, one of such branch conduits 39 communicating with each of the conduits 29, and adapted to supply water to each of the loop seals 23 through conduits 29. A flow restriction orifice 41 is provided in each of the conduits 29 to control the rate of flow of water therethrough. A valve 43 is provided in the common water supply conduit 35 to control the passage of water therethrough and to the branch conduits 39. A temperature detecting device 45, such as a non-invasive strap-on type of temperature detector is provided on each of the loop seals 23. The temperature detecting device 45 has a lead 47 which is operatively connected to the valve 43, preferably a solenoid valve, and is effective to open or close the valve 43 in response to a rise or drop in temperature detected in a loop seal 23. The operation of the present pressure control system, showing one of the power operated relief valves and flow of water to replenish the water seal in an associated loop seal is illustrated in FIGS. 2 through 4. In normal operation, (FIG. 2) with the pressurizer under the predetermined pressure which would actuate the power operated relief valve 15, the loop seal 23 is filled with water such that the valve seat of the power operated relief valve is water covered and protected from steam in line 17. In this condition, the temperature detector 45 senses the temperature of the water w, a relatively low temperature in comparison with the steam temperature, in the loop seal and through lead 47 maintains the valve 43 in common water supply line 35 in closed position. When pressure rises in the pressurizer, the relief valve opens and the initial water seal w is blown from the loop seal through line 25 to the pressurizer relief tank 27, and steam from line 17 will also pass through the loop seal 23, power operated relief valve 15, and line 25 to the pressurizer relief tank 27. With passage of steam through the loop seal 23, the loop seal area temperature rises with the invasion of the high temperature steam. The temperature increase is sensed by the temperature detector 45, which, through lead 47 actuates the solenoid valve 43 on the common water supply line 35 which charges water to fill line 39, and through flow control orifice 41 in line 29 to the loop seal 23 (FIG. 3). As the pressure in the pressurizer 3 returns to below the predetermined pressure for actuating the power operated relief valve 15, the valve 15 will close. As the power operated relief valve 15 closes, water injected through the orifice is available to quickly form a supply of water in the loop seal 23 (FIG. 4). Condensation of steam in the loop seal 23 and injection of water into the loop seal 23 through the orifice 41 will continue until the temperature detector 45 senses a drop in temperature in the area of the loop seal due to the presence of water, and with the drop in temperature, the temperature detector 45, through lead 47, will close the valve 43 in the water supply line 35, resulting in a quickly formed water seal, without the normal delay that results in formation of such a water seal solely through condensation of steam in the loop seal 23. At this stage, the loop seal is again under the normal condition illustrated in FIG. 2. It is estimated that using the present invention, complete valve closure through formation of the water seal w in the loop seal 23 can be effected at a rate of least four to five times faster than conventional condensation formation of the water seal. While the temperature detector 45 is illustrated as a strap-on non-invading type and on the upstream side of the loop seal, other types of temperature detectors could be used, and placement of the detectors at other locations could be made, provided that the same is effective to actuate the valve in the water supply line at the desired times. Since conventional pressurizer water reactor nuclear plants operate normally at about 2235 to 2285 psig (pounds per square inch gauge), with a water temperature of about 266.degree.-635.degree. F. (328.degree.-335.degree. C.), and are adapted to withstand a pressure of about 2485 psig and water temperature of about 685.degree. F. (363.degree. C.), the pressure operated relief valves on the pressurizer are normally set to open at about a pressure of 2375-2385 psig, while the safety relief valves on the pressurizer are normally set to open at a pressure of about 2435 psig. Upon such opening, the steam passing through the valves will be at or below about 680.degree. F. (360.degree. C.). The water in the loop seal, due to cooling to the ambient is normally at a temperature of about 100.degree.-150.degree. F. (38.degree.-65.degree. C.), under normal operating conditions. According to the present invention, the temperature detector on the loop seal would be set to open the water supply valve to the loop seal at a temperature of about 275.degree.-450.degree. F. (135.degree.-232.degree. C.). Thus, upon discharge of the water from the loop seal, the temperature would rise above the preset temperature of the detector and initiate injection of water thereto. Although the water fed from the line to the pressurizer sprayers may be normally at a temperature of 520.degree.-580.degree. F. (271.degree.-305.degree. C.), upon passage through the water supply line and upon containment within the loop seal, the temperature of the water will drop rapidly due to loss of heat to ambient, and below the setpoint for the temperature detector from the valve to the supply line, and when the water seal is replenished, the temperature detector will close that valve. In conventional systems, it can take a time period of about two hours to fill the loop seal with water through condensation of steam therein. Using the system of the present invention, it is believed that the time period can be shortened by a factor of at least four or five times, and the time period could be shortened to as low as five to fifteen minutes. |
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047864630 | description | DESCRIPTION OF PREFERRED EMBODIMENT FIG. 1 shows the heat exchanger, referred to as a whole by reference 1, in position inside the vessel of the fast-neutron nuclear reactor filled with liquid sodium up to level 2. The heat exchanger 1 crosses the slab 3 via a passage 4 and rests through the intermediary of a flange 5 on a support flange 6 carried by the shell of the passage 4 through the slab 3. To the upper part 1a of exchanger 1 are fixed insulated lines 7 and 8 ensuring, respectively, the return of the secondary sodium cooled in the heat exchanger and the withdrawal of the heated secondary sodium which is sent, in order to be cooled, to a sodium-air heat exchanger (not shown) arranged outside the vessel and situated in the secondary sodium circuit. The lower part 1b of the exchanger consists of a shell with a vertical axis incorporating perforations and surrounding the exchange bundle. The structure of the heat exchanger 1 will now be described in greater detail with reference to FIGS. 2a and 2b. It can be seen that the upper part of the heat exchanger incorporates an outer enclosure to which are fixed sodium lines 7 and 8 communicating inside the heat exchanger enclosure with, respectively, a chamber 10 for arrival of the secondary liquid sodium and a chamber 11 for return of the heated secondary sodium. The arrival and return chambers 10 and 11 for secondary liquid sodium are coaxial and have the vertical axis ZZ' of the heat exchanger as their common axis. The secondary sodium arrival chamber 10 is arranged in the central part and incorporates a double wall. The return chamber 11 for the heated secondary sodium, annular in shape, is arranged at the periphery of chamber 10. Chambers 10 and 11 consist of cylindrical shells and frusto-conical shells welded end to end. The space included between the two walls of chamber 10 is filled with an inert gas. The space included between the outer wall of the cylindrical part of chamber 11 and the outer enclosure of the heat exchanger is filled with lagging blocks 12. Lagging is also arranged in the extension of these blocks 12 around lines 7 and 8. A metal block 13, arranged around the frusto-conical part of chambers 10 and 11, makes it possible to implement biological protection of the passage 4. Under flange 5 are fixed two coaxial shells 14 between which is left a very narrow space sufficient in height to surround the heat exchanger enclosure 1 over the entire height of the passage 4. These shells 14 form a conventional thermal protection of the passage. Also fixed under flange 5 is a thicker shell 15 forming the outer wall of the heat exchanger joining the flange 5 to the lower part 1b of the exchanger. In this part 1b of the exchanger is the bundle 17 formed by a set of hairpin-bend tubes, each of which comprises an end connected to an outer tube plate 18 of annular shape and an end connected to a central tube plate 19 of circular shape. The tube plates 18 and 19 are both coaxial with the axis ZZ' of the heat exchanger face each other at the same elevation in this heat exchanger, the annular plate 18 surrounding the circular plate 19. The tube plate 18 is connected over its periphery to the heat exchanger shell 15, which thus ensures the connection between the tube plate 18 and the flange 5. On its inner edge, the annular plate 18 is connected to one of the walls of the secondary sodium arrival chamber 10. Lastly, over its periphery and in its upper part, the central plate 19 is connected to the second enclosure of chamber 10. The enclosure of chamber 11 is connected to the shell 15 in its lower part through the intermediary of a Y-shaped component 21. The shell 15 is extended below the tube plates 18 and 19 by the shell 1b surrounding the heat exchanger tube bundle. This shell 1b is fixed by welding along the outer edge of the annular plate 18, below this plate. Along the inner edge of the plate 18, on its lower face, is fixed a short shell 20. The lower part of this shell 20 is connected to an annular connecting piece 22 with a Y-shaped cross-section, which makes it possible to connect the shell 20 to a shell 23, substantially identical in length, coaxial with shell 20, and fixed along the edge of the central plate 19 on its lower face. Tie rods 25, whose circumferential distribution can be seen in FIGS. 3a and 3b, are fixed to the lower part of the annular piece 22 with a Y-shaped cross-section. These tie rods 25 hold, through the intermediary of short sleeves 26, a set of spacer grids 27 ensuring the transverse retention of the tubes 28 of the bundle 17. Each of the bundle tubes 28 incorporates a descending straight part 28a fixed at its top end in the tube plate 19, a bent part for returning the tube 28b, a straight return part 28c, a horizontal circular portion 28e which can be seen in FIG. 3a and, finally, a straight end part 28f fixed inside the tube plate 18. In this manner, for each of the tubes 28, the inlet end communicates with the sodium arrival chamber 10 and the outlet end with the liquid sodium return chamber 11. Since the lower part of the heat exchanger up to the liquid sodium level 2 is immersed in the primary sodium to be cooled, the secondary sodium circulating in the tubes 28 heats up before emerging into the chamber 11. The various parts of the tubes and of the heat exchanger are thus at different temperatures. The primary sodium is in contact with the bundle over its entire immersed length and perforations 30 are provided for the passage of the primary sodium into the enclosure 1b. The upper part of the tube portions 28a, the circular portions 28e as a whole and the portions 28f are arranged above the primary liquid sodium level 2. The differential expansion of the tube portions subjected to fluids at different temperatures is largely compensated by the circular portion 28e of the tube, which is arranged above the liquid sodium level. These portions are thus subjected to flexions which they are able, however, to absorb without undue difficulties, given their length corresponding to an arc of circumference supporting a center angle of the order of 140.degree. and in any case greater than 120.degree., i.e., to one-third of the circumference. Furthermore, these circular portions 28e are not subjected to excessively favourable use conditions, being situated above the primary liquid sodium level. The two tube plates 18 and 19 incorporate means of connection both to each other and to the exchanger support flange 5, which make it possible to absorb any distortion of the bundle and of the exchanger shells. At the same time, these connecting means permit an efficient retention of the tube plates and of the outer shell 1b of the bundle. In addition, the transverse retention of the bundle against vibrations is ensured by the spacers 27 fixed to the lower part of the annular connecting piece 22. The bundle base, consisting of the bent portions 28b which can be seen in FIGS. 2b and 3c, consists of a mere placing side by side of hairpin tubes having good distortion resistance in transverse directions. FIG. 4 shows an embodiment of a spacer grid 27 for fixing the tubes 28. This spacer grid 27 consists of a set of circular and concentric hoops 34, all coaxial with the heat exchanger axis ZZ', and between which there are arranged metal strips 32 with sinusoidal folds, fixed on each side to the corresponding hoops. The hoops 34 consist of successive portions connected by welded connecting pieces 35. The sinusoidally folded strips 32 ensure the connection between the various hoops and form therewith three outer retaining rings 36a, 36b and 36c and six inner rings 37. Between the set of inner rings 37 and the outer rings 36 a space is provided in which the sleeves 26 for retaining the tie rods 25 are fixed by virtue of pieces which also permit the connection between the inner part of the spacer grid and the outer part. The tie rods 25 ensure the suspension of the spacer grid 27 under the tube plates. The process for assembling the tubes 28 in the spacer grids 27 will be described hereinbelow. FIGS. 5, 6 and 7 show a second embodiment of a spacer grid, in this case incorporating a set of concentric hoops 40, all coaxial with the heat exchanger axis ZZ'. These hoops 40 incorporate rectangular cutouts 41 such as can be seen in FIG. 6, and the skeleton of the grid consists, in addition to the hoops 40, of radial members 42 and a metal strip 43 folded so as to provide a housing for the tubes 28 between the metal strip 43 and the corresponding hoop 40. Between two portions which are folded cylindrically to come into contact with the tubes 28, the metal strip 43 is folded at right angles to form a part corresponding in size to the cutouts 41 in the hoop 40. These rectangular portions 44 folded at right angles are introduced into the cutouts 41 in the hoop 40 and held in place by the components 45 acting as a stirrup. These components 45 have the shape of ring portions cut out slot-wise, as can be seen in FIG. 7, or of combs. The concentric hoops 40, the radial components 42 and the metal strip 43, forming the skeleton of the grid 27, are connected together to ensure the cohesion of the structure. The radial components 42 also carry the sleeves 26 for fixing the tie rods 25 by which the grid 27 is suspended. Both in the case of the grid shown in FIG. 4 and in the case of the grid shown in FIGS. 5, 6 and 7, the assembly and the fixing of the various components of which they consist are carried out for the set of the six inner rings, before the assembly of the bundle. For assembling the bundle, the lower parts of the spacer grids suspended by the tie rods 25 are installed under the tube plates 18 and 19 and then the branches 28a of the tubes 28 are introduced into the spacer grids one by one so as to form a complete first inner layer. The ends of the tubes 28 are then connected to the tube plates 18 and 19, respectively and the outer hoops are installed so as to form a first outer ring for fixing the tubes 28. The fixing components 32 (FIG. 4) or such as 43 and 45 (FIG. 5) are connected to the hoop(s) installed in the outer part of the grid. The two succeeding layers are built up in succession in the same manner. When the whole of the bundle and the spacer grids. have been assembled in this way, the outer shell 1b surrounding the bundle is installed, and then this shell 1b is fixed by welding on the tube plate 18. In the case of the grid shown in FIGS. 5, 6 and 7, the tubes 28 are first installed against the hoops 40, then the fixing components 43 are introduced into the cutouts 41 in the hoops 40. Finally, the whole is immobilized by the comb-shaped components 45. For assembling the preassembled inner parts of the spacer grids and for assembling the tubes in these preassembled parts, use is made of the means shown in FIG. 8, which shows the end 28a of the tube 28 during assembly in a grid 27. An ogive-shaped tip 50 is fitted to the end of the tube 28a to be introduced into the grid 27 which incorporates sleeves 51 having the same inner and outer diameters as the tubes 28 which have been installed at the time of the assembly of the grid components in the location to be occupied by the tubes, to maintain a separation of these components which corresponds exactly to the dimension of the tubes 28. The sleeves 51 are retained by the radial forces exerted by the resilient components forming the grid 27. When the end of the tube 28 incorporating the ogive-shaped tip 50 is introduced into the sleeve 51, the latter is driven out by pushing, while the tube 28 takes up its place in the spacer grid 27. The tube 28a is thus held perfectly in the spacer grid. The principal advantages of the heat exchanger according to the invention are to permit expansions of the various parts of this exchanger during its operation and, in particular, of the tubes of the bundle, without producing excessive stresses in these components. The whole assembly of the exchanger components is also perfectly held against vibrations, in particular in the transverse direction. The fitting of the tube plates at the same height in the exchanger makes it possible to optimize the structure of the heat exchanger while allowing them relative movements under the effective of expansions. Finally, the heat exchanger according to the invention may be produced by simple and perfectly defined assembly operations. The invention is not restricted to the embodiment which has just been described; on the contrary, it incorporates all the alternative forms. Thus, the length of the shells 20 and 23 for connecting the tube plates and for suspending the spacer grids can vary within certain limits. In practice, this length L of the shells 20 and 23, in the case of a heat exchanger such as is employed in a fast-neutron nuclear reactor, may be such that it obeys the following inequalities: EQU 3.sqroot.Rt<L<5.sqroot.Rt where R is the radius of the outer shell 1b of the heat exchanger and t the thickness of the connection shells. In the case of the heat exchangers in fast-neutron nuclear reactors, this thickness is generally between 6 and 10 mm. In such heat exchangers the difference in temperature T between the hottest and the coldest parts is generally in the region of 200.degree. C. It is also possible to produce spacer grids in a manner different from those which have been described. Finally, the folding of the bundle tubes can be slightly different from that which has been described and shown. The invention applies in all the cases where an emergency exchanger is used for cooling the primary fluid of a nuclear reactor, this heat exchanger being immersed in a vessel containing the primary fluid. |
claims | 1. An ion beam irradiating apparatus which irradiates a target with an ion beam extracted from an ion source, said apparatus comprising:a field emission electron source, which is disposed in a vicinity of a path of the ion beam and which emits electrons to neutralize space charge of the ion beam, said field emission electron source having a conductive cathode substrate, a plurality of minute emitters, which are formed on the conductive cathode substrate and each of which has a pointed shape, and an extraction electrode which surrounds respectively vicinities of tip ends of said emitters with forming a minute gap,wherein said field emission electron source is placed in a direction along which an incident angle formed by electrons emitted from said field emission electron source and a direction parallel to a traveling direction of the ion beam is in a range from −15 deg. to +45 deg., where an inward direction of the ion beam is +, and an outward direction is −, andwherein said electrons emitted from said field emission electron source directly travel into said path of the ion beam without any deflection members guiding said electrons between said electron source and said path of the ion beam. 2. The ion beam irradiating apparatus according to claim 1, wherein said field emission electron source is placed in a direction along which the incident angle is in a range from −15 deg. to +30 deg. 3. The ion beam irradiating apparatus according to claim 1, wherein said field emission electron source is placed in a direction along which the incident angle is in a range from substantially 0 deg. to +15 deg. 4. The ion beam irradiating apparatus according to claim 1, wherein said field emission electron source is placed in a direction along which the incident angle is substantially 0 deg. 5. The ion beam irradiating apparatus according to claim 1, wherein said field emission electron source is placed in a direction along which electrons are emitted toward a downstream side of the traveling direction of the ion beam. 6. The ion beam irradiating apparatus according to claim 1, wherein said field emission electron source is placed in a direction along which electrons are emitted toward an upstream side of the traveling direction of the ion beam. 7. The ion beam irradiating apparatus according to claim 1, wherein said field emission electron source is placed on both sides of the path of the ion beam. 8. The ion beam irradiating apparatus according to claim 1, wherein, at a position of said field emission electron source, the ion beam has a shape in which a dimension of a Y direction in a plane intersecting with the traveling direction X is larger than a dimension of a Z direction perpendicular to the Y direction, and said field emission electron source has a shape which extends in the Y direction. 9. A method of producing a semiconductor device wherein a semiconductor substrate as a target is irradiated with the ion beam by using an ion beam irradiating apparatus according to claim 1 to perform ion implantation, thereby producing plural semiconductor devices on said semiconductor substrate. |
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claims | 1. A computer implemented method for analyzing transitions in processor states, the computer implemented method comprising:collecting idle counts occurring during execution of code to form collected idle counts; andproviding the idle counts to an application for analyzing why a processor becomes idle, wherein collecting idle counts comprises:collecting information for a system having a transition between an idle state and a non-idle state to form collected system information; andproviding the collected system information for analysis by an application; and wherein collecting information comprises:generating trace records in response to events in which the processor transitions to the idle state and from the idle state; andstoring counts of times a processor associated with a thread has been in an idle state in nodes in a tree of entries into and exits out of routines. 2. The computer implemented method of claim 1, wherein the storing step comprises:storing a first count of a number of times a processor has been idle in a current node in response to an entry into a second routine from a first routine; andstoring a second count of the number of times the processor has been idle in the current node in response to an exit from the first routine. 3. The computer implemented method of claim 2, wherein the first count is a difference between a base count of the number of times the processor has been idle when the first routine was entered and a current count of the number of times the processor has been idle when the entry into the second routine from the first routine occurs. 4. The computer implemented method of claim 2, wherein the second count is a difference between a base count of the number of times the processor has been idle when the first routine was entered and a current count of the number of times the processor has been idle when the exit from the first routine occurs. 5. The computer implemented method of claim 4 further comprising:combining the trace records with the nodes in the tree using node identifiers. 6. The computer implemented method of claim 2, wherein the second count is a difference between a base count of the number of times the system has been idle when the first routine was entered and a current count of the number of times the system has been idle when the exit from the first routine occurs. 7. The computer implemented method of claim 1, wherein each trace record in the trace records includes a node identifier of a current node present when each trace record was generated. |
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summary | ||
039390381 | abstract | A nuclear reactor includes a pressure vessel having a bottom wall above which a core vessel is suspended with its lower end spaced above this bottom wall. In case the core vessel accidentally falls, it is intercepted by a construction transmitting the force of the falling core vessel to the pressure vessel's bottom wall throughout a plurality of widely interspaced positions so that the bottom wall does not have to withstand the force in a localized concentrated manner. Preferably these positions are adjacent to the pressure vessel's side wall, and the intercept construction is made of ductile metal having upper portions reduced in cross-sectional area so that these upper portions are stressed beyond their elastic limit and deform in a ductile shock-absorbing manner if required to intercept the falling core vessel. Various other features of construction are included. |
039502201 | abstract | The pressure vessel of a boiling water reactor has several openings, one for each of a set of internal primary recirculating pumps. The body of each pump extends into the respective opening and is provided with a ring-shaped chamber which receives feed water and surrounds the pump shaft which is driven by a normal, wet or canned electric motor. The shaft carries a single-stage or multi-stage turbine which is located upstream of the pump rotor and serves to prolong the deceleration of the pump rotor to zero speed in the event of unintentional motor stoppage due to current failure. The pressure chambers of the turbine and pump rotor communicate with each other by way of an annular flow restricting bypass. |
abstract | A pressurized water reactor (PWR) includes a pressure vessel and a nuclear reactor core disposed in the pressure vessel. A baffle plate is disposed in the pressure vessel and separates the pressure vessel into an internal pressurizer volume disposed above the baffle plate and an operational PWR volume disposed below the baffle plate. The baffle plate comprises first and second spaced apart plates and includes a pressure transfer passage having a lower end in fluid communication with the operational PWR volume and an upper end in fluid communication with the internal pressurizer volume at a level below an operational pressurizer liquid level range. A vent pipe has a lower end in fluid communication with the operational PWR volume and an upper end in fluid communication with the internal pressurizer volume at a level above the operational pressurizer liquid level range. |
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abstract | An integrated storage, transportation and disposal system for used fuel assemblies is provided. The system includes a plurality of sealed canisters and a cask sized to receive the sealed canisters in side by side relationship. The plurality of sealed canisters include an internal basket structure to receive a plurality of used fuel assemblies. The internal basket structure includes a plurality of radiation-absorbing panels and a plurality of hemispherical ribs generally perpendicular to the canister sidewall. The sealed canisters are received within the cask for storage and transportation and are removed from the cask for disposal at a designated repository. The system of the present invention allows the handling of sealed canisters separately or collectively, while allowing storage and transportation of high burnup fuel and damaged fuel to the designated repository. |
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062018477 | abstract | A T-box assembly to facilitate attaching a core spray line to a reactor core spray nozzle safe end without welding is described. In one embodiment, the T-box assembly includes a T-box housing, a cruciform wedge, and a draw bolt. The T-box housing is configured to be positioned so that a first end is located inside a core spray nozzle and engages the core spray nozzle safe end. Two other ends are configured to be in substantial alignment and configured to couple to core spray line header pipes. The T-box housing also includes a cover opening configured to receive a T-box cover plate. The T-box cover plate includes a draw bolt opening configured to receive the draw bolt. The first end of the T-box also includes a plurality of positioning lugs configured to engage the core spray nozzle to center the T-box housing in the nozzle bore. The cruciform wedge includes four web members extending from a central member and configured so as to form an X shaped configuration. Two support members extend between the ends of adjacent web members and are configured to conform to the bore of the core spray nozzle safe end. The draw bolt is configured to extend through a cruciform wedge bore and the draw bolt opening in the T-box cover plate and to threadenly engage a draw bolt nut. |
claims | 1. A floating nuclear power reactor, comprising:a floating vessel having a bottom positioned beneath the water level of a body of water, sides extending upwardly from said bottom, and an upper end which is positioned above the water level of the body of water;a cylindrical first containment member;said first containment member having a lower end, an open upper end, and a cylindrical side wall with inner and outer sides;said lower end of said first containment member being positioned on said bottom of said floating vessel;a cover closing said open upper end of said first containment member;a cylindrical second containment member positioned within said first containment member;said second containment member including a bottom, an upstanding side wall with inner and outer sides, and a domed upper end;said second containment member having an interior compartment with upper and lower ends;said bottom of said second containment member being positioned on said bottom of said floating vessel;said outer side of said side wall of said second containment member being spaced inwardly of said inner side of said side wall of said first containment member to define a first space therebetween;said first space being filled with sand;said domed upper end of said second containment member, and said inner side of said first containment member forming a vent chamber above the upper end of the sand in said first space;said vent chamber being filled with a filter material;at least a first steam exhaust pipe extending from said vent chamber to the atmosphere;at least a second steam exhaust pipe extending upwardly and outwardly from said upper end of said interior compartment of said second containment member into said vent chamber, thence downwardly in said vent chamber;an upstanding reactor vessel, having upper and lower ends, positioned in said interior compartment of said second containment member;said lower end of said reactor vessel being positioned on said bottom of said second containment member;said reactor vessel having an interior compartment with upper and lower ends;a third steam exhaust pipe extending from said upper end of said interior compartment of said reactor vessel outwardly through said second and first containment members to a turbine;one or more by-pass steam exhaust pipes positioned in said first space extending from said third steam exhaust pipe to said vent chamber;a normally closed first valve in each of said by-pass steam exhaust pipes;a normally open second valve in each of said third steam exhaust pipe in said first space;at least one first return pipe extending outwardly from said upper end of said interior compartment of said reactor vessel into said interior compartment of said second containment member, thence downwardly, and thence inwardly into said interior compartment of said reactor vessel at said lower end thereof and thence upwardly to create a closed loop heat exchange structure;a first water passageway, having inner and outer ends, extending through said bottom of said second containment member;said outer end of said first water passageway being in fluid communication with the body of water;said inner end of said first water passageway being, in fluid communication with said interior compartment of said second containment member;a first hatch associated with said first water passageway;said first hatch being movable between a closed position and an open position;said first hatch, when in said closed position, closing said first water passageway;said first hatch, when in said open position, permitting water from the body of water to flow inwardly through said first water passageway into said interior compartment of said second containment member;a second water passageway, having inner and outer ends, extending through said bottom of said second containment member;said outer end of said second water passageway being in fluid communication with the body of water;said inner end of said second water passageway being in fluid communication with said interior compartment of said reactor vessel;a second hatch movably associated with said second water passageway;said second hatch being movable between a closed position and an open position;said second hatch, when in said closed position, closing said second water passageway;said second hatch, when in said open position, permitting water from the body of water to flow inwardly through said second water passageway into said interior compartment of said reactor vessel;said first hatch being movable from its said closed position to its said open position when a condition within said interior compartment of said second containment member reaches a predetermined level thereby permitting water from the body of water to flow into said interior compartment of said second containment member; andsaid second hatch being movable from its said closed position to its said open position when a condition within said interior compartment of said reactor vessel reaches a predetermined level thereby permitting water from the body of water to flow into said interior compartment of said reactor vessel. 2. The floating nuclear power reactor of claim 1 wherein the predetermined condition level within said interior compartment of said second containment member is lower than the predetermined condition level within said interior compartment of said reactor vessel whereby said first hatch will move from its said closed position to its said open position prior to said second hatch moving from its said closed position to its said open position so that said interior compartment of said second containment member will be flooded prior to said interior compartment of said reactor vessel being flooded. 3. The floating nuclear power reactor of claim 1 wherein a plurality of first steam exhaust pipes extend from said vent chamber to the atmosphere. 4. The floating nuclear power reactor of claim 1 wherein a plurality of second steam exhaust pipes extend from said upper end of said interior compartment of said second containment member into said vent chamber. 5. The floating nuclear power reactor of claim 1 wherein said filter material is comprised of rocks, chemicals and water. 6. The floating nuclear power reactor of claim 1 wherein a plurality of first return steam pipes extend outwardly from said upper end of said interior compartment of said reactor vessel, thence downwardly, and thence inwardly into said interior compartment of said reactor vessel at said lower end thereof and thence upwardly to form a closed loop heat exchanger structure. 7. The floating nuclear power reactor of claim 1 wherein said second steam exhaust pipe has a generally inverted V-shape. 8. The floating nuclear power reactor of claim 4 wherein each of said second steam exhaust pipes have a generally inverted V-shape. 9. A floating nuclear power reactor, comprising:a floating vessel having a bottom positioned beneath the water level of a body of water, sides extending upwardly from said bottom, and an upper end which is positioned above the water level of the body of water;a cylindrical first containment member;said first containment member having a lower end, an open upper end, and a cylindrical side wall with inner and outer sides;said lower end of said first containment member being positioned on said bottom of said floating vessel;a cover closing said open upper end of said first containment member;a cylindrical second containment member positioned within said first containment member;said second containment member including a bottom, an upstanding side wall with inner and outer sides, and a domed upper end;said second containment member having an interior compartment with upper and lower ends;said bottom of said second containment member being positioned on said bottom of said floating vessel;said outer side of said side wall of said second containment member being spaced inwardly of said inner side of said side wall of said first containment member to define a first space therebetween;said first space being filled with sand;said domed upper end of said second containment member, and said inner side of said first containment member forming a vent chamber above the upper end of the sand in said first space;said vent chamber being filled with a filter material;at least one first steam exhaust pipe extending from said vent chamber to the atmosphere;at least one second steam exhaust pipe extending upwardly and outwardly from said upper end of said interior compartment of said second containment member into said vent chamber, thence downwardly in said vent chamber;an upstanding reactor vessel, having upper and lower ends, positioned in said interior compartment of said second containment member;said lower end of said reactor vessel being positioned on said bottom of said second containment member;said reactor vessel having an interior compartment with upper and lower ends;a third steam exhaust pipe extending from said upper end of said interior compartment of said reactor vessel outwardly through said second and first containment members to a turbine;one or more by-pass steam exhaust pipes positioned in said first space extending from said third steam exhaust pipe to said vent chamber;a normally closed first valve in each of said by-pass steam exhaust pipes;a normally open second valve in said third steam exhaust pipe in said first space;at least one first return pipe extending outwardly from said upper end of said interior compartment of said reactor vessel into said interior compartment of said second containment member, thence downwardly, and thence inwardly into said interior compartment of said reactor vessel at said lower end thereof and thence upwardly to create a closed loop heat exchange structure;said at least one first return pipe being filled with a liquid coolant material;a first water passageway, having inner and outer ends, extending through said bottom of said second containment member;said outer end of said first water passageway being in fluid communication with the body of water;said inner end of said first water passageway being, in fluid communication with said interior compartment of said second containment member;a normally closed first hatch associated with said first water passageway;said first hatch being movable between a closed position and an open position;said first hatch, when in said closed position, closing said first water passageway;said first hatch, when in said open position, permitting water from the body of water to flow inwardly through said first water passageway into said interior compartment of said second containment member;a second water passageway, having inner and outer ends, extending through said bottom of said second containment member;said outer end of said second water passageway being in fluid communication with the body of water;said inner end of said second water passageway being in fluid communication with said interior compartment of said reactor vessel;a second hatch movably associated with said second water passageway;said second hatch being movable between a closed position and an open position;said second hatch, when in said closed position, closing said second water passageway;said second hatch, when in said open position, permitting water from the body of water to flow inwardly through said second water passageway into said interior compartment of said reactor vessel;said first hatch being movable from its said closed position to its said open position when a condition within said interior compartment of said second containment member reaches a predetermined level thereby permitting water from the body of water to flow into said interior compartment of said second containment member; andsaid second hatch being movable from its said closed position to its said open position when a condition within said interior compartment of said reactor vessel reaches a predetermined level thereby permitting water from the body of water to flow into said interior compartment of said reactor vessel. 10. A floating nuclear power reactor, comprising:a floating vessel having a bottom positioned beneath the water level of a body of water, sides extending upwardly from said bottom, and an upper end which is positioned above the water level of the body of water;a cylindrical first containment member;said first containment member having a lower end, an open upper end, and a cylindrical side wall with inner and outer sides;said lower end of said first containment member being positioned on said bottom of said floating vessel;a cover closing said open upper end of said first containment member;a cylindrical second containment member positioned within said first containment member;said second containment member including a bottom, an upstanding side wall with inner and outer sides, and a domed upper end;said second containment member having an interior compartment with upper and lower ends;said bottom of said second containment member being positioned on said bottom of said floating vessel;said outer side of said side wall of said second containment member being spaced inwardly of said inner side of said side wall of said first containment member to define a first space therebetween;said first space being filled with a particulate material;an upstanding reactor vessel, having upper and lower ends, positioned in said interior compartment of said second containment member;said lower end of said reactor vessel being positioned on said bottom of said second containment member;said reactor vessel having an interior compartment with upper and lower ends;a steam exhaust pipe extending from said upper end of said interior compartment of said reactor vessel outwardly through said second and first containment members to a turbine;a first water passageway, having inner and outer ends, extending through said floating vessel into said interior compartment of said second containment member;said outer end of said first water passageway being in fluid communication with the body of water;said inner end of said first water passageway being, in fluid communication with said interior compartment of said second containment member;a first hatch associated with said first water passageway;said first hatch being movable between a closed position and an open position;said first hatch, when in said closed position, closing said first water passageway;said first hatch, when in said open position, permitting water from the body of water to flow inwardly through said first water passageway into said interior compartment of said second containment member;said first hatch being movable from its said closed position to its said open position upon the temperature or pressure in said interior compartment of said second containment member reaching a predetermined level;a second water passageway, having inner and outer ends, extending through said floating vessel into said interior compartment of said reactor vessel;said outer end of said second water passageway being in fluid communication with the body of water;a second hatch movably associated with said second water passageway;said second hatch being movable between a closed position and an open position;said second hatch, when in said closed position, closing said second water passageway;said second hatch, when in said open position, permitting water from the body of water to flow inwardly through said second water passageway into said interior compartment of said reactor vessel;said second hatch being movable from its said closed position to its said open position upon the temperature or pressure in said interior compartment of said reactor vessel reaching a predetermined level. |
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abstract | Reduced source spacing for multi-source, multi-detector X-ray imaging systems is provided by allowing channels within an X-ray collimator to intersect within the body of the collimator. As a result, the channels are not independent, and the source spacing can be significantly reduced. Although such collimators have a much more “open” structure than conventional collimators having independent channels, they can still provide efficient collimation performance (e.g., predicted leakage <5%). Several high attenuation layers having through holes and stacked together can provide collimators according to the invention, where the through holes combine to form the intersecting channels. |
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description | This invention was made with Government support under Contract No. DE-AC09-08SR22470, awarded by the U.S. Department of Energy. The Government has certain rights in the invention. The present invention generally involves an instrument for assaying radiation. In particular embodiments, a collimator, camera, and/or dosimeter may be incorporated into the instrument to enhance sensitivity and positioning of the instrument in the area being assayed. The use of radioactive material occasionally results in radiation and/or contamination areas that require decontamination or other remedial efforts. In some cases, the radiation and/or contamination levels may be significant, and the specific locations of the radiation and/or contamination may not be accurately known. As a result, various instruments have been developed to assay radiation and contamination areas so that the costs and personnel exposures associated with the decontamination or other remediation efforts can be reduced. Various factors are considered in the design and selection of instruments to assay radiation and/or contamination areas. For example, the responsive range of the instruments should be selected so that the instruments are capable of reliably measuring varying levels of radiation without requiring excessive exposure times while also having sufficient sensitivity to discriminate between separate sources of radiation and/or locations of contamination. In addition, remote positioning and operation of the instruments is often desirable to reduce personnel exposure, particularly when the radiation and/or contamination levels are high or unknown. As a result, various improvements in instruments used to assay radiation and/or contamination areas that enhance sensitivity and/or remote positioning of the instruments would be useful. Aspects and advantages of the invention are set forth below in the following description, or may be obvious from the description, or may be learned through practice of the invention. In one embodiment of the present invention, an instrument for assaying radiation includes a radiation sensor and a collimator that covers at least a portion of the radiation sensor. The collimator defines a first field of view to the radiation sensor. An insert in the collimator defines a second field of view to the radiation sensor that is less than the first field of view. Another embodiment of the present invention is an instrument for assaying radiation that includes a plurality of radiation sensors and a separate collimator that covers at least a portion of each of the plurality of radiation sensors. Each collimator defines a first field of view. A separate insert in each collimator defines a second field of view that is less than the first field of view. In yet another embodiment of the present invention, an instrument for assaying radiation may include a radiation sensor and means for collimating the radiation into the radiation sensor. Those of ordinary skill in the art will better appreciate the features and aspects of such embodiments, and others, upon review of the specification. Reference will now be made in detail to present embodiments of the invention, one or more examples of which are illustrated in the accompanying drawings. The detailed description uses numerical and letter designations to refer to features in the drawings. Like or similar designations in the drawings and description have been used to refer to like or similar parts of the invention. As used herein, the terms “first”, “second”, and “third” may be used interchangeably to distinguish one component from another and are not intended to signify location or importance of the individual components. The terms “upstream,” “downstream,” “radially,” and “axially” refer to the relative direction with respect to particle movement. For example, “upstream” refers to the direction from which the particle flows, and “downstream” refers to the direction to which the particle flows. Similarly, “radially” refers to the relative direction substantially perpendicular to the particle flow, and “axially” refers to the relative direction substantially parallel to the particle flow. Each example is provided by way of explanation of the invention, not limitation of the invention. In fact, it will be apparent to those skilled in the art that modifications and variations can be made in the present invention without departing from the scope or spirit thereof. For instance, features illustrated or described as part of one embodiment may be used on another embodiment to yield a still further embodiment. Thus, it is intended that the present invention covers such modifications and variations as come within the scope of the appended claims and their equivalents. Various embodiments of the present invention include an instrument for assaying radiation. The instrument generally includes one or more radiation sensors, and a separate collimator covers at least a portion of each of the radiation sensors. Each collimator defines a first field of view, and an insert in the collimator defines a second field of view that is less than the first field of view. In particular embodiments, for example, the first field of view may be greater than 60 degrees, and the first field of views of the separate collimators may overlap one another. The insert may define a frustoconical shape and a through bore so that the second field of view may be less than or equal to 60 degrees. In this manner, the first fields of view of the collimators may provide panoramic coverage around the instrument, while the second fields of views of the inserts may enhance detection and discrimination of closely spaced radioactive sources. Referring now to the drawings, wherein identical numerals indicate the same elements throughout the figures, FIG. 1 provides a perspective view of an instrument 10 for assaying radiation according to one embodiment of the present invention. The instrument 10 may include a housing 12 that defines one or more faces 14 with a radiation sensor 16 in each face 14. The housing 12 may be formed from shielding material such as tungsten or a tungsten alloy to reduce or prevent radiation from passing through the housing 12 and interacting with multiple radiation sensors 16, facilitating analysis of the radiation sensors 16 after exposure to radiation. For example, a tungsten layer having a thickness of approximately 1.5 cm will provide adequate shielding to sufficiently reduce or prevent radiation from passing through the housing 12 and interacting with the radiation sensors 16. If desired, the interior portion of the housing 12 may be made from aluminum or aluminum alloys. The aluminum and/or aluminum alloys provide sufficient shielding inside the housing 12 while also reducing the weight of the housing 12 to facilitate deployment and positioning of the instrument 10. The instrument 10 may include a separate shutter 20 for each radiation sensor 16 to shield the radiation sensors 16 from exposure prior to being positioned for operation. Each shutter 20 may have a drive mechanism 22 to alternately open or close the shutter 20, and each drive mechanism 22 may be operated in concert or independently from the other drive mechanisms 22 to allow for different exposure times for each radiation sensor 16. The drive mechanism 22 may include any electrical, mechanical, electro-mechanical, servo-mechanical, or other mechanism known in the art for sliding, pivoting, rotating, or otherwise positioning the shutter 20. As shown in FIG. 1, for example, the exemplary drive mechanism 22 may include a motor 24 connected to the shutter 20 by one or more drive wheels 26 and a pulley 28 to pivot or retract the shutter away from the radiation sensor 16, thereby exposing the radiation sensor 16 to the radiation and/or contamination area. The motor 24 may be operated locally, remotely, or by a timing circuit, as desired, to reduce personnel exposure during operation of the instrument 10. In this manner, each shutter 20 may have a closed position to shield the associated radiation sensor 16 from exposure during transport and positioning of the instrument 10 and an open position once the instrument 10 is positioned and ready for operation. The radiation sensors 16 may be recessed in the housing 12 to enhance the shielding provided by the housing 12, and the number and arrangement of the faces 12 and radiation sensors 16 may be selected to provide a desired coverage for the instrument 10. As shown in FIG. 1, for example, six faces 14 and six radiation sensors 16 may be arranged on the instrument 10 to provide continuous, overlapping coverage around the instrument 10. In this manner, a single instrument 10 may provide 411 steridian coverage in a radiation and/or contamination area. FIG. 2 provides a perspective view of the exemplary radiation sensor 16 shown in FIG. 1. As shown in FIG. 2, the radiation sensor 16 may include a casing 30 that holds one or more radiation sensitive film layers 32 sandwiched around attenuation layers 34. The casing 30 facilitates installation and removal of the film layers 32 and attenuation layers 34 from the housing 12 and may be made from tungsten, aluminum, aluminum alloys, or other material that may supplement the shielding provided to the radiation sensor 16. The geometry, number, and thickness of the film layers 32 and attenuation layers 34 may be selected based on the anticipated source and/or energy level present in the radiation and/or contamination area. In particular embodiments, for example, the film layers 32 may include x-ray imaging photographic film used in conventional medical applications. Alternately or in addition, the film layers 32 may include Phosphorous Storage Plate (PSP) technology as described in U.S. Patent Publication 2012/0112099 and assigned to the same assignee as the present application, the entirety of which is incorporated herein for all purposes. The attenuation layers 34 are similarly selected to partially shield radiation that passes through the film layers 32. Suitable attenuation layers 34 may include, for example, metal, plastic, or glass, depending on the anticipated source and/or energy level present. The attenuation layers 34 produce a different exposure for each film layer 32 exposed to radiation. For example, radiation exposed to the radiation sensor 16 will produce the largest exposure in the outermost film layer 32, with progressively decreasing exposures to each interior film layer 32, depending on the particular attenuation layer 34 between each film layer 32. The number of film layers 32 and attenuation coefficients for the attenuation layers 34 may be varied as desired to achieve a desired sensitivity to radiation and/or discrimination of different energy levels. After an exposure to radiation, the individual films layers 32 may be removed from the casing 30 for analysis, and the amount and/or energy level of the radiation present may be calculated based on the known attenuation layers 34 and different exposures received by each film layer 32. The instrument 10 may further include means for collimating the radiation into the radiation sensor 16. The function of the means is to channel, focus, or narrow the radiation exposed to the film layers 32. As shown in FIG. 2, the structure for performing this function may include a collimator 40 (shown in phantom) that covers at least a portion of the radiation sensor 16. The collimator 40 may be constructed from shielding material with an aperture 42 to block radiation from reaching the film layers 32 except through the aperture 42. FIG. 3 provides a cross-section view of the radiation sensor 16 and collimator 40 shown in FIG. 2, and FIG. 4 provides a perspective cross-section view of the collimator 40 shown in FIGS. 2 and 3. As shown most clearly in FIGS. 3 and 4, the collimator 40 defines a first field of view 44 to the radiation sensor 16. The first field of view 44 is created by the slope of the surface of the collimator 40 proximate to the aperture 42 and is defined as the angle between opposing surfaces of the collimator 40 proximate to the aperture 42. The size of the first field of view 44 may be selected based on the number of faces 14 and radiation sensors 16 on the instrument so that the first fields of view 44 of the collimators 40 overlap to provide panoramic coverage around the instrument 10. In the particular embodiment shown in FIGS. 1-4, the first field of view 44 is approximately 96 degrees so that the six radiation sensors 16 shown in FIG. 1 provide 360 degrees of sensitivity to radiation around the instrument 10. In other particular embodiments, the first field of view 44 may be between 60 and 120 degrees to provide the desired overlap between adjacent radiation sensors 16; however, the specific size of the first field of view 44 is not a limitation of the present invention unless specifically recited in the claims. The means for collimating the radiation into the radiation sensor 16 may further include an insert 46 in the collimator 40 that defines a second field of view 48 to the radiation sensor 16 that is less than the first field of view 44. The size of the second field of view 48 may be selected based on the number of faces 14, the size of the first field of view 44, and/or the anticipated radiation sources present so that the insert 46 enhances discrimination between discrete radiation sources that are close to one another. In the particular embodiment shown in FIGS. 1-4, the second field of view 48 is approximately 60 degrees to focus the first field of view 44 of 96 degrees and enhance discrimination of gamma radiation having an energy level between approximately 0.6 MeV and 1.3 MeV. In other particular embodiments, the second field of view 48 may be less than 60 degrees to complement the first field of view 44 and/or enhance discrimination of radiation having different energy levels. The combination of the collimator 40 and insert 46 enables the means for collimating the radiation into the radiation sensor 16 to define the first field of view 44 to the radiation sensor 16 that is greater than 60 degrees and the second field of view 48 to the radiation sensor 16 that is less than or equal to 60 degrees. The insert 46 may be constructed from shielding material to define a frustoconical inner shape 50 and a through bore 52, and the slope of the internal surface of the insert 46 proximate to the through bore 52 may define the second field of view 48. A material 54 transparent to radiation may be used to connect the insert 46 to the collimator 40 to hold the insert 46 in place. In this manner, the first and second fields of view 44, 48 define the paths that radiation may travel through the insert 46 and/or collimator 40 to reach the film layers 32, and the shielding provided by the insert 46 may block a portion of the radiation from passing through the collimator 40 to the film layers 32 to enhance discrimination of discrete radiation sources that are close to one another. In particular embodiments, the instrument 10 may optionally include one or more dosimeters 60 and/or cameras 62 on the housing 12 aligned with the radiation sensors 16. Returning to FIG. 1, for example, a separate dosimeter 60 arid/or camera 62 may be mounted on each face 14 of the housing 12. The dosimeter(s) would enhance accurate placement of the instrument 10 in the radiation and/or contamination areas in situations in which existing surveys are either unavailable or unreliable. In addition, readings from the dosimeters 60 may be used to independently adjust the exposure time of each radiation sensor 16, allowing for more effective imaging of areas having substantially different radiation levels in different directions. Each camera 62 may include a wide-angle lens, supporting electronics, and a shared file storage media to record still and/or motion images during deployment of the instrument 10. The still and/or motion images may then be integrated and overlaid with the exposure information from the radiation sensors 16 to produce a composite image that visually correlates radiation levels to images of the radiation and/or contamination area. This written description uses examples to disclose the invention, including the best mode, and also to enable any person skilled in the art to practice the invention, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they include structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal languages of the claims. |
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abstract | A double strip mixing grid for nuclear reactor fuel assemblies is disclosed. This grid is fabricated by intersecting at right angles a plurality of double strips, each fabricated by welding two thin sheets together into a single structure with coolant channels. The mixing grid, having the channels, effectively mixes low temperature coolant with high temperature coolant within a fuel assembly, thus improving the thermal efficiency of the fuel assemblies. This mixing grid also effectively prevents the coolant from being partially overheated, thus improving the soundness of nuclear reactors. This mixing grid also has swirling flow blades and/or lateral flow blades to further improve the thermal efficiency of the fuel assembly. This mixing grid elastically supports the fuel rods by the sheets of the double strips, collaterally acting as positioning springs. Each double strip also has a vertical slot at a position around each channel, and so the elastic range of the positioning springs of the grid is preferably enlarged. The slots also enlarge the fuel rod contact area of the grid, thereby effectively protecting the fuel rod from fretting corrosion. In addition, the intersecting strips are welded together at the intersections through a continuous welding process, thus improving the mechanical strength of the grid. |
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abstract | A uniformity correction module for improving the uniformity of a radiation distribution in a rectangular illumination slit having two longer sides and two shorter sides, including a plurality of movable blades arranged along each long side of the illumination slit and a chamber containing a fluid wherein said movable blades are at least partly immersed in said fluid, and wherein the difference between the refractive index of each blade and the refractive index of said fluid is sufficiently small to prevent significant reflection and refraction at the surface of each blade. |
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05999889& | description | DESCRIPTION OF THE INVENTION The following description is presented solely for the purpose of disclosing how the present invention may be made and used. The scope of the invention is defined by the claims. FIG. 1 diagrams an equivalent circuit for a typical transmitting antenna 15. Transmitter 16 is represented by voltage source Vt in series with impedance Zt to model the reactance and losses in the transmitter. An impedance matching transformer 17 is typically used to match impedance Zt to the antenna impedance. The antenna impedance comprises gross resistance Rg, gross inductance Lg, and gross capacitance Cg. Cg includes the stray capacitive reactance of the antenna coupling to ground and the connecting cables. Lg includes the inductive reactance of the stray inductance in the connecting cables and the series inductance of a tuning coil or variometer typically used for tuning the resonant frequency of the antenna. Rg includes the resistance of the antenna feed cables and the antenna structure causing power to be lost as heat and the radiation resistance of the antenna. The voltage at the antenna feed point is designated as Va, and the current as Ia. The antenna voltage and current are functions of time that characterize the antenna impedance characteristics described above. Antenna voltage Va and current Ia may be measured according to well known techniques when the antenna is operating with a single frequency sinusoidal signal, but in modulated signals such as frequency shift keying each single frequency signal is of such short duration that measuring Va and Ia becomes a significant problem. Referring now to FIG. 2, antenna performance monitor 30 comprises antenna sensor 20, A/D converter 40, and data processor 50. Antenna sensor 20 comprises a capacitive voltage divider 21 connected between the antenna feedpoint at impedance transformer 17 and ground to generate antenna input voltage signal Vm and a current probe 22 connected in series with antenna 15 to generate antenna input current signal Im. The capacitors in voltage divider 21 have a capacitance ratio and a series reactance selected to scale antenna voltage Va to an appropriate voltage signal Vm. Current probe 22 senses antenna current Ia and generates a corresponding voltage signal Im. Current probe 22 may be, for example, a Pearson Electronics Model 310 RF Current Transformer. In operation, voltages Vm and Im are input to A/D converter 40. A/D converter 40 may be, for example, a Rapid Systems Model R2000 Analog to Digital Converter. Signals Vm and Im may be conducted to A/D converter 40 by signal link 23. Signal link 23, may be, for example, a double shielded cable to minimize interference from the magnetic field of the antenna. Alternatively, signal link 23 may be a fiber optic transmitter and receiver link for each of signals Vm and Im, such as a Dymec Model 6721 Fiber Optic Transmitter and Model 6722 Fiber Optic Receiver. A/D converter 40 is initialized and triggered by data processor 50 to digitize signals Vm and Im. The digitized Vm and Im data output from A/D converter 40 are input to data processor 50. A/D converter 40 typically includes anti-aliasing filters to filter out signals having frequencies higher than half the A/D sample rate. The sample rate should be higher than twice the highest transmitter signal frequency. FIG. 3 is a flow chart exemplifying the processing of signals Vm and Im through A/D converter 40 and data processor 50. Signals Vm and Im are anti-aliased by filters 402 and digitized by digitizers 404. The digitized samples are then bandpass-filtered by bandpass filters 406 to remove out-of-band frequencies and base-banded by complex mixers 408. The base-banded complex data is lowpass filtered by lowpass filters 409 and resampled by decimators 410 to a sample rate appropriate to the modulation bandwidth of the radio frequency signal. The decimated data is then subjected to a complex FFT 412. FFT 412 may have, for example, 1024 points. The complex FFT data is averaged over, for example, a 500 point evenly weighted average by averagers 414 resulting in frequency bin averages for Vm and Im at each of the frequencies in the modulation bandwidth of the radio frequency signal. Magnitude functions 416 generate the magnitude of Vm and Im respectively by calculating the square root of the sum of the squares of the real and imaginary coefficients of signals Vm and Im respectively for each frequency bin. Arctangent functions 418 generate the phase angles of Vm and Im by calculating the arctangent of the ratio of the real to the imaginary coefficients for each frequency bin. Impedance magnitude function 420 divides the magnitude of Vm by the magnitude of Im to output the impedance magnitude Zm for each frequency bin. Impedance phase function 422 subtracts the phase angle of Im from the phase angle of Vm to output impedance phase angle Zp for each frequency bin. Rg, Lg, Cg, and the resonant frequency of the antenna may be found from Zm and Zp at two or more frequencies as described in U.S. Pat. No. 5,233,537, included herein by reference thereto. The resonant frequency of the antenna and Rg may also be found by selecting the frequency bin having an impedance phase angle Zp closest to zero. The corresponding impedance magnitude Zm at this frequency is approximately Rg. The reactance for each frequency may also be found by subtracting Rg from Zm of the corresponding frequency bin. The resulting antenna performance parameters may be displayed according to well known techniques or transmitted to a remote location for further processing. Other modifications, variations, and applications of the present invention may be made in accordance with the above teachings other than as specifically described to practice the invention within the scope of the following claims. |
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042773067 | summary | The present invention is directed to methods and apparatus for confining and controlling plasmas, and more particularly, to such methods and apparatus for maintaining the purity of high temperature toroidal plasmas. Various methods and apparatus have been developed for generating and confining plasmas, which are ionized gases comprising approximately equal numbers of positively charged ions and free electrons at high temperatures. One general type of device for plasma confinement comprises an endless, closed tube, such as a toroid, with a geometrically co-extensive, externally imposed magnetic field (e.g., a toroidal magnetic field) in which magnetic lines of induction extend around the toroid generally parallel to its minor axis. Such a magnetic field is conventionally provided by electrical currents in one or more conductive coils encircling the minor axis of the toroid. Illustrative of such devices are the toroidal diffuse pinch plasma confinement devices of the Tokamak configuration, and such devices may be generally referred to hereinafter as tokamak devices or systems. The toroidal configuration may be advantageously employed with plasmas and plasma confinement systems or noncircular cross-section either with respect to planes perpendicular to the minor axis or the major axis such as those involving plasma configurations which are axisymmetrically elongated in a direction parallel to the major toroidal axis. In this connection, U.S. Pat. Nos. 3,692,626 and 3,801,438 illustrate plasma generation and confinement apparatus of the toroidal type having a noncircular cross-section in respect of a plane parallel to and intercepting the major toroidal axis. As previously indicated, toroidal systems for the containment of high-temperature plasmas comprise means for providing a strong, toroidal magnetic field in which the plasma is to be embedded, and which is conventionally provided by electrical current in one or more conductive coils encircling the minor toroidal axis. The term "axis" as used herein to include multiple axes or axial surfaces, such that reference to toroidal systems may include such systems having a noncircular cross-section such as utilized in the various Doublet devices of the assigness of the present invention. Toroidal plasma systems, which are hereinafter generally referred to as tokamak systems, may also comprise means for providing a toroidal electric field to produce a current flowing in the plasma, generally in the direction of the minor axis, and this plasma current in turn may generate a magnetic field component which is poloidal (i.e., the magnetic flux lines are closed about the minor toroidal axis). The combination of the poloidal magnetic field produced by the plasma current, with the toroidal magnetic field produced by the toroidal cell current, is suitable for providing helix-like magnetic field lines that generally lie on closed, nested magnetic surfaces. The plasma is accordingly subjected to confining, constricting forces generated, at least in part, by the current flowing in the plasma. The resulting magnetic field provides for a diffused pinching force in the confining magnetic field which may be substantially greater than the outward pressure of the plasma. The generation of a current in the plasma may conventionally be provided in various ways, such as by providing current in an inductive primary coil configured such that the plasma serves as the secondary coil of a transformer system. Such inductive current further provides for inductive, ohmic heating of the plasma, and systems for more continuous heating of tokamak plasmas are known in the art. An important difficulty in the initial formation and sustained maintenance of a high temperature plasma is the problem of excluding impurity atoms from the plasma, and the substantial and potentially disabling plasma energy losses which result from the presence of such impurities. The impurities in a plasma generally originate from two principal sources. First, contaminants such as oxygen, nitrogen or carbon may be absorbed on the chamber walls surrounding the plasma zone, and driven therefrom by the conditions which are employed to initially form the plasma. The other principal source of contaminants results from the bombardment of the chamber wall material itself by energetic plasma particles and radiation. Further, fusion reactions may generate high energy particles which will increase the problem of contaminants from wall bombardment. Suitable vacuum techniques and high temperature baking may be employed to minimize the adverse effect of absorbed contaminants, but the problem of contaminants produced by bombardment and erosion of the chamber walls have provided substantial difficulties. Complicated magnetic divertor systems have been designed in an effort to overcome the problem in some types of plasma confinement systems, but such divertors are expensive, complex and have various other disadvantages. Conventional divertors are intended to skim off the most contaminated plasma near the wall and are generally structured orthogonally to the minor toroidal axis, such that partical diversion occurs radially outwardly of the minor axis in a cross sectional plane through the plasma. Such poloidal divertors, such as that of the Poloidal Divertor experiment, are designed essentially to bury hot protons into a divertor plate away from the main plasma, to differentially pump away any sputtered atoms before they reach the main plasma, and to ionize sputtered atoms produced by hot neutral hydrogen at the wall facing the main plasma, and carry the ionized atoms to the divertor plate. Conventionally, a magnetic configuration with a separatrix encircling the divertor coil is employed to neck down the passage between the divertor region and the main plasma for differential pumping in order to perform these functions, but such divertor coils must be in the vacuum and also must be shielded from fusion neutrons in a reactor. Such considerations make a plasma confinement system or a plasma fusion reactor very complicated and expensive. The presence in the plasma of impurities, such as those originating from the walls of the chamber surrounding the plasma, leads to undesirable energy loss in the form of radiaton, which in turn has a deleterious effect on the formation and/or maintenance of a high temperature plasma. These energy losses arise because the contaminants generally have a higher atomic number than hydrogen, and the type of electronic excitation, ion recombination and bremsstrahlung radiation losses produced by their presence in a hydrogen plasma (i.e., hydrogen, deuterium, tritium and mixtures thereof) become increasingly deleterious with increasing atomic number of the contaminant. The problem of plasma contamination by impurities may be further aggravated in toroidal confinement systems by the toroidal geometry itself. In toroidal plasma configurations, the inward flow of contaminant impurity ions from the chamber zone surrounding the plasma is enhanced by Pfirsch-Schluter effects. In this regard, each different contaminant ion species has a characteristic flow pattern in which an upward (or downward depending on the polarity of the toroidal magnetic field) flow with respect to the major axis, due to the toroidal drift in the toroidal configuration, is followed by the return flow along the magnetic field line. However, because of the difference of electric charge between the various species of impurity ions, the flow velocities of the different species are correspondingly different. The resulting collisional friction between the different species will disrupt the otherwise established pattern and result in the enhanced inward motion of impurity ions from the surrounding zone into the plasma. [P. Rutherford, Princeton Plasma Laboratory MATT-1039 (1974)]. Methods and apparatus without the undesirable internal coils of poloidal divertors have been devised which utilize an axisymmetric source-sink system for impurity flow control or reversal [K. Burrell, "Effect of Particle and Heat Sources on Impurity Transport in Tokamak Plasmas," Phys. Fluids, 19, 401 (1976); T. Ohkawa, Kakuyugo-Kenkyu, 32, 61 (1974)], but further developments in respect of impurity control are desirable. Accordingly, it is an object of the present invention to provide a method and apparatus for control of impurity ions in toroidal plasma systems without the use of internal coils. It is a further object to provide such a method and apparatus which may be relatively simple, which do not unduly disrupt the delicate dynamics of the toroidal plasma confinement systems, and which may be used with existing toroidal systems without prohibitively substantial structural or design alterations. |
055770835 | summary | FIELD OF THE INVENTION This invention generally relates to reducing the corrosion potential of components exposed to high-temperature (i.e., about 150.degree. C. or greater) water. BACKGROUND OF THE INVENTION The high-temperature (.about.288.degree. C.) water coolant in a boiling water reactor (BWR) is highly oxidizing due to dissolved, radiolytically produced chemical species, such as oxygen and hydrogen peroxide. These molecules are generated as the water passes through the reactor core and is exposed to very high gamma and neutron fluxes. The dissolved oxidants create a relatively high electrochemical potential (ECP) for structural materials in the coolant. Because of the high ECP, reactor structural materials in contact with the coolant, such as stainless steels and nickel-base alloys, can suffer intergranular stress corrosion cracking (IGSCC). This can limit the useful lifetime of reactor components, such as piping and pressure vessel internal structures, or result in a large inspection and repair cost in an effort to mitigate IGSCC effects in nuclear plants. A number of countermeasures have been developed to mitigate IGSCC in BWRs. Of the various mitigation strategies, reducing the environmental aggressiveness (i.e., oxidizing potential, or ECP, of the coolant), can provide the best approach, since the coolant contacts all the potentially susceptible surfaces of interest. A primary strategy to reduce the ECP to some benign value has been to add hydrogen gas to the reactor feedwater in sufficient quantity that it is available to chemically combine, in the presence of a radiation field, with the dissolved oxygen and hydrogen peroxide to form water, thereby reducing the ECP below the IGSCC threshold value. Another strategy is directed towards providing IGSCC protection of selected high cost-impact reactor systems, such as piping, by reducing the ECP of these particular systems by inserting a catalytic recombiner upstream of the piping, or other system requiring IGSCC protection. The recombiner facilitates the reaction of a small (stoichiometric) hydrogen addition with the dissolved oxidants, and the oxidizing power of the water exiting the recombiner is reduced below the IGSCC threshold value downstream of the recombiner, up to the point where the water either mixes with higher oxidant-containing coolant, or again passes through the reactor core where radiolysis call recur. The origin of ECP is based in the fundamental nature of metals, which are characterized by atoms consisting of an equal number of positive and negative charges (protons and electrons). Metals are formed from naturally occurring ores, or oxides, in which the metallic atoms are ionized. In the refining process, high energy and strongly reducing conditions are supplied to force the metallic ions in the ore to become a neutral metal by accepting additional electrons. In subsequent use, however, metal atoms attempt to reject the added electrons to return to the lower energy (natural) state occurring in ores. If the metal is in contact with an electron acceptor, such as water containing dissolved oxidants, then electronic transfer from the metal to the acceptor is energetically favored, and an oxidation reaction (corrosion) can occur. The electrochemical potential is a measure, under certain fixed conditions, of the thermodynamic tendency for a metal to lose electrons and corrode. Forcing electrons into a metal contained in an oxidizing environment reverses this tendency and prevents, or inhibits, corrosion. When a metal is in contact with an oxidizing solution, the ECP is a measure of the thermodynamic tendency for the metal atoms to ionize and enter the solution, leaving the metal with a net surface charge. This charge distribution is balanced by ions in the solution, which rearrange themselves in response to the electric field produced by the surface charge density. A boundary layer charge distribution results, and a potential difference exists across the boundary layer, between the metal surface and the neutral bulk solution. This potential difference can be measured, if combined with another "half-cell" electrode forming a crude battery. If the other half-cell accepts electrons, a corrosion reaction is allowed; if it supplies electrons to the metal, no corrosion can occur. ECP is directly related to intergranular attack in thermally sensitized metals (IGSCC), if the dissolved oxidant concentration is sufficient to provide the necessary electrochemical driving force for this type of corrosion reaction. Typically, the ECP of austenitic stainless steels in the BWR piping coolant environment is about 100 mV on the standard hydrogen electrode (SHE) scale. The core and internals regions of the reactor are even more oxidizing due to higher levels of dissolved oxygen and hydrogen peroxide, produced radiolytically as the coolant flows through the high radiation fields of the core. Typical ECP values of 250 mV (SHE) are encountered in the reactor. Empirically, it is known that a threshold exists for onset of IGSCC, depending on the condition of the metal. If thermally sensitized, the threshold is -230 mV (SHE); if non-thermally sensitized, the threshold for irradiation-assisted IGSCC is -140 mV (SHE). Therefore, all strategies to date are based on lowering ECP below the threshold for IGSCC, either globally by addition of hydrogen gas to the reactor feedwater, or locally by promoting catalytic recombination of hydrogen and oxygen/peroxide dissolved in the coolant. Both techniques involving hydrogen addition have the effect of reducing the oxidizing environment in contact with stainless steel piping and structural members. Many years of laboratory and reactor testing and analysis have led to the conclusion that these techniques are more or less effective, but massive additions of hydrogen required to globally suppress ECP have serious side effects that are undesirable in practice. For example, radiochemistry effects that produce the isotope N-16 in excessive amounts increase the radiation burden of the reactor system. Catalytic recombiners are expensive, bulky and add to the reactor pressure drop. Their effectiveness in suppressing oxidant concentrations is yet to be fully demonstrated. Therefore, alternative methods are required to lower ECP directly, without expensive hydrogen injection systems and catalytic recombiners. SUMMARY OF THE INVENTION The present invention is a method and an apparatus for electrically suppressing ECP near highly susceptible components of the BWR internals and piping. A method is described of providing self-contained means of locally protecting critical portions of metals, such as welds, by suppressing ECP in the immediate vicinity of that portion of the metal requiring protection in operating BWR plants. The method has the advantage over prior art in that a global reduction of ECP, through water chemistry control or large internal recombiners, is not required to adequately protect susceptible components. Rather, a small self-powered, electrical device is affixed to the metal area to be protected, which device has the capacity to locally suppress ECP automatically and continuously without provision for external power supplies, cables, penetrations, or other paraphernalia usually associated with electrical and electronic systems. The result is that IGSCC-susceptible components and piping are not as sensitive to the details of the water chemistry flowing over them and do not crack as much, or as rapidly, as presently. The new technique disclosed herein is based on the concept of supplying electrons directly and locally to the sensitized zone(s) of the metal, thereby inhibiting IGSCC. The basic principles of this technique have been previously demonstrated at high temperature in laboratory tests of the straining electrode tests (SET) in impure environments using large equipment. Fortunately, only limited portions of the BWR piping and internals are sensitized to IGSCC, typically in the heat affected zones of welds and in certain crevices subject to stagnation conditions. Global suppression of ECP below -230 mV (SHE) by massive hydrogen addition may not be required, if the novel technique of the present invention is deftly applied, thereby avoiding costly installations and detrimental side effects of hydrogen water chemistry and/or catalytic recombiners. |
description | The present invention relates to a yellow room system that shields a wavelength of light for exposing resist in manufacture of a semiconductor device or similar device. In recent years, the manufacturing line for semiconductor devices includes a plurality of units called bays in which treatment apparatuses with the same type of functions are brought together within a vast clean room. A layout that employs a job-shop system has become mainstream. In the job-shop system, the bays are coupled together by a transfer robot and a belt conveyer. As the workpiece treated in that manufacturing line, a wafer with a large diameter of, for example, 12 inches is used. In the production system, thousands of semiconductor chips are manufactured from one wafer. However, with this job-shop system, in the case where a plurality of similar treatment processes are repeated, the conveyance within the bay or the conveyance distance between bays significantly increase in length, and the wait time increases. Thus, the manufacturing time increases. This causes a cost increase, for example, causes an increase in work in process. Therefore, the low productivity may become a problem as a manufacturing line for treating a large amount of the workpieces. Therefore, instead of the conventional manufacturing line in the job-shop system, a manufacturing line in a flow-shop system is also proposed. In this manufacturing line, semiconductor treatment apparatuses are arranged in the order corresponding to the treatment processes. While this manufacturing line in the flow-shop system is optimal for manufacturing singular products in large quantities, it is necessary to rearrange the location of the respective semiconductor treatment apparatuses in the manufacturing line in the order corresponding to the treatment flow of the workpiece in the case where the manufacturing procedure (recipe) needs to be changed due to a change of products. However, this rearrangement every time the products are changed is not realistic considering labor and time for the rearrangement. Especially, under the circumstances in which huge semiconductor treatment apparatuses are fixedly disposed within the closed space that is the clean room, it is realistically impossible to rearrange the semiconductor treatment apparatuses each time. Further, in the conventional semiconductor manufacturing systems, because simultaneous productivity (production quantity per unit time) has been emphasized the most as a critical factor in order to minimize manufacturing costs, diameter scale-up in the workpiece size (silicon wafer size) and increase in the manufacturing unit count (number of orders with respect to a single product) have been given priority, pointing to gigantic manufacturing systems, megafab so to say. In very large-scale manufacturing systems of this sort, the number of processes has exceeded several hundred, and in proportion to that, the number of bays and number of apparatuses has grown considerably. Accordingly, although for that reason the throughput of the manufacturing lines as a whole has improved, constructing such megafab requires a facilities investment of several billion dollars, making the overall investment cost a huge sum. Furthermore, along with such manufacturing systems going very large-scale, apparatus control grows complex and conveyance time and wait time in the conveyance system increase significantly. In response to that the number of works in process that dwell along the production line also increases significantly. Since the unit cost of the large-diameter wafers employed here is extraordinarily high, increase in the number of works in process leads to elevation in costs. Given these and other such circumstances, productivity as a whole, including facilities investment, is said to be turning in a decreasing direction. Therein, an approach in which the cleanroom is scaled down by means of a local cleaning production system or similar technique is beginning to gain recognition as an expeditious means in order to reduce the facilities investment having grown that huge. This local cleaning is also effective to reduce environmental control costs at the plant. As a production example in which a local cleaning production system is applied to the entirety of the process stages at a plant, the front-end process of semiconductor integrated circuit manufacture can be given as a unique example as described in Non-Patent Literature 1. In the front-end process of this semiconductor integrated circuit manufacture, the wafers that are products are housed in containers in, and conveyed among, isolated manufacturing apparatuses. The apparatuses are each equipped with a front chamber. The front chambers have two doors. One is between the apparatus main body and the front chamber, and the other is between the front chamber and the exterior. By operating the apparatus such that one or the other of the doors is always shut, the main-body interior is shielded from the exterior at all times. The wafer containers are coupled to the front chambers. In the coupled state, this has the capacity to shield the wafer atmosphere from the exterior at a certain level of performance, enabling the exchange of wafers between the containers and the manufacturing apparatuses. Lightness, compactness, and simplicity of the mechanisms are demanded of the containers in order to secure ease of conveyance. To fulfill these demands requires ingenuity in the way the containers open and close—in particular, in the way the container doors are housed when the doors are opened. Specifically, a method for housing the container doors within the wafer containers in being coupled with the front chambers must heed the fact that door-housing space becoming necessary will mean running counter to the demands. Given these factors means that for the doors of the wafer containers, being housed into the inside of the front chamber is an appropriate coupling structure. Hewlett-Packard Co. obtained a patent (Patent Literature 1) on a coupling method in which this point is taken into consideration. The main features with this patent are that there are three subsystems: (1) front chambers, (2) wafer conveyance containers, and (3) there is a wafer transfer mechanism within the front chambers, and that the two doors are combined together and are moved into a clean internal space. The combination of the two doors is due to the following reasons. On the outside surfaces where the two doors contact the exterior containing fine particles, fine particles will cling to each. The combination of the doors traps these fine particles in between the two, and they are housed into the inside of the front chamber, making it possible to prevent diffusion of the fine particles into the local clean environment. As illustrated in FIG. 1 (a), a container 1 is composed of a container main body 3 and a container door 4, and a front chamber 2, of a front-chamber main body 5 and a front-chamber door 6, with sealing portions provided in three locations: (a) container main body 3—container door 4, (b) front-chamber main body 5—front-chamber door 6, and (c) container main body 3—front-chamber main body 5. The key point with this patent is the sandwiching capture by the two doors for fine particles attached to the door surfaces, but that does not mean that the sandwiched fine particles are eliminated from that region. And countermeasures against the risk of fine particles scattering off the edge surfaces of the sandwiched doors and contaminating the wafers are not taken. Furthermore, since it does not amount to a structure that seals the coupling between the front chamber and with the wafer conveyance container, it lacks function of completely preventing invasion of external wafer contaminating material into the front chamber and into the wafer conveyance container. Next, Asyst Technologies Inc. patented (Patent Literature 2) an improved mechanism for adding hermeticity to that of the Hewlett-Packard Co. patent, making it practicable for 200-mm wafer systems. With the Asyst Technologies Inc. patent, as illustrated in FIG. 1(b), the coupled portion consists of four structures, namely, a container (“box”), a container door (“box door”), a front chamber (“port”), and a front-chamber door (“port door”), and is characterized in that among the contacts between these four structures, the four structural intervals (a) container main body 3—container door 4, (b) front-chamber main body 5—front-chamber door 6, (c) container main body 3—front-chamber main body 5, and (d) container door 4—front-chamber door 6 are sealed in order to make them hermetically tight. Thereafter, given that the sealing system was not perfect, some patents as improvements over the Asyst Inc. patent have been registered. However, the series of improvement patents themselves have given rise to detriment such as follows, complicating the mechanisms, that is, stepped-up manufacturing costs, weight increase, creation of new fine particle generation sources, difficulties with container washing, or similar detriment. Even by means of the improvements in these patents, not only has the gas shield-off not been at a practical level, but also the fine particle shield-off has been imperfect. Later on, in about the year 2000 the wafer size had become 300-mm, a system separate from Asyst Inc.'s above-described system was proposed, and it became a world standard for 300-mm wafer conveyance systems. This standard system is called the Front-opening Interface Mechanical Standard (FIMS) system, and while being SEMI standards (chiefly SEMI Std. E57, E47.1, E62, and E63), has been patented (Patent Literature 3). FIMS employs a container-door opening that is horizontally directed and a horizontal coupling system. This is in contradistinction to the vertical coupling with the Asyst system. Further, with the Asyst system, given that the coupling is vertical, the wafers are housed in cassettes inside the containers. The two doors having been combined after coupling are housed inside, and then are moved together with the cassettes into the front chambers. In contrast, with FIMS, the cassettes are omitted. The two doors having been horizontally combined are moved into the front chamber. Then, after the doors subsequently have been lowered in the vertical direction, the wafers within the container are directly taken out to the front chamber using a wafer-transfer robot within the front chamber. Furthermore, in the FIMS patent, as differing from the Asyst patent, there is no concrete structural definition regarding the sealing structure for the contact portions of the individual structural elements. In actuality, in a practical FIMS system, a structure is rendered in which clearances of about 1 to 2 mm are deliberately provided between the individual structural elements. Specifically, clearances are provided between container—front chamber, and between front chamber—front-chamber doors. One reason for this is because if a sealing structure that relies on physical contact is provided, mechanical friction is generated in the sealing areas, and that invites large-quantity fine particle generation. But given that the clearances are provided, a drawback that occurs is that hermeticity against gas molecules is lacking in principle. It should be noted that also in the Asyst system for 200-mm wafers, based on two reasons that are: for reducing the problem of pressure fluctuations that arise within the local environment during the opening/closing of the container doors and front-chamber doors after coupling and the problem of fine particle occurrence caused by air currents stemming due to the pressure fluctuations; and for preventing the container door from becoming difficult to open under negative pressure due to a sealed container, a pressure-relief hole that passes through the exterior is established in the container. These factors result in a structure unable to actually have the shielding performance, in particular, for gas molecules. What may be understood from the foregoing illustrative antecedent instances is that in sealed-type mechanisms for sealing the individual areas, while it is possible to construct a local cleaning production system with an effective internal/external separation capacity with respect to small molecules such as gases, the downside is that the mechanical friction and the like in the sealing portions produces the side effect of fine particles occurring in numerous amounts. Conversely, if the structure with the clearances is employed, the fine particle generation can be reduced while it is unable to secure the capacity to separate gas molecules internally/externally. This is a shortcoming that the SMIF system has as a self-contradiction. The consequent problem has been that the practical systems cannot avoid the structures with imperfect hermeticity. Actually, with FIMS systems introduced as the worldwide standard in all semiconductor integrated circuit manufacturing plants handling the latest 300-mm wafers, because they have the clearances, they lack the complete shielding performance not only for gas molecules, but also for particles. As a deleterious effect, although a perfect local cleaning production system originally does not need a clean room because of shielding performance, in all actual plants, the FIMS system still has been introduced within the clean rooms. That is, the current situation is that two kinds of cleaning, by a cleanroom and by local cleaning, have become necessary. This fact has increased facilities investment expenditures and requires high-level control, thus pushing up manufacturing costs significantly. Thus, downsizing is being tried in the front-end process of semiconductor manufacturing by introducing local cleaning system. However, this does not go beyond application to manufacturing systems up to now on extended lines, in which simultaneous productivity (production quantity per unit time) has been emphasized the most as a critical factor in order to minimize manufacturing costs. That is, as is typified by the above-described FIMS, diameter scale-up in the workpiece size (silicon wafer size) and increase in the manufacturing unit count (number of orders with respect to a single product) have been given priority, thus still pointing to giant-scaled manufacturing systems, megafab so to say. FIG. 13 illustrates the effect of size on the semiconductor manufacturing system based on this megafab. For a cutting-edge semiconductor plant (megafab) in which where the wafer size is 12 inches in the current status, an apparatus count is 300 machines, the number of work in process for wafers that stays in the system is 17,000, the number of masks to be used is 34, and a floor surface area is 20,000 square meters, and the facilities investment total comes to approximately three billion dollars. In this case, the monthly production capacity provides 140 million items per year expressed in terms of 1-cm chips. However, the wafer utilization is less than 1% and the resource usage efficiency is less than 0.1%. Here, as preconditions, assume that the time required by each process (cycle time) is 1 minute/wafer, the process count for semiconductor with eight metallic layers is 500 processes, and the design rule is 90 nm. Meanwhile, there is the need for manufacturing semiconductor in very small quantities, for example, several pieces to several hundreds of pieces in a manufacturing unit for engineer samples or ubiquitous sensors. Except this very large-scale manufacturing system, this ultra-small production can be carried out without having to sacrifice cost performance that much. However in a very large-scale manufacturing system, the flow-shop system extremely reduces the cost performance for manufacturing semiconductor in very small quantities in the manufacturing line. Therefore, other kinds of products need to be manufactured in that manufacturing line at the same time. However, when a wide variety of products are input at the same time for mixed production in that manner, the productivity of the manufacturing line further decreases with increasing number of types of products. As a result, in this very large-scale manufacturing system, very small-quantity production and multiproduct production cannot be appropriately managed. Conventionally, in a device manufacturing system that employs a flow-shop system or a job-shop system, various measures against drop in utilization in with each system have been proposed (Patent Literature 4 or Patent Literature 5). PATENT LITERATURE 1: U.S. Pat. No. 4,532,970 PATENT LITERATURE 2: U.S. Pat. No. 4,674,939 PATENT LITERATURE 3: U.S. Pat. No. 5,772,386 PATENT LITERATURE 4: Japanese Unexamined Patent Application Publication No. 2005-197500 PATENT LITERATURE 5: Japanese Unexamined Patent Application Publication No. 2008-227086 NON-PATENT LITERATURE 1: “The World of Local Cleaning” (Shiro Hara, Kogyo Chosakai Publishing Co., Ltd. ISBN 4-7693-1260-1 (2006)) The inventions discussed in Patent Literature 4 and Patent Literature 5 are designed for streamlining in the flow-shop system and the job-shop system. However, with either very small-quantity production of multi-product types or large-volume production of single product types, they are not sufficient to improve the cost performance while ensuring product quality. That is, they are not sufficient to flexibly manage type-changing/volume-changing production. Further, in conventional very large-scale semiconductor manufacturing systems, the individual manufacturing apparatuses are gigantic, and thus cannot be easily moved once these are set within the plant. Consequently, it is difficult to move these apparatuses, and it is almost impossible to change the arrangement so as to shorten the conveyance paths for the products. Additionally, maintenance and repairs must be performed on-site because the apparatuses cannot be sent back to their manufacturing plant. Thus, there is the need for large-expenditure labor costs for workers sent out and for a lot of time as difficulties. The enormity of the apparatuses has been a significant factor in huge apparatus price and huge product manufacturing cost. In addition, in the front-end process of semiconductor manufacturing systems as described above, a yellow room system that shields the photosensitive resist formed onto the semiconductor wafer from the exposing light (UV light) are constructed. At this time, shielding from the exposing light is usually necessary in three processes from resist application to exposure to developing. Therefore, arranging the three stages together within the yellow room proves efficient. However, while putting these three stages into the yellow room seems to be efficient, it brings about the limitation of always having to dispose all the apparatuses for the three stages together. Specifically, this limitation does not allow an apparatus layout in the flow-shop system in which arranging apparatuses in the manufacturing-recipe order can minimize the conveyance distances, thus ensuring high-speed conveyance and minimizing the contamination opportunities. The processes from the application to the exposure to the developing are continuous processes. However, if the preceding cleaning and film deposition, the etching and the resist removal process after those three processes, and similar process cannot be included in the yellow room, the yellow room must be provided for each of these three processes. These three processes are repeated 30 to 40 times. Thus, 30 to 40 yellow rooms are required. This means that extraordinarily inefficient manufacturing facilities are necessary. In order to avoid this, the three processes alone are put together into one location as one yellow room. The result is that an efficient flow shop cannot be realized. A drawback of a yellow room in which the three processes are put together is that it necessitates the cost of building and preparing a room that blocks the exposure light. Since the room is isolated, the conveyance distances within the plant become longer. Moreover, for the workers, it is not a comfortable work environment. The current manufacturing apparatuses for microfabrication in practical use are premised on arrangement within a yellow room, thus having structure without any consideration for shielding light. The present invention has been made in view of the above-described actual situation, and its object is to provide, similarly to the above-described local cleaning production system, a local yellow-room production system that can flexibly manage type-changing/volume-changing production in the front-end process for manufacturing devices such as semiconductors. A further object is to provide a local yellow-room production system that can significantly reduce the apparatus price, the product manufacturing cost, or the maintenance cost. In particular, an object is to provide a local yellow-room production system as a coupling system that needs not to collect the apparatuses regarding the three processes together in one location, can completely shield the conveyance of workpieces between these three processes from the light for exposing the photosensitive resist on the workpiece, can shield gas molecules with a physical space separation structure, and can further eliminate the generation of fine particles. In order to solve the above-described problem, the present invention is a yellow room system that includes a plurality of portable unit process apparatuses, a conveyance container, and a light-shielding coupling structure. The plurality of portable unit process apparatuses has a same standardized outer shape. The unit process apparatus includes a yellow room configured to shield a exposure light to a photosensitive material formed on a workpiece. The conveyance container is configured to convey the workpiece between the unit process apparatuses. The conveyance container is formed as the yellow room. The light-shielding coupling structure couples the unit process apparatus and the conveyance container together. Furthermore, in the yellow room system, the conveyance container includes a conveyance-container main body, a conveyance-container door, and a first sealing structure. The conveyance-container main body forms a housing space for the workpiece. The conveyance-container door is configured to shield the housing space. The first sealing structure is configured to seal the housing space by tight coupling between the conveyance-container main body and the conveyance-container door. Each of the conveyance-container main body, the conveyance-container door, and the first sealing structure is formed of a member configured to shield a exposure light to the photosensitive material formed on the workpiece. The unit process apparatuses each include: a front chamber to be coupled to the conveyance container; and a treatment chamber to be coupled to the front chamber. The front chamber includes a front-chamber main body, an opening portion, a front-chamber door, and a second sealing structure. The front-chamber main body is formed of a member configured to shield the exposure light. The opening portion is disposed at the front-chamber main body. The opening portion is opened to the treatment chamber. The front-chamber door is configured to shield the front-chamber main body from the exposure light. The second sealing structure is configured to seal the front chamber by tight coupling between the front-chamber door and the front-chamber main body and configured to shield the exposure light. The conveyance container and the front chamber have a third sealing structure configured to: ensure sealing by tight coupling between the conveyance container and the front chamber; and shield the exposure light. The conveyance container and the front chamber have a structure configured to form one indivisible coupling chamber sealed by the third sealing structure only while the conveyance container and the front chamber are tightly coupled together so as to separate the conveyance-container door from the conveyance container. Furthermore, the following configuration is possible. A work area and a conveyance area for the workpiece are configured to shield the exposure light. The work area includes at least a treatment position of the workpiece within the treatment chamber. The conveyance area is disposed from the work area to a door opening position of the conveyance-container door. Also, the following configuration is possible. A structure is further provided and configured to open the conveyance-container door by attracting the conveyance-container door to the front-chamber door using a magnetic force of a magnet of the front-chamber door. Also, the following configuration is possible. A clearance is disposed between an magnetized object of the conveyance-container door and a magnetic material of the conveyance-container main body and a clearance is disposed between the magnetic material of the conveyance-container door and the magnet of the front-chamber door, so as to open and close the conveyance-container door. Also, the following configuration is possible. The unit process apparatus is a sealed-type treatment apparatus configured to perform a singular treatment process in a device manufacturing process. The unit process apparatus is portable. The conveyance container is a sealed-type conveyance container configured to house one wafer as a workpiece target. The wafer housed in the sealed conveyance container has a wafer size for manufacturing a device in a minimized unit. Also, the following configuration is possible. The minimized unit is one. The wafer size is 0.5 inches in diameter. Furthermore, the following configuration is possible. The unit process apparatus is constituted as an application apparatus for a photosensitive material on a workpiece. The application apparatus includes a sealed-type container main body, a supplying member, and a plug-in connector. The container main body houses the photosensitive material and is configured to shield the exposure light. The supplying member is configured to supply the photosensitive material onto a workpiece. The plug-in connector removably couples the container main body and the supplying member together. The plug-in connector has a structure configured to shield the exposure light. The plug-in connector includes a valve configured to open during coupling. Herein, “unit process apparatus” means an apparatus for treating a process unit that can be housed within the capacity of a single container with conveyability, for example, one among processes such as application, exposure, developing, and ion implantation. In addition to indicating a single treating process among conventional device-treating processes, the treating process includes a plurality of conventional treating processes as long as they can be housed within the capacity of the container (for example, together with the aforementioned, an water cleaning or a drying treatment, included in the same processing apparatus), or otherwise includes what is conventionally carried out as a single treating process divided into a plurality. Also, “including a yellow room” means either that the unit process apparatus itself is formed as a yellow room configured to shield out the exposure light, or else that a treatment space that shields out the exposure light is provided within the unit process apparatus. Further, “front chamber” means a space coupled with the treatment chamber where the workpiece is treated. However, in situations where spatial partition from the treatment chamber is not necessary, the front chamber may be the treatment chamber itself. The present invention allows providing a yellow room system that can flexibly handle type-changing/volume-changing production and that can greatly reduce apparatus prices and the product manufacturing costs, as well as maintenance costs. Also, since workers need not be present within the yellow room, the workplace environment can be improved. More specifically, the respective atmospheric pressures of the container interior, the space constituted by the three seals, and the front chamber interior can be put at the same level. This allows providing a yellow room system that does not require the container interior at the same atmospheric pressure as the external air and that can prevent debris, dust, particles, and similar material from invading the front chamber interior during opening/closing. Moreover, detaching/attaching of the container door and front-chamber door is carried out by magnetic force. Therefore, the following yellow room system can be provided. There are no sliding parts in detaching/attaching, and there is no generating of fine particles. In cases where a magnetically closed circuit is formed, the magnetism does not leak to the exterior and also the photosensitive resist on the workpiece can be reliably shielded from the exposure light. With the present invention, a conveyance container and a unit process apparatus are each constituted as a yellow room system that shields a photosensitive material formed on a workpiece, for example, a photosensitive resist formed on a wafer from an exposure light. Furthermore, the conveyance container and a front chamber in the unit process apparatus are air-tightly coupled together, only two doors required for moving the content between them are provided. One is a door to the container, and the other is a door to the front-chamber main body. These two doors have shapes that form a coupling chamber only while the conveyance container and the front chamber are air-tightly coupled together. Given that the inner sides of the coupling chamber are originally the outer sides of the two doors, they are surfaces for which there is a possibility of contamination by being exposed to exterior space. Accordingly, in the case where the coupling chamber is formed and the inside of the coupling chamber is equipped with a cleaning mechanism, this configuration can ensure more cleanliness and realize the separation between the internal space and the outside. The internal space is formed by the inner portion of the conveyance container, the inner portion of the front chamber, and the coupling chamber. With the present invention, because a spatially anchored front chamber is not required, a door furnished in between the front chamber and the treatment chamber need not necessarily be provided. Corresponding to this door, not only the required number of doors is reduced by one, but also resolve the imperfect internal/external shielding performance of the conventional local cleaning production system is resolved. In the present invention, when the front chamber and the conveyance container are coupled, a coupling chamber hermetically shield from the outside is formed. For that purpose, the following three sealing structures are furnished. To begin with, the conveyance container is constituted from a member that shields the photosensitive resist or other photosensitive material formed onto the workpiece made internally present from the exposure light. It may be constituted such that a shielding film that shields the exposure light is formed on the surface of the conveyance container. Then, by means of tight coupling between the conveyance-container main body and the conveyance container door, they have a hermetically sealable first sealing structure (Seal 1). As a mechanism employed for the tight coupling, a publicly known means such as a latch can be adopted. Next, the front chamber is configured to shield the photosensitive resist from the exposure light. Then, by means of a tight coupling between the front-chamber main body and the front-chamber door, they have a hermetically sealable second sealing structure (Seal 2). Finally, the conveyance-container main body and the front-chamber main body, by means of a tight coupling between the two, have a hermetically sealable third sealing structure (Seal 3). During coupling of the conveyance container and the front chamber, since the third seal is established in addition to the first two seals, one indivisible hermetically sealed coupling chamber is formed. These first through third sealing structures (that is, Seal 1 through Seal 3) are each constituted by a member that shields the exposure light. Therein, adopting a publicly known sealing means such as O-rings or gaskets for these sealing structures is possible. In order that the coupling chamber that is created during coupling constitutes a hermetically-sealed chamber, environments such as the pressure, fine particle-concentration, and gas-concentration in the coupling chamber is controllable. In order to control the environments, the coupling chamber is equipped with an input port and an output port, with the objective of in/outputting gas or pressure control. In this structure, combining the container door and the front-chamber door to trap and store fine particles is not necessary. With this structure, since a function of mutually shielding the exterior and manufacturing-article space completely with respect to both fine particles and gas molecules is obtained, the structure is referred to as a cleaning airtight coupling (Particle Lock Air-tight Docking, abbreviated PLAD) structure. The walls forming the coupling chamber that is formed when the front chamber and the conveyance container are combined are constituted by respective single sections of the conveyance-container main body, the conveyance container door, the front-chamber main body, and the apparatus door. In a state in which the front chamber and conveyance container are not combined, the surface of the sections that become the chamber's internal walls are in contact with external space. Thus, contaminant substances and gas molecules in the external space are attached and contaminate the surfaces. These surfaces that are exposed to the external space are still contaminated even after forming the interior walls of the coupling chamber. This contamination adhering to the walls can be discharged through an exhausting port such that a clean gas is ejected through a clean-gas injection port provided in the coupling chamber to strip away fine particles adhering to the coupling chamber interior walls from the surfaces by the blowing force of the gas. By the introduction of clean gas, gas molecules chemically adsorbed to the surfaces can be stripped away from the surfaces by replaced with the clean gas. What is crucial is that hard-stuck substances and molecules remaining on the surfaces with a strong bonding force, which cannot be eliminated by the introduction of a clean gas, can be ignored, since they will not separate off the surfaces even after the conveyance container door and the front-chamber door have been opened, because the conveyance container and the apparatus become unitary. Furthermore, the fine particles and gas molecules generated due to friction or similar reason by physical contact between the conveyance container and the front chamber during combining can also be eliminated from the coupling chamber by the introduction of a clean gas before the two doors are opened. Thus, contamination inside the coupling chamber that arises due to the formation of Seal 3 is eliminable by the present method. Also, if the atmosphere inside the coupling chamber is controlled into an atmosphere that is identical with the atmosphere of the front chamber interior, the composition of the atmosphere inside the front chamber will not vary before and after the conveyance container door and the front-chamber door are opened. After the coupling chamber has been cleaned by the clean gas, Seal 1 and Seal 2 are released. That is, by opening the conveyance container door and the front-chamber door being directed at the apparatus interior, the spaces within the conveyance container and the front chamber become unitary. This enables conveyance of objects between the two. At this time, when Seal 1 and Seal 2 are physically pulled apart, there is a possibility that some fine particles and gas molecules might issue from the locations where these seals and the two doors each face against the members of the conveyance container and the front chamber. If these contaminants that have been generated invade the conveyance container interior and the front chamber interior, they become a source of contamination of the conveyed objects. Consequently, an expedient to move the contaminants that have been generated at the seals toward the coupling chamber is necessary. Movement of the contaminating substances into the coupling chamber is made possible by setting the atmospheric pressure of the coupling chamber lower than atmospheric pressure of both the inside of the conveyance container and the inside of the front chamber. This is because matter flows in the direction of lower atmospheric pressure. Contaminant substances attracted to the coupling chamber are discharged through the exhaust hole to the outside. Thus eliminating contaminant substances generated at the coupling sections is possible as long as the inside of the container is airtight and the coupling chamber is provided. In cases where the atmospheric pressure of the coupling chamber is at a pressure differential of a certain extent with respect to the atmospheric atmospheric of the conveyance container interior and the front chamber interior, however, there is a possibility that working against this pressure differential to open the conveyance container door and the front-chamber door may prove difficult. As is clear from the foregoing structures and operations, the coupling chamber that is temporarily formed can be vacuum-exhausted. Accordingly, even in situations where the front-chamber main body and the conveyance container interior are at vacuum pressure, drawing a vacuum on the coupling chamber makes it possible to open the door in a state where there is essentially no pressure differential between the two sides of the door. In general, in vacuum devices, it is often the case that the vacuum-device body is always maintained at a vacuum in order to avoid the time for returning the vacuum in the vacuum-device body to air and to avoid contamination produced on that account. For that purpose, ordinarily a chamber is provided in the vacuum device. The chamber goes back and forth between air and a vacuum. For that reason the chamber is sometimes called an air-lock chamber. With the present invention, inasmuch as the coupling chamber plays the role of the air-lock, that is, because it goes back and forth between air and a vacuum, a fixed chamber of the conventional type is unnecessary. Ordinarily, since the chamber itself possesses a door and a conveyance mechanism, the volumetric capacity of the chamber is relatively large. Thus, a fair amount of time is required also to exhaust the chamber. On the other hand, with the present invention, the rather small space made when the container and the front chamber are combined is enough for the coupling chamber. Accordingly, purification of the coupling chamber itself during coupling does not take that much time, and it is enough that the device required therefor be small-scale. In situations where contamination of the product due to fine particles becomes a problem, especially, an operation to purify the coupling chamber is necessary. On the other hand, in situations where fine particle contamination is not a problem, but gas-molecule contamination is a problem, if the influence of the contamination is not relatively serious, it is possible to omit the gas-introduction and gas-exhaust ports from the coupling chamber. The volumetric capacity of the coupling chamber is extremely small compared with conventional front chambers. Therefore, the absolute quantity of the contaminating substances in the interior is slight. Then, the contaminating substances are diluted by dispersing inside the volume of the conveyance container and the manufacturing apparatus. The concentration of the contaminating substances drops by, for example, four digits or more. In applications in which, with a diluted contaminant concentration, there are no problems, drawing a vacuum on the coupling chamber in order to purify it, installing a port in order to introduce clean gas, or the like are not necessary. Next, a method of opening/closing the conveyance container will be described. The conveyance container door has a structure whereby it opens onto the front chamber interior after it is combined with the front chamber. With a method, supposing, whereby the container door is opened outward of the container prior to it being combined, one more door would be necessary, so that the container interior not be exposed to the exterior. Therefore, this would be disadvantageous in terms of economy of space and efficiency of the mechanisms. With a method whereby the conveyance container door is housed into the interior of the container, drawing it in depth-ward increases the volumetric capacity by the amount used by the movement of the conveyance container door. Therefore, the conveyance container scales up, which is not desirable. Accordingly, the door of the conveyance container is housed into the front chamber interior. For the structure for housing the door inside the conveyance container, it is possible to adopt the system employed in residential doors, in which hinges are put on the door to open and close it. But since large quantities of fine particles are generated from a sliding portion of the hinges, this also is not a suitable method. In the present invention, the conveyance container door is separately housed into the front-chamber main body. Seal 1, hermetically sealing the conveyance container door and the conveyance-container main body, is positioned in between the conveyance container door and the conveyance-container main body. When the conveyance container door moves perpendicularly to be housed into the front-chamber main body, there is no lateral slipping against the seal, and therefore friction between the door and the body is held to a minimum. The container door opens/closes by means of a door-hook mechanism or the like provided with the front-chamber door. In the present invention, as a mechanism to reduce the generation of fine particles and gas molecules, a magnetic hook mechanism is utilized. With generally used mechanical key mechanisms, in which the sliding parts are numerous, large quantities of fine particles are generated by the sliding movements that arise during opening/closing. Consequently, they should not be used in cases where high-level purification is demanded. The opening/closing mechanism using magnetism does not involve mechanical operations and does not cause sliding movements. Therefore, the quantity of fine particles generated is markedly slight. Thus, this mechanism suits high-level purification. With the present invention, magnetic materials (at least one of which is a magnet) are provided on the conveyance-container main body and the conveyance container door. The conveyance-container main body and the conveyance container door are closed by the attractive force between the magnetic materials. With a magnet incorporated into the front-chamber door, the conveyance container door is attracted to the front-chamber door by the magnetic force. Thus, the conveyance container door is opened. In that case, in order to adjust the magnetic force that operates, depending on the situation, it may be necessary not to bring the electromagnets, magnetic materials, or similar member into close contact with one another. Although a magnetic opening/closing mechanism as in the present invention is superior to a mechanical opening/closing mechanism in terms of purification, the magnetic opening/closing mechanism is inadequate in some respects as an actual opening/closing mechanism for the conveyance container. One of the reasons is that magnetic force is strongly dependent on the interval between the magnetic materials, the attractive force rapidly grows strong at the interval of 1 mm or less, and conversely, the attractive force rapidly grows weak at the greater interval. Thus, advanced precision is demanded of the product structures. Especially in situations where the magnetic materials have come into contact, seen from a micro-scale, the magnetic-material surfaces are rough. If the precision does not reach the micron level, the force of magnetic attraction will not be what is intended. And in situations where there are a large number of the same items like the conveyance containers, since the individual containers will have slightly different dimensions, there is a likelihood that the magnetic attractive force will differ among the individual containers. In order to avoid the foregoing problems, in the present invention, a structure may be adopted whereby the distances between the magnetic materials are controllable. Since the change in attractive force at the micro-scale distances at which the two magnetic materials contact is abrupt, the objective is to avoid such approaching distances so as not to use them in practice. Having the design be to keep the distance apart at the level of several tens of microns ensures a comparatively reduced difference in attractive force at a 10 μm precision tolerance. In addition, in order to compensate this reduced difference in attractive force, the magnetic force of the release mechanism on the apparatus side is determined using a magnetic force that provides the weakest attractive force as reference. [Conveyance Container] A conveyance container in the present invention is a hermetic container for conveying objects (workpieces) that produce some hindrance such as contamination or reactions by being exposed directly to the external air, and is configured so as to shield photosensitive material formed on the objects from an exposure light. The “objects” widely employ objects to be handled at present within apparatuses such as clean rooms and glove boxes that are used in a variety of applications such as semiconductor substrates and sensor substrates. In accordance with the characteristics of the properties of the objects to be conveyed, the materials and characteristics of the conveyance-container main body and door can be selected. For example, materials excellent in moisture resistance and dimensional stability, such as poly(meth)acrylate, polycarbonate, polyethylene terephthalate, quartz, and glass are preferably employed. In order to open/close the conveyance container door under magnetic force as described above, a magnetic material and a magnet are disposed in locations tightly sealed with the door on the conveyance-container main body formed by at least these materials. And in order that the conveyance container have light-blocking properties, these materials are selected as materials that shield the exposure light, or a shielding layer that shields the exposure light is provided on the surface of the materials. Of course, the size of the conveyance containers is decided in connection with the size of what is conveyed. Further, it is possible to provide a plurality of chambers in one conveyance container in order to house a plurality of objects. For example, it is possible to provide one door on each of the front and rear surfaces of one conveyance container, and provide an isolated chamber in the interior thereof. Alternatively, it is possible to provide a plurality of doors adjacent to one another on the surface of a discoid conveyance container, and provide respective chambers corresponding to doors. When conveyance container is used solitarily as a container, for example, in the midst of conveyance of the conveyance container, it is preferred to provide a mechanism for locking the door so that the door does not open accidently or to provide a mechanism for automatically releasing the lock when the conveyance container and the front chamber are air-tightly coupled together from a usability aspect. Accidental movement of the object housed within the conveyance container makes it difficult to open the door of the conveyance container so as to introduce the object into the front chamber interior or increases the possibility of damage of the housed object itself. Therefore, it is necessary to provide some sort of means such as a pressing member for anchoring the housed object. [Interface Between Conveyance Container and Front Chamber] The surface on the door side of the conveyance container coupled to the front-chamber door. Here, it is necessary to position the door of the conveyance container with respect to the front-chamber door with high-level precision and without displacement. In this respect, this is the same in instances where the conveyance container is coupled manually to the front-chamber door or instances where it is coupled in the conveyance apparatus. If there are areas where there is sliding friction between the conveyance container and the front-chamber door, those areas will cause particles and then may contaminate the front chamber interior or contaminate the objects in the conveyance container interior. For this reason it is necessary to provide a specialized structure on the door side of the conveyance container. Firstly, the conveyance container door is installed in a way to be embedded into the conveyance-container main body. Then on the peripheral edge portion of the surface on the door side of the conveyance-container main body, an inclined portion over the lateral surface of the conveyance container is provided. This inclined portion is disposed to engage an inclined portion that is provided on the peripheral edge portion of a port in the front-chamber main body and provided directed toward the center portion of the port. In addition, in a portion of the conveyance-container main body around the door of the conveyance container, a plurality of protrusion portions is provided, and the protrusion portions are fit to depressed portions provided in the port of the front-chamber main body. Furthermore, three distal ends are provided as hemispherical projections on the exterior surface of the conveyance container door. Corresponding to the protrusions, three V-shaped grooves are provided radially in the front-chamber door surface. Utilizing the conveyance-container main body, the conveyance container door, the front-chamber main body, and the front-chamber door in this structure, the conveyance container is coupled to the front-chamber door in the following manner at a high level of precision. At first, the conveyance container having been drawn close to the front-chamber main body begins to be inserted to fit the above-described inclined portion provided on the peripheral edge portion of the surface on the door side of the conveyance-container main body with the inclined portion provided on the peripheral edge portion of the port in the front-chamber main body. In the middle of the insertion, the conveyance container is positioned with the front-chamber main body to an extent where there is a certain amount of looseness. Subsequently, the plurality of protrusion portions provided on the portion of the conveyance-container main body around the conveyance container door are fitted into the depressed portions provided in the front-chamber main body port. At that point, the aforementioned certain amount of looseness is fairly curtailed so as to control rotation of the conveyance container with respect to its perpendicular axis to a certain extent. In that state, when the conveyance-container main body draws nearer to the front-chamber door, the three protrusions with the hemispherical distal ends provided in the door of the conveyance container enter into the aforementioned three V-shaped grooves provided in the door of the front-chamber main body. At that time, the two opposing diagonal surfaces that constitute one of the V-shaped grooves each come into contact with the hemispherical protrusion. The hemispherical protrusion comes into contact with the two opposing diagonal surfaces in two locations. As a result, jerking of the conveyance container in the rotation direction with respect to the perpendicular axis disappears, and also jerking in the horizontal direction is eliminated by the three V-shaped radially patterned grooves. This mechanism does not allow the conveyance container to move other than along the vertical with respect to the apparatus and anchors the conveyance container. The following describes an exemplary embodiment of the present invention by referring to the accompanying drawings. With the present invention, a conveyance container and a unit process apparatus are each constituted to shield a photosensitive material formed on an object (workpiece), for example, a photosensitive resist formed on a wafer from an exposure light. FIGS. 10 through 12 are diagrams for explaining the overall unit process apparatus of the present invention. As illustrated in the diagram, a unit process apparatus 50 is made up of a lower treatment apparatus 51, an upper treatment apparatus 52, and a coupling portion 60 that separably couples them, and is configured to move by portable devices 61 provided on the lower part. These unit process apparatuses have an identical external form, with the outer shape standardized to desktop size. Herein, “desktop size” is a size on the order at which a person can relatively easily carry it about, and is specifically set to x: 294 mm, y: 450 mm, Z1: 700 mm, and Z2: 740 mm. The upper treatment apparatus 52 houses a wafer exposure apparatus as a treatment apparatus. In the lower treatment apparatus 51, control devices for controlling these apparatuses and similar device are disposed. On the lateral surface of the upper treatment apparatus 52, an inspection window 57 is formed. The inspection window 57 is constituted from a light shielding material having transparency, so that the exposure light for the photosensitive resist does not enter the treatment apparatus interior. Further, a space of requisite size is disposed to hollow the upper treatment apparatus 52 along its front side toward depth side. An upper stage 55 is disposed facing this space. On top of the upper stage 55, a docking port 56 for coupling to the conveyance container is provided. Beneath this docking port 56, a front chamber 80 is provided. That is, the upper treatment apparatus 52 is constituted by the front chamber 80 and a treatment chamber 81 that is coupled to the front chamber. This front chamber 80 includes a conveyance apparatus (not-illustrated) that transfers a workpiece conveyed in from the docking port 56 to the front chamber 80 interior between it and the treatment chamber 81. At the same time, on the front side of the front chamber 80, a front-face panel 53 is detachably provided. By removing the front-face panel 53, maintenance of the conveyance apparatus or similar apparatus can be performed. On top of the upper stage 55, switches including a power-source switch or similar switch are disposed. Above the front chamber 80, across a space therefrom, a display device 54 doubling as an operation panel is provided. Above the display device 54, a status display device 54′ constituted of light emitting diodes or similar member for displaying the operational status of the unit process apparatus is provided. It should be noted that if it is necessary to spatially segregate the front chamber 80 and the treatment chamber 81, as illustrated in FIGS. 2 through 4, a shutter 82 can be provided for convenience, but the shutter 82 is not essential to the present invention. The weight of the unit process apparatuses 50 differs according to the content of the treatment apparatuses that each unit process apparatus 50 includes, but standardly they are approximately 60 kilograms. Accordingly since they may be hauled easily utilizing the portable device 61 or similar device, the layout change among flow-shop and job-shop, multi-cell shop, class-shop layouts, and similar layout is facilitated. Further, the upper treatment apparatus 52 has approximately a rectangular parallelepiped shape in desktop size, and a standard weight of approximately 30 kilograms. Accordingly, only the upper treatment apparatus 52 is easily hauled separately from the unit process apparatus 50 by the coupling portion 60. Thus separating the upper treatment apparatus 52 and moving it to a requisite place facilitates the inspection/repair, improvement, or similar work for the functions as the unit process apparatus 50. As illustrated in FIG. 11 and FIG. 12, for this embodiment, an exposure apparatus is housed in the treatment chamber 81, and above a work table 65 on which the workpiece conveyed from the front chamber 80 is placed, a UV light source 70, a workpiece detection camera 71, and a monitoring camera 72 for alignment are arranged. Furthermore, these are configured so as to be selectively arranged in predetermined positions on the workpiece, by sliding in the left right directions set forth in FIG. 12. Accordingly in situations where the alignment is finished and the step transitions to the exposure step, the UV light source 70 is arranged on the work table 65, and the light is irradiated directly downward. Accordingly as illustrated in FIG. 11, a space in the vicinity of underneath the docking port 56 in the front chamber 80, that is, the space where at least the workpiece is conveyed is a space that is optically shielded from the UV light source 70. Reference numbers 61, 62 and 63 are, respectively, x-, y- and z-axis adjusting mechanisms of the work table 65. FIG. 1(c) is a diagram in which a conveyance container 7 and a front chamber 8 (same as the front chamber 80) that constitute a coupling system of the present invention are air-tightly coupled together. As described above, as a result of air-tight coupling between the conveyance container 7 and the front chamber 8, a coupling chamber 10 that is defined by a container door 12 of the conveyance container 7 and a front-chamber door 9 of the front chamber 8 is formed to fulfill the role of a front chamber in conventional coupling systems. A front chamber in conventional technology functions in order to couple the external air and an apparatus interior under different environments, for example, under atmospheric pressure and under reduced pressure, or under atmospheric pressure and under a specified atmosphere, so as to carry an object housed in a conveyance container into the apparatus interior. In contrast, in the present invention, with the above-described coupling chamber 10 as if this sort of front chamber is used, the environment in the coupling chamber 10 interior can be adjusted from the same environment as that of the exterior directly after tight coupling so as to be the similar atmosphere to the atmosphere inside the front chamber through a gas supplying port 15 and a gas discharging port 16 that are coupled to the coupling chamber in the interval until the container door 12 and the front-chamber door 9 become integral and are moved toward the inside of the front chamber to open the two doors. For what is associated with processes for treatment under a vacuum like semiconductors, particularly, this sort of supply and discharge of cleaning gas are demanded. In this case, in manufacturing facilities utilizing apparatuses that differ per each of the plurality of processes, the respective apparatuses employed in the processes each require a coupling system of the present invention. If the atmosphere within an apparatus is a vacuum, the gas inside of the coupling chamber 10 is discharged from the gas discharging port 16 by a vacuum pump or similar method, subsequently if necessary, an inert gas is introduced into the coupling chamber from the gas supplying port 15, and then the operation for discharging this gas from the gas discharging port 16 is repeated an arbitrary number of times. This allows putting the environment inside the coupling chamber 10 containing fine particles at the same level as that of the environment inside the front chamber. Of course, in accordance with the objective level of cleanness and the atmosphere within the front chamber, if necessary, the environment within the coupling chamber 10 can be made to approach the environment within the front chamber. In this way, the present invention enables tight coupling of a conveyance container directly to a front chamber. Therefore, the gas supplying port 15 and gas discharging port 16 can be provided in the front chamber 8 such that these ports are connected in the coupling chamber 10 formed by the tight coupling. To circulate the gas within the coupling chamber 10 so as to clean the inside by these ports, it is necessary that the gas circulate entirely throughout the coupling chamber 10 and it is also necessary that the gas circulate so as to remove particles or similar material attached to the opening portion in the conveyance container 7 and the opening portion in the front chamber 8 where the container door 12 and the front-chamber door 9 have been in close contact with each other. The details of the tight coupling between the conveyance container 7 and the front chamber 8 utilized in the coupling system of the present invention will be described as follows, giving the example of introducing a wafer 17 for manufacturing semiconductor devices into the apparatus. The example is not limited to this. For example, microorganism cultures or unstable chemical compounds can be introduced. In FIG. 2, the conveyance container 7 is formed of a conveyance-container main body 11 and a container door 12. The conveyance-container main body 11 and the container door 12 are air-tightly sealed by publicly known sealing means. Accordingly, the conveyance container 7 interior is shielded from exposure lights. The conveyance-container main body 11 includes a member that supports the wafer 17 from the container door 12 toward the interior of the conveyance-container main body 11. Taking into consideration the container 7 and the front chamber 8 after having been tight coupled, the conveyance container 7 can be provided with a magnet 18 on a wall portion of the conveyance-container main body 11, and a magnetic material 19 such as iron can be provided in a location of the container door 12 that abuts the wall portion of the conveyance-container main body 11. In that case, the locations where the wall portion of the conveyance-container main body 11 and the magnetic material 19 in the conveyance container door 12 are provided are extended, and an electromagnet 14 is arranged in a location of the front-chamber door 9 that abuts with the location of the conveyance container door 12 where the magnetic material 19 is provided. In the state of FIG. 2, as for the conveyance container 7, the conveyance-container main body 11 powerfully adheres tightly to the container door 12 under magnetic force, and the interior of the conveyance-container main body 11 is securely shielded from the external air. The front-chamber door 9 of the front chamber 8 is tightly adhered to the front-chamber main body 13 securely by whatever means. Also, the front-chamber main body 13 is reliably shielded from the external air. It should be noted that as described above, in the front chamber 8 (that is, the front chamber 80 in the unit process apparatus), a partitioning door 82 for spatial partition from the treatment chamber 81 as needed is provided at the coupling portion with the treatment chamber. This is provided in cases where, for example, it is necessary to prevent the direct irradiation of the exposure light from the treatment chamber 81 onto the workpiece within the front chamber 80. However, when there is no such risk, the partitioning door 82 is not necessarily required. In situations where the partitioning door 82 is not provided, the front chamber 80 and the treatment chamber 81 have the same environments such as atmospheric pressure. Therefore, placement of the conveyance container 7 on the docking port 56 in the upper part of the front chamber 80 will be the same as direct coupling between the conveyance container 7 and the treatment chamber 81. From the state as in FIG. 2, next, as illustrated in FIG. 3, the conveyance container 7 with the container door 12 directed downward is placed so as to overlap front-chamber door 9 of the front chamber 8. In that situation, it is important to accurately overlap the conveyance container 7 and the front chamber 8 by, for example, providing an alignment pin in one of either the conveyance container 7 or the front chamber 8 while providing a hole for fitting over the alignment pin. The mechanism for aligning is not limited to a pin, adopting a publicly known aligning means is possible. The front-chamber main body 13 and the front-chamber door 9 are also sealed airtight by publicly known sealing means. Accordingly, with the front-chamber door in a closed-door state, the front chamber interior is shielded from the exposure light. After the conveyance container 7 has been placed in the accurate position on the front chamber 8, an operation to tightly coupling the two is carried out. If a tight coupling is not performed, the conveyance container 7 and the front chamber 8 are not sealed airtight and a clearance is to be formed between them. When the door is opened in that state, external air invades into the conveyance container 7 and into the front chamber 8, and their interiors become contaminated with the external air, fine particles, and similar material. As the means for tight-adhere coupling, a publicly known means such as a latching mechanism is satisfactory. For the tight-adherence strength, strength to an extent that a seal of a gasket or other publicly known sealing means interposed between the conveyance-container main body 11 and the front-chamber main body 13 functions effectively is favorable. This tight-adhere coupling ensures a structure where the exposure light does not escape from the tightly adhering areas. After the conveyance container 7 and the front chamber 8 have been tightly adhered, an airtight sealing structure is formed by a publicly known sealing means provided in any one or both of the conveyance-container main body 11 and the front-chamber main body 13. Then, to set the environment in the coupling chamber 10 formed between the container door 12 and the front-chamber door 9 partitioned by the sealing means to be the same as the environment within the front chamber, the gas supplying port 15 and the gas discharging port 16 provided in the front chamber in advance are utilized to adjust the environment within the coupling chamber 10. A specific adjusting method is to reduce the pressure by exhausting the air within the coupling chamber 10 whose environment initially is the same as the external air through the gas discharging port 16. Subsequently, an adoptable method includes introducing, for example, desiccated nitrogen gas from the gas supplying port 15 and then exhausting it through the gas discharging port 16 to reduce the pressure, as well as a method for repeating this method. According to such methods, in the coupling chamber 10 initially under the same environment as that of the external air and where contaminant substances such as fine particles other than reactive gases such as oxygen exist, the fine particles and similar material removable by gas flows due to exhausting and supplying gases are removed. Also, the reactive gases such as oxygen are discharged at the same time. Thereafter the environment is adjusted to be the same as the environment inside the front chamber 8. That is, if the front chamber 8 interior is at reduced pressure, the coupling chamber 10 is adjusted to be also at reduced pressure. If the front chamber 8 interior is under an inert-gas atmosphere, the coupling chamber 10 is also adjusted to be under an inert-gas atmosphere. Of course, adjustment of the environment within the coupling chamber 10 may be performed by a different process. This adjustment of the environment within the coupling chamber 10 is not particularly changed from adjustment that has taken place in front chambers in conventional apparatuses (that is, front chambers physically spaced apart from the treatment chamber). However, compared with conventional front chambers, the space within the coupling chamber defined by the doors of both the conveyance container 7 and the front chamber 8 or similar member is overwhelmingly small. Accordingly, it is sufficient that the apparatuses required to supply and exhaust the gases be smaller-scale apparatuses and a far shorter period of time is enough for the requisite amount of time. In addition, a description will be given of a method for moving the wafers housed within the transport container 7 to the front chamber 8 interior. Although not illustrated in the figures, a device such as an elevator for opening/closing the front-chamber door 9 is provided within the front chamber 8. The wafer fixed to the container door of the conveyance container 7 is transported to the inside of the front chamber 8 along with the container door 12 and the front-chamber door 9 to undergo treatment by treatment means within the apparatus. When the container door 12 and the front-chamber door 9 that are integrated together are moved to the inside of the front chamber 8, the tight adherence between the container door 12 and the conveyance-container main body 11 is released. As an example of means for this releasing, the following means may be given. The magnetic material 19 provided on the container door 12 adheres magnetically to the magnet 18 while receiving the magnetic force of the magnet 18 provided on the wall of the conveyance-container main body 7. Accordingly, in order to release the container door 12 from the conveyance-container main body 11, it is necessary to apply force to the magnetic material 19 against the magnetic force from the magnet 18 acting on the magnetic material 19 in the releasing direction of the container door 12. In FIG. 3, by passing a current into the electromagnet 14 provided on the front-chamber door 9, magnetic force is applied to the magnetic material 19. Thus, the magnetic force acting on the magnetic material 19 becomes stronger by the electromagnet 14 rather than by the magnet 18. As a result, a closed magnetic circuit is formed so as to magnetically adhere the container door 12 to the front-chamber door 9. By moving the front-chamber door 9 downward in a state in which the container door 12 is magnetically adhered to the front-chamber door 9 in this way, as indicated in FIG. 4, the front-chamber door 9 and the container door 12 are together entered into the front chamber interior. The passing of electricity into the electromagnet may be halted at the point when the magnetic force from the magnet 18 into the container door 12 has weakened to a certain extent. In this state, the coupling chamber 10 constituted from the front-chamber door 9 and the container door 12 communicates with the space inside the front chamber 8. However, since the coupling chamber 10 is already under an environment that is the same as the environment within the front chamber 8, contamination within the front chamber originating in the coupling chamber 10 is not to be seen. It should be noted that this example is an instance in which the gas supplying port 15 and the gas discharging port 16 are provided on the front chamber 8, but in some cases these ports need not be provided. Such a case is where comparing the volumetric capacity of the front chamber 8 with the volumetric capacity of the coupling chamber 10, the internal volume of the coupling chamber 10 is overwhelmingly small such that even supposing that fine particles and gases present in the coupling chamber 10 were to mix into the atmosphere within the apparatus, the level of contamination would be extremely small such as to be ignorable. In that case, in order to have environments such as atmospheric pressure in the formed coupling chamber 10 and inside the front chamber 8 be the same, an open/closable channel communicating the front chamber 8 interior and the coupling chamber 10 interior may be provided on the front-chamber door 9, so that after the conveyance container 7 and the front chamber 8 have tightly adhered so as to form the coupling chamber 10, opening this channel communicates the coupling chamber 10 and the front chamber 8 interior. Furthermore, it is possible to have the orientation of the front chamber 8 and the front-chamber door 9 of the above-described embodiment example be directed sideways or downward, and container door 12 of the conveyance container 7 be directed sideways or upward. A different mechanism for opening/closing the container door and the front-chamber door will be described based on FIG. 5. FIG. 5 is a diagram of a state in which a conveyance container 21 is tightly adhered to a front chamber 20, and a container door 23 opposes the upper surface of the front-chamber door 22, and a portion of the conveyance-container main body 25 around the container door 23 opposes the front-chamber main body 24. In the front-chamber door 22, an electromagnet 26 is embedded and the leading edge thereof is exposed onto the upper surface of the front-chamber door 22. Magnetic materials 27 are embedded penetrating the container door 23 from its front surface to its rear surface so as to oppose a position on the leading edge of the electromagnet 26. The magnetic materials 27 are embedded as a plurality, and this plurality of magnetic materials 27 is coupled to either end of a magnet 36 by magnetic force. Then, one or more sets composed thus of two magnetic materials 27 and a magnet 36 are embedded. Furthermore, on the inner side of the container door 23, that is, in locations where the magnetic materials 27 are exposed on the conveyance-container main body side, magnetic materials 28 embedded in the conveyance-container main body 25 exert magnetic force. The container door 23 is fixed to the conveyance-container main body 25 by the attractive force from the magnetic force produced between the magnetic materials 27 embedded inside and the magnetic materials 28 embedded in the conveyance-container main body 25. Therefore, the interior of the conveyance-container main body 25 is hermetically sealed by the container door 23. The plurality of magnetic materials 28 embedded in the conveyance-container main body 25 are coupled by a magnetic material 29 in locations separated from areas opposing the container door 23. In that state, the magnetic force couples the container door to the conveyance-container main body so as to form a closed circuit. Inside the conveyance-container main body 25, a treatment target object 30 is housed. The treatment target object 30 is fixed to the container door 23 to be movable together with the container door 23 between it and the front chamber 20 interior. In order to have the treatment target object be movable within the front chamber or within the container while preventing the invasion of external air and invasion of fine particles into the front-chamber main body 24 or conveyance-container main body 25, the conveyance container 21 and the front chamber 20 need to closely adhere so as to form a coupling chamber that is airtight with respect to the external air. For that purpose, in FIG. 5, a sealing member 31 such as an O-ring for air-tightly sealing between the conveyance-container main body 25 and the container door 23 is provided, a sealing member 33 such as an O-ring for air-tightly sealing between the front-chamber main body 24 and the front-chamber door 22 is provided, and a sealing member 32 such as an O-ring for air-tightly sealing the conveyance-container main body 25 and the front-chamber main body 24 is provided. These sealing members enable the interior of the conveyance container 21 and the interior of the front chamber 20 to enter into a state in which the interiors are shielded from the external air, of course when the conveyance container 21 is coupled to the front chamber 20, but also when it is not. Furthermore, to enable the conveyance container 21 to couple accurately to the front chamber 20, and the treatment target object 30 inside the conveyance container 21 to traverse the interior of the front-chamber main body 24 and be accurately treated, it is necessary to accurately fit a plurality of alignment pins 34 provided in the conveyance-container main body 25 into a plurality of holes or grooves provided in the front-chamber main body 24 or similar measure. While of course the alignment pins may be provided on the front chamber side and the holes or grooves provided on the container side, taking operability into consideration it is preferable that the alignment pins be provided on the container side and the holes or grooves be formed on the front chamber side so as to fit together with the alignment pins. The shape of the tips of the alignment pins 34 may be globular, conical or pyramidal insofar as the pins have distinct tips. The holes or grooves 35 may have an inner-surface shape reflecting the shape of the tips of the alignment pins so as to fit together with the alignment pins 34. In particular, V-shaped grooves or U-shaped grooves are preferable. At this time, two points near the tips of the alignment pins 34 may be made to come into contact with two points near the bottom parts of the holes or grooves 35. Then, for example, in the case where the tips of the alignment pins 34 are globular and the holes or grooves are V-shaped grooves, the globular portion of the tip of the alignment pins may be positioned into the center part of the V-shaped grooves 35. Such aligning means enable the conveyance container 21 to be accurately and securely coupled to the scheduled position in the docking port 56 of the front chamber 20. Although not illustrated in FIG. 5, a gas supplying port and a gas discharging port as represented in FIG. 2 are provided in the front chamber 20. The interval between the conveyance-container main body 25 and the front-chamber main body 24 is sealed airtight by a sealing member 32. Therefore, filling the coupling chamber with any gas as well as putting the coupling chamber under any pressure are possible so as to accord the coupling chamber formed between the front-chamber door 22 and the container door 23 with the atmosphere inside the front chamber 20 and the conveyance container 21. In FIG. 5, the shape of the container, the front chamber and their doors, the shape of the electromagnet, the shape of the magnetic materials, and the pins and holes or grooves are not limited to what is illustrated in the drawings. Insofar as the same functions are demonstrable, they may have any shapes. Also, it is possible to have the electromagnet 26 be a magnet instead. Further, as illustrated in FIGS. 2 through 4, the apparatus illustrated in FIG. 5 is one in which the container door is moved together with the front-chamber door into the front chamber, and where predetermined treatment take place within the front chamber. In the state illustrated in FIG. 5 and the state in which the conveyance container is positioned in a place separated from the front chamber, only the relationship between the respective magnetic materials and electromagnet is illustrated in FIG. 6. In FIG. 6 the conveyance container is positioned in a place separated from the electromagnet, and the electromagnet does not have electromagnetic force. Meanwhile, in the conveyance container, two magnetic materials 27 coupled together by the magnet 36 embedded in the container door are present. The magnetic materials 28 provided on the conveyance-container main body are coupled to the respective the magnetic materials 27. Further, these magnetic materials 28 are coupled together by the magnetic material 29. As a result of this coupling, a circuit is formed by the magnetic forces from the respective magnetic materials, in the direction of the arrow as illustrated in FIG. 6. Likewise, FIG. 7 illustrates the relationship between the magnetic materials and the electromagnet in a state in which the container door has not yet been opened when magnetic force from the electromagnet 26 has been generated after the conveyance container has been coupled to the front chamber. At first, when current is flowed into the electromagnet 26 and electromagnetic force is generated, the magnetic force lines directed toward the magnetic materials 28 inside the magnetic materials 27 prior to this magnetic force generation stops being directed toward the magnetic materials 28 under the magnetic force of the electromagnet. Then, the magnetic force lines are redisposed in the direction of the electromagnet. As a result, a magnetic circuit from magnet 36 to magnetic material 27 to electromagnet 26 to electromagnet 26 to magnetic material 27 is formed. The magnetic materials 27 and the electromagnet 26 thereby come to possess strong attractive force. This fact means that in the magnetic circuit constituted with the conveyance-container main body 25 and the container door 23, the magnetic lines between the magnetic materials 27 and the magnetic materials 28 weaken considerably, such that as an actual magnetic circuit it is severed. That is, with the attractive force between the magnetic materials 27 and the magnetic materials 28 growing extremely weak, the magnetic lock between the conveyance-container main body 25 and the container door 23 is released. In the manner above, generating magnetic force through the electromagnet releases the magnetic lock between the conveyance-container main body and the container door, and the electromagnet and the container door are magnetically locked. Thus, the container door can be opened. In this way, since opening/closing of the container door and opening/closing of the front-chamber door can be carried out at the same time by the action of the electromagnet. This allows preventing external air and external fine particles from flowing into the inside of the container and the inside of the front chamber. At this time, a closed magnetic circuit is formed both before and after the opening/closing of the container door. This eliminates escaping of magnetic force to the exterior. FIG. 8 illustrates a schematic diagram of a structure viewed from the inner side of the conveyance-container door. This container door 12 is configured such that the door is embedded in an opening portion of the conveyance container 11 to be closed. The container door 12 has a disk shape that has an inclined surface 37 non-vertical to the top and inferior surfaces of the container door 12 in the whole circumference. On the inner side of the container door 12, three stops 38 for holding a conveyance target object (not illustrated). For example, a conveyance target object in a circular plate shape is placed on or fitted to these stops 38 to be held. On the exterior surface of this container door 12, grooves 41 are disposed. In this container door 12, magnetic materials 39 and magnets 40 are embedded. Based on FIG. 8 and FIG. 9, a description will be given of a process for closing the container door 12 with respect to the conveyance-container main body 11 After the conveyance target object (not illustrated) is held by the stops 38 of this container door 12, the container door 12 is fitted to the conveyance-container main body 11 that includes alignment pins 34 with respect to the front chamber to enclose the conveyance target object in this conveyance container 11. In this case, the conveyance-container door illustrated in FIG. 8 is flipped upside down so as to fit the inclined surface 37 of this container door 12 to an inclined surface 43 on the inner side of the conveyance container 11. At this time, the grooves 41 disposed in the peripheral area of this container door 12 engage with pins 44 disposed inside of the conveyance container. Additionally, at the same time, the inclined surface 37 that is disposed in the peripheral area of the conveyance-container door and disposed conforming to the inclined surface 43 approaches the inclined surface 43 forming the inner surface of this conveyance-container main body to be gradually brought into contact with the inclined surface 43. Consequently, this conveyance-container door is fitted to this conveyance-container main body, and the inclined surfaces 37 and 43 are brought into contact with each other at the same time. Furthermore, as described above, the magnetic materials 39 of this container door 12 are arranged to face the magnetic materials 42 disposed inside of the conveyance-container main body 11. At this time, the magnetic field lines of the magnets 40 are oriented in the direction of the magnetic materials 42 through the magnetic materials 39. Accordingly, the magnetic materials 42 on the conveyance-container main body 11 side is attracted to the magnetic materials 39 on this conveyance-container door side by magnetic force. Thus, this container door 12 is fixed to this conveyance-container main body 11. Accordingly, the conveyance container and the front chamber of this unit process apparatus are air-tightly coupled together. Only two doors are required for moving the content between these members. One is the door of the container and the other is the door of the front-chamber main body. These two doors have shapes that can form the coupling chamber only while the conveyance container and the front chamber are air-tightly coupled together. Originally, since the inner surface of this coupling chamber is formed by the exterior surfaces of the two doors, the inner surface is a surface that may be exposed to the external space and contaminated. Accordingly, in the case where the coupling chamber is formed and a cleaning mechanism for the inside of the coupling chamber is disposed, this configuration can ensure more cleanliness and realize the separation between the internal space and the outside. The internal space is formed by the inner portion of the conveyance container, the inner portion of the front chamber, and the coupling chamber. A description will be given of the case where the unit process apparatus is constituted as an application apparatus for photosensitive material. In the conventional yellow room, even when photosensitive material is supplied to the application apparatus installed within the room, there is no possibility that the photosensitive material to be supplied is not exposed because the entire room is shielded. However, for the yellow room of the present invention, even though the photosensitive material is introduced in the shielded container, the lid of the container needs to be opened when the container is set within the apparatus. Accordingly, at that time, the leakage of light may expose the resist inside. Thus, the need exists for devising a countermeasure. With the present invention, the photosensitive material is sealed by a bottle-shaped container (not illustrated) made of the material that shields the exposure light so as to be supplied to the unit process apparatus 50. The lower treatment apparatus 51 of the unit process apparatus 50 includes the housing space for the container. The container is inserted into the housing space. In the upper treatment apparatus 52, what is called a spin coater that includes a workpiece placing table, a spitting nozzle, and a rotation unit (all not illustrated) is arranged. The spitting nozzle put a drop of the photosensitive material on the workpiece (wafer) on the workpiece placing table. The rotation unit rotates the workpiece placing table. In the case where the inspection window 57 is disposed at the upper treatment apparatus 52, the inspection window 57 is constituted of the material that shields the exposure light. Further, in the housing space of the lower treatment apparatus 51, the end portion of the hose for supplying the photosensitive material to the spitting nozzle is arranged as an electrical outlet. This hose is also constituted of the material that shields the exposure light. On the container, a plug-in type resist supplying connector is mounted. This connector is closed when the container is provided alone, and has a structure in which a pipe is opened to be mounted to the electrical outlet. The connector itself is constituted of a light-shielding member. This plug-in connector itself may employ a well-known configuration. However, this plug-in connector causes a problem that fine particles are generated due to the friction during removal/mounting of the connector and mixed with the resist material. In order to prevent this problem, in the present invention, a fine-particle removal filter is mounted from the electrical outlet side to the spitting nozzle. The above-mentioned structural function eliminates the need for light-shielding circumference environment during mounting of the resist container. As described above, the “singular treatment process” performed by the unit process apparatus 50 means one unit of treatment processes that can be housed within the volume of one desktop-size container. This meaning will be described using an example. The actual wafer process for semiconductor device mainly includes processes of cleaning, application, exposure, developing, etching, deposition (such as CVD and sputtering), impurity control (such as ion implantation and diffusion), inspection, CMP (polishing), and similar process. Each process includes more detailed element processes. For example, the cleaning process for silicon wafer is an inclusive term for the following process group. (1) ultrapure water cleaning (rough cleaning), (2) SPM (Sulfuric acid-Hydrogen Peroxide Mixture) cleaning (organic matter removal), (3) ultrapure water cleaning (rinsing), (4) NH4OH—H2O2—H2O (SC-1) cleaning (particulate removal), (5) diluted hydrogen fluoride cleaning (attached particulate removal by oxide removal), (6) HCl—H2O2—H2O (SC-2) cleaning (metal atom removal), (7) diluted hydrogen fluoride cleaning (oxide removal), (8) ultrapure water cleaning (rinsing), (9) IPA (Isopropyl Alcohol) vapor drying (water vapor removal) According to the exemplary embodiment, one unit process apparatus may perform this sequence of cleaning processes of (1) to (9), or two unit process apparatuses may be configured such that one unit process apparatus performs the organic matter removal of (1) and (2), and the other unit process apparatus performs the particulate removal and the metal atom removal of (3) to (9). An application process, which is an example of another process in the semiconductor process, is an inclusive term for (a) surface treatment, (b) resist application, and (c) prebake (resist hardening). In these processes, (a) is a hydrophilicity/hydrophobicity control process of the wafer surface. Thus, the surface treatment (a) can be performed by the unit process apparatus which performs (3) to (9) in the cleaning process described above. As described above, according to the present invention, the unit process apparatus basically brings together the element processes which perform similar processing methods, and handles those processes in one unit process apparatus. Even though the processing methods are very different from one another, one unit process apparatus 1 may handle two consecutive processes insofar as it is technically advantageous that those two consecutive processes are handled in the same apparatus. For example, it is preferred that the IPA vapor drying process (9) after the rinsing process (8) in the above-described cleaning process be performed in one unit process apparatus after the process (8), when possible. It is because residual moisture on the wafer has an action to etch atoms on the wafer surface in the atomic scale. This causes a problem that etching residue condenses as a watermark if it is left as it is. In order to prevent this problem, the IPA vapor drying needs to be performed before the etching proceeds. An object which is processed by this unit process apparatus is a semiconductor device in a minimized unit, which has a wafer size for manufacturing one semiconductor device from the wafer in 0.5 inch size according to an exemplary embodiment. One wafer is processed at a time. In other words, the process in the level similar to that of the semiconductor treatment apparatus in an experiment phase is performed. Accordingly, even a research and development achievement in the experiment phase in a research laboratory can be easily introduced as a treatment apparatus in the unit process apparatus. The present invention facilitates transportation, positioning tasks, or similar tasks for the unit process apparatus, which are associated with a layout change of this unit process apparatus 50. This can flexibly handle the varied number of the unit of manufacturing. That is, a layout can be changed extremely easily among the flow shop layout, the class shop layout, and the multicell shop layout. This enables each manufacturing apparatus not to be in a non-operational state, and a flexible device manufacturing system, which is tolerant of economic change or economic upturn and downturn, can be easily achieved. The configuration for coupling each unit process apparatus to outside, the configuration of the conveyance means for conveying the conveyance container, or the configuration for arranging the unit process apparatuses can be also standardized for example. This allows reducing the cost of the device manufacturing apparatus itself. Furthermore, a conveyance control of the conveyance container can be also simplified or streamlined. Furthermore, a workpiece object is one wafer for one device for single wafer processing. This allows simplifying the unit process apparatus, the conveyance container, the conveyance means, and similar unit. This allows the manufacturing line to be established at a far lower price. With the present invention, the yellow room system and the local cleaning system are both provided. The unit process apparatus and the inside of the conveyance system are sealed from the work space for operators. This eliminates the need for a clean room or a yellow room which houses the entire device manufacturing apparatus and improves the operation efficiency of operators. Moreover, since the wafer to be treated has a wafer size in a minimized unit and there is no need for a conventional clean room or a yellow room, the energy efficiency for manufacturing is extremely better than a conventional megafab. More specifically, the apparatus installation of groups of application, exposure, and developing equipment to be set in a yellow room has been a quarter of the overall area of the front-end process. On the other hand, with a yellow room system constituted like the present invention, the volume in which light needs to be controlled can be reduced to approximately 1/30 or less of the conventional configuration. 1 conventional conveyance container 2 front chamber of conventional apparatus 3 main body of conventional conveyance container 4 container door of conventional conveyance container 5 main body of conventional apparatus 6 apparatus door of conventional apparatus 7, 21 conveyance container 8, 80, 20 front chamber 9, 22 front-chamber door 10 coupling chamber 11, 25 conveyance-container main body 12, 23 container door 13, 24 front-chamber main body 14, 26 electromagnet 15 gas supplying port 16 gas discharging port 17, 30 treatment target object (wafer) 18, 36 magnet 19, 27, 28, 29, 39, 42 magnetic material 31, 32, 33 sealing member 50 unit process apparatus 51 lower treatment apparatus 52 upper treatment apparatus 54 operation panel 55 upper stage 56 docking port 57 inspection window 60 coupling portion 61 portable device 80 front chamber 81 treatment chamber |
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059441909 | abstract | A radiopharmaceutical capsule safe has a two-piece capsule vial that is sealed within a two-piece radiopaque safe which, in turn, is preferably contained within an outer jar. The cap of the two-piece vial is radiotransmissive such that the radiopharmaceutical capsule can be assayed simply by removing the lid portion of the safe from the bottom of the safe while leaving the radiopharmaceutical capsule environmentally sealed within the vial. After replacing the safe lid, the vial is opened by rotating the safe lid, which automatically turns the vial cap to disengage it from the vial bottom for dosing of the capsule to a patient. |
048333344 | abstract | Protective box for electronic circuits hardened with respect to X-rays. The protective box comprises a base and a cover fixed to the base, formed from a rigid mechanical structure constituted by a composite material formed by a fibre-reinforced resin, an X-ray protection material partly covering the outer surface of the mechanical structure, said X-ray protection material being formed by a resin matrix containing a powder of a metal with an atomic number at least equal to 47 and with a melting point at least equal to 630.degree. C., a material formed from an element with a low atomic number forming the outer surface of the cover and optionally a good electricity conducting material covering the inner surface of the mechanical structure. |
summary | ||
046559973 | summary | BACKGROUND OF THE INVENTION This invention relates to nuclear reactors in which a nuclear fuel assembly is contained in a concrete containment. One example of nuclear reactor of this description is a liquid metal cooled fast reactor. Another is a gas-cooled nuclear reactor of either the fast or thermal variety. In the case of the former, a nuclear fuel assembly is disposed in a liquid metal containing primary vessel which is housed in a concrete containment vault, heat being transferred from the fuel to the liquid metal and from thence to steam generators via intermediate heat exchangers. In the case of the latter, a nuclear fuel assembly is supported within a prestressed concrete pressure vessel and gaseous coolant is circulated between fuel assembly and steam generators to transfer heat thereto. In both cases it is necessary to provide thermal insulation to protect the concrete. In the former example, the concrete of the roof of the vault as well as that of the vault sides and base needs to be protected. In the latter example, the concrete of the roof of the pressure vessel as well as that of the wall and floor, requires protection. This invention is concerned with such roof insulation and not with the insulation of walls or base of concrete vault or pressure vessel as the case may be. Such thermal insulation is generally suspended from the appropriate roof by hangers or tie rods, and various proposals have been made for compensating for the changes in dimensions of the insulation as temperature-dictated expansion and contraction, depending on the state of operation of the reactor, occur. One proposal has been to provide both upper and lower ends of the hangers or tie rods with spherical bearings or seatings, but these are liable to stick and then unacceptable straining of insulation and/or hangers or tie rods can occur which can result in insulation becoming detached from the roof. It is an object of the present invention to provide a construction for the securing of heat insulation to a concrete roof structure which is less liable to damage as aforesaid. FEATURES AND ASPECTS OF THE INVENTION According to the invention, the roof of a concrete containment or pressure vessel of a nuclear reactor has thermal insulation secured to it by hanging therefrom, through the medium of a plurality of hangers, wherein each hanger is secured to the said roof by a linkage connection at its upper end and which permits movement of the hanger in two dimensions, and the other end of each hanger being adapted to support the thermal insulation from beneath by means which permit lateral movement of the insulation in two dimensions. The said linkage connection may comprise an eye or hook on the said roof for engagement with an eye or hook constituting the said upper end of the respective hanger. Thus combinations involving double hook, or double eye, or eye and hook, or hook and eye, are all envisaged. Preferably according to the invention, in a nuclear reactor having a roof, depending hangers supported at the upper ends thereof from the roof by hook and eye type connections to allow two dimensional movement of the hangers, and thermal insulation located under the roof and defining apertures through which the hangers extend to support the insulation, there is provided the improvement comprising a support assembly at a lower end of each hanger, the assembly comprising a first element about the hanger and defining a first one dimensional ridge at the upper end of the first element, the first ridge engaging the underside of the insulation to support the insulation and being pivotal on the insulation, a second element about the hanger and below the first element, a second one dimensional ridge at the upper end of the second element to allow relative pivotal movement between the first element and the second element, means for aligning the first element and the second element such that the first ridge and the second ridge are aligned at substantially 90.degree. with respect to each other, and securing means for retaining the first element and the second element on the hanger. |
summary | ||
claims | 1. An ion implanter comprising:an ion source adapted to direct charged ions having an initial mass and energy along a path;a mass analyzer downstream of the ion source for selecting ions based on the mass and energy of the ions;a multi-stage linear accelerator downstream of the mass analyzer comprising:a plurality of acceleration gaps; anda plurality of RF electrodes for accelerating the ions therebetween;wherein each stage of the multi-stage linear accelerator has at least one RF electrode and an acceleration gap adjacent to the electrode, and wherein each RF electrode is operatively associated with an accelerator energy source adapted to create an accelerating alternating electric field to accelerate the ions to a second energy;an end station adapted to position a workpiece so that the accelerated charged ions impact the workpiece; anda direct digital synthesis (DDS) controller coupled to the energy source and adapted to digitally synchronize a frequency and phase of the electric fields of each stage in the linear accelerator, the DDS controller comprising:a plurality of digital phase synthesis (DPS) circuits individually coupled to each of the plurality of RF electrodes to modulate the phase of the voltage applied to each RF electrode; anda digital frequency synthesis circuit (DFS) connected to each of the plurality of DPS circuits and adapted to digitally synthesize a master frequency and phase applied to each of the DPS circuits. 2. The ion implanter of claim 1, wherein the DDS controller further comprises a PLL connected between one of the plurality of DPS circuits and a corresponding one of the plurality of RF electrodes. 3. The ion implanter of claim 1, wherein the DDS controller further comprises a phase locked loop (PLL) connected between the master oscillator and one of the plurality of DPS circuits. 4. The ion implanter of claim 1, wherein each of the plurality of DPS circuits of the DDS controller further comprises a summation circuit adapted to receive a sample input and a phase offset value and connected to a digital storage register adapted to modulate the phase of the electric field applied to each RF electrode within a stage of the accelerator. 5. The ion implanter of claim 1, wherein the master oscillator (DFS) further comprises a digital accumulator and a look-up table adapted to digitally synthesize a master frequency and phase for each of the DPS circuits connected thereto, by reconstructing digitally calculated samples derived from the look-up table by correlating the phase of each sample to a corresponding voltage amplitude. 6. The ion implanter of claim 5, wherein the accumulator comprises a summation circuit adapted to receive a sample input and is connected to a digital storage register that is feedback connected to the summation circuit. 7. The ion implanter of claim 6, wherein the master oscillator (DFS) further comprises a plurality of phase shifter circuits adapted to digitally synthesize a master frequency and phase for each of the DPS circuits connected thereto comprising one of:a DFS circuit adapted to receive the master oscillator output frequency and a DPS circuit adapted to receive a phase offset value;a PLL circuit adapted to receive the master oscillator output frequency, a DFS circuit connected to the PLL circuit, and a first DPS phase offset circuit connected to the DFS circuit to produce a reference phase feedback connected to the PLL circuit, and a second DPS circuit connected to the DFS circuit and adapted to receive a phase offset input to produce a variable phase output to the RF electrode; anda summation circuit adapted to receive a phase offset value input and connected to a look-up table adapted to digitally synthesize a master frequency and phase for each of the DPS circuits connected thereto, by reconstructing digitally calculated samples derived from the look-up table by correlating the phase of each sample to a corresponding voltage amplitude. 8. The ion implanter of claim 1, wherein the DDS controller is configured such that the master oscillator and the DPS phase control circuits are centrally located within a single integrated circuit. 9. The ion implanter of claim 1, wherein the DDS controller is configured such that the DPS phase control circuits are centrally located within a single integrated circuit. 10. The ion implanter of claim 9, wherein the DPS phase control circuits are uniformly located for minimal delay variation at the perimeter of the integrated circuit. 11. The ion implanter of claim 10, wherein output registers of the DPS phase control circuits are uniformly located for minimal delay variation at the perimeter of the integrated circuit. 12. The ion implanter of claim 1, wherein the DDS controller is configured such that the DPS circuits are distributed locally to each stage of the accelerator, each stage comprising a PLL circuit adapted to receive the master oscillator output frequency, and a first DPS phase offset circuit connected to the PLL circuit to produce a reference phase feedback connected to the PLL circuit, and a second DPS circuit connected to the PLL circuit and adapted to produce a variable phase output to the RF electrode. 13. The ion implanter of claim 1, wherein the DDS controller is configured such that the DPS phase control circuits are centrally located within a single integrated circuit, and wherein the output signal terminals therefrom are uniformly spaced at the perimeter of the integrated circuit. 14. The ion implanter of claim 1, wherein the DDS controller is configured such that the DPS phase control circuits are centrally located within a single integrated circuit, and wherein the output signal terminals therefrom are uniformly spaced and are each located adjacent to a common ground or supply terminal at the perimeter of the integrated circuit. 15. The ion implanter of claim 1, wherein the DDS controller is configured such that the DPS phase control circuits are centrally located within a single integrated circuit, and wherein the DPS output signals comprise differential outputs from the integrated circuit. |
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abstract | An electrostatic deflection circuit and method of an electronic beam measuring apparatus which can achieve the high precision of the electronic beam measuring and contribute to the simplification of the structure of the apparatus is provided. In an analog arithmetic circuit included in an analog operation part constituting an electrostatic deflection circuit, output voltages of multipliers are added and output by an adder. When the magnification is low, as the side of an ordinarily closed contact is closed driven by a relay driving circuit, the output of the adder is amplified by a high gain amplifier with a high amplification factor and applied to an electrostatic deflecting board. When the magnification is high, the side of an ordinarily open contact is closed and it is amplified by a low gain amplifier with a low amplification factor and applied to the electrostatic deflecting board in the same way. |
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044951418 | description | DETAILED DESCRIPTION OF THE INVENTION Referring to FIG. 1 illustrating one embodiment of the tagging gas releasing element of the present invention, the tagging gas releasing element 1 comprises a number of circular thin discs 2 laminated closely to one another, and each circular thin disc comprises an injection substrate 3 and a tagging gas-injected layer 4 formed on the surface of the substrate 3. For formation of the injection substrate 3, there may be employed metals such as titanium, aluminum, zirconium, nickel and stainless steel; alloys of these metals; metal films formed by depositing these metals or alloys on surfaces of same or different metals or alloys or other solid carriers by using plating, sputtering, ion-plating or the like; and amorphous metals or heat-resistant solid having a high activity of adsorbing xenon, krypton or the like, such as zeolite, activated carbon and boron nitride (BN). The tagging gas may be composed of at least two isotopes of a rare gas such as xenon, krypton, neon, helium or the like. One rare gas may be used singly, and a mixture comprising two or more rare gases at a predetermined mixing ratio may also be used. A mixture of stable isotopes of xenon and/or krypton is preferred. Injection of the tagging gas into the substrate may be accomplished by using ion injection, high pressure induced diffusion, thermal diffusion, physical adsorption or combination of two or more of these methods. When a thin metal film is used as the injection substrate, there can be attained an advantage that the film thickness can optionally be determined. When sputtering or ion-plating is adopted for formation of such thin metal film, a vacuum device or ion generating device may also be used for ion injection at the step of injecting the tagging gas into the thin metal film. It is therefore preferred to adopt the the sputtering method or ion-plating method for formation of the thin metal film. When a thin metal film is formed by using the plating method or ion-plating method, an amorphous metal film is resulted. If the operation of forming a thin metal film and the operation of injecting a tagging gas into the thin metal film are alternately repeated several times, a structure in which a plurality of gas-injected metal films are laminated as shown in FIG. 1 is effectively prepared. The ion injection method is most preferred as the method for injecting the tagging gas. According to this method, the tagging gas is ionized by, for example, low pressure gaseous discharge, the resulted ions are accelerated by an electric field, and thus the ions are held in an inorganic solid material by injection and/or adsorption. It is possible by this method to inject ions at such a degree as up to about 50% to the metal atoms, and the amount of the injected ions is much larger than that in other injection methods. In case of physical adsorption, there is a fear that the tagging gas once adsorbed is substituted by other gas during manufacture or storage of the element. Accordingly, a care must be taken so that such substitution of tagging gas is not caused. More definitely, when krypton-84 is accelerated at 50 KeV and is ion-injected into aluminum, the ions can be injected at a surface density of up to 1.times.10.sup.17 ions per cm.sup.2. Accordingly, when an aluminum foil having a diameter of 5 mm and a thickness of 6.mu. is employed as a thin metal disc, 5.4.times.10.sup.19 ions of krypton are held in 2470 layers of aluminum foil to form a tagging gas releasing element having a height of about 16 mm. That is, 2 ml of krypton at 0.degree. C. and 1 atmosphere are held. The thus held krypton is released at a temperature higher than about 340.degree. C. Therefore, as shown in FIG. 2, when this gas releasing element 1 is disposed in a gas plenum 11 of a nuclear fuel rod 10, the tagging gas is released at an operation temperature of a fast reactor and is filled in the interior of the nuclear fuel rod 10. In FIG. 2, reference numerals 12, 13, 14, 15 and 16 represent a lower end plug, a cladding tube, an upper end plug, a nuclear fuel pellet and a plenum spring, respectively. Release of the once injected or adsorbed tagging gas is caused by thermal diffusion releasing, high temperature desorption and melting of the metallic substrate under operation conditions of the unclear reactor, or by action of radiation, or by combination of these releasing mechanisms. FIG. 3 illustrates another embodiment of the present invention. In the case where the injected tagging gas is released by melting of the thin metal disc 2 of the injection substrate, a capsule is constructed by a cylinder 5 composed of a hardly fusible metal and porous walls 6 of the same hardly fusible metal formed on both ends of the cylinder 5, and a laminate of the thin discs 2 as shown in FIG. 1 is inserted into the capsule. If the compatibility between the thin metal disc 2 and the nuclear fuel pellet is poor, it is required to construct a capsule of a metal having a good compatibility, into which a laminate of the thin discs is inserted. Since the amount of the tagging gas held in the injection substrate is generally in proportion to the surface area of the injection substrate, a large amount of the tagging gas can be effectively held by adopting a multi-layer structure as described in the foregoing embodiments. However, the present invention is not limited to such multi-layer structure, and the shape and size may optionally be changed according to the function of the gas releasing element. For example, as shown in FIG. 4, there may be adopted a structure in which a metal film 17 is applied on the surface of a nuclear fuel pellet 15 and a tagging gas is injected in the outer surface of the metal film 17. Further, as shown in FIG. 5, there may be adopted another structure in which a metal foil 18, in the outer surface of which a tagging gas has been previously injected, is helically wrapped around the peripheral surface of a nuclear fuel pellet 15. Moreover, as shown in FIG. 6, it is possible to charge a porous granular material 19, in which a tagging gas has been previously adsorbed, in a capsule same as that in FIG. 3. As shown in foregoing, since the tagging gas is held by a solid material and release of the tagging gas depends mainly on the temperature determined by the holding solid material, the manufacture of the tagging gas releasing element of the present invention can be remarkably facilitated and the structure thereof can be remarkably simplified. Moreover, since the tagging gas is present in the substantially pressurized state in the solid, the size of the entire element can be remarkably diminished. Accordingly, limitations on designing of nuclear fuel rods can be moderated. For example, the dead space of the gas plenum can be remarkably reduced. Furthermore, the element is tough and strong, and has a good adaptability to operation, and release of the tagging gas can be accomplished with high reliability. Still in addition, a variety of tagging gases can optionally be combined by using unit solids for respective gases, and discrimination of tags can be performed very easily. Furthermore, by using the element of the present invention, the application range of the tagging method can be remarkably broadened. Thus, various effects and advantages can be attained according to the present invention. While the present invention is described by exemplifying preferred embodiments, various modifications can be made without departing from the spirit and scope of the present invention. |
052971872 | description | DESCRIPTION OF THE PREFERRED EMBODIMENT Turning now to the drawings, there is shown in FIG. 1 a pressurizer 10 for a nuclear steam supply system comprising a carbon steel pressure vessel 1 having, at its upper end, a manway 3 and a spray system 5. A surge outlet 7 and a plurality of electric immersion heaters 9 are disposed at the lower end of pressure vessel 1. Immersion heaters 9 are supported within tubular nickel alloy heater sleeves 11 which penetrate pressure vessel 1 and are sealed thereto. An annular bushing 13 is welded to the outside of each heater sleeve 11 and threadedly engages a locking collar 15 which serves to retain the associated heater 9 against the internal pressure of pressurizer 10. The sealing device of the present invention includes a hollow carbon steel cylinder 17 best seen in FIG. 3. Cylinder 17 has an external diameter substantially equal to the internal diameter of heater sleeves 11 and a length exceeding the length thereof. A tapered nose portion 17a of cylinder 17 is divided, by axially extending slots 19, into a number of radially displaceable segments 21 each of which includes an outwardly extending flange 21a proximate its distal end. An annular band 23 of a soft nickel alloy is formed on the external surface of cylinder 17. In the event that a leak develops in one of heaters 9 or heater sleeves 11, the affected heater 9 is removed and replaced with a cylinder 17. It will be appreciated that, as cylinder 17 is inserted into heater sleeve 11, engagement between the inner surface of heater sleeve 11 and tapered nose portion 17a of cylinder 17 results in a radially inward displacement of segments 21 such that nose portion 17a is enabled to pass therethrough. As nose portion 17a emerges from heater sleeve 11 into the interior of pressure vessel 1, segments 21 reassume their unstressed positions whereat outwardly extending flanges 21a engage heater sleeve 11 as seen in FIG. 2. This engagement restrains cylinder 17 against ejection by the steam pressure within pressure vessel 1. With cylinder 17 in position, a solid, nickel alloy, cylindrical rod 25 is inserted into the interior thereof. Rod 25 has a smooth diameter substantially equal to the internal diameter of cylinder 17 and a length exceeding the length thereof. A slightly tapered nose portion 25a is provided to facilitate insertion into cylinder 17. Rod 25 serves to seal the passage through cylinder 17 and to lock segments 21 into their sleeve-engaging position. It will, further, be appreciated that rod 25 urges cylinder 17 against heater sleeve 11 to provide an interference seal therebetween. In particular, soft nickel band 23 is compressed between heater sleeve 11 and cylinder 17 to comprise a further seal therebetween. Advantageously, band 23 is disposed at the point where cylinder 17 passes through pressure vessel 1, whereby the pressure vessel wall provides additional stiffening and support to heater sleeve 11. Before replacement of locking collar 15, which is removed to provide access to heater 9, cylinder 17 is welded to heater sleeve 11 and rod 25 is welded to cylinder 17. It is to be noted that the present sealing device will resist being ejected and will maintain an effective seal even in the event of a full circumferential failure of the portion of the heater sleeve 11 external to the pressure vessel 1. |
description | This disclosure relates to the generation of electricity and steam. In particular, this disclosure relates to the generation of electricity and steam from a helium-cooled high temperature nuclear reactor by means of a closed helium Brayton cycle and a heat recovery steam generator. Fossil fuel combustion has been identified as a significant contributor to numerous adverse environmental effects. For example, poor local air quality, regional acidification of rainfall that extends into lakes and rivers, and a global increase in atmospheric concentrations of greenhouse gases (GHG), have all been associated with the combustion of fossil fuels. In particular, increased concentrations of GHG's are a significant concern since the increased concentrations may cause a change in global temperature, thereby potentially contributing to global climatic disruption. Further, GHG's may remain in the earth's atmosphere for up to several hundred years. One problem associated with the use of fossil fuel is that the consumption of fossil fuel correlates closely with economic and population growth. Therefore, as economies and populations continue to increase worldwide, substantial increases in the concentration of GHG's in the atmosphere are expected. A further problem associated with the use of fossil fuels is related to the inequitable geographical distribution of global petroleum resources. In particular, many industrialized economies are deficient in domestic supplies of petroleum, which forces these economies to import steadily increasing quantities of crude oil in order to meet the domestic demand for petroleum derived fuels. Nuclear reactors do not emit appreciable pollutants or GHG's into the atmosphere and can provide energy independence to economies that are deficient in fossil fuels. The majority of today's nuclear reactors are water-cooled and generate electricity through steam generation and subsequent expansion through a steam turbine. Because of the relatively low temperature steam produced by these reactors (generally below 300° C.), the net thermal efficiency for electrical generation is relatively low (generally below 35%). An additional shortcoming of these reactors is that the steam produced is too cold for many potential industrial applications, such as hydrogen production by steam methane reforming (SMR) of natural gas or hydrogen production by solid oxide electrolysis of steam. Intermediate temperature solid oxide electrolyzer systems generally operate at temperatures of about 700 to about 900° C. Steam undergoes electrolysis in the cathode side of a solid oxide electrolyzer cell to generate hydrogen. Electrical energy is required to electrolyze the steam, so it is desirable to have a nuclear reactor system that can produce high-temperature steam as well as electrical energy. Graphite-moderated nuclear reactors that are cooled with helium gas can achieve very high helium exit temperatures, from 700° C. to potentially 1,000° C. Many systems have been proposed for the production of electrical energy and high-temperature steam using helium-cooled reactors. Systems have been proposed that indirectly couple a steam Rankine cycle to the primary helium coolant loop. High pressure steam is generated in a boiler heated by the helium used to cool the primary loop. The high pressure steam is partially expanded through a steam turbine to produce electrical energy. A portion of the partially expanded steam is then reheated through a second heat exchanger heated by primary loop helium. This intermediate pressure reheated steam can then be used for applications such as solid oxide electrolysis. This type of system has a risk of steam ingress into the nuclear core due to the high-pressure steam generators, where the steam can be at a higher pressure than the primary helium coolant. Steam ingress into the core is undesirable because it can corrode the graphite moderator and graphite-coated fuel, and can also cause a reactivity insertion due to the moderating effect of steam. Other systems have been proposed that indirectly couple a Brayton topping cycle to the primary helium coolant loop and further indirectly couple a steam Rankine bottoming cycle to the Brayton cycle, in a concept known generally as an indirect combined cycle. Heat is transferred through an intermediate heat exchanger to a Brayton cycle employing a compressed gaseous working fluid, such as air or helium. This heated gas is expanded through a turbine to produce electricity. Expanded gas then passes through a heat recovery steam generator to produce steam, which can be expanded through a steam turbine for additional electrical production or alternatively can be used for industrial applications. This system does not produce steam with the required high temperature for solid oxide electrolysis, however. Furthermore, this system requires the use of a very large and expensive gas-to-gas intermediate heat exchanger. Other systems have been proposed that directly expand the helium through a turbine to produce electricity using a direct Brayton cycle. To produce steam in addition to electricity, systems have been proposed that divert a fraction of the helium coolant exiting the nuclear core to a second loop in parallel with the Brayton cycle loop. Helium in this second parallel loop generates steam in a steam generator. Such systems have several undesirable features—they do not efficiently use the high energy available in the high-temperature helium in the second parallel loop and they use a second compressor in the second parallel loop. In addition, they use a large and expensive gas-to-gas recuperator to transfer heat from the turbine exhaust to the reactor inlet for efficient electrical generation. It is therefore desirable to have a system that produces both electricity and low-pressure steam using a helium-cooled nuclear reactor in an economical and safe manner. Disclosed herein is a method comprising heating helium in a core of a nuclear reactor; extracting heat from the helium; superheating water to steam using the heat extracted from the helium; expanding the helium in a turbine; wherein the turbine is in operative communication with an electrical generator; and generating electricity in the electrical generator. Disclosed herein too is a system for producing electricity and steam comprising a Brayton power conversion cycle employing helium as the working fluid in a first closed loop wherein the first closed loop comprises a heat source comprising a nuclear reactor; wherein the core of the nuclear reactor is cooled using helium; a power conversion system comprising a turbine, a compressor, and an electrical generator, wherein the compressor, the turbine, and the electrical generator are in operative communication with each other; wherein the turbine is located downstream from the heat source and is in fluid communication with the heat source; a heat recovery steam generator, located downstream of the turbine and in fluid communication with the turbine, where the steam generated is at a pressure that is less than or equal to about the pressure of the helium in the first closed loop; and a waste heat removal heat exchanger, located downstream of the heat recovery steam generator and in fluid communication with the heat recovery steam generator. It is to be noted that the terms “first,” “second,” and the like as used herein do not denote any order, quantity, or importance, but rather are used to distinguish one element from another. The terms “a” and “an” do not denote a limitation of quantity, but rather denote the presence of at least one of the referenced item. The modifier “about” used in connection with a quantity is inclusive of the stated value and has the meaning dictated by the context (e.g., includes the degree of error associated with measurement of the particular quantity). It is to be noted that all ranges disclosed within this specification are inclusive and are independently combinable. Furthermore, in describing the arrangement of components in embodiments of the present disclosure, the terms “upstream” and “downstream” are used. These terms have their ordinary meaning. For example, an “upstream” device as used herein refers to a device producing a fluid output stream that is fed to a “downstream” device. Moreover, the “downstream” device is the device receiving the output from the “upstream” device. However, it will be apparent to those skilled in the art that a device may be both “upstream” and “downstream” of the same device in certain configurations, e.g., a system comprising a recycle loop. Disclosed herein is a system that produces electricity and low-pressure steam from a helium-cooled high temperature nuclear reactor by using a closed helium Brayton cycle and a heat recovery steam generator (HRSG). In one embodiment, electricity and steam are produced for use in a solid oxide electrolyzer system that is in operative communication with a helium cooled nuclear reactor. This system produces steam and electricity in the proper proportion for use by a solid oxide electrolysis cell or cells for the production of hydrogen, such that the system does not export or import additional steam or electricity to or from external sources. In one embodiment, the system uses helium as a medium for transferring heat (generated in a nuclear core) to steam that can optionally be electrolyzed into hydrogen and oxygen in a solid oxide electrolyzer cell. The helium is used to cool the core of a high temperature nuclear reactor. The heat extracted by the helium in the process of cooling the core is then used to drive a gas turbine that operates using a direct Brayton power conversion cycle. The gas turbine is in operative communication with a generator that generates electricity. The hot helium is also advantageously used to generate steam that can be optionally used for the generation of hydrogen. The system is advantageous since there is a minimization of the possibility of water ingress into the core of the nuclear reactor because the water and steam at all points in the system are at an equal or lower pressure than the helium coolant. Further, the helium coolant is a single phase coolant that is inert and has minimal reactivity effects. With reference now to FIG. 1, the system 10 comprises a first closed loop comprising a heat source 102. The heat source 102 comprises a nuclear reactor that employs helium as a coolant. The heat source 102 is in operative communication with a power conversion system comprising a turbine 106, a compressor 120, and an electrical generator 126 that operates on a Brayton cycle. As can be seen in the FIG. 1, the turbine 106 is located downstream from the heat source 102 and is in fluid communication with the heat source 102. A heat recovery steam generator (HRSG) 112 is located downstream of the turbine 106 and is in fluid communication with the turbine 106, where the steam generated is at a pressure that is less than or equal to about the pressure of the helium in the first closed loop. The system 10 further comprises a waste heat removal heat exchanger 118, located downstream of the HRSG 112 and in fluid communication with the HRSG 112. In one embodiment, the heat source 102 is a nuclear reactor that employs machined graphite blocks as the moderator and as the core structural element. Coated fuel particles containing fissile material are compacted into cylindrical pellets and inserted into holes drilled into the graphite blocks. Helium coolant flows through additional holes drilled through the graphite blocks. In another embodiment, the heat source is a nuclear reactor that employs coated fuel particles containing fissile material that are compacted into pebbles. These pebbles are then assembled to form a “pebble bed” comprising the core of the reactor. Helium coolant flows between the pebbles. In one embodiment, the power conversion system comprises a turbine 106, an electric generator 126, and a compressor 120 on a common horizontal shaft. In another embodiment, the power conversion system comprises a turbine, an electric generator, and compressors on a common vertical shaft. In one embodiment, the electrical generator may be located at the compressor end of the shaft, as shown in FIG. 1. In another embodiment, the electrical generator may be located at the turbine end of the shaft. In one embodiment, the generator is directly coupled to the shaft and rotates synchronously with the turbomachine. In another embodiment, the generator is coupled to the shaft via a gearbox that reduces the speed of rotation of the generator relative to the turbomachine shaft. The HRSG 112 is operative to extract heat from the helium in the first loop and transfer it to water to convert water into steam. In one embodiment, the HRSG 112 is a shell-and-tube heat exchanger, where hot helium passes over tubes filled with water or steam. In one embodiment, the tubes are coiled. In another embodiment, the tubes have exterior fins attached to improve heat transfer. In an exemplary embodiment, the HRSG 112 is segmented into three sections. Referring now to FIG. 2, the HRSG 112 is segmented into three sections: the steam superheater 110, the steam evaporator 113, and the economizer 114. The steam superheater 110 transfers heat from hot helium to saturated steam generated in the evaporator, and heats the steam to a temperature above its saturation temperature to become superheated steam. The steam evaporator 113 transfers heat from hot helium to saturated liquid water from the economizer, and heats the water causing it to boil and become saturated steam. The economizer 114 transfers heat from hot helium to liquid water and heats the water up to its saturation temperature. Referring again to FIG. 1, the waste heat removal heat exchanger 118 is operative to remove waste heat from the helium prior to compression in the compressor 120. In one embodiment, the waste heat removal heat exchanger 118 is a shell-and-tube heat exchanger employing water as a cooling fluid. In one embodiment, this cooling water is extracted from a source of cool water such as a lake and is returned to this source after flowing through the waste heat removal heat exchanger. In another embodiment, the cooling water is circulated in a closed loop and is pumped through a cooling tower for ultimate rejection of the waste heat to the atmosphere. In another embodiment, the waste heat removal heat exchanger 118 utilizes forced-circulation air as a cooling fluid. As detailed in FIG. 2, the system 10 can comprise additional optional features that can be used for the optional generation of hydrogen, if desired. The first loop 100 is in operative communication with a second loop 200 that optionally comprises the solid oxide electrolyzer cell 202. In an alternative embodiment, the second loop 200 may comprise a steam methane reformer in lieu of the solid oxide electrolyzer cell 202. In yet another alternative embodiment, the second loop 200 may comprise a radiator in lieu of the steam methane reformer or the solid oxide electrolyzer cell 202. In one embodiment, the solid oxide electrolyzer cell 202 is an intermediate temperature operating cell that functions at a temperature of about 700 to about 850° C. The solid oxide electrolyzer cell 202 may be tubular or planar in assembly. The solid oxide electrolyzer cell 202 is partitioned into an anode side and a cathode side by a hermetic membrane comprising a solid oxide electrolyte. Alternating-current (AC) electrical power is converted into direct current (DC) electric power by an AC-DC converter, and the direct current electric power is supplied to the solid oxide electrolyzer cell 202. The electrical energy facilitates the conversion (electrolysis) of the high-temperature steam supplied to the cathode side into molecular hydrogen and negative oxygen ions. Oxygen ions pass through the solid oxide electrolyte to the anode, where they combine to form molecular oxygen. In one embodiment, the solid oxide electrolyzer cell 202 uses an electrolyte that comprises yttria-stabilized-zirconia (YSZ), gadolinia-doped-ceria, samaria-doped-ceria, or lanthanum-strontium-gallium-magnesium oxide. Suitable anode materials include mixed-ionic-electronic-conducting (MIEC) ceramics such as lanthanum-strontium-ferrite, lanthanum-strontium-cobaltite, or lanthanum-strontium-cobaltite-ferrite, and their combinations with an electrolyte material such as those listed above. In an example according to this embodiment, the solid oxide electrolyzer cell 202 can further comprise an ion-conducting barrier layer to separate the anode from the electrolyte. For example, a suitable barrier layer that can be used between a YSZ electrolyte and a lanthanum-strontium-cobaltite-ferrite includes samaria-doped-ceria and gadolinia-doped-ceria. Suitable cathode materials include the composite Ni/YSZ. In one embodiment, the Ni/YSZ is used at the operating temperature. In an example according to this embodiment, the solid oxide electrolyzer cell 202 can further comprise a reducing environment maintained on the cathode side. For example, maintaining hydrogen in the steam feed of at least about 5 mole percent can provide a reducing environment on the cathode side. In another embodiment, the solid oxide electrolyzer cell 202 uses an electrolyte-supported design. In one embodiment, the thickness of the electrolyte is about 10 micrometers to about 400 micrometers, more specifically about 25 micrometers to about 300 micrometers, most specifically about 50 micrometers to about 200 micrometers. The electrolyte can be fabricated by tape-casting, pressing, extruding, slip-casting, tape-calendaring, sintering, or the like, or a combination comprising at least one of the foregoing. The thickness of the cathode and anode are each independently about 1 micrometer to about 200 micrometers, more specifically about 5 micrometers to about 100 micrometers, most specifically about 10 micrometers to about 50 micrometers. The electrodes can be fabricated by screen printing, wet particle spraying, tape-calendaring, tape-casting, sintering, or the like, or a combination comprising at least one of the foregoing. In another embodiment, the solid oxide electrolyzer cell 202 uses a cathode-supported design. In this embodiment, the thickness of the cathode is about 25 micrometers to about 2000 micrometers, more specifically about 50 micrometers to about 1000 micrometers, most specifically about 200 micrometers to about 500 micrometers. The cathode can be fabricated by tape-casting, pressing or tape-calendaring and sintering. The thickness of the electrolyte can be about 1 micrometer to about 100 micrometers, more specifically about 2 micrometers to about 50 micrometers, and most specifically about 5 micrometers to about 15 micrometers. The electrolyte can be fabricated by tape-casting, tape-calendaring, screen-printing, or wet particle spraying and sintering. In some cases, the cathode and electrolyte are co-sintered. The thickness of the anode can be about 2 micrometers to about 200 micrometers, more specifically about 5 micrometers to about 100 micrometers, most specifically about 10 micrometers to about 50 micrometers. The anode can be fabricated by pressing, screen printing, wet particle spraying, tape-calendaring, tape-casting, sintering, or the like, or a combination comprising at least one of the foregoing. As noted above, the second loop 200 may comprise a steam methane reformer or a radiator (not shown) in lieu of the solid oxide electrolyzer cell 202. The steam methane reformer is located downstream of the heat recovery steam generator 112 and is in fluid communication with the heat recovery steam generator. The steam methane reformer is operative to produce hydrogen from natural gas. In another embodiment, the steam radiator is located downstream of the heat recovery steam generator 112 and in fluid communication with the heat recovery steam generator 112. The steam radiator is operative to heat a building. In one embodiment, the first loop 100 is in operative communication with the second loop 200 via a steam superheater 104. The steam superheater is upstream of the turbine 106 and is in fluid communication with turbine. In one embodiment, the steam superheater 104 can be a shell-and-tube type heat exchanger that facilitates the transfer of heat from hot helium to the steam present inside the tubes. In another embodiment, the steam superheater can be a plate-fin type heat exchanger that facilitates the transfer of heat from hot helium on one side of the plates to the steam to steam present on the other side of the plates. In one embodiment, the first loop 100 comprises a recuperator 116 that is operative to transfer heat from the hot helium exiting the HRSG 112 to the cold helium exiting the compressor 124. The hot side of the recuperator 116 is located downstream of the HRSG 112 and is in fluid communication of the HRSG 112. The cold side of the recuperator is located downstream of the compressor 124 and is in fluid communication with the compressor 124. In one embodiment, the recuperator 116 is a gas-to-gas heat exchanger. In an exemplary embodiment, the recuperator 116 is a brazed plate-fin type heat exchanger. In one embodiment, the first loop 100 comprises an intercooler 122 that is operative to cool helium exiting the low-pressure compressor 120 prior to further compression in the high-pressure compressor 124. In one embodiment, the intercooler 122 is a shell-and-tube type heat exchanger, with cooling water passing through the tubes to extract heat from the helium. Helium exiting the nuclear reactor heat source 102 generally has a pressure of about 40 to about 90 kg/cm2 and a temperature of about 700 to about 1,000° C. In one embodiment, the helium exits the nuclear reactor heat source at a pressure of about 50 to about 75 kg/cm2 and a temperature of about 800 to about 950° C. In an exemplary embodiment, the helium exits the nuclear reactor heat source at a pressure of about 52 to about 57 kg/cm2 and a temperature of about 825 to about 875° C. As can be seen from FIG. 1, the hot helium is transferred to the turbine 106 and the HRSG 112. If a superheater 104 is included upstream of the turbine 106 as in the FIG. 2, then hot helium is first transferred to the superheater 104 prior to being transferred to the turbine 106. The hot helium is used to heat steam to a temperature of about 400 to about 900° C. The pressure of the steam in the second loop is lower than or equal to the pressure of the helium in the first closed loop. The helium exits the superheater 104 at a temperature of about 600 to about 900° C. and at a pressure of about 40 to about 90 kg/cm2. An exemplary temperature for the helium exiting the superheater 104 is about 750 to about 850° C. and an exemplary pressure is about 50 kg/cm2 to about 60 kg/cm2. Helium is transferred to the high-pressure turbine 104 from the first superheater 106. The high-pressure turbine 106 is in mechanical communication with a low-pressure gas compressor, a high-pressure gas compressor and an electrical generator. Heated helium from the reactor expands through the turbine to drive the generator and gas compressors. The helium pressure decreases from about 50 to about 90 kg/cm2 prior to entering the turbine 106 to about 4 to about 12 kg/cm2 after exiting the turbine 106. The temperature drops from about 600 to about 900° C. prior to entering the gas turbine 106 to about 200 to about 500° C., after exiting the turbine 106. An exemplary pressure for the helium exiting the turbine is about 6 to about 9 kg/cm2 and an exemplary temperature is about 250 to about 300° C. The helium after the expansion is transferred to the HRSG 112. Heat from the helium is extracted in the HRSG 112 and is used to generate steam that is optionally used for the generation of hydrogen in the solid oxide electrolyzer cell 202. As noted above, in an exemplary embodiment, the HRSG 112 comprises a steam superheater 110, an evaporator 113 and an economizer 114. The temperature of the helium is further reduced in the process of transferring its heat to the steam generated in the HRSG 112. The helium temperature generally decreases to about 100 to about 300° C. at the exit point of the HRSG 112, while the pressure of the helium also decreases slightly. An exemplary temperature for helium exiting the heat exchanger 108 is about 200 to about 225° C. In one embodiment, helium exiting the HRSG 112 is then transferred to the hot side of a recuperator 116. The temperature of the helium exiting the hot side of the recuperator is decreased to about 100 to about 300° C. The helium is then transferred to the waste heat removal heat exchanger 118. In one embodiment, the temperature of the helium exiting the waste heat removal heat exchanger is decreased to about 20 to about 75° C. In an exemplary embodiment, the temperature of the helium exiting the waste heat removal heat exchanger is decreased to about 25 to about 40° C. In one embodiment, the helium is then transferred to a low-pressure compressor 120. The low-pressure compressor compresses the helium to a pressure of about 15 to about 30 kg/cm2, increasing the helium temperature to about 150 to about 250° C. In an exemplary embodiment, the helium exits the low-pressure compressor at a pressure of about 18 to about 22 kg/cm2 and a temperature of about 190 to about 220° C. In one embodiment, the helium is then transferred to an intercooling heat exchanger 122. Helium exiting the intercooling heat exchanger 122 is cooled to about 25 to about 75° C. In an exemplary embodiment, helium exiting the intercooling heat exchanger 122 is cooled to about 30 to about 45° C. In one embodiment, the helium is then transferred to a high-pressure compressor 124. The high-pressure compressor further compresses the helium to a pressure of about 40 to about 90 kg/cm2, increasing the helium temperature to about 150 to about 250° C. In an exemplary embodiment, the helium exits the high-pressure compressor at a pressure of about 50 to about 60 kg/cm2 and a temperature of about 190 to about 220° C. In one embodiment, the helium is then transferred to the cold side of a recuperator. The temperature of the helium exiting the cold side of the recuperator is increased to about 150 to about 300° C. In one embodiment, the amount of electricity generated by the electrical generator is about 8,000 to about 15,000 kilojoules of electricity per kilogram of steam generated. In an exemplary embodiment, the amount of electricity generated by the electrical generator is about 9,000 to about 10,000 kilojoules of electricity per kilogram of steam generated. In one embodiment, the second loop 200 of the system is in operative communication with the first loop 100 and comprises an optional solid oxide electrolyzer cell 202 that is used to electrolyze steam at a temperature of about 700 to about 900° C. to form hydrogen and oxygen. As can be seen from the FIG. 2, the second loop 200 comprises the HRSG 112, the superheater 104 and a solid oxide electrolyzer cell 202. The solid oxide electrolyzer cell 202 comprises a cathode side and an anode side. Steam is electrolyzed to generate hydrogen on the cathode side, while oxygen generated may be swept away on the anode side by compressed air obtained from an air compressor (not shown). On the cathode side, the second loop 200 can comprise other devices such as, for example, condensers (not shown) for separating steam from hydrogen, heat exchangers (not shown) for extracting heat from hydrogen and steam to preheat air used to sweep oxygen from the anode side, feed water heaters for preheating water, or the like. On the anode side, the second loop 200 can comprise other devices, such as for example, compressors (not shown) for compressing air to sweep oxygen from the anode side, turbines (not shown) for driving an electrical generator (not shown) that is used to generate electricity, or the like. In the second loop 200, water enters the HRSG 112 at a temperature of about 25° C. and a pressure less than or equal to the pressure of the helium exiting the turbine 106. In one embodiment, steam leaves the HRSG 112 at a temperature of about 200 to about 400° C. and a pressure and a pressure less than or equal to the pressure of the helium exiting the turbine 106. In an exemplary embodiment, steam leaves the HRSG 112 at a temperature of about 250 to about 275° C. and a pressure less than or equal to the pressure of the helium exiting the turbine 106. In one embodiment, steam exits the steam superheater 104 at a temperature of about 400 to about 900° C. and a pressure less than or equal to the pressure of the helium exiting the turbine 106. In an exemplary embodiment, steam exits the steam superheater 104 at a temperature of about 700 to about 775° C. and a pressure less than or equal to the pressure of the helium exiting the turbine 106 In one embodiment, the hydrogen and oxygen derived from the solid oxide electrolysis system 200 can be stored in hydrogen and oxygen tanks respectively for use in a reversible type solid oxide electrolytic cell (not shown) that serves as a fuel battery to generate electricity as the occasion demands. The hydrogen obtained from solid oxide electrolyzer cell 202 has a purity of greater than or equal to about 90%, based on the moles of the hydrogen and any impurities present. In one embodiment, the hydrogen obtained has a purity of greater than or equal to about 95%, based on the moles of the hydrogen and any impurities present. In another embodiment, the hydrogen obtained has a purity of greater than or equal to about 98%, based on the moles of the hydrogen and any impurities present. In another embodiment, the hydrogen obtained has a purity of greater than or equal to about 99%, based on the moles of the hydrogen and any impurities present. In another embodiment, the hydrogen obtained has a purity of greater than or equal to about 99.9%, based on the moles of the hydrogen and any impurities present. The aforementioned method of generating hydrogen is advantageous in that the use of a direct Brayton cycle can be used to produce electricity as well as low pressure, high temperature steam for a solid oxide electrolyzer system. The system is self-contained in that no electricity or steam is exported or imported from external devices. Since the helium is always at higher pressure than the steam at all points in the system, the risk of water ingress from the second loop 200 into the first loop 100 (that contains only helium) is minimized, especially when compared with systems that employ a Rankine cycle. The disclosed balanced system 10 also employs a lower helium mass flow rate, lower helium coolant return temperatures and lower system pressures than direct Brayton cycle systems that produce only electricity. This permits simplification of the nuclear reactor design as well as materials of construction used in the nuclear reactor. The following examples, which are meant to be exemplary, not limiting, illustrate the methods of operation of the system described herein. This numerical example has been performed to demonstrate one exemplary method of functioning the system. This example has been conducted to demonstrate the advantages that are available by generating electricity along with steam according to the disclosed method. FIG. 3 is a depiction of the system upon which the numerical example was performed. FIG. 3 comprises the same elements depicted in the FIG. 2, with the exception of the recuperator 116. Each element in the FIG. 3 however, has its inlet and outlet points numbered. Table 1 shows the respective values (at each of the inlet and outlet points) for the helium pressure, temperature and mass flow rate for an optimized system that generates electricity and steam. Table 2 shows the respective values (at each of the inlet and outlet points) for the water/steam pressure, temperature and mass flow rate for an optimized system that generates electricity and steam. TABLE 1Mass flow ratePoint #Pressure (kg/cm2)Temperature (° C.)(kg/second)153.86850180253.75850180352.67830.1180452.57830.1180552.52830.118067.67279.718077.617279.718087.601279.718097.449274.9180107.442274.9180117.293232180127.286232180137.14221.5180146.99731180156.983311801619.89210.71801719.75210.71801819.71210.71801919.51311802019.48311802119.46311802255.41212.81802355.11212.81802655.00212.8180277.14221.5180 TABLE 2Mass flow ratePoint #Pressure (kg/cm2)Temperature (° C.)(kg/second)401.02518.81416.825.0418.81426.6148.218.81436.4161.418.81446.2267.218.81456.072518.81 From the Tables 1 and 2, it can be seen that while the mass flow of helium is maintained at about 180 kilograms/second in the first loop 100, mass flow of steam of about 18.81 kilograms/second can be maintained in the second loop. The helium flow in the first loop can be used to generate electricity of about 8,000 to about 10,000 kilojoules per kilogram of steam. From Table 2, it may also be seen that the helium can be used to raise the temperature of steam from room temperature (25° C.) to about 725° C., which is sufficient to permit electrolysis of steam to obtain hydrogen and oxygen in a solid oxide electrolyzer cell 202. While the invention has been described with reference to exemplary embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this invention. |
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description | The disclosure herein relates to X-ray detectors, particularly relates to semiconductor X-ray detectors. X-ray detectors may be devices used to measure the flux, spatial distribution, spectrum or other properties of X-rays. X-ray detectors may be used for many applications. One important application is imaging. X-ray imaging is a radiography technique and can be used to reveal the internal structure of a non-uniformly composed and opaque object such as the human body. Early X-ray detectors for imaging include photographic plates and photographic films. A photographic plate may be a glass plate with a coating of light-sensitive emulsion. Although photographic plates were replaced by photographic films, they may still be used in special situations due to the superior quality they offer and their extreme stability. A photographic film may be a plastic film (e.g., a strip or sheet) with a coating of light-sensitive emulsion. In the 1980s, photostimulable phosphor plates (PSP plates) became available. A PSP plate may contain a phosphor material with color centers in its lattice. When the PSP plate is exposed to X-ray, electrons excited by X-ray are trapped in the color centers until they are stimulated by a laser beam scanning over the plate surface. As the plate is scanned by laser, trapped excited electrons give off light, which is collected by a photomultiplier tube. The collected light is converted into a digital image. In contrast to photographic plates and photographic films, PSP plates can be reused. Another kind of X-ray detectors are X-ray image intensifiers. Components of an X-ray image intensifier are usually sealed in a vacuum. In contrast to photographic plates, photographic films, and PSP plates, X-ray image intensifiers may produce real-time images, i.e., do not require post-exposure processing to produce images. X-ray first hits an input phosphor (e.g., cesium iodide) and is converted to visible light. The visible light then hits a photocathode (e.g., a thin metal layer containing cesium and antimony compounds) and causes emission of electrons. The number of emitted electrons is proportional to the intensity of the incident X-ray. The emitted electrons are projected, through electron optics, onto an output phosphor and cause the output phosphor to produce a visible-light image. Scintillators operate somewhat similarly to X-ray image intensifiers in that scintillators (e.g., sodium iodide) absorb X-ray and emit visible light, which can then be detected by a suitable image sensor for visible light. In scintillators, the visible light spreads and scatters in all directions and thus reduces spatial resolution. Reducing the scintillator thickness helps to improve the spatial resolution but also reduces absorption of X-ray. A scintillator thus has to strike a compromise between absorption efficiency and resolution. Semiconductor X-ray detectors largely overcome this problem by direct conversion of X-ray into electric signals. A semiconductor X-ray detector may include a semiconductor layer that absorbs X-ray in wavelengths of interest. When an X-ray photon is absorbed in the semiconductor layer, multiple charge carriers (e.g., electrons and holes) are generated and swept under an electric field towards electrical contacts on the semiconductor layer. Cumbersome heat management required in currently available semiconductor X-ray detectors (e.g., Medipix) can make a detector with a large area and a large number of pixels difficult or impossible to produce. Disclosed herein is an apparatus suitable for detecting x-ray, comprising: an X-ray absorption layer comprising an electrode; an electronics layer, the electronics layer comprising: a substrate having a first surface and a second surface, an electronics system in or on the substrate, an electric contact on the first surface, a via, and a redistribution layer (RDL) on the second surface; wherein the RDL comprises a transmission line; wherein the via extends from the first surface to the second surface; wherein the electrode is electrically connected to the electric contact; wherein the electronics system is electrically connected to the electric contact and the transmission line through the via. According to an embodiment, the substrate has a thickness of 200 μm or less. According to an embodiment, the electronics system comprises: a first voltage comparator configured to compare a voltage of the electrode to a first threshold; a second voltage comparator configured to compare the voltage to a second threshold; a counter configured to register a number of X-ray photons reaching the X-ray absorption layer; a controller; wherein the controller is configured to start a time delay from a time at which the first voltage comparator determines that an absolute value of the voltage equals or exceeds an absolute value of the first threshold; wherein the controller is configured to activate the second voltage comparator during the time delay; wherein the controller is configured to cause the number registered by the counter to increase by one, if the second voltage comparator determines that an absolute value of the voltage equals or exceeds an absolute value of the second threshold. According to an embodiment, the controller is configured to deactivate the first voltage comparator at a beginning of the time delay. According to an embodiment, the controller is configured to deactivate the second voltage comparator at expiration of the time delay or at a time when the second voltage comparator determines that the absolute value of the voltage equals or exceeds the absolute value of the second threshold, or a time in between. According to an embodiment, the apparatus further comprises a capacitor module electrically connected to the electrode, wherein the capacitor module is configured to collect charge carriers from the electrode. According to an embodiment, the controller is configured to activate the second voltage comparator at a beginning or expiration of the time delay. According to an embodiment, the apparatus further comprises a voltmeter, wherein the controller is configured to cause the voltmeter to measure the voltage upon expiration of the time delay. According to an embodiment, the controller is configured to determine an X-ray photon energy based on a value of the voltage measured upon expiration of the time delay. According to an embodiment, the controller is configured to connect the electrode to an electrical ground. According to an embodiment, a rate of change of the voltage is substantially zero at expiration of the time delay. According to an embodiment, a rate of change of the voltage is substantially non-zero at expiration of the time delay. According to an embodiment, the X-ray absorption layer comprises a diode. According to an embodiment, the X-ray absorption layer comprises silicon, germanium, GaAs, CdTe, CdZnTe, or a combination thereof. According to an embodiment, the apparatus does not comprise a scintillator. According to an embodiment, the apparatus comprises an array of pixels. Disclosed herein is a system comprising the apparatus disclosed herein and an X-ray source, wherein the system is configured to perform X-ray radiography on human chest or abdomen. Disclosed herein is a system comprising the apparatus disclosed herein and an X-ray source, wherein the system is configured to perform X-ray radiography on human mouth. Disclosed herein is a cargo scanning or non-intrusive inspection (NII) system, comprising the apparatus disclosed herein and an X-ray source, wherein the cargo scanning or non-intrusive inspection (NII) system is configured to form an image using backscattered X-ray. Disclosed herein is a cargo scanning or non-intrusive inspection (NII) system, comprising the apparatus disclosed herein and an X-ray source, wherein the cargo scanning or non-intrusive inspection (NII) system is configured to form an image using X-ray transmitted through an object inspected. Disclosed herein is a full-body scanner system comprising the apparatus disclosed herein and an X-ray source. Disclosed herein is an X-ray computed tomography (X-ray CT) system comprising the apparatus disclosed herein and an X-ray source. Disclosed herein is an electron microscope comprising the apparatus disclosed herein, an electron source and an electronic optical system. Disclosed herein is a system comprising the apparatus disclosed herein, wherein the system is an X-ray telescope, or an X-ray microscopy, or wherein the system is configured to perform mammography, industrial defect detection, microradiography, casting inspection, weld inspection, or digital subtraction angiography. Disclosed herein is a method comprising: obtaining an X-ray absorption layer comprising an electrode; obtaining an electronics layer, the electronics layer comprising: a substrate having a first surface and a second surface, an electronics system in or on the substrate, an electric contact on the first surface, a via, and a redistribution layer (RDL) on the second surface; bonding the X-ray absorption layer and the electronics layer such that the electrode is electrically connected to the electric contact; wherein the RDL comprises a transmission line; wherein the via extends from the first surface to the second surface; wherein the electronics system is electrically connected to the electric contact and the transmission line through the via. FIG. 1A schematically shows a semiconductor X-ray detector 100, according an embodiment. The semiconductor X-ray detector 100 may include an X-ray absorption layer 110 and an electronics layer 120 (e.g., an ASIC) for processing or analyzing electrical signals incident X-ray generates in the X-ray absorption layer 110. In an embodiment, the semiconductor X-ray detector 100 does not comprise a scintillator. The X-ray absorption layer 110 may include a semiconductor material such as, silicon, germanium, GaAs, CdTe, CdZnTe, or a combination thereof. The semiconductor may have a high mass attenuation coefficient for the X-ray energy of interest. The X-ray absorption layer 110 may include one or more diodes (e.g., p-i-n or p-n) formed by a first doped region 111, one or more discrete regions 114 of a second doped region 113. The second doped region 113 may be separated from the first doped region 111 by an optional the intrinsic region 112. The discrete portions 114 are separated from one another by the first doped region 111 or the intrinsic region 112. The first doped region 111 and the second doped region 113 have opposite types of doping (e.g., region 111 is p-type and region 113 is n-type, or region 111 is n-type and region 113 is p-type). In the example in FIG. 1A, each of the discrete regions 114 of the second doped region 113 forms a diode with the first doped region 111 and the optional intrinsic region 112. Namely, in the example in FIG. 1A, the X-ray absorption layer 110 has a plurality of diodes having the first doped region 111 as a shared electrode. The first doped region 111 may also have discrete portions. FIG. 1B shows a semiconductor X-ray detector 100, according an embodiment. The semiconductor X-ray detector 100 may include an X-ray absorption layer 110 and an electronics layer 120 (e.g., an ASIC) for processing or analyzing electrical signals incident X-ray generates in the X-ray absorption layer 110. In an embodiment, the semiconductor X-ray detector 100 does not comprise a scintillator. The X-ray absorption layer 110 may include a semiconductor material such as, silicon, germanium, GaAs, CdTe, CdZnTe, or a combination thereof. The semiconductor may have a high mass attenuation coefficient for the X-ray energy of interest. The X-ray absorption layer 110 may not include a diode but includes a resistor. When an X-ray photon hits the X-ray absorption layer 110 including diodes, it may be absorbed and generate one or more charge carriers by a number of mechanisms. An X-ray photon may generate 10 to 100000 charge carriers. The charge carriers may drift to the electrodes of one of the diodes under an electric field. The field may be an external electric field. The electrical contact 119B may include discrete portions each of which is in electrical contact with the discrete regions 114. In an embodiment, the charge carriers may drift in directions such that the charge carriers generated by a single X-ray photon are not substantially shared by two different discrete regions 114 (“not substantially shared” here means less than 5%, less than 2% or less than 1% of these charge carriers flow to a different one of the discrete regions 114 than the rest of the charge carriers). In an embodiment, the charge carriers generated by a single X-ray photon can be shared by two different discrete regions 114. FIG. 2 shows an exemplary top view of a portion of the device 100 with a 4-by-4 array of discrete regions 114. Charge carriers generated by an X-ray photon incident around the footprint of one of these discrete regions 114 are not substantially shared with another of these discrete regions 114. The area around a discrete region 114 in which substantially all (more than 95%, more than 98% or more than 99% of) charge carriers generated by an X-ray photon incident therein flow to the discrete region 114 is called a pixel associated with the discrete region 114. Namely, less than 5%, less than 2% or less than 1% of these charge carriers flow beyond the pixel. By measuring the drift current flowing into each of the discrete regions 114, or the rate of change of the voltage of each of the discrete regions 114, the number of X-ray photons absorbed (which relates to the incident X-ray intensity) and/or the energies thereof in the pixels associated with the discrete regions 114 may be determined. Thus, the spatial distribution (e.g., an image) of incident X-ray intensity may be determined by individually measuring the drift current into each one of an array of discrete regions 114 or measuring the rate of change of the voltage of each one of an array of discrete regions 114. The pixels may be organized in any suitable array, such as, a square array, a triangular array and a honeycomb array. The pixels may have any suitable shape, such as, circular, triangular, square, rectangular, and hexangular. The pixels may be individually addressable. When an X-ray photon hits the X-ray absorption layer 110 including a resistor but not diodes, it may be absorbed and generate one or more charge carriers by a number of mechanisms. An X-ray photon may generate 10 to 100000 charge carriers. The charge carriers may drift to the electrical contacts 119A and 119B under an electric field. The field may be an external electric field. The electrical contact 119B includes discrete portions. In an embodiment, the charge carriers may drift in directions such that the charge carriers generated by a single X-ray photon are not substantially shared by two different discrete portions of the electrical contact 119B (“not substantially shared” here means less than 5%, less than 2% or less than 1% of these charge carriers flow to a different one of the discrete portions than the rest of the charge carriers). In an embodiment, the charge carriers generated by a single X-ray photon can be shared by two different discrete portions of the electrical contact 119B. Charge carriers generated by an X-ray photon incident around the footprint of one of these discrete portions of the electrical contact 119B are not substantially shared with another of these discrete portions of the electrical contact 119B. The area around a discrete portion of the electrical contact 119B in which substantially all (more than 95%, more than 98% or more than 99% of) charge carriers generated by an X-ray photon incident therein flow to the discrete portion of the electrical contact 119B is called a pixel associated with the discrete portion of the electrical contact 119B. Namely, less than 5%, less than 2% or less than 1% of these charge carriers flow beyond the pixel associated with the one discrete portion of the electrical contact 119B. By measuring the drift current flowing into each of the discrete portion of the electrical contact 119B, or the rate of change of the voltage of each of the discrete portions of the electrical contact 119B, the number of X-ray photons absorbed (which relates to the incident X-ray intensity) and/or the energies thereof in the pixels associated with of the discrete portions of the electrical contact 119B may be determined. Thus, the spatial distribution (e.g., an image) of incident X-ray intensity may be determined by individually measuring the drift current into each one of an array of discrete portions of the electrical contact 119B or measuring the rate of change of the voltage of each one of an array of discrete portions of the electrical contact 119B. The pixels may be organized in any suitable array, such as, a square array, a triangular array and a honeycomb array. The pixels may have any suitable shape, such as, circular, triangular, square, rectangular, and hexangular. The pixels may be individually addressable. The electronics layer 120 may include an electronic system 121 suitable for processing or interpreting signals generated by X-ray photons incident on the X-ray absorption layer 110. The electronic system 121 may include an analog circuitry such as a filter network, amplifiers, integrators, and comparators, or a digital circuitry such as a microprocessors, and memory. The electronic system 121 may include components shared by the pixels or components dedicated to a single pixel. For example, the electronic system 121 may include an amplifier dedicated to each pixel and a microprocessor shared among all the pixels. The electronic system 121 may be electrically connected to the pixels by vias 131. Space among the vias may be filled with a filler material 130, which may increase the mechanical stability of the connection of the electronics layer 120 to the X-ray absorption layer 110. Other bonding techniques are possible to connect the electronic system 121 to the pixels without using vias. FIG. 3A schematically shows the electronics layer 120 according to an embodiment. The electronic layer 120 comprises a substrate 122 having a first surface 124 and a second surface 128. A “surface” as used herein is not necessarily exposed, but can be buried wholly or partially. The electronic layer 120 comprises one or more electric contacts 125 on the first surface 124. The one or more electric contacts 125 may be configured to be electrically connected to one or more electrodes of the X-ray absorption layer 110. The electronics system 121 may be in or on the substrate 122. The electronic layer 120 comprises one or more vias 126 extending from the first surface 124 to the second surface 128. The electronic layer 120 comprises a redistribution layer (RDL) 123 on the second surface 128. The RDL 123 may comprise one or more transmission lines 127. The electronics system 121 is electrically connected to the electric contacts 125 and the transmission lines 127 through the vias 126. The RDL 123 is particularly useful when multiple chips each with an electronic layer 120 are arranged in an array to form a detector with a larger size, or when the electronic layer 120 is bigger than an area that can be exposed simultaneously in a photolithography process. The substrate 122 may be a thinned substrate. For example, the substrate may have at thickness of 750 microns or less, 200 microns or less, 100 microns or less, 50 microns or less, 20 microns or less, or 5 microns or less. The substrate 122 may be a silicon substrate or a substrate or other suitable semiconductor or insulator. The substrate 122 may be produced by grinding a thicker substrate to a desired thickness. The one or more electric contacts 125 may be a layer of metal or doped semiconductor. For example, the electric contacts 125 may be gold, copper, platinum, palladium, doped silicon, etc. The vias 126 pass through the substrate 122 and electrically connect electrical components (e.g., the electrical contacts 125) on the first surface 124 to electrical components (e.g., the RDL) on the second surface 128. The vias 126 may be used to provide electrical power and transmit signals to and from the electrical components in the detector 100. The vias 126 are sometimes referred to as “through-silicon vias” although they may be fabricated in substrates of materials other than silicon. The RDL 123 may comprise one or more transmission lines 127. The transmission lines 127 electrically connect electrical components (e.g., the vias 126) in the substrate 122 to bonding pads at other locations on the substrate 122. The transmission lines 127 may be electrically isolated from the substrate 122 except at certain vias 126 and certain bonding pads. The transmission lines 127 may be a material with small attenuation of X-ray, such as Al. The RDL 123 may redistribute electrical connections to more convenient locations. FIG. 3B schematically shows the electronics layer 120 according to an embodiment similar to the embodiment shown in FIG. 3A. Each of the electrical contacts 125 may have its dedicated controller 310. FIG. 3C schematically shows a top view of the electronics layer 120 according to an embodiment where a group of electrical contacts 125 share a peripheral circuit 319. The peripheral circuit 319 may be arranged on the first surface 124 in areas not occupied by other components (e.g., the group of electrical contacts 125, and the electronic system 121. If the electronics layer 120 is fabricated using photolithography, all or some of the electrical contacts 125 within an area exposed simultaneously may share one peripheral circuit 319. The peripheral circuit 319 may be connected to more than one transmission line 127 by more than one vias 126. FIG. 3D schematically shows a top view of the electronics layer 120 according to an embodiment, with a different arrangement of the peripheral circuit 319. The arrangement of the peripheral circuit 319 is not limited to these examples. The peripheral circuit 319 may have redundancy. Redundancy allows the semiconductor X-ray detector 100 not to be disabled due to a partial failure of the peripheral circuit 319. If one part of the peripheral circuit 319 fails, another part may be activated. For example, if multiple pixels share the same peripheral circuit 319, total failure of the peripheral circuit 319 will disable all these pixels and likely render the entire detector 100 inoperable. Having redundancy reduces the chance of total failure. The peripheral circuit 319 may be configured to perform various functions, such as multiplexing, input/output, providing power, data caching, etc. The peripheral circuit 319 is not necessarily arranged on the first surface. FIG. 3E schematically shows a cross-sectional view of the electronics layer 120 according to an embodiment where the peripheral circuit 319 is arranged on a surface 128 of a substrate 123A sandwiched between the substrate 122 and the RDL 123. The peripheral circuit 319 may be electrically connected to the electrical contacts 125 by a first group of vias 126A extending in the substrate 122 and electrically connected to the transmission lines 127 by a second group of vias 126B extending in the substrate 123A. Each of the electrical contacts 125 may have a dedicated vias 126A for connection to the peripheral circuit 319. The peripheral circuit 319 may be arranged on multiple surfaces. FIG. 4A schematically shows direct bonding between the X-ray absorption layer 110 and the electronic layer 120 at discrete portion of the electrical contact 119B and the electrical contacts 125. Direct bonding is a wafer bonding process without any additional intermediate layers (e.g., solder bumps). The bonding process is based on chemical bonds between two surfaces. Direct bonding may be at elevated temperature but not necessarily so. FIG. 4B schematically shows flip chip bonding between the X-ray absorption layer 110 and the electronic layer 120 at discrete portion of the electrical contact 119B and the electrical contacts 125. Flip chip bonding uses solder bumps 199 deposited onto contact pads (e.g., the electrodes of the X-ray absorption layer 110 or the electrical contacts 125). Either the X-ray absorption layer 110 or the electronic layer 120 is flipped over and the electrodes of the X-ray absorption layer 110 are aligned to the electrical contacts 125. The solder bumps 199 may be melted to solder the electrodes and the electrical contacts 125 together. Any void space among the solder bumps 199 may be filled with an insulating material. Other materials such as thermal copper or gold pillar bump may be used to achieve similar function as solder bumps. FIG. 5 schematically shows a bottom view of the RDL 123, with other components obstructing the view omitted. The transmission lines 127 can be seen to electrically connect to vias 126 and redistribute vias 126 to other locations. FIG. 6A shows that the electronics layer 120 as shown in FIG. 3A, FIG. 3B, FIG. 3C, FIG. 3D, or FIG. 3E allows stacking multiple semiconductor X-ray detectors 100 because the RDL 123 and the vias 126 facilitate routing of signal paths through multiple layers and because the electronic system 121 as described below may have low enough power consumption to eliminate bulky cooling mechanisms. The multiple semiconductor X-ray detectors 100 in the stack do not have to be identical. For example, the multiple semiconductor X-ray detectors 100 may differ in thickness, structure, or material. FIG. 6B schematically shows a top view of multiple semiconductor X-ray detectors 100 stacked. Each layer may have multiple detectors 100 tiled to cover a larger area. The tiled detectors 100 in one layer can be staggered relative to the tiled detectors 100 in another layer, which may eliminate gaps in which incident X-ray photons cannot be detected. According to an embodiment, the semiconductor X-ray detector 100 may be fabricated using a method including: obtaining an X-ray absorption layer comprising an electrode; obtaining an electronics layer, the electronics layer comprising: a substrate having a first surface and a second surface, an electronics system in or on the substrate, an electric contact on the first surface, a via, and a redistribution layer (RDL) on the second surface; bonding the X-ray absorption layer and the electronics layer such that the electrode is electrically connected to the electric contact; wherein the RDL comprises a transmission line; wherein the via extends from the first surface to the second surface; wherein the electronics system is electrically connected to the electric contact and the transmission line through the via. FIG. 7A and FIG. 7B each show a component diagram of the electronic system 121, according to an embodiment. The electronic system 121 may include a first voltage comparator 301, a second voltage comparator 302, a counter 320, a switch 305, a voltmeter 306 and a controller 310. The first voltage comparator 301 is configured to compare the voltage of an electrode of a diode 300 to a first threshold. The diode may be a diode formed by the first doped region 111, one of the discrete regions 114 of the second doped region 113, and the optional intrinsic region 112. Alternatively, the first voltage comparator 301 is configured to compare the voltage of an electrical contact (e.g., a discrete portion of electrical contact 119B) to a first threshold. The first voltage comparator 301 may be configured to monitor the voltage directly, or calculate the voltage by integrating an electric current flowing through the diode or electrical contact over a period of time. The first voltage comparator 301 may be controllably activated or deactivated by the controller 310. The first voltage comparator 301 may be a continuous comparator. Namely, the first voltage comparator 301 may be configured to be activated continuously, and monitor the voltage continuously. The first voltage comparator 301 configured as a continuous comparator reduces the chance that the system 121 misses signals generated by an incident X-ray photon. The first voltage comparator 301 configured as a continuous comparator is especially suitable when the incident X-ray intensity is relatively high. The first voltage comparator 301 may be a clocked comparator, which has the benefit of lower power consumption. The first voltage comparator 301 configured as a clocked comparator may cause the system 121 to miss signals generated by some incident X-ray photons. When the incident X-ray intensity is low, the chance of missing an incident X-ray photon is low because the time interval between two successive photons is relatively long. Therefore, the first voltage comparator 301 configured as a clocked comparator is especially suitable when the incident X-ray intensity is relatively low. The first threshold may be 5-10%, 10%-20%, 20-30%, 30-40% or 40-50% of the maximum voltage one incident X-ray photon may generate in the diode or the resistor. The maximum voltage may depend on the energy of the incident X-ray photon (i.e., the wavelength of the incident X-ray), the material of the X-ray absorption layer 110, and other factors. For example, the first threshold may be 50 mV, 100 mV, 150 mV, or 200 mV. The second voltage comparator 302 is configured to compare the voltage to a second threshold. The second voltage comparator 302 may be configured to monitor the voltage directly, or calculate the voltage by integrating an electric current flowing through the diode or the electrical contact over a period of time. The second voltage comparator 302 may be a continuous comparator. The second voltage comparator 302 may be controllably activate or deactivated by the controller 310. When the second voltage comparator 302 is deactivated, the power consumption of the second voltage comparator 302 may be less than 1%, less than 5%, less than 10% or less than 20% of the power consumption when the second voltage comparator 302 is activated. The absolute value of the second threshold is greater than the absolute value of the first threshold. As used herein, the term “absolute value” or “modulus” Ix′ of a real number x is the non-negative value of x without regard to its sign. Namely, x = { x , if x ≥ 0 - x , if x ≤ 0 . The second threshold may be 200%-300% of the first threshold. The second threshold may be at least 50% of the maximum voltage one incident X-ray photon may generate in the diode or resistor. For example, the second threshold may be 100 mV, 150 mV, 200 mV, 250 mV or 300 mV. The second voltage comparator 302 and the first voltage comparator 310 may be the same component. Namely, the system 121 may have one voltage comparator that can compare a voltage with two different thresholds at different times. The first voltage comparator 301 or the second voltage comparator 302 may include one or more op-amps or any other suitable circuitry. The first voltage comparator 301 or the second voltage comparator 302 may have a high speed to allow the system 121 to operate under a high flux of incident X-ray. However, having a high speed is often at the cost of power consumption. The counter 320 is configured to register a number of X-ray photons reaching the diode or resistor. The counter 320 may be a software component (e.g., a number stored in a computer memory) or a hardware component (e.g., a 4017 IC and a 7490 IC). The controller 310 may be a hardware component such as a microcontroller and a microprocessor. The controller 310 is configured to start a time delay from a time at which the first voltage comparator 301 determines that the absolute value of the voltage equals or exceeds the absolute value of the first threshold (e.g., the absolute value of the voltage increases from below the absolute value of the first threshold to a value equal to or above the absolute value of the first threshold). The absolute value is used here because the voltage may be negative or positive, depending on whether the voltage of the cathode or the anode of the diode or which electrical contact is used. The controller 310 may be configured to keep deactivated the second voltage comparator 302, the counter 320 and any other circuits the operation of the first voltage comparator 301 does not require, before the time at which the first voltage comparator 301 determines that the absolute value of the voltage equals or exceeds the absolute value of the first threshold. The time delay may expire before or after the voltage becomes stable, i.e., the rate of change of the voltage is substantially zero. The phase “the rate of change of the voltage is substantially zero” means that temporal change of the voltage is less than 0.1%/ns. The phase “the rate of change of the voltage is substantially non-zero” means that temporal change of the voltage is at least 0.1%/ns. The controller 310 may be configured to activate the second voltage comparator during (including the beginning and the expiration) the time delay. In an embodiment, the controller 310 is configured to activate the second voltage comparator at the beginning of the time delay. The term “activate” means causing the component to enter an operational state (e.g., by sending a signal such as a voltage pulse or a logic level, by providing power, etc.). The term “deactivate” means causing the component to enter a non-operational state (e.g., by sending a signal such as a voltage pulse or a logic level, by cut off power, etc.). The operational state may have higher power consumption (e.g., 10 times higher, 100 times higher, 1000 times higher) than the non-operational state. The controller 310 itself may be deactivated until the output of the first voltage comparator 301 activates the controller 310 when the absolute value of the voltage equals or exceeds the absolute value of the first threshold. The controller 310 may be configured to cause the number registered by the counter 320 to increase by one, if, during the time delay, the second voltage comparator 302 determines that the absolute value of the voltage equals or exceeds the absolute value of the second threshold. The controller 310 may be configured to cause the voltmeter 306 to measure the voltage upon expiration of the time delay. The controller 310 may be configured to connect the electrode to an electrical ground, so as to reset the voltage and discharge any charge carriers accumulated on the electrode. In an embodiment, the electrode is connected to an electrical ground after the expiration of the time delay. In an embodiment, the electrode is connected to an electrical ground for a finite reset time period. The controller 310 may connect the electrode to the electrical ground by controlling the switch 305. The switch may be a transistor such as a field-effect transistor (FET). In an embodiment, the system 121 has no analog filter network (e.g., a RC network). In an embodiment, the system 121 has no analog circuitry. The voltmeter 306 may feed the voltage it measures to the controller 310 as an analog or digital signal. The system 121 may include a capacitor module 309 electrically connected to the electrode of the diode 300 or which electrical contact, wherein the capacitor module is configured to collect charge carriers from the electrode. The capacitor module can include a capacitor in the feedback path of an amplifier. The amplifier configured as such is called a capacitive transimpedance amplifier (CTIA). CTIA has high dynamic range by keeping the amplifier from saturating and improves the signal-to-noise ratio by limiting the bandwidth in the signal path. Charge carriers from the electrode accumulate on the capacitor over a period of time (“integration period”) (e.g., as shown in FIG. 8, between t0 to t1, or t1-t2). After the integration period has expired, the capacitor voltage is sampled and then reset by a reset switch. The capacitor module can include a capacitor directly connected to the electrode. FIG. 8 schematically shows a temporal change of the electric current flowing through the electrode (upper curve) caused by charge carriers generated by an X-ray photon incident on the diode or the resistor, and a corresponding temporal change of the voltage of the electrode (lower curve). The voltage may be an integral of the electric current with respect to time. At time to, the X-ray photon hits the diode or the resistor, charge carriers start being generated in the diode or the resistor, electric current starts to flow through the electrode of the diode or the resistor, and the absolute value of the voltage of the electrode or electrical contact starts to increase. At time t1, the first voltage comparator 301 determines that the absolute value of the voltage equals or exceeds the absolute value of the first threshold V1, and the controller 310 starts the time delay TD1 and the controller 310 may deactivate the first voltage comparator 301 at the beginning of TD1. If the controller 310 is deactivated before t1, the controller 310 is activated at t1. During TD1, the controller 310 activates the second voltage comparator 302. The term “during” a time delay as used here means the beginning and the expiration (i.e., the end) and any time in between. For example, the controller 310 may activate the second voltage comparator 302 at the expiration of TD1. If during TD1, the second voltage comparator 302 determines that the absolute value of the voltage equals or exceeds the absolute value of the second threshold at time t2, the controller 310 causes the number registered by the counter 320 to increase by one. At time te, all charge carriers generated by the X-ray photon drift out of the X-ray absorption layer 110. At time ts, the time delay TD1 expires. In the example of FIG. 8, time ts is after time te; namely TD1 expires after all charge carriers generated by the X-ray photon drift out of the X-ray absorption layer 110. The rate of change of the voltage is thus substantially zero at ts. The controller 310 may be configured to deactivate the second voltage comparator 302 at expiration of TD1 or at t2, or any time in between. The controller 310 may be configured to cause the voltmeter 306 to measure the voltage upon expiration of the time delay TD1. In an embodiment, the controller 310 causes the voltmeter 306 to measure the voltage after the rate of change of the voltage becomes substantially zero after the expiration of the time delay TD1. The voltage at this moment is proportional to the amount of charge carriers generated by an X-ray photon, which relates to the energy of the X-ray photon. The controller 310 may be configured to determine the energy of the X-ray photon based on voltage the voltmeter 306 measures. One way to determine the energy is by binning the voltage. The counter 320 may have a sub-counter for each bin. When the controller 310 determines that the energy of the X-ray photon falls in a bin, the controller 310 may cause the number registered in the sub-counter for that bin to increase by one. Therefore, the system 121 may be able to detect an X-ray image and may be able to resolve X-ray photon energies of each X-ray photon. After TD1 expires, the controller 310 connects the electrode to an electric ground for a reset period RST to allow charge carriers accumulated on the electrode to flow to the ground and reset the voltage. After RST, the system 121 is ready to detect another incident X-ray photon. Implicitly, the rate of incident X-ray photons the system 121 can handle in the example of FIG. 8 is limited by 1/(TD1+RST). If the first voltage comparator 301 has been deactivated, the controller 310 can activate it at any time before RST expires. If the controller 310 has been deactivated, it may be activated before RST expires. FIG. 9 schematically shows a temporal change of the electric current flowing through the electrode (upper curve) caused by noise (e.g., dark current, background radiation, scattered X-rays, fluorescent X-rays, shared charges from adjacent pixels), and a corresponding temporal change of the voltage of the electrode (lower curve), in the system 121 operating in the way shown in FIG. 8. At time to, the noise begins. If the noise is not large enough to cause the absolute value of the voltage to exceed the absolute value of V1, the controller 310 does not activate the second voltage comparator 302. If the noise is large enough to cause the absolute value of the voltage to exceed the absolute value of V1 at time t1 as determined by the first voltage comparator 301, the controller 310 starts the time delay TD1 and the controller 310 may deactivate the first voltage comparator 301 at the beginning of TD1. During TD1 (e.g., at expiration of TD1), the controller 310 activates the second voltage comparator 302. The noise is very unlikely large enough to cause the absolute value of the voltage to exceed the absolute value of V2 during TD1. Therefore, the controller 310 does not cause the number registered by the counter 320 to increase. At time te, the noise ends. At time ts, the time delay TD1 expires. The controller 310 may be configured to deactivate the second voltage comparator 302 at expiration of TD1. The controller 310 may be configured not to cause the voltmeter 306 to measure the voltage if the absolute value of the voltage does not exceed the absolute value of V2 during TD1. After TD1 expires, the controller 310 connects the electrode to an electric ground for a reset period RST to allow charge carriers accumulated on the electrode as a result of the noise to flow to the ground and reset the voltage. Therefore, the system 121 may be very effective in noise rejection. FIG. 10 schematically shows a temporal change of the electric current flowing through the electrode (upper curve) caused by charge carriers generated by an X-ray photon incident on the diode or the resistor, and a corresponding temporal change of the voltage of the electrode (lower curve), when the system 121 operates to detect incident X-ray photons at a rate higher than 1/(TD1+RST). The voltage may be an integral of the electric current with respect to time. At time to, the X-ray photon hits the diode or the resistor, charge carriers start being generated in the diode or the resistor, electric current starts to flow through the electrode of the diode or the electrical contact of resistor, and the absolute value of the voltage of the electrode or the electrical contact starts to increase. At time t1, the first voltage comparator 301 determines that the absolute value of the voltage equals or exceeds the absolute value of the first threshold V1, and the controller 310 starts a time delay TD2 shorter than TD1, and the controller 310 may deactivate the first voltage comparator 301 at the beginning of TD2. If the controller 310 is deactivated before t1, the controller 310 is activated at t1. During TD2 (e.g., at expiration of TD2), the controller 310 activates the second voltage comparator 302. If during TD2, the second voltage comparator 302 determines that the absolute value of the voltage equals or exceeds the absolute value of the second threshold at time t2, the controller 310 causes the number registered by the counter 320 to increase by one. At time te, all charge carriers generated by the X-ray photon drift out of the X-ray absorption layer 110. At time th, the time delay TD2 expires. In the example of FIG. 10, time th is before time te; namely TD2 expires before all charge carriers generated by the X-ray photon drift out of the X-ray absorption layer 110. The rate of change of the voltage is thus substantially non-zero at th. The controller 310 may be configured to deactivate the second voltage comparator 302 at expiration of TD2 or at t2, or any time in between. The controller 310 may be configured to extrapolate the voltage at te from the voltage as a function of time during TD2 and use the extrapolated voltage to determine the energy of the X-ray photon. After TD2 expires, the controller 310 connects the electrode to an electric ground for a reset period RST to allow charge carriers accumulated on the electrode to flow to the ground and reset the voltage. In an embodiment, RST expires before te. The rate of change of the voltage after RST may be substantially non-zero because all charge carriers generated by the X-ray photon have not drifted out of the X-ray absorption layer 110 upon expiration of RST before te. The rate of change of the voltage becomes substantially zero after te and the voltage stabilized to a residue voltage VR after te. In an embodiment, RST expires at or after te, and the rate of change of the voltage after RST may be substantially zero because all charge carriers generated by the X-ray photon drift out of the X-ray absorption layer 110 at te. After RST, the system 121 is ready to detect another incident X-ray photon. If the first voltage comparator 301 has been deactivated, the controller 310 can activate it at any time before RST expires. If the controller 310 has been deactivated, it may be activated before RST expires. FIG. 11 schematically shows a temporal change of the electric current flowing through the electrode (upper curve) caused by noise (e.g., dark current, background radiation, scattered X-rays, fluorescent X-rays, shared charges from adjacent pixels), and a corresponding temporal change of the voltage of the electrode (lower curve), in the system 121 operating in the way shown in FIG. 10. At time t0, the noise begins. If the noise is not large enough to cause the absolute value of the voltage to exceed the absolute value of V1, the controller 310 does not activate the second voltage comparator 302. If the noise is large enough to cause the absolute value of the voltage to exceed the absolute value of V1 at time t1 as determined by the first voltage comparator 301, the controller 310 starts the time delay TD2 and the controller 310 may deactivate the first voltage comparator 301 at the beginning of TD2. During TD2 (e.g., at expiration of TD2), the controller 310 activates the second voltage comparator 302. The noise is very unlikely large enough to cause the absolute value of the voltage to exceed the absolute value of V2 during TD2. Therefore, the controller 310 does not cause the number registered by the counter 320 to increase. At time te, the noise ends. At time th, the time delay TD2 expires. The controller 310 may be configured to deactivate the second voltage comparator 302 at expiration of TD2. After TD2 expires, the controller 310 connects the electrode to an electric ground for a reset period RST to allow charge carriers accumulated on the electrode as a result of the noise to flow to the ground and reset the voltage. Therefore, the system 121 may be very effective in noise rejection. FIG. 12 schematically shows a temporal change of the electric current flowing through the electrode (upper curve) caused by charge carriers generated by a series of X-ray photons incident on the diode or the resistor, and a corresponding temporal change of the voltage of the electrode (lower curve), in the system 121 operating in the way shown in FIG. 10 with RST expires before te. The voltage curve caused by charge carriers generated by each incident X-ray photon is offset by the residue voltage before that photon. The absolute value of the residue voltage successively increases with each incident photon. When the absolute value of the residue voltage exceeds V1 (see the dotted rectangle in FIG. 12), the controller starts the time delay TD2 and the controller 310 may deactivate the first voltage comparator 301 at the beginning of TD2. If no other X-ray photon incidence on the diode or the resistor during TD2, the controller connects the electrode to the electrical ground during the reset time period RST at the end of TD2, thereby resetting the residue voltage. The residue voltage thus does not cause an increase of the number registered by the counter 320. FIG. 13 schematically shows a system comprising the semiconductor X-ray detector 100 described herein. The system may be used for medical imaging such as chest X-ray radiography, abdominal X-ray radiography, etc. The system comprises an X-ray source 1201. X-ray emitted from the X-ray source 1201 penetrates an object 1202 (e.g., a human body part such as chest, limb, abdomen), is attenuated by different degrees by the internal structures of the object 1202 (e.g., bones, muscle, fat and organs, etc.), and is projected to the semiconductor X-ray detector 100. The semiconductor X-ray detector 100 forms an image by detecting the intensity distribution of the X-ray. FIG. 14 schematically shows a system comprising the semiconductor X-ray detector 100 described herein. The system may be used for medical imaging such as dental X-ray radiography. The system comprises an X-ray source 1301. X-ray emitted from the X-ray source 1301 penetrates an object 1302 that is part of a mammal (e.g., human) mouth. The object 1302 may include a maxilla bone, a palate bone, a tooth, the mandible, or the tongue. The X-ray is attenuated by different degrees by the different structures of the object 1302 and is projected to the semiconductor X-ray detector 100. The semiconductor X-ray detector 100 forms an image by detecting the intensity distribution of the X-ray. Teeth absorb X-ray more than dental caries, infections, periodontal ligament. The dosage of X-ray radiation received by a dental patient is typically small (around 0.150 mSv for a full mouth series). FIG. 15 schematically shows a cargo scanning or non-intrusive inspection (NII) system comprising the semiconductor X-ray detector 100 described herein. The system may be used for inspecting and identifying goods in transportation systems such as shipping containers, vehicles, ships, luggage, etc. The system comprises an X-ray source 1401. X-ray emitted from the X-ray source 1401 may backscatter from an object 1402 (e.g., shipping containers, vehicles, ships, etc.) and be projected to the semiconductor X-ray detector 100. Different internal structures of the object 1402 may backscatter X-ray differently. The semiconductor X-ray detector 100 forms an image by detecting the intensity distribution of the backscattered X-ray and/or energies of the backscattered X-ray photons. FIG. 16 schematically shows another cargo scanning or non-intrusive inspection (NII) system comprising the semiconductor X-ray detector 100 described herein. The system may be used for luggage screening at public transportation stations and airports. The system comprises an X-ray source 1501. X-ray emitted from the X-ray source 1501 may penetrate a piece of luggage 1502, be differently attenuated by the contents of the luggage, and projected to the semiconductor X-ray detector 100. The semiconductor X-ray detector 100 forms an image by detecting the intensity distribution of the transmitted X-ray. The system may reveal contents of luggage and identify items forbidden on public transportation, such as firearms, narcotics, edged weapons, flammables. FIG. 17 schematically shows a full-body scanner system comprising the semiconductor X-ray detector 100 described herein. The full-body scanner system may detect objects on a person's body for security screening purposes, without physically removing clothes or making physical contact. The full-body scanner system may be able to detect non-metal objects. The full-body scanner system comprises an X-ray source 1601. X-ray emitted from the X-ray source 1601 may backscatter from a human 1602 being screened and objects thereon, and be projected to the semiconductor X-ray detector 100. The objects and the human body may backscatter X-ray differently. The semiconductor X-ray detector 100 forms an image by detecting the intensity distribution of the backscattered X-ray. The semiconductor X-ray detector 100 and the X-ray source 1601 may be configured to scan the human in a linear or rotational direction. FIG. 18 schematically shows an X-ray computed tomography (X-ray CT) system. The X-ray CT system uses computer-processed X-rays to produce tomographic images (virtual “slices”) of specific areas of a scanned object. The tomographic images may be used for diagnostic and therapeutic purposes in various medical disciplines, or for flaw detection, failure analysis, metrology, assembly analysis and reverse engineering. The X-ray CT system comprises the semiconductor X-ray detector 100 described herein and an X-ray source 1701. The semiconductor X-ray detector 100 and the X-ray source 1701 may be configured to rotate synchronously along one or more circular or spiral paths. FIG. 19 schematically shows an electron microscope. The electron microscope comprises an electron source 1801 (also called an electron gun) that is configured to emit electrons. The electron source 1801 may have various emission mechanisms such as thermionic, photocathode, cold emission, or plasmas source. The emitted electrons pass through an electronic optical system 1803, which may be configured to shape, accelerate, or focus the electrons. The electrons then reach a sample 1802 and an image detector may form an image therefrom. The electron microscope may comprise the semiconductor X-ray detector 100 described herein, for performing energy-dispersive X-ray spectroscopy (EDS). EDS is an analytical technique used for the elemental analysis or chemical characterization of a sample. When the electrons incident on a sample, they cause emission of characteristic X-rays from the sample. The incident electrons may excite an electron in an inner shell of an atom in the sample, ejecting it from the shell while creating an electron hole where the electron was. An electron from an outer, higher-energy shell then fills the hole, and the difference in energy between the higher-energy shell and the lower energy shell may be released in the form of an X-ray. The number and energy of the X-rays emitted from the sample can be measured by the semiconductor X-ray detector 100. The semiconductor X-ray detector 100 described here may have other applications such as in an X-ray telescope, X-ray mammography, industrial X-ray defect detection, X-ray microscopy or microradiography, X-ray casting inspection, X-ray non-destructive testing, X-ray weld inspection, X-ray digital subtraction angiography, etc. It may be suitable to use this semiconductor X-ray detector 100 in place of a photographic plate, a photographic film, a PSP plate, an X-ray image intensifier, a scintillator, or another semiconductor X-ray detector. While various aspects and embodiments have been disclosed herein, other aspects and embodiments will be apparent to those skilled in the art. The various aspects and embodiments disclosed herein are for purposes of illustration and are not intended to be limiting, with the true scope and spirit being indicated by the following claims. |
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052992446 | description | DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A fuel assembly which is one of the preferred embodiments of the present invention is explained hereinafter referring to FIG. 1. The fuel assembly 10A of the present embodiment comprises a channel box 1 having fuel rods 3 arranged in triangle lattices. The fuel assembly 10A has a water rods group 7A and four water rods groups 7B. The water rods group 7A is arranged at the center of the cross section of the fuel assembly 10A, and the water rods groups 7B are arranged at surrounding of the water rods group 7A. The water rods group 7A has no fuel rod 3 inside but seven water rods 2 arranged adjacently each other. The water rods group 7B has also no fuel rod 3 inside but three water rods 2 arranged adjacently each other. The water rods 2 in the water rods groups are arranged in triangle lattices as same as fuel rods 3. The arranging pitch of the water rods 2 is same as the arranging pitch of the fuel rods 3. The water rods group 7A and the water rods groups 7B, and the water rods groups 7B themselves are not arranged adjacently each other, and fuel rods 3 are necessarily arranged among the groups. Each of the water rods groups are surrounded with fuel rods. As shown in FIG. 8, an upper end and lower end of each of the water rod 2 and the fuel rod 3 are supported by an upper tie plate 13 and a lower tie plate 14 respectively with fuel spacers 15 maintaining intervals between the fuel rods. In the present embodiment, the fuel rods are arranged in the channel box 1 in triangle lattices with 11 lines by 10 rows. When taking 134 mm for inside width of the channel box as same as the conventional fuel assembly, it is necessary to make diameter of the fuel rod 10.3 mm and the pitch between fuel rods 13 mm in order to make uranium inventory in the fuel assembly 10A same per unit volume as the conventional fuel assembly. The fuel assembly of the present embodiment can be loaded with five more fuel rods than the conventional fuel assembly which has a fuel arrangement of square lattices of 10 lines by 10 rows. In accordance with the fuel assembly 10A, taking for the longitudinal pitch of the fuel rods in FIG. 1, the horizontal pitch of the fuel rods becomes .sqroot.3a/2 (=0.87a). Therefore, in the present embodiment, it is preferable to make the ratio of the number of arranged fuel rods in longitudinal direction and horizontal direction an integer close to 1 to 0.87 as possible, and make the shape of the whole fuel rods arrangement a square. By the arrangement as above described, the fuel rods arranged in the manner of the present embodiment can be inserted effectively in the conventional channel box having a square cross section which is used for conventional fuel assembly. The fuel assembly 10A has smaller coolant path area in the channel box by about 5% than the conventional fuel assembly having same cross sectional area of the channel box. The coolant path means the path formed among the fuel rods 3 and the water rods 2. Next, the number of the water rods is explained. The optimum number of the water rods 2 is determined by the characteristics of the relation shown in FIG. 2. That is, FIG. 2 shows the relation between the water rods 2 fraction (the fraction in number of water rods to the total number of rods 3 which are able to be arranged in the fuel assembly, that is to say, the sum of the number of the fuel rods 3 and the number of the water rods 2) and the infinite multiplication factor with average enrichment of the fuel assembly as parameters. According to the relation, it is understandable that the void reactivity coefficient can be decreased and, further, high burn up and economical use of the fuel assembly can be achieved with highly enriched fuel by making the water rod fraction at least 10%. Accordingly, the number of the water rods has to be increased as the average enrichment of the fuel assembly is increased. In case of the present embodiment, the average enrichment of the fuel assembly 10A is 4.9% and number of the water rods 2 is 19. The water rods 2 are divided into a several water rods groups as above described, and the water rods groups are arranged not adjacently so as to make distribution of the moderator and the fuel in the fuel assembly homogeneous as possible. The fuel assembly 10A of the present embodiment improves fuel economy as same level as the fuel assembly disclosed in JP-A-62-217186 (1987) by arranging a plurality of fuel rods and a plurality of water rods in the conventional fuel assembly. And, in accordance with the present embodiment, as arranged lattices of the fuel rods are increased with concurrent arrangement of many water rods 2 in keeping the water to fuel volume ratio almost same as the fuel assembly disclosed in JP-A-62-217186 (1987), void generating region caused by reduction of coolant path area is decreased. Consequently, the void reactivity coefficient becomes small and improvement in safety and operability of the boiling water reactors is realized. According to the present embodiment, as the outer diameter of the water rod 2 is smaller than the fuel rods pitch, the water rods 2 in each water rods groups are not contacted each other and the coolant path is formed between the water rods 2. Therefore, the coolant path area in the fuel assembly 10A, especially the coolant path in the upper vapor-liquid two phase flow portion of the fuel assembly, can be increased. The increment causes reduction of pressure loss of the fuel assembly 10A, and maintenance of preferable nuclear thermal hydraulic stability is realized. It can be considered that the water rods having larger outer diameter than the fuel rod pitch as disclosed in FIG. 1 of JP-A-63-82391 (1988) are arranged in the fuel assembly having fuel arrangement in triangle lattices as the present embodiment instead of the water rods groups of the present embodiment. In this case, coolant flow in the fuel assembly is not uniform because of forming wider local portion of coolant path than the coolant path which is formed between the water rod and adjacent fuel rod. The ununiformity of coolant flow becomes a cause of lowering of maximum allowable power with the fuel assembly having dense fuel rods arrangement in triangle lattices. In accordance with the present embodiment, as the water rods 2 having smaller outer diameter than the fuel rods pitch are arranged, coolant flow in the fuel assembly 10A is uniform and the problem described above is not caused. In accordance with the present embodiment, as a plurality of water rods in the water rods group are arranged adjacently each other, the void fraction in the coolant path which is formed among water rods 2 becomes small. Making the void fraction small relates to the expanding of the saturated water region area, namely, the region being substantially occupied with saturated water, which is formed around the water rods 2 in the water rods group, and consequently the void reactivity coefficient becomes small. Accordingly, safety and operability of the boiling water reactors are improved. The water rods group having the function as above described behaves as if it were a large water rod having same cross sectional area with the water rods group. Fuel economy is also increased because a plurality of water rods groups are arranged dispersedly in the fuel assembly. The composition of the embodiment of the present invention applied to the fuel assembly 11 for the reactor core having large lattices shown in FIGS. 3 and 4 is illustrated in FIG. 5. In FIGS. 3 and 4, the numeral 12 indicates control rods. The length of a side of the cross section of the fuel assembly of the present embodiment shown in FIG. 5 is .sqroot.2 times of the side of the cross section of the fuel assembly shown in FIG. 1. The fuel assembly of the present embodiment 10B comprises fuel rods 3 and water rods 2 which are arranged in triangle lattices in the channel box 1A as same as the fuel assembly 10A. The water rods group including a plurality of water rods 2 is arranged as same as the fuel assembly 10A. In accordance with the present embodiment, the same effect as the fuel assembly 10A is realized. Especially, as the present embodiment has more water rods 2 (the fraction of number of water rods 2 to the sum of the numbers of water rods 2 and fuel rods 3 is at least 10%) than the fuel assembly 11 shown in FIG. 4 (the fuel assembly disclosed in JP-A-62-259086 (1987)), unboiled region is increased. Accordingly, the void reactivity coefficient of the present embodiment becomes small. Especially, the void fraction becomes small in the coolant path formed between adjacent water rods 2 as described above, the e saturated water region is substantially increased in the coolant path. The void reactivity coefficient becomes small also by the function above described. The fuel assembly relating to other embodiment of the present invention is illustrated in FIG. 6. The embodiment is same as fuel assembly 10A except the fuel rods 5 which replaced a part of fuel rods 3 and the water rods 4 which replaced all of the water rods 2. The fuel rod 5 has a shorter length in axial direction than the fuel rod 3. The fuel rod 5 is a fuel rod having a partial length. The water rod 4 has also a shorter length in axial direction than the fuel rod 3, and substantially same length as the fuel rod 5. The lower ends of the water rod 4 and fuel rod 5 are supported with the lower tie plate. Therefore, the space which becomes the coolant path is formed above the water rod 4 and the fuel rod 5. The space locates among the fuel rods 3. Almost of the fuel rods 5 are surrounded with the fuel rods 3. In the manner described above, by using of the water rod 4 and the fuel rod 5 both of which have shorter length in axial direction, the area of cooling water path at the upper portion of the fuel assembly (vapor-liquid two phase flow region) having large pressure loss can be increased more than the lower portion of the fuel assembly. Accordingly, pressure loss of the fuel assembly 10C is reduced, and the hydraulic stability of the fuel channel is improved. The reason of the improvement is explained hereinafter. For improvement of hydraulic stability of the fuel channel, it is important to reduce the pressure loss in the fuel channel. The friction pressure loss .DELTA.Pf caused by vapor-liquid two phase flow in the boiling water reactor is expressed by following equation: ##EQU1## Where, W : flow rate in the channel, g : acceleration of gravity, PA1 .rho. : density of water, PA1 D : hydraulic diameter of the channel, PA1 A :area of the channel flow path, PA1 f :friction pressure loss coefficient, and PA1 .PHI. :two phase flow friction pressure loss multiplication factor. The upper region from the upper end of the effective fuel length of the fuel rod (the axial length of the fuel pellets loaded portion in the fuel rod) is scarcely effected by the fission reaction of the fissile material in the reactor core. The void fraction in this region is large. In the above equation (1), the two phase flow friction pressure loss multiplication factor becomes larger as the void fraction increases. Therefore, loading of water rods 4 and fuel rods 5 relates to increment of the coolant flow path area (the channel flow path area A) by forming the space above the water rods 4 and fuel rods 5 and shortening of the channel length L. Accordingly, the pressure loss of the fuel assembly 10C can be reduced depending on the relation expressed by the equation (1). In accordance with the present embodiment, same effect as the fuel assembly 10A is realized. The fuel assembly 10D, which is other embodiment of the present invention, is illustrated in FIG. 7. In the present embodiment, the water rods 4 and the fuel rods 5 are applied to the fuel assembly 10B as same as the fuel assembly 10C. In accordance with the present embodiment, same effect with the fuel assembly 10C is realized. |
claims | 1. A plasma processing method, comprising the steps of:mounting a sample on a sample electrode disposed in a vacuum container, exhausting the vacuum container while supplying a source gas to inside the vacuum container, and generating plasma in the vacuum container by supplying high-frequency power to a plasma source; andapplying plasma to a surface of the sample while being adjusted so that thickness of an ion sheath is made uniform on the surface of the sample, in a state that a conductor ring is disposed so as to surround an outer perimeter of the sample. 2. The plasma processing method according to claim 1, wherein the plasma is adjusted so as to amorphyze a surface layer of the sample. 3. The plasma processing method according to claim 1, wherein the plasma is adjusted so as to introduce an impurity into a surface layer of the sample. 4. The plasma processing method according to claim 1, wherein the conductor ring has a surface that is approximately the same in height as the surface of the sample. 5. The plasma processing method according to claim 4, wherein a distance between the outer perimeter of the sample and an inner perimeter of the conductor ring is in a range of 1 mm to 10 mm. 6. The plasma processing method according to claim 4, wherein a difference in height between the surface of the sample and a surface of the conductor ring is in a range of 0.001 mm to 1 mm. 7. The plasma processing method according to claim 4, wherein a voltage is applied to a pedestal in a state that the sample electrode has a layered structure in which a first dielectric layer, an electrostatic chuck electrode, a second dielectric layer, and the pedestal are arranged in this order from the side that is closer to the sample, that the first dielectric layer, the electrostatic chuck electrode, and the second dielectric layer project from the pedestal, and that a third dielectric layer is disposed between the conductor ring and the pedestal. 8. The plasma processing method according to claim 7, wherein Ca=1/(d1/∈1 +d2/∈2) is larger than or equal to 0.5 times Cb=∈3/d3 and smaller than or equal to 2 times Cb, where ∈1 and d1 are relative permittivity and thickness of the first dielectric layer, ∈2 and d2 are relative permittivity and thickness of the second dielectric layer, and ∈3 and d3 are relative permittivity and thickness of the third dielectric layer. 9. The plasma processing method according to claim 4, wherein a voltage is applied to an electrostatic chuck electrode in a state that the sample electrode has a layered structure in which a first dielectric layer, the electrostatic chuck electrode, a second dielectric layer, and a pedestal are arranged in this order from the side that is closer to the sample, that the first dielectric layer, the electrostatic chuck electrode, and the second dielectric layer project from the pedestal, and that a third dielectric layer is disposed between the conductor ring and the pedestal. 10. The plasma processing method according to claim 9, wherein Cc=∈1/d1 is larger than or equal to 0.5 times Cd=1/{(d2×S2)/(∈2×S1)+d3/∈3} and smaller than or equal to 2 times Cd, where ∈l and dl are relative permittivity and thickness of the first dielectric layer, ∈2 and d2 are relative permittivity and thickness of the second dielectric layer, ∈3 and d3 are relative permittivity and thickness of the third dielectric layer, S1 is an area of a surface, exposed to the plasma, of the sample, and S2 is an area of a surface, exposed to the plasma, of the conductor ring. 11. A plasma processing method, comprising the steps of:mounting a sample on a sample electrode disposed in a vacuum container, exhausting the vacuum container while supplying a source gas to inside the vacuum container, and generating plasma in the vacuum container by supplying high-frequency power to a plasma source; andperforming plasma processing while being adjusted so that thickness of an ion sheath is made uniform on the surface of the sample, in a state that a focus ring having a surface that is higher than the surface of the sample by 1 mm or more is disposed outside an outer perimeter of the sample. 12. The plasma processing method according to claim 11, wherein a distance between the outer perimeter of the sample and an inner perimeter of the focus ring is in a range of 1 mm to 10 mm. 13. The plasma processing method according to claim 11, wherein a difference in height between the surface of the sample and a surface of the focus ring is in a range of 1 mm to 15 mm. 14. A plasma processing method, comprising the steps of:mounting a sample on a tray disposed in a vacuum container and having a step inside which the sample is mounted, exhausting the vacuum container while supplying a source gas to inside the vacuum container, and generating plasma in the vacuum container by supplying high-frequency power to a plasma source; andapplying plasma to the surface of the sample while making an adjustment so that a surface of a portion outside the recess of the tray is approximately the same in height as the surface of the sample, and being adjusted so that thickness of an ion sheath is made uniform on the surface of the sample. 15. The plasma processing method according to claim 14, wherein a distance between the outer perimeter of the sample and the step is in a range of 1 mm to 10 mm. 16. The plasma processing method according to claim 14, wherein a difference in height between the surface of the sample and a surface of the portion, outside the step, of the tray is in a range of 0.001 mm to 1 mm. 17. The plasma processing method according to claim 14, wherein the sample is a silicon wafer and the tray is made of silicon. 18. The plasma processing method according to claim 14, wherein the plasma processing is performed in a state that the tray is pressed against the sample electrode. 19. The plasma processing method according to claim 14, wherein:a step of generating plasma and a step of suspending the plasma generation are performed alternately and repeatedly; andpressure in the vacuum container is set higher in the step of suspending the plasma generation than in the step of generating plasma. 20. The plasma processing method according to. claim 19, wherein a difference between the pressure in the vacuum container in the step of suspending the plasma generation and that in the step of generating plasma is in a range of 100 Pa to 1,000 Pa. 21. A plasma processing apparatus comprising:a vacuum container;a sample electrode disposed in the vacuum container and to be mounted with a sample;a gas supply apparatus for supplying a gas to inside the vacuum container;an exhaust apparatus for exhausting the vacuum container;a pressure control device for controlling pressure in the vacuum container;a plasma source;a high-frequency power source for supplying high-frequency power to the plasma source;a voltage source for applying a voltage to the sample electrode; andan auxiliary member disposed around the sample electrode so that plasma is applied to a surface of a sample while being adjusted so as to have a uniform energy state on the surface of the sample. 22. The plasma processing apparatus according to claim 21, wherein the plasma is adjusted so as to amorphyze a surface layer of the sample. 23. The plasma processing apparatus according to claim 21, wherein the plasma is adjusted so as to introduce an impurity into a surface layer of the sample. 24. The plasma processing apparatus according to claim 21, wherein:the sample electrode has a projecting portion to be mounted with the sample; andthe auxiliary member is a conductor ring disposed so as to surround an outer perimeter of the sample and to have a surface that is approximately the same in height as the surface of the sample. 25. The plasma processing apparatus according to claim 24, wherein a distance between the outer perimeter of the sample and an inner perimeter of the conductor ring is in a range of 2 mm to 11 mm. 26. The plasma processing apparatus according to claim 24, wherein a difference in height between the surface of the sample and a surface of the conductor ring is in a range of 0.001 mm to 2 mm. 27. The plasma processing apparatus according to claim 21, wherein the sample electrode has a layered structure in which a first dielectric layer, an electrostatic chuck electrode, a second dielectric layer, and a pedestal are arranged in this order from the side that is closer to the sample, the first dielectric layer, the electrostatic chuck electrode, and the second dielectric layer project from the pedestal, and a third dielectric layer is disposed between the conductor ring and the pedestal; and wherein a voltage is applied to the pedestal. 28. The plasma processing apparatus according to claim 27, wherein Ca=1/(d1/∈1 +d2/∈2) is larger than or equal to 0.5 times Cb=∈3/d3 and smaller than or equal to 2 times Cb, where ∈1 and d1 are relative permittivity and thickness of the first dielectric layer, ∈2 and d2 are relative permittivity and thickness of the second dielectric layer, and ∈3 and d3 are relative permittivity and thickness of the third dielectric layer. 29. The plasma processing apparatus according to claim 21, wherein the sample electrode has a layered structure in which a first dielectric layer, an electrostatic chuck electrode, a second dielectric layer, and a pedestal are arranged in this order from the side that is closer to the sample, the first dielectric layer, the electrostatic chuck electrode, and the second dielectric layer project from the pedestal, and a third dielectric layer is disposed between the conductor ring and the pedestal; and wherein a voltage is applied to the electrostatic chuck electrode. 30. The plasma processing apparatus according to claim 29, wherein Cc=∈1/d1 is larger than or equal to 0.5 times Cd=1/{(d2×S2)/(∈2×S1) +d3/∈3} and smaller than or equal to 2 times Cd, where ∈1 and d1 are relative permittivity and thickness of the first dielectric layer, ∈2 and d2 are relative permittivity and thickness of the second dielectric layer, ∈3 and d3 are relative permittivity and thickness of the third dielectric layer, S1 is an area of a surface, exposed to the plasma, of the sample, and S2 is an area of a surface, exposed to the plasma, of the conductor ring. 31. The plasma processing apparatus according to claim 21, wherein:the sample electrode has a projecting portion to be mounted with the sample; andthe auxiliary member is a focus ring disposed so as to surround the sample and to have a surface that is higher than the surface of the sample being mounted on the sample electrode by 1 mm or more. 32. The plasma processing apparatus according to claim 31, wherein a distance between the outer perimeter of the sample and an inner perimeter of the focus ring is in a range of 2 mm to 11 mm. 33. The plasma processing apparatus according to claim 30, wherein a difference in height between the surface of the sample and a surface of the focus ring is in a range of 2 mm to 16 mm. |
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description | The present invention relates generally to apparatus used in diagnostic imaging and, more particularly, to a method and apparatus for loading and storing radioactive source pins used in combination PET/CT imaging systems. The combination PET/CT system has been recognized as an effective medical imaging system that can improve patient diagnosis by producing high quality medical images that not only provide anatomical information and images, but also provides physiological information on the patient. In the combination PET/CT system, radioactive source pins are used to calibrate the PET detector system and to provide attenuation correction during system use or imaging. Because the pins are radioactive, they are stored in a shielded storage device when not in use. The storage device is structurally secure and shields the environment from radiation exposure from the radioactive source pin. Typically, the storage devices and source pins (i.e., source loaders) are generally stored within the PET system, which adds to the overall space requirements for the PET/CT system. The shielded storage device in existing systems is rather large and takes up a considerable amount of space due in part to the fact that the source pin is a rigid member. During use, the source pin or pins are withdrawn from storage and placed in a rotatable transmission ring within a bore of the PET detector system. The rotatable transmission ring rotates the radioactive source pin about the PET detector system gantry to calibrate the PET detectors. However, because of the large size of the storage device, it is not possible to mount the source pin directly to the rotatable transmission ring. Thus, the storage device and source pin are mounted to the PET system gantry at a location separate from the rotatable transmission ring. When calibration is desired, the source pin is transported to the rotatable transmission ring. This source pin transport time creates potential non-beneficial radiation exposure that should be minimized. In addition to unwanted radiation exposure, the transport of the source pin from the storage device to the rotation ring also creates a greater opportunity for mechanical or electrical failure to occur in the system. That is, the transition of the radioactive source pin from the storage shield to its mounting on the rotatable transmission ring involves a number of motion steps in which problems can arise. Because the shielding requirements limit the placement of the storage device, the automatic source pin handling and these motion steps are often complex and unreliable. Therefore, it would be desirable to design a PET/CT system that includes a compact shielded storage device and radioactive source that minimizes storage space requirements within the system. Furthermore, a PET/CT system design that minimizes the probability of mechanical and electrical failure associated with positioning the radioactive source for PET calibration, by eliminating components and motion steps for positioning the radioactive source, is also desired. The present invention is a directed method and apparatus for loading and storing radioactive source pins used in combination PET/CT imaging systems. A radioactive source loader including a radioactive source therein is attached to a rotatable CT gantry in a combination PET/CT imaging system. The radioactive source loader rotates with the CT gantry to calibrate the PET imaging system. According to one aspect of the present invention, a medical imaging system includes a positron emission tomography (PET) imaging apparatus and a computed tomography (CT) imaging apparatus having a rotatable gantry. The medical imaging system also includes a radioactive source loader that is attached to the rotatable gantry. The radioactive source loader includes a radioactive source therein to calibrate the PET imaging apparatus. In accordance with another aspect of the present invention, a combination CT/PET scanning system includes a PET scanner to acquire a PET image of a patient, the PET scanner having a detector array therein. The combination CT/PET scanning system also includes a CT scanner to acquire a CT image of the patient, the CT scanner having a rotatable gantry. A calibration device is also included in the combination CT/PET scanning system and is attached to the CT scanner to rotate with the rotatable gantry and calibrate the detector array in the PET scanner. A radiation shield is positioned about the calibration device to selectively shield radiation produced by the calibration device. In accordance with yet another aspect of the present invention, a method of constructing a medical imaging device includes the step of positioning a CT image scanner having a rotatable gantry therein in a fixed position relative to a PET image scanner. The method also includes the step of mounting a radioactive source loader on the rotatable gantry of the CT image scanner, wherein the radioactive source loader is configured to calibrate the PET image scanner. Various other features and advantages of the present invention will be made apparent from the following detailed description and the drawings. Referring to FIG. 1, a combination PET/CT imaging system 100 as known in the prior art is shown. The PET/CT system 100 is constructed to include a PET system 102 and CT system 104 mounted on separate gantries 106, 108. Before scanning of a patient takes place in the system, calibration of the PET system 102 is necessary to ensure accurate readings by the PET detectors therein. In order to calibrate the PET system 102, a radioactive source 110 must be rotated about the PET gantry 106. However, the PET gantry 106 is not capable of rotation, and as such, the rotation of this radiation source 110 in the prior art PET/CT system 100 is achieved by way of a rotation ring 112. During a calibration process the radiation source 110 is placed in the rotation ring 112, which is configured as a separate structure that is mounted to the PET gantry 106 to allow for rotation of the radiation source 110. Because the radiation emitted by the radiation source 110 is not desirable outside of the calibration process, the radiation source 110 is stored in a source housing 114 when not in use to shield the surrounding environment from radiation exposure. The combination of the radiation source 110 and the source housing 114 is too large to mount to the rotation ring 112 and is therefore positioned adjacent to the rotation ring. When calibration of the PET system 102 is desired, the radiation source 110 is removed from the source housing 114 by a source loader mechanism 116 and placed in the rotation ring 112. The placement of the radiation source 110, source housing 114, and source loading mechanism 116 adjacent to the rotation ring 112 and PET gantry 106 adds to the overall size of the PET/CT system 100 and creates a greater opportunity for mechanical or electrical failure to occur in the system because of the movement associated with the radiation source 110 between the rotation ring 112 and the source housing 114. Referring now to FIG. 2, one embodiment of a combination PET/CT system 10 according to the present invention is shown. Included in the PET/CT system 10 is a PET system 12 and a CT system 14 positioned in fixed relationship to one another. The PET system 12 and CT system 14 are aligned to allow for translation of a patient (not shown) therethrough. In use, a patient is positioned within a bore 16 of the PET/CT system 10 to image a region of interest of the patient as is known in the art. The PET system 12 includes a gantry 18 that is configured to support a full ring annular detector array 20 thereon. The detector array 20 is positioned around the central opening/bore 16 and can be controlled to perform detector calibration scans to acquire corrective data and also to perform a normal “emission scan” in which positron annihilation events are counted. To this end, the detectors forming array 20 generally generate intensity output signals corresponding to each annihilation photon. The CT scanner 14 includes a rotatable gantry 22 having an x-ray source 24 thereon that projects a beam of x-rays 26 toward a detector assembly 28 on the opposite side of the gantry 22. The detector assembly 28 senses the projected x-rays that pass through a patient and measures the intensity of an impinging x-ray beam and hence the attenuated beam as it passes through the patient. During a scan to acquire x-ray projection data, gantry 22 and the components mounted thereon rotate about a center of rotation. Also mounted to the rotatable gantry 22 of CT scanner 14 is a radioactive source loader 30 that functions as a calibration device for the detector array 20 of PET scanner 12. As shown in FIG. 3A, one embodiment of radioactive source loader 30 includes a storage shield 32 (i.e., radiation shield) that encloses a radioactive source pin 34. The storage shield 32 surrounds radioactive pin 34 when it is not in use during calibration of the PET detector array 20 and functions to shield the surrounding environment from radiation produced by the pin 34. The storage shield 32 can be circular or rectangular in shape depending on the exact configuration of radioactive pin 34 and is configured to fit about the radioactive pin 34 in a close-fit manner to minimize the overall size of source loader 30, which allows for mounting directly to rotatable gantry 22. As rotatable gantry 22 includes dummy parts (not shown) for weight balance, the mounting of the radioactive source loader 30 thereto will not effect the rotation of the gantry 22 or the performance of the CT system 14. As shown in FIG. 3B, when calibration of the PET detector array 20 is desired, a majority of radioactive pin 34 is slid out from storage shield 32 to emit radiation as it rotates about the bore 16 on rotatable gantry 22. Radioactive pin 34 travels in a one-dimensional, linear motion relative to the storage shield 32 to extend out therefrom and be exposed to the surrounding environment. After calibration has been completed, radioactive pin 34 is slid back into the storage shield 32 to block radiation. The exact mechanism to move/translate radioactive pin 34 into and out of storage shield 32 can comprise an electric motor (not shown) or another suitable mechanism known in the art As shown in FIG. 4A, in another embodiment of PET/CT system 10 the radioactive source used for calibration is configured to be a flexible member. That is, a radioactive wire, strip, or tubing 36 is positioned within radiation shield 32 and is removable therefrom as desired for calibration of the PET detector array 20. The radioactive wire 36 is composed primarily of wire that is non-radioactive, but is embedded with radioactive segments or inserts 38 in portions thereof. The radioactive wire 36 contained in radiation shield 32 is wound about a roller or spool 40 for storage of the wire 36 when not in use during a calibration process. A means for winding and unwinding the radioactive wire 36 from the spool 40 is included in the radioactive source loader 30. In one embodiment, the means for winding and unwinding the wire is an electric control motor 42 to rotate the spool 40. As shown in FIG. 4B, when the radioactive wire 36 is unwound from spool 40, it is guided out from radiation shield 32 by plastic tubing 44. Plastic tubing 44 extends out from radiation shield 32 and is configured to receive the radioactive wire 36 therein. Plastic tubing 44 straightens radioactive wire 36 as it extends into the tubing to form a linearly shaped radioactive source extending out from radiation shield 32. Radiation is emitted from radioactive insert 38 that extends out from plastic tubing 44. It is also envisioned that plastic tubing 44 could extend out further and that radioactive insert would be positioned therein to emit radiation, as the tubing is not configured to provide radiation shielding. In another embodiment, and as shown in FIG. 5A, radioactive source loader 30 includes a first spool 46 and a second spool 48 positioned within radiation shield 32 that contain a radioactive strip 36 wound thereabout. Radioactive source loader 30 also includes a tensioning member 50 located outside radiation shield 32. Radioactive strip 36 is wound about the first spool 46 and stretched out from radiation shield 32 to wrap around tensioning member 50 and return into the radiation shield to join to second spool 48. An electric motor 52 attached to first roller 46 unwinds radioactive strip 36 therefrom and correspondingly winds the strip 36 onto the second spool 48. A spring-type retractor 54 is included in second spool 48 to unwind radioactive strip 36 therefrom and back onto first spool 46. Radioactive strip 36 includes radioactive inserts 56, 58 thereon that comprise both low radiation inserts 56 and high radiation inserts 58. In one embodiment, low strength germanium-68 is used as the low radiation insert and high strength germanium-68 is used as the high radiation insert. As shown in FIGS. 5B and 5C, an operator can selectively position one of the low and high radiation inserts 56, 58 outside the radiation shield 32 by winding and/or unwinding the radioactive strip 36 a desired amount. The selection of the low or high radiation insert 56, 58 can be performed by an operator based on a desired calibration of the PET detector array 20 shown in FIG. 2. In another embodiment, additional radioactive source loaders 30 can be added to the PET/CT system 10. As shown in FIG. 6, three radioactive source loaders 30 are mounted to rotatable gantry 22 of CT scanner 14. The radioactive source of source loaders 30 is shown as a radioactive pin 34, but the radioactive source can also be a radioactive wire, strip, or tubing as set forth in other embodiments of the source loader 30 described in detail above. In one embodiment, radioactive source loaders 30 are positioned equidistant from one another about the rotatable gantry 22, although they can also be spaced in other configurations about the gantry 22. The inclusion of additional radioactive pins 34 about the gantry cuts down on calibration time of the PET system 12 by decreasing the time it takes to rotate the sources about the PET detector array 20. The inclusion of multiple radioactive source loaders 30 also functions to reduce a maximum radiation dose emitted from radioactive pins 34 at any one spot adjacent to the PET detector array 20. Therefore, according to one embodiment of the present invention, a medical imaging system includes a positron emission tomography (PET) imaging apparatus and a computed tomography (CT) imaging apparatus having a rotatable gantry. The medical imaging system also includes a radioactive source loader that is attached to the rotatable gantry. The radioactive source loader includes a radioactive source therein to calibrate the PET imaging apparatus. According to another embodiment of the present invention, a combination CT/PET scanning system includes a PET scanner to acquire a PET image of a patient, the PET scanner having a detector array therein. The combination CT/PET scanning system also includes a CT scanner to acquire a CT image of the patient, the CT scanner having a rotatable gantry. A calibration device is also included in the combination CT/PET scanning system and is attached to the CT scanner to rotate with the rotatable gantry and calibrate the detector array in the PET scanner. A radiation shield is positioned about the calibration device to selectively shield radiation produced by the calibration device. According to yet another embodiment of the present invention, a method of constructing a medical imaging device includes the step of positioning a CT image scanner having a rotatable gantry therein in a fixed position relative to a PET image scanner. The method also includes the step of mounting a radioactive source loader on the rotatable gantry of the CT image scanner, wherein the radioactive source loader is configured to calibrate the PET image scanner. 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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046817328 | description | SPECIFIC DESCRIPTION In FIG. 1 we have shown a porous graphite body 14 forming a quenching element 10 which can be introduced into a gas-cooled nuclear reactor and in which particles 11 are embedded. Each particle 11, as is also apparent from this Figure, can comprise a rare earth metal shell 12 melting at the appropriate activation temperature and containing the neutron absorptive compound, e.g. a gadolinium halide as represented at 13. Such elements have been introduced into a nuclear reactor together with the fuel charge, the elements having the same dimension and shape as the fuel elements. When the desired threshold temperature is reached, the shells 12 melt and at the high temperatures the gadolinium halide is released to pass through the porous body 14 and coat gadolinium onto the graphite surfaces of the fuel elements. The particles shown in FIG. 2 comprise a pyrolytic carbon shell 15 enclosing the neutron absorptive halide 16. This shell is characterized by the fact that at about 1000.degree. C., with increasing temperature, the pores increasingly open to allow progressively increasing release of the neutron absorptive material. FIG. 3 represents a diagram of a core 17 of a gas-cooled nuclear reactor in which the fuel elements have been represented as rods 18 and are disposed in the core together with a rod 19 containing the particles of FIGS. 1 and 2 as described. While the rod 19 can be inserted into the core together with the fuel elements, it may also be introduced by a safety control 23 of the type used to insert a moderator rod. The more common application of the invention, however, is not a ball element nuclear reactor as described in the aforementioned U.S. patent and will be discussed below. The primary gas circulation is represented by the pump 20 and a secondary cooler 21. It will be apparent that the safety system of the invention is effective even upon failure of the primary coolant system. SPECIFIC EXAMPLES In the following specific examples 1-3, we will describe graphite elements of a type which pass through the reactor core of a piled ball reactor together with the fuel elements. The elements contain, as a neutron-absorbing substance, a halogen compound of a rare earth metal, for example a gadolinium, samarium or europium halogen compound, especially fluoride, bromide or iodide, or mixtures thereof. This shutdown substance is coated with or enclosed in (ensheathed in) a metal which has a melting point corresponding to the threshold for release of the reactivity-reducing substance. The latter then in a gaseous form can penetrate the graphite body in which the element or particle is embedded because of the porosity of the graphite and in the ambient space around the body can come into direct contact with the fuel elements to be absorptively deposited thereon. EXAMPLE 1 The shutdown element as a hollow ball formed of graphite whose size corresponds to the size of the fuel element balls of a stacked ball of a reactor. The absorption substance was gadolinium-III-bromide which was introduced in the form of particles with a particle size of less than 5 mm in the graphite element. The graphite shutdown element was added to a graphite ball filling simulating the fuel element packing of a stacked ball reactor. The filling was heated together with the shutdown element to 850.degree. C. As soon as this temperature was achieved, the absorptive substance was detected at spacings up to 750 mm from the shutdown elements, i.e. it had been dispersed to a volume with a diameter 1.5 mm in the pile so that the gadolinium was detected on the surfaces of the balls of this packing. EXAMPLE 2 A graphite element is provided with particles of the absorption substance in a sheath of metallic gadolinium. The gadolinium is practically impermeable at temperatures below the melting point. As to the absorption substance, however, the gadolinium sheath melts or fuses at a temperature between 1300.degree. C. and 1350.degree. C. and at this temperature liberates the absoprtion substance which was the gadolinium-III-bromide used in Example 1. The gadolinium-III-bromide upon melting of the metallic gadolinium sheath has a partial pressure of 0.28 bar and is effectively distributed in the fuel element bed of the reactor. It was found that the metallic gadolinium serving as a coating for the neutron absorption substance also serves as a protective shield from neuclitic burn of the enclosed absorption substance. With similar effects, we can use for high temperature shutdown of a nuclear reactor, europium which has a melting point of about 830.degree. C., samarium which has a melting point of 1070.degree. C. and dysprosium which has a melting point of about 1400.degree. C. For a shutdown temperature of about 1500.degree. C., erbium may be used which has a corresponding melting point. EXAMPLE 3 Naturally the halogen compounds of the rare earths which were employed must have an effective vapor pressure at the melting point at which the protective sheath decomposes. One criterion for the use of selection of these halogen compounds is their melting point, because above the melting point the vapor pressure generally increases very rapidly. This melting point should be close to the usual operating temperature of the nuclear reactor for which the graphite element is employed. For stacked ball reactors the most important shutdown range is a temperature between 900.degree. C. and 1300.degree. C. and the melting point of the following shutdown substances are thus given below so that the worker in the art may make use of the appropriate rare earth halide for the desired shutdown temperature: ______________________________________ SmBr.sub.3 melting point 913.degree. C. EuBr.sub.3 975.degree. C. GdBr.sub.3 1038.degree. C. GdJ.sub.3 1198.degree. C. GdF.sub.3 1228.degree. C. EuF.sub.3 1276.degree. C. SmF.sub.3 1305.degree. C. ______________________________________ EXAMPLE 4 A graphite element containing a particle of a shutdown substance of the type used in Examples 1-3 has a pyrolytic carbon sheath. The pyrolytic carbon coating, depending upon its quality, is not suddenly gas permeable at a temperature above 1000.degree. C. but generally tends to become permeable with increasing temperature. We are thus able to use this element to progressively reduce the reactivity by progressive release of the shutdown substance with increasing temperature of the reactor core. When the temperature of the reactor core drops below the threshold, as the pyrolytic carbon coating has progressively reduced porosity, eventually the release of the absorption substance is cut off. EXAMPLE 5 A graphite element contain particles of a diameter of 10 mm, the particles corresponding to those of Examples 1-3. On the pyrolytically coated particle of Example 4 the quenching element is supplied into the reactor core in a ratio to the fuel elements of 1:1000. The reactivity of the reactor core is reliably reduced below 0.1%. EXAMPLE 6 When such a particle (Example 5) comprises metallic gadolinium and contain gadolinium-III-bromide, after 1000 days in the reactor core substantially 100% of the shutdown substance in the particle remain active. Consequently, practically neuclidic burn-out occurs. EXAMPLE 7 A fuel element is provided with a particle of a diameter of about 1 mm of the shutdown substance in addition to its nuclear fuel particles. The incorporation of the shutdown particles in fuel elements is advantageous because they eliminate the need for additional shutdown elements. The absorptive substance is protected by self-shielding against neuclidic burn-out. With gadolinium compounds, the self-shielding effect with a sheath of a thickness of 0.01 mm is noticeable and is practically complete in a thickness of the compound of 0.5 mm which is satisfactory where the particle diameter is 1 mm. The burn-out of the absorptive material can be proportioned to the burn-out of the fuel element in which it is incorporated so that as the fuel element is depleted, the availability of the absorptive material is reduced. Where each fuel element contain a particle of the absorptive substance, we are able to eliminate errors of loading the reactor with the fuel absorption elements. Such fuel elements carry its safety particle from its production process to its reworking or final storage. Apart from the rear earth halogen compounds of Examples 1-3, we make use of other gadolinium compounds, samarium compounds as long as their vapor pressure and stability suffice for the purposes described. |
055966128 | summary | The present invention relates to a testing arrangement for materials testing at lead-throughs, especially for control rods, in pressurized-water reactors, to a probe sword suitable for the mentioned testing arrangement and to a method for materials testing at lead-throughs. BACKGROUND OF THE INVENTION At a pressurized-water reactor in a nuclear power plant there is a dome-shaped cap, with cap lead-throughs for a control rod mechanism, which is detachable attached to the cap. In the pressurized-water reactor there are also, in the cap or in the bottom, other lead-throughs for different instruments and vent pipes, which are connected to a kind of expansion vessel in the shape of an external pressure vessel with a water column. A lead-through for a control rod consists of a tube passing through the cap, which tube is welded to the cap at its lower side. The lead-through ends at the inside of the cap with a downward inner conical opening having a cone angle of a few degrees, normally about 3 degrees. In the lead-through there is an essentially coaxial tubular sleeve, which ends with a downward essentially funnel-shaped end-piece. The lead-through sleeve is at a seat at the top sealingly joined to the projecting end of the tube. Between the tube and the sleeve, there is a gap with a nominal width of a few millimeters, normally about 3 mm. The purpose of the interior sleeve in a control rod lead-through is to make the longitudinal axis of the lead-through opening adjustable in relation to axial openings in means located inside the reactor. Therefore, the annular gap does not normally have equal width around the sleeve, due to the fact that it is used as a trimming allowance. In a cap, there is normally a total of about 60-75 control rod lead-throughs. It has been found that leakage can arise at the control rod lead-throughs and that the leakage is due to cracks in the tubes of the lead-throughs, more particularly in the area close to the weld that connects a tube with the cap. If there is a crack in the tube above the weld, water can come up on the outside of the cap when the reactor is pressurized, while a crack below the weld is less dangerous since it does not give any external leakage. For the sake of security, it is necessary to test the material at the lead-throughs in order to detect cracks and determine their characteristics, such as size, position and orientation. According to prior art, inspection of a reactor cap is carried out by dismounting the cap with the control rod mechanism from the reactor and place it on a biological concrete shield. The occurrence of defects at each lead-through is checked with the aid of a manipulator and by means of eddy current technology, whereby an eddy current probe is inserted into said gap between the sleeve and the tube. The eddy current probe is inserted into the gap by means of a thin metal sword, the probe being mounted at the top of the sword. The sword is bent past the end-piece of the sleeve and into the gap by means of reels. The sword can only be led forwards in the vertical direction because of the flexibility of the sword, and has to be pulled out of the gap before a displacement around the sleeve can be carried out. If defects are detected at one or more lead-throughs with said eddy current testing, the whole control rod mechanism and the lead-through sleeve with its end-piece are dismounted for the lead-through at issue. For the dismounting of the sleeve, the control rod mechanism with the associated sealing means at the top of the lead-through is disassemble, the end-piece is dismounted and the sleeve is pulled out of the tube. Thereafter, the characteristics, such as depth, length, position and orientation of each defect is determined by means of ultrasonic testing and with the aid of a manipulator placed above the cap, whereby the interest today is mostly focused on longitudinal cracks. Such a reactor inspection is expensive, time-consuming, entails the dismounting of the sleeves only for the ultrasonic testing of the insides of the tubes and entails manual handling which results in radiation exposure of the persons carrying out the inspection. Today, there is in a number of countries an acute need for testing pressurized water reactors with respect to cracks in the lead-throughs and a need for an appropriate testing equipment that eliminates unnecessary irradiation of people. Thus, it is desirable to be able to determine the characteristics of the defects without the disadvantageous dismounting of the sleeves. It is a purpose of the present invention to provide a simplified and improved arrangement and method for testing a pressurized-water reactor. In particular, it should be possible to carry out both the detection of the cracks and the determination of their characteristics without the expensive and hazardous disassembling of the control rod mechanism and the lead-through sleeve, and thereby reduce the dose of radiation for people. In accordance with the preferred embodiment, it should be possible to carry out the entire testing by means of the manipulator which, according to prior art, is placed inside the dismounted cap. The above mentioned and other purposes and advantages are obtained with a testing arrangement, a probe sword and a method as set out in the independent claims 1, 4 and 10, respectively. The invention will now be described further by the explanation of an embodiment and in conjunction with the drawings. It is shown in: FIG. 1--an explanatory overview of a pressurized-water reactor cap with a testing arrangement according to the invention mounted at a manipulator placed under the cap, FIG. 2--an explanatory sketch of a lead-through, FIG. 3--a sketch of a weld joint unfolded in a plane, FIG. 4--a sketch of a preferred embodiment of a testing arrangement according to the invention, FIG. 5--an elevating motor arrangement in a lifting arrangement of a testing arrangement according to the invention, FIG. 5A--is a top plan view of FIG. 5, FIG. 6--a brake arrangement in a lifting arrangement of a testing arrangement according to the invention, FIG. 6A--is a top plan view of FIG. 6, FIG. 7--an explanatory sketch of the testing arrangement according to the invention with associated peripheral equipment, whereby the testing arrangement is docked to a cap lead-through, FIG. 8--the upper part of a testing arrangement according to the invention docked to a cap lead-through, FIG. 9a--an explanatory cross-section of a lead-through after a deflection of the sleeve, FIG. 9b--an explanatory longitudinal cut through a lead-through, with the essential shape of a probe sword in an inserted position drawn in the gap, FIG. 10--an explanatory sketch of a probe sword according to the invention, FIG. 11--an explanatory sketch of the upper part of a probe sword according to the invention, with five cross-sections of the sword, FIGS. 12a and 12b--a probe sword head with a cleaning probe according to the invention, FIGS. 13a and 13b--a probe sword head with an eddy current probe according to the invention, FIGS. 14a and 14b--a probe sword head with an ultrasonic probe according to the invention. |
abstract | A collimator for X-ray apparatus has an aperture defined by the edges of four movable flexible shutters. Each shutter can be moved independently of the other shutters; thus, the position and the size of the aperture can be adjusted at will. The shutters are moved by winding them onto drums; each drum is driven by a stepping motor. Springs bias the shutters towards the closed position of the collimator. |
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abstract | A neutron generator and isotope production apparatus and method of using the same to produce commercially and medically useful neutrons. The gamma,n reaction produces neutrons in beryllium and deuterium and the spectrum of the neutrons generated is shaped to optimize capture of the neutrons in a gamma emitting isotope. The gammas interact with target materials to produce large quantities of neutrons. |
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052395685 | summary | BACKGROUND OF THE INVENTION This invention is generally concerned with a collimator for removing unwanted divergent beams of radiation received from a source, leaving a well resolved radiation beam for detection and analysis. More particularly, the invention is directed to a collimator having a layered structure for removing not only unwanted angularly divergent radiation beams, but also for removing radiation inelastically scattered by the collimator structure itself. Radiographic imaging methods and apparatus are undergoing rapid evolution as efforts are being made to improve the ability to image selected portions of a specimen or diffract and sense radiation from the specimen. The effectiveness of these various methodologies and even the ability to use certain techniques depends primarily on spatial resolution and on the associated signal to noise ratio in the data being accumulated. Present technology is able to generate a radiation intensity adequate to image and evaluate structure and analyze a number of abnormalities. However, current technology cannot effectively collimate this radiation intensity without counting certain divergent radiation and thus including substantial unwanted noise in the resulting data. Such divergent, unwanted signal derives, for example, from radiation which has been inelastically scattered from the collimator structure itself. This deficiency therefore requires exposing the specimen to larger intensities of radiation in order to achieve a desired resolution. Unfortunately, such increased radiation exposure can be hazardous, and moreover there are some divergent radiation sources whose deleterious effects cannot be alleviated even by increasing the radiation signal level. It is therefore an object of the invention to provide an improved method of manufacture and method for collimation of radiation. It is another object of the invention to provide a new method of manufacture of a collimator for a radiation beam. It is a further object of the invention to provide an improved collimating device for removing divergent radiation beams received from, or passed through, a specimen undergoing diagnostic analysis. It is an additional object of the invention to provide a new radiation collimator assembly for providing highly resolved, high intensity data characteristic of a specimen but without having to increase exposure to radiation. It is yet another object of the invention to provide an improved radiation collimator assembly having a layered wall material structure for substantially reducing inelastic scattered radiation present in the detected data signal. It is still a further object of the invention to provide a new collimator having a lead base structure with an outer layer of a material which preferentially absorbs a X-rays generated from inelastic scattering of gamma rays from the lead base collimator structure. It is yet an additional object of the invention to provide a radiation collimator having a selectable collimator length using a stack of different predetermined height collimator units. It is still a further object of the invention to provide a gamma ray collimator of lead with a thin tin layer on the collimator walls to absorb lead X-rays generated by inelastic gamma ray scattering from the lead collimator. Other objects, features and advantages of the present invention will be readily apparent from the following description of the preferred embodiments thereof, taken in conjunction with the accompanying drawings described below wherein like elements have like numerals throughout the several views. |
042382912 | description | Referring now more specifically to the drawing and first, particularly, to FIG. 1 thereof, there is shown a pressure vessel 1 of a boiling water reactor, only part of the casing wall 2 thereof with a union or connecting stub 3 being visible in the figure. A first line section 4a of a core flood-line or spray-line generally identified by the reference numeral 4 is fastened within the union 3. The first line section 4a is formed as a thermosleeve pipe or tube. The core flood-lines or spray-line 4 belongs to a core flood or spray system of the boiling water reactor which is formed of several core flood or spray lines 4 that are distributed over the periphery of the pressure vessel 1 and, respectively, extend through the cover 5a of the core container 5 and are connected to ring or circular line 6 disposed in the interior of the core-container cover 5a and terminate in the core container 5 through otherwise non-illustrated nozzles or holes provided in the ring line 6. A second line section 4b of the core flood or spray line 4 is connected by a coupling 7 to the first line section 4a. Cams or platings or any other suitable spacing means 4a3 welded to the outer periphery of the thermosleeve pipe 4a serve as guides therefor when the thermosleeve pipe 4a is inserted in axial direction thereof into the union 3; in the illustrated embodiment, four of such cams 4a3 are uniformly distributed over the periphery of the pipe 4a although only two thereof are actually visible in FIG. 1. A welding seam 3b, as clearly shown in FIG. 1, is provided between the union 3 and the wall 2 of the pressure vessel 1. The second line section 4b of the core flood or spray line 4, together with the cover 5a of the core container 5 and an array of steam separators DA, forms a structural unit B (FIG. 2), note the supporting or retaining dogs 6a for the flood ring 6 at the inner periphery of the container cover 5a, and is liftable together with the core-container cover 5a out of the pressure vessel 1 if the pressure vessel 1 is opened for the purpose of inspection and/or servicing, and is reintroducible into the pressure vessel 1. During the lifting, uncoupling of the two line sections 4a and 4b in the region of the coupling location 7 is automatically effected and, likewise, coupling is effected automatically when the core-container cover 5a is reinstalled. For this purpose, the first and the second line sections 4a and 4b are in mutual contact at the coupling location 7 by means of coaxial sealing surfaces 8a and 8b, the contact pressure between the sealing surfaces 8a and 8b being applied by the bracing forces oriented in axial direction of the pressure vessel 1, inclusive of the weight per se of the core-container cover 5a and of the remaining parts of the structural unit B, namely the second part of the line section 4b and the steam separators DA. The axial forces exerted by the core-container cover on the coupling 7 through the line section 4b are represented symbolically by the arrow P.sub.5, and the reaction forces, that are applied by the first line section 4a and the holder thereof, are identified as P.sub.5 '. Since the line section 4b is bent in a somewhat U-shaped manner and overlaps the line section 4a, certain moments are also produced upon the line section 4b. Likewise, moments occur which stress the line section 4a because the latter projects inwardly. These bending moments are able to be controlled, however, through suitably sturdy dimensioning of the line sections 4a and 4b and bracing or stiffening struts 4b1 (note FIG. 2) in the course of the line section 4b. In vicinity of pipe joints 4b11 and 4b12, where the pipe sections are disposed opposite one another with respective gaps S1 and S1' therebetween and are surrounded by rings 4b13 welded thereon, an axial and radial tolerance equalization is able to be attained during assembly i.e. before being finally welded together. Moreover, due to the hereinafore-described course of the lines, the thermal elasticity of the core flood line 4 is increased. Of special significance for the thermal elastic seal at the sealing surfaces 8a and 8b is, however, the spring-loaded contact or engagement by means of the compression spring arrangement 9 regarding which further reference will be made hereinbelow. The first and the second line section 4a and 4b are in engagement with one another by means of a ball-and-socket seat of the sealing surfaces 8a and 8b thereof. The sealing surface 8b is conically formed, the sealing surface 8a spherical, so that an application or contact mainly along a circular line in the region 8c is produced, it being also clear that an exchange of the members i.e. the surface 8a being conical and the surface 8b spherical, is possible. As is apparent, the first line section 4a is provided with an upwardly directed ball seat-mouthpiece 4a1 which is formed as a pipe connection or union and is welded at the location 10 to the line section 4a. The latter is closed from the interior of the reactor by means of an end wall 4a2, so that the water that is to be sprayed in can take its path only through the coupling location 7. For developing the ball seat-mouthpiece 4a1, the pipe union associated therewith is reinforced at the outer end thereof. The second line section 4b is provided with a downwardly directed cone seat-counter bearing member 4b2. This is constructed as a pipe bushing which is mounted with spring loading on a guidance collar or throat 4b3 of the second line section 4b with the intermediary of the hereinaforementioned compression spring elements 9 longitudinally displaceable in axial direction a of the pressure vessel 1. The counter-bearing member 4b2 is guided in axial direction a with axially normal, inwardly directed pins 11 in longitudinal grooves 12 formed in the guidance collar 4b3, the lift or stroke of the counter-bearing member 4b2 being limited in both axial directions by the end flanks 13 of the grooves 12. The groove end flanks 13 serve, accordingly, as stops, and the grooves 12 per se produce together with the pins 11 a safety device against torsion for the counter-bearing member 4b2. When the coupling is disassembled, these pins 11 hold the entire unit 4b2, 4b3 together. Between the opposing mutually aligned and stepwise separated end flanges 14a and 14b of the counter-bearing member 4b2, on the one hand, and of the guidance collar or throat 4b3, on the other hand, the helical compression spring arrangement 9 is inserted and, in fact, two coaxial and concentric helical compression springs 9a and 9b are provided that are mounted on a respective step-shaped landing of the end flanges 14a and 14b. The compression spring elements 9 are covered by a pipe apron 15 at the inner periphery of the line section 4b. The line section 4b is guided in the core container cover 5a by means of a thermal elastic passageway member 16. The latter is formed of an outer sleeve or bushing 16a welded at the lower end thereof sealingly to the cover 5a by means of inner and outer round welding seams 17, and an inner sleeve or bushing 16b seated on the line section 4b, the inner sleeve 16b surrounding the pipe 4b with the gap S and welded at both ends thereof to the pipe 4b at the location 18. About half of the axial length of the inner sleeve 16b is surrounded by the outer sleeve 16a, and this overlapping region, which forms a sealed sliding seat, respresents an axial guide; the actual fastening location is formed between the supporting or retaining dogs 6a and the flood ring 6. The pipe 4 is provided at the lower end thereof with an offset or angular bend 4b4 which is connected with a box-shaped end portion 4b5 to the flood ring 6. The upper U-loop of the pipe 4b is formed by pipe members 19a having trapezoidal longitudinal section and pipe members 19b having a semi-trapezoidal longitudinal section, which are welded to one another. Within the coupling 7, there is shown the effective surface f.sub.11 which is exposed to the floodwater pressure p.sub.k. The surface f.sub.12 (which extends to the contact surface 8c in the region of the sealing surface 8a and 8b exposed to the pressure p.sub.k) is to be subtracted from this effective surface f.sub.11. In the outer region of the coupling 7, the pressure of the reactor water p.sub.R, which exists in the interior of the pressure vessel 1, prevails, the effective pressure f.sub.21 being associated therewith (it is the outer part of the conical sealing surface 8b up to the application or contact location 8c). Since the floodwater pressure p.sub.k is greater than the pressure p.sub.R in the interior of the pressure vessel 1, the surface force applied to the sealing surfaces 8a and 8b, which act in the direction P.sub.5, is increased during operational start-up of the core flood system. What is essential therefor is that the effective surfaces f.sub.11 to be associated with the floodwater pressure produce a force in the direction P.sub.5 that is greater than the reacting or opposing force. In FIGS. 2 and 3, like parts to those shown in FIG. 1 are identified by the same reference characters. The axially normal parting line 20 between the core-container cover 5a and the lower part 5b of the core container 5 is clearly shown in FIG. 2. The core container 5 is clamped together by means of axial tension or tie rods 21 (shown at the left-hand side of FIG. 2) i.e. a multiplicity of such tension rods 21 are distributed over the periphery of the core container 5. The tension rods 21 engage or grip respective brackets 5a1 and 5a2 of the cover 5a and the core container 5b, respectively. The tension rod 21 has a shaft 21a and a threaded bushing 21b, which, at the upper end (note FIG. 4), are tightened together by means of a nut 21c and, accordingly, the cover 5a is also pressed against the lower part of the core container 5b. A hammerhead 5a3 extends through a slot formed in the lower bracket 5a2 and grips behind this bracket 5a2 when the tension rod 21 is rotated through an angle of 90.degree. as shown in FIG. 2. To define the latched and unlached position, a guidance groove is formed in the bushing and a pin provided at the tension rod, both at the location 5a4. By means of a pair of pipe sleeves 22 and 22', the tension rod 21 is guided, in upper and middle regions thereof, at respective ring plates 23 and 23' which, for their part, are firmly connected to the steam separators DA and upper and middle support grids G and G' therefor. Riser tubes DA1 of the steam separator DA are fitted into corresponding cover openings 5c and welded in this region to the core-container cover 5a. In the right-hand side of FIG. 2, the construction of FIG. 1 is shown in reduced scale. Another tension or tie rod 24 (at least three of which are to be considered as being distributed likewise over the periphery of the core container 5) extends through the ring plates 23 and 23' and the lower end thereof, at the bracket 5d, engages the cover 5a. The tension rod 24 is provided at the upper end thereof with a support member 25 formed with an eye 26 in which a hook of a non-illustrated lifting device can engage. Above the steam separator DA, the fragmentarily illustrated steam dryers DT are connected by means of support plates 27a and support rings 27b into one unit and are mounted on brackets 27c at the inner periphery of the pressure vessel 1. A cylindrical apron 27d is connected to the support ring 27b, and has water outlet boxes 27e fastened to the inner periphery thereof, wherein outlet pipes 27f of the steam dryers DT terminate. The water level W in the pressure vessel 1 is clearly shown in FIG. 2. After the steam dryer DT disposed above the structural unit B has been removed from the pressure vessel 1 (for this purpose, the pressure vessel 1 is opened beforehand and non-illustrated tensioning or clamping means for the steam dryers DT have been loosened or released) and, after loosening the nuts 21c and the hammerhead latch 5a3, the flange connection 5a1, 5a2 can be opened and the steam separator DA together with core-container cover 5a and the core flood line 4b (structural unit B) can be lifted upwardly, the tension rods 24 with the support members 25 serving for the engagement of the lifting tool. The coupling 7 between the core flood-line sections 4a and 4b thereby loosens or is released automatically, whereas during insertion and lowering of the structural unit B, they are again automatically coupled. Consequently, with the otherwise non-illustrated feedwater distributor or manifold (which should be considered to be connected to the union 28), a similar automatic coupling in the vicinity of a coupling location can be provided. What is essential for the coupling location 7 is that an axial (and, to a slight extent, also radial and tangential) displacement, dependent upon thermal expansion, of the line 4 is afforded without impairing the sealing effect. It is furthermore, essential that the axial forces that are required for applying contact pressure to the cone-and-sphere or ball-and-socket seat within the coupling 7, are applied through the compression springs 9 due to the axial tensioning, including the weight per se, of structural unit B. The axial forces are transmitted by the core container 5 through the support brackets or paws 5d to the brackets 5e welded to the inner periphery of the pressure vessel 1 (a multiplicity of paws and brackets 5d, 5e being distributed over the periphery). In the modified embodiment according to FIG. 3, the core container casing 5b is braced or supported upon the base calotte or bottom spherical end wall 1a and welded thereto at the location 29. Also shown in FIG. 3 is a surrounding vertical frame of the pressure vessel. In FIG. 2, a guidance grid support plate 30 for non-illustrated fuel elements, as well as one of a plurality of guide rods 31 fastened to the inner periphery of the pressure vessel 1 for guiding the structural unit B, when inserting or removing the same, are shown. |
claims | 1. A method comprising:sterilizing a column assembly with a sterilizer, the column assembly including a column having a parent radionuclide contained therein;transferring the column assembly from the sterilizer to a first clean room environment;transferring the column assembly from the first clean room environment to a second clean room environment; andcollecting a sterility test sample from the column assembly within the second clean room environment. 2. The method of claim 1 including:transferring the column assembly directly from the sterilizer to the first clean room environment; andtransferring the column assembly directly from the first clean room environment to the second clean room environment. 3. The method of claim 1, wherein collecting a sterility test sample includes eluting the column assembly through a collection canister including a filter. 4. The method of claim 3, further including adding growth media to the collection canister. 5. The method of claim 1, wherein sterilizing the column assembly includes exposing the column assembly to at least one of saturated steam and a steam-air mixture. 6. The method of claim 1, wherein collecting the sterility test sample includes collecting the sterility test sample from the column assembly within 4 hours of sterilizing the column assembly. 7. The method of claim 1, wherein the first clean room environment has at least a Grade B classification, and the second clean room environment has a Grade A classification. 8. The method of claim 1, wherein the first clean room environment is a negatively pressurized clean room environment, and the second clean room environment is a positively pressurized clean room environment. 9. The method of claim 1, wherein transferring the column assembly from the first clean room environment to the second clean room environment includes loading the column assembly into a transfer door located between the first and second clean room environments. 10. The method of claim 9, further including rotating the transfer door from a first position, in which an interior cavity of the transfer door is accessible from the first clean room environment, to a second position, in which the interior cavity of the transfer door is accessible from the second clean room environment. |
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043081002 | description | DETAILED DESCRIPTION Referring first to FIG. 1 which shows in simplified manner a portion of the building forming the chamber of the reactor, the vessel 1 of the reactor which occupies the center of the building is shown here in readiness for a recharging operation, i.e. with its cover removed along with the upper apparatus for control of the control rods. The plane of the upper joint of the vessel on which the cover normally bears is then level with the bottom of the pool 2 of the reactor. During all of the recharging operations, the pool 2 is filled with boron-containing water. The manipulation device 3 which is the subject of the invention travels in the manner of a rolling bridge on the rails 5 just above the upper level of the pool. The device 3 can therefore be displaced between a position situated above the vessel of the reactor and another position above a trench of the pool where racks are provided to form transit stations for new combustible assemblies before they are put in place in the reactor or for spent combustible assemblies for evacuation. Reference is now made to the assembly in FIGS. 3-5 for the description of the manipulation device itself designated generally by reference numeral 3 in FIG. 1. As in the machines previously utilized, the device comprises a main platform 10 forming a beam for the rolling bridge which rolls on rails 5 by wheels 11. Taking into account the scale of the drawings and in order not to encumber the figures, neither the motors nor the drive apparatus for the longitudinal displacement of the assembly on the rails 5 is shown. Such apparatus is of conventional type for rolling bridges. Similarly, there is not shown in detailed fashion the means for effecting transverse displacement of the carriage 14 on the rail 15 carried by the platform 10, the carriage 14 being displaced in the same fashion as on a conventional rolling bridge. The carriage 14 supports a turnable turret 17 which can be driven in rotation by means of a reduction motor assembly 18 driving in conventional fashion a pinion in mesh with an exterior toothed ring around the turret 17. The turret 17 carries three vertical tubular masts 20,21, and 22 angularly equidistant with respect to the axis of rotation of the turret 17 and cross braces 23 connecting the masts. The assembly carrying mast 20 is adapted, as in conventional recharging machines, to manipulate the complete combustible assemblies, i.e. with their auxiliary cluster. For this purpose, the mast 20 comprises an interior tubular telescopic element 24 (FIG. 5) which includes longitudinal ribs 25 guided along the length of tube 20 by radial rollers 26 and lateral rollers 27. The lower portion of the telescopic tube 24 is provided with a mouth forming a grapple 29 which can be adapted to the upper portion of a complete assembly 30. Lifting is effected by a cable 32 fixed to the tube 24 and operable from a winch 34 disposed in a tower 35 forming the superstructure of the turret 17 and turnable therewith. From a totally retracted position, the operation of taking an assembly is effected by unwinding the cable 32. The tube 24 descends to the point where the grapple 29 centers itself by bearing on the extremity of the assembly 30 and engages the assembly thereat. Of course, the locking of the grapple 29 is remotely controlled by electrical and pneumatic means and the tower 35 also supports unwinders for the electrical and pneumatic supply channels in order to permit them to follow the movements of raising and lowering the telescopic tube 24 and the grapple 29. In the raised position, the assembly of the tube 24 and the assembly 30 is displaced as a unit up to the extreme position shown in FIG. 3 in which the assembly 30 penetrates totally into the tube 20. In this position, the machine can be freely displaced above the pool of the reactor, no element then projecting below the lower level of the tubes 20, 21 and 22 which are situated above the upper level of the vessel. The mast 21 is equipped in similar manner for the manipulation of the control clusters. Here the telescopic element sliding in the tube 21 and guided by the same type of rollers distributed along the length of the tube is constituted by a series of grills 40 connected by cross-pieces, the cut in each grill following the envelope of the absorbent rods and the star branches which connect them at their upper portions to the grapple member. The tube 21 is also associated with a lifting cable 41 and a locking grapple. The cable 41 is operated from a winch disposed in the superstructure 35 in the same manner as the winch 34 associated with the tube 20. Upon decent of the cable 41, the guide member with grills 40 descends, first to come to bear on the head of the assembly then the grappling apparatus continues to descend in the guide up to its locking on the cluster. In raising the control rods, the assembly 40 first rests fixed by bearing on the assembly and serves to guide the assembly of the rods of the control cluster; when this is entirely supported by the grills 40 the assembly is raised as a unit to totally penetrate into the tube 21 thus leaving all freedom of movement to the assembly of the manipulation machine 3. In a further analogous fashion, the mast 22 is equipped with a lower telescopic element, a cable and a raising grapple with special accessory devices determined for the manipulation of the clusters of consumable poisons or of sealing clusters. The three masts, 20,21, and 22 are thus each equipped with their proper manipulation means, their telescopic element and their proper cable and raising winch and can each take three positions by rotation of the turret 17. One of these positions, fixed with respect to the carriage, is an active work position where the manipulations are possible. In FIGS. 2,3 and 4 it is the mast 20 which occupies the active position. We have not described here the safety locking apparatus which can be of any conventional type adapted to prevent the movement of the mast other than that in the active work position nor those means adapted to prevent the movement of the turret and the carriage whenever the manipulated mast has not been returned to totally retracted position. The turret 17 also carries, along the axis of rotation, an auxiliary telescopic mast 45 which does not extend beyond the lower level of the tubes 20,21 and 22; in extended position it permits carrying a T.V. camera 46 or the like up to the upper level of the assemblies. With a machine thus realized according to the invention a complete operation of recharging comprises, for example, the raising of a used combustible assembly, a transposition of the assemblies in the core and the transport of a new combustible assembly effected according to the following sequences after raising the cover of the vessel and the mechanism for control of the control rods. The machine 3 is taken above an assembly to be raised with the mast 20 in working position. One then raises the used assembly with the sealing cluster with which it has been associated and the assembly is taken to the transfer position where the assembly is deposited into a container. After retracting the telescopic arm 24 and without moving the carriage 14 one can turn the turret 120 degrees to place the arm 22 above the assembly in the container and extract the sealing cluster from the assembly. The machine 3 is then moved above the vessel to a position above an assembly just completing the second tier of its cycle and still provided with a control cluster. By effecting a new rotation of 120 degrees of the turret 17, the arm 21 is put in working position and it is utilized to raise the control cluster. Without displacing the machine 3 or the carriage 14, by effecting rotation of 120 degrees of the turret the arm 22 already carrying the sealing cluster is brought above the assembly used through the second tier which then receives the sealing cluster for the last tier of its activity in the reactor. The machine thus carrying a control cluster can then be utilized with its arm 20 which is free to transport a complete assembly from the periphery towards the center of the vessel. Finally, while carrying a control assembly on the arm 21 the machine is taken to the transfer station above a new assembly while waiting but still without a cluster. The new assembly is then provided with the control cluster by means of arm 21 and the assembly is raised by the arm 20 to be then taken to its place. It is seen that there is thus effected with the same machine both transfer or transposition of a complete assembly while also realizing transposition of clusters, mostly in the intermediate time between operations, by a simple rotation of one stage of rotation of the turret 17. All these operations are realized with visual control due to the camera 46 which also permits examination of the state of different clusters in the course of their manipulation. Of course the sequence described above is only one example from a greater number of possible sequences depending on the particular conditions of use of the reactor and the nature of the different clusters utilized. However, one will find in all cases the same benefit realized from the success of operations by simple rotation of the turret without having to displace the bridge 10 or the carriage 14. As a consequence, a substantial gain of time is first obtained in the operations of recharging but additionally the possibility is achieved of effecting these diverse manipulations with a single operator. The simultaneous reduction of the number of persons necessary to enter the chamber of the reactor and the time during which it must close down is an important safety factor in the protection against radiation. Of course, the invention is not strictly limited to the single embodiment which has been described by way of example but it also covers embodiments which differ only by details and variants of execution or by the utilization of equivalent means. One could thus also imagine an analogous machine with four arms on the turret, each arm then having a still more powerful specialization. |
abstract | Provided is a water jet peening apparatus and a water jet peening method including: a clamping cylinder (201) which is able to be disposed at the outer peripheral side of an instrumentation nozzle (83) with a predetermined gap therebetween; a clamping piece (210) which is able to fix the clamping cylinder (201) to the instrumentation nozzle (83); a nozzle guide (221) which has a cylindrical shape, is provided inside the clamping cylinder (201), and is positioned to a position adjacent to the upper end of the instrumentation nozzle (83); an inner surface WJP nozzle (105) which is movable upward and downward inside the nozzle guide (221); and a drainage hole (224) which radially penetrates the nozzle guide (221). Accordingly, it is possible to improve the safety of the operation by preventing a thimble tube from being popped out due to a water jet peening operation. |
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summary | ||
039375137 | abstract | An apparatus for inserting and removing both control rods and fuel elements from holes in a nuclear reactor has a vertically and horizontally displaceable support pivotally carrying a head which has a pair of grabs on its opposite ends, one of which is formed as a pair of pawls adapted to lock on the collar at the end of a fuel element and lift this element and the other of which is adapted to engage within a group of control rods to unlock them from their respective fuel elements and grip them so that they can be lifted from the respective fuel element. To this end the housing having the two grabs is provided with a small pneumatic cylinder whose piston is displaceable against spring force in one direction and is connected to both of the grabs so that on displacement in this direction it opens both of the grabs, the spring therefore serving to hold these grabs closed should pneumatic pressure fail. The grab head is pivotal on the support about a horizontal axis on pins serving as the pivot for this head and provided with pinions meshing with racks that can be displaced up and down so as to rotate the head through 180.degree., thereby aligning either of the grabs with a respective object. In addition locking means is provided so as to hold this head in either of these positions, thereby preventing it from tilting and dropping a group of control rods or a fuel element. |
046719237 | abstract | A holddown spring retention assembly for use in a nuclear reactor having a pressure vessel, a core barrel having an upper outwardly extending flange, an inner barrel having an upper outwardly extending flange and an annular holddown spring, the barrels and the spring being installed in the pressure vessel during normal operation, with the inner barrel flange disposed above the core barrel flange and the holddown spring interposed between the core barrel flange and the inner barrel flange, the holddown spring retention assembly is composed of a plurality of assembly units disposed around the periphery of the holddown spring, each unit including a lift lug secured to the outer periphery of the spring and having at least one outwardly radially projecting portion and a hanger secured to the inner barrel flange and having a lower portion suspended below the inner barrel flange and below the radially projecting portion of the lift lug means; the lower portion being arranged to support the radially projecting portion during lifting of the inner barrel upwardly away from the core barrel so that the spring is lifted together with the inner barrel. |
039420230 | summary | The present invention relates to a protective screen based on mortar, used in the field of radiology and intended to be placed directly or indirectly on a patient's skin. Hitherto, mortars based on plaster, mixed with a constituent which absorbs medical radiation, were used in order to protect the zone of the patient adjacent to the zone of the patient to be irradiated. By medical irradiation or medical radiation, there is to be understood any irradiation of the type comprising X, .alpha., .beta. or .gamma. rays. It is known to use barium sulphate as the absorbing constituent. The positioning of a mortar based on plaster and barium sulphate requires working by hand and with a trowel, since the mortar in the viscous state must be applied by hand and used on the skin of the patient, so that it has an even thickness calculated as a function of the position and of the nature of the irradiation zone. Very frequently, the thickness of the mortar applied cannot be kept constant and the layer applied always shows some unevenness which, after the mortar has set, cannot be corrected. It is obvious that the application of the mass of plaster-based mortar is a dirty and unpleasant operation for the medical staff and the patient. It is an object of the present invention to overcome the abovementioned disadvantages and to produce a protective screen which can be applied directly or indirectly to a patient's skin, that is to say ready for use without requiring any unpleasant and long preparation, and which has a perfectly continuous surface. According to the invention there is provided a mortar based protective screen, for radiological purposes and intended to be placed directly or indirectly on a patient's skin, comprising: a flexible and leakproof jacket, two parallel walls to said jacket; a side wall joining the said two parallel walls and having a surface area small relative to that of each parallel wall; at least one settable resin within said jacket; a fine particulate filler of at least one substance which absorbs medical radiation and is evenly mixed with the said resin; and a window permeable to medical radiation and positioned to permit radiation to pass between the parallel walls of the jacket. A curing agent may be brought into contact with the settable resin, inside the jacket, and mixed with the contents of the jacket in order that the curing agent reacts with all the thermosetting resin. This jacket, still in the malleable state, is then applied to the zone of the patient to be treated, taking good care that the zone to be irradiated coincides accurately with the window in the jacket. A flat metal plate may be applied to the free face of the jacket parallel to the patient's body in order to shape the synthetic mass present inside the jacket by flattening. The plate is removed after the mass has hardened to form a synthetic mortar. It can thus be seen that, with the screen of this invention, there is no longer any contact between the product and its handler or the patient, and that moreover, after irradiation, this jacket can be removed easily from the patient. If the temperature is too high during the hardening of the synthetic mortar it is advantageous to place a flexible heat insulating mass, for example a sheet of foam rubber, on that side of the jacket which faces the patient. |
abstract | In a nuclear power plant, thermal power in a second operation cycle of a nuclear reactor is uprated from thermal power in a first operation cycle preceding the second operation cycle by at least one operation cycle. A proportion of steam extracted from a steam system and introduced to a feedwater heater, which is in particular extracted from an intermediate point and an outlet of a high pressure turbine, with respect to a flow rate of main steam, is reduced in the second operation cycle from that in the first operation cycle such that the temperature of feedwater discharged from the feedwater heater is lowered by 1° C. to 40° C. in the second operation cycle. |
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claims | 1. An X-ray phase grating used for X-ray phase-contrast imaging based on Talbot interference, comprising:a first substrate having a first pattern in which first faces and second faces making an angle of α with the first faces are periodically arranged, where α≠0 and α≠90°; anda second substrate having a second pattern in which third faces and fourth faces making an angle of α with the third faces are periodically arranged;wherein the first substrate and the second substrate are configured integrally with each other,wherein the second pattern has a same period as the first pattern, andwherein the first pattern and the second pattern are combined so as to be shifted from each other. 2. The X-ray phase grating according to claim 1, wherein the first faces are parallel to the third faces, and the second faces are parallel to the fourth faces. 3. The X-ray phase grating according to claim 1, wherein the first pattern and the second pattern are formed on different substrates. 4. The X-ray phase grating according to claim 3, wherein a region between the first pattern and the second pattern is filled with a material having a different refractive index from a material forming the first and second patterns. 5. The X-ray phase grating according to claim 1, wherein the first substrate and the second substrate are the same substrate, and the first pattern and the second pattern are formed on opposing sides of the same substrate. 6. The X-ray phase grating according to claim 1, wherein the angle between the first faces and the plane of the substrate having the first faces decreases from the center to the periphery of the first substrate, and the angle between the third faces and the plane of the substrate having the third faces decreases from the center to the periphery of the second substrate. 7. The X-ray phase grating according to claim 1, wherein the first pattern and the second pattern are formed in two dimensions. 8. The X-ray phase grating according to claim 1,wherein the first pattern and the second pattern are shifted from each other by one half period of the first pattern and the second pattern. 9. The X-ray phase grating according to claim 1,wherein a shape of the second pattern is the same as a shape of the first pattern, andwherein the third faces correspond to the first faces and the fourth faces correspond to the second faces. 10. An X-ray phase grating used for X-ray phase-contrast imaging based on Talbot interference, comprising:a first substrate having a first pattern in which first faces and second faces making an angle of α with the first faces are periodically arranged, where α≠0 and α≠90°; anda second substrate having a second pattern in which third faces and fourth faces making an angle of α with the third faces are periodically arranged;wherein the first pattern and the second pattern are combined so as to be shifted from each other,wherein the first pattern and the second pattern are formed on different substrates, andwherein the first substrate having the first pattern and the second substrate having the second pattern have joint portions for joining the substrates. 11. The X-ray phase grating according to claim 10,wherein the second pattern has a same period as the first pattern. 12. The X-ray phase grating according to claim 11,wherein the first pattern and the second pattern are shifted from each other by one half period of the first pattern and the second pattern. 13. The X-ray phase grating according to claim 10,wherein the first pattern and the second pattern are shifted from each other by one half period of the first pattern and the second pattern. 14. An X-ray phase grating used for X-ray phase-contrast imaging based on Talbot interference, comprising:a first substrate having a first pattern in which first faces and second faces making an angle of α with the first faces are periodically arranged, where α≠0 and α≠90°; anda second substrate having a second pattern in which third faces and fourth faces making an angle of α with the third faces are periodically arranged;wherein the first pattern and the second pattern are combined so as to be shifted from each other,wherein the first pattern and the second pattern are formed on different substrates, andwherein the first substrate is in contact with the second substrate. 15. The X-ray phase grating according to claim 14,wherein the second pattern has a same period as the first pattern. 16. The X-ray phase grating according to claim 14,wherein the first pattern is in contact with the second pattern. 17. The X-ray phase grating according to claim 14,wherein a face, of the first substrate, opposing to a face on which the first pattern is formed is in contact with a face, of the second substrate, opposing to a face on which the second pattern is formed. 18. A Talbot interferometer comprising:the X-ray phase grating according to claim 1, anda detector detecting interference fringes reflecting a shape of the X-ray phase grating. 19. A Talbot interferometer comprising:the X-ray phase grating according to claim 10, anda detector detecting interference fringes reflecting a shape of the X-ray phase grating. 20. A Talbot interferometer comprising:the X-ray phase grating according to claim 11, anda detector detecting interference fringes reflecting a shape of the X-ray phase grating. |
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description | The present invention relates to a target for a neutron-generating device and a method for manufacturing the target that is irradiated with proton beams to generate neutrons. A boron compound containing boron (10B) is likely to accumulate in cancer cells, but is unlikely to accumulate in normal cells. In this boron compound, a 10B(n,α)7Li reaction is utilized. That is, when boron (10B) captures a thermal neutron or epidermal neutron, an a particle and a lithium atom (7Li) are generated. Such an α particle and a lithium atom can selectively kill the cancer cells. This therapy has been known as boron neutron capture therapy. Conventionally, this boron neutron capture therapy has been carried out using a research reactor. However, the therapy schedule should be adjusted so as not to interfere with the operation schedule of the research reactor. Accordingly, it is not easy to make a therapy schedule. Also, problems have been caused in maintenance costs and a service life of the existing research reactor. In addition, in view of the cost and management, etc., it is markedly difficult to use a nuclear reactor as a neutron-generating device in regular hospitals. Recently, much attention has been paid to neutron-generating devices in which protons are accelerated by an accelerator to have a predetermined energy level; and a given target material is then irradiated with the resulting protons to generate neutrons. Such neutron-generating devices are made as simple equipment when compared with nuclear reactors. Generally speaking, target materials for these neutron-generating devices have been disclosed in Patent Literatures 1 and 2, and examples of the possible target materials include: lithium in which a 7Li(p,n)7Be reaction can be utilized; beryllium in which a 9Be(p,n) reaction can be utilized; and solid heavy metals, such as uranium, tantalum, tungsten, lead, bismuth, and mercury, in which high-energy proton-and/or deuterium-mediated nuclear spoliation reactions are utilized. In a neutron-generating device, high-energy protons and deuterium are accelerated by an accelerator; a solid heavy metal target material is irradiated with the resulting protons and deuterium; and a nuclear spoliation reaction is used to generate high-density neutrons. Unfortunately, the accelerator of this neutron-generating device is large and expensive, and the device is therefore difficult to be installed in regular hospitals. In addition, the neutrons generated during the nuclear spoliation reaction have markedly higher energy levels. Consequently, a large-scale neutron irradiation unit is required, including: a target having a target material; a moderate that can moderate the energy levels of the neutrons to a predetermined energy level of thermal and epidermal neutrons used for boron neutron capture therapy; and a shield that prevents the high-energy neutrons from being leaked. Here, Patent Literature 3 discloses that the energy threshold of a proton required for the 7Li(p,n)7Be reaction is 1.889 MeV. Because of this, a proton accelerator can be small and relatively inexpensive. Thus, it has been proposed to use a metal lithium (7Li) thin film as a target material that is irradiated with accelerated protons. The metal lithium, however, is highly reactive and easily reacts with oxygen, nitrogen, and/or moisture content in the air. In view of the above, the following target structure has been disclosed (see Patent Literature 3). A process such as vapor deposition is used to form a 7Li thin film at a thickness of several dozen μm on a metal substrate. A very thin stainless steel sheet is disposed on the thin film to seal the film onto the metal substrate. Also, this target includes coolant passages through which a coolant is made to circulate to cool the metal substrate holding the metal lithium. Patent Literature 1: JP2008-22920A Patent Literature 2: JP2007-303983A Patent Literature 3: We2008/025737 Meanwhile, patients should not be irradiated with neutrons for a prolonged time during boron neutron capture therapy. Also, the levels of thermal and/or epidermal neutron flux that requires for irradiation on an affected tissue should be obtained. To achieve the above, for example, proton beams should have a current value of a predetermined level or higher. In this regard, however, when a target retaining metal lithium is irradiated with proton beams from the stainless steel sheet side, the stainless steel sheet is heated and expanded. Once the stainless steel sheet is expanded and a contact between metal lithium and the stainless steel sheet is lost, the stainless steel sheet may not be cooled any more. Consequently, the stainless steel sheet may be broken and sealing of the metal lithium may be damaged. In addition, even in the target structure disclosed in Patent Literature 3, melting of the metal lithium sealed using the stainless steel sheet is unavoidable because metal lithium has a relatively low melting point of 180° C. Accordingly, the stainless steel sheet may be expanded, so that the liquefied lithium is unevenly distributed at one portion of the metal substrate included in the target. As a result, the target may have markedly poor performance. Hence, the target has to be replaced by another expensive target before such a situation occurs. The present invention has been developed to solve the above conventional problems. It is an object of the present invention to provide a long-lived target for a neutron-generating device and a method for manufacturing the target that has a simple structure and can maintain a function as a target even if metal lithium as a target material is progressively heated. In order to solve the above problems, an aspect of the present invention provides a target for a neutron-generating device that generates neutrons by using a 7Li(p,n)7Be reaction while lithium as a target material is irradiated with proton beams accelerated by an accelerator. Herein, the target includes: a metal substrate that retains the target material; and a metal thin film for sealing that seals the target material onto the metal substrate at a retention surface side that holds the target material. The metal substrate includes: on the retention surface side, an frame portion; and an embossed structure including: a plurality of island portions surrounded by the frame portion, the island portions having the same height as the frame portion; and the rest including a recessed portion that is created by decreasing a thickness of a region other than the frame portion and the island portions by a thickness of the target material. Herein, the metal thin film for sealing is used to seal the target material onto the recessed portion of the metal substrate. Preferably, the recessed portion of the embossed structure includes: a plurality of circular recessed portions that are hexagonally arranged inside the surrounding frame portion and are circular in a planar view; and communicating recessed portions in communication with the adjacent circular recessed portions. Preferably, the bottom of the recessed portion has an attachment-promoting layer that causes the target material to better attach to the metal substrate. Preferably, the metal substrate also includes a plurality of elongated coolant passages through which a coolant flows at a surface side opposite to the retention surface side. Preferably, the metal substrate is made of iron or tantalum and the metal thin film for sealing is made of a stainless steel sheet, titanium sheet, titanium alloy sheet, beryllium sheet, or beryllium alloy sheet. Preferably, the attachment-promoting layer is a thin film layer made of copper, aluminum, magnesium, or zinc. Preferably, in view of increasing an efficiency of generating neutrons, a material for the island portions of the embossed structure is a lithium alloy containing any of 1 to 20 mass % of Cu, 20 to 40 mass % of Al, and 45 to 60 mass % of Mg, and the remainder consisting of Li and unavoidable impurities. According to an aspect of the present invention having the above features, the metal substrate includes: on the retention surface side holding the target material, an frame portion; and an embossed structure including: a plurality of island portions surrounded by the frame portion, the island portions having the same height as the frame portion; and the rest including a recessed portion that is created by decreasing a thickness of a region other than the frame portion and the island portions by a thickness of the target material. Herein, the metal thin film for sealing and surfaces of the frame portion and the island portions are subjected to, for example, HIP bonding; and the metal thin film for sealing is used to seal the target material onto the recessed portion of the metal substrate. As a result, even if lithium of the target material is irradiated through the metal thin film with proton beams and the metal thin film is heated by the proton beams to be expanded, bonding the metal thin film to the surfaces of the island portions can prevent the metal thin film from being expanded and can maintain conditions in which the target material is tightly attached to the metal thin film. Here, the metal substrate is cooled with a coolant, so that the metal thin film for sealing is also cooled by means of the metal substrate and lithium. This makes it possible to reduce probabilities of metal thin film damage due to excessive heat. FIG. 7 illustrates a Comparative Embodiment where the metal thin film for sealing is attached only onto the frame portion. In this case, when the metal thin film for sealing is expanded, the expansion volume tends to be larger around the center of the frame portion. As a result, when metal lithium as a target material is irradiated with proton beams and is heated and melted, the metal lithium is dislocated to a lower portion between the metal substrate and the metal thin film of the target. Accordingly, almost no metal lithium may be present in the site of the irradiation with the proton beams. According to an aspect of the present invention, the metal thin film for sealing and the surfaces of the frame portion and the island portions are subjected to HIP bonding, and the metal thin film is bonded to the retention surface side of the metal substrate. Meanwhile, irradiation with proton beams may cause metal lithium sealed within the recessed portion to be heated and melted. Even in this case, a change in the thickness of the target material, caused by the expansion of the metal thin film for sealing, may be small. Hereby, metal lithium can be evenly distributed inside the surrounding target frame portion between the metal substrate and the metal thin film for sealing. Consequently, the target may have an extended service life, so that a cumulative irradiation time of proton beams can be extended until the target is replaced by another expensive target. That is, this helps reduce treatment costs paid by patients who receive boron neutron capture therapy. In addition, another aspect of the present invention provides a target for a neutron-generating device that generates neutrons by using a 7Li(p,n)7Be reaction while lithium as a target material is irradiated with proton beams accelerated by an accelerator. The target includes: a metal substrate that retains the target material; and a metal thin film for sealing that seals the target material onto the metal substrate at a retention surface side that holds the target material. Herein, the target material is a lithium alloy containing any of 1 to 20 mass % of Cu, 20 to 40 mass % of Al, and 45 to 60 mass % of Mg, and the remainder consisting of Li and unavoidable impurities. According to this aspect of the present invention having the above features, a melting point of the target material is several hundred degrees higher than a relatively low melting point of pure metal lithium as a target material. This may result in preventing the target material from being melted by heat due to the irradiation with the proton beams. Further, this can also prevent the melted target material from being unevenly distributed at one portion of the metal substrate, thereby preventing target performance from being deteriorated. The present invention can provide a long-lived target for a neutron-generating device and a method for manufacturing the target that has a simple structure and can maintain a function as a target even if metal lithium as a target material is progressively heated. The following describes a neutron-generating device 100 for boron neutron capture therapy (BNCT) by referring to FIGS. 1 to 4. The device 100 uses a target for a neutron-generating device according to an embodiment of the present invention. FIG. 1 outlines a whole neutron-generating device. As shown in FIG. 1, the neutron-generating device 100 primarily includes: a proton beam-generating unit 1; a beam conduit 4 that guides vacuum proton beams 6 generated in the proton-beam-generating unit 1 to a target section 5; and an irradiation unit 2 that produces neutron beams 9 to irradiate a patient's affected tissue (i.e., a treatment unit 3) with the neutron beams 9 while decreasing energy levels of neutrons generated in the target section 5 irradiated with the proton beams 6 to a predetermined energy level. (Proton Beam-generating Unit 1) The proton beam-generating unit 1 includes: an ion source 1a that generates a predetermined amount of protons (i.e., hydrogen ion); and an accelerator 1b that accelerates the protons. The neutron-generating device 100 according to this embodiment is used for BNCT. Metal lithium is used as a target material of its target section 5. The target material is then irradiated with protons and a 7Li(p,n)7Be reaction is utilized to generate neutrons. Here, the accelerator 1b is used to be able to variably set a proton energy range to be from 1.889 MeV, which is a threshold of the 7Li(p,n)7Be reaction occurring in the target material, to 3.0 MeV. Then, a current value of the proton beams 6 may be about 15 to 20 MA while a patient's treatment period for neutron irradiation should be not so long and be intended to last, for example, about 30 min. As a target level of epidermal neutrons of the neutron beams 9 with which a patient is irradiated from the irradiation unit 2, neutron flux has a level of 2×109 n/cm2s at a position 2.5 cm deep from the body surface. The proton beam-generating unit 1 should satisfy such a required specification and may be small and inexpensive. The proton beam-generating unit 1 may employ an EcR (Electron Cyclotron Resonance) ion source as the ion source 1a and an electrostatic accelerator as the accelerator 1b. In the ion source 1a, electron cyclotron resonance is herein used to generate hydrogen (1H) plasma; a solenoid coil or a permanent magnet and sextuple permanent magnet are used to confine the hydrogen (1H) plasma; and the ion source 1a then generates hydrogen ions (1H+). The ECR ion source can stably and continuously perform electrode less discharge for a long period and is characterized in that the ECR ion source can generate high-intensity ion beams. The electrostatic accelerator is a device in which high voltage direct current is applied between electrodes and a potential difference between the electrodes is used to accelerate charged particles. An accelerator according to this embodiment can output low-energy continuous ion beams at a relatively high current level. Examples of the accelerator used include a Dynamiter (a registered trademark of Ion Beam Applications S.A. (IBA Inc.), Belgium) (see JP2012-500454A). This accelerator 1b is highly likely to produce proton beams 6 at a current level of 15 to 20 mA. The proton beams 6 as obtained by this accelerator 1b may have an energy level of from about 1.889 to 3.0 MeV. As shown in FIG. 1, a beam-condensing lens 7 is installed partway through the beam conduit 4 (i.e., at the left side in FIG. 1) before the irradiation unit 2. When a target material 54 (see FIG. 4) of the target section 5 is irradiated with the proton beams 6, the proton beams 6 may spread inside the beam conduit 4 and collide with the inner wall of the beam conduit 4, so that the intensity of the proton beams 6 may decrease. The beam-condensing lens 7 is to prevent this decrease. As the beam-condensing lens 7, a combination of quadruple electromagnets, whose polarity is reversed in the proton beam 6 direction, is generally used. An end portion of the beam conduit 4 has a collimator 10 attached to the target section 5. The collimator 10 adjusts how the proton beams spread in vertical and lateral directions. The collimator 10 focuses the proton beams 6 traveling to the target section 5 on a region positioned in the target material 54 of the target section 5. The collimator 10 has, for example, a cylindrical inner wall and has a water-cooled jacket (not shown) outside of its inner wall to cool the inner wall. In addition, as shown in FIG. 1, the proton beam-generating unit 1 and the beam-condensing lens 7 are linearly arranged on the beam conduit 4, and nothing else is presently disposed therebetween. As disclosed in JP2008-22920A, however, a rotary gantry may be deployed in such a manner that the irradiation unit 2 can irradiate an affected tissue in the treatment unit 3 with neutron beams 9 from an appropriate direction. The gantry portion includes a plurality of deflection electromagnets that can deflect the proton beams 6 in a certain direction. After the deflection electromagnets, the beam-condensing lens 7 may be disposed. In this case, it is convenient to have a rotating seal member on a part of the beam conduit 4. The proton beams 6 are bent at the part. (Irradiation Unit 2) The appearance of the irradiation unit 2 is substantially cylindrical in an incident direction of the proton beams 6. A cylindrical moderate 21 is disposed at the forward side of the target section 5. A reflector 22 covers the circumference and the rear side (i.e., in a direction opposite to the incoming direction of the proton beams 6). The beam conduit 4 penetrates through a through hole disposed in a center portion of the reflector 22. The circumference of the reflector 22 has a cylindrical neutron absorber 23 so as to shield radiation. A filter (not shown) is disposed at the forward side (i.e., irradiation side) of the moderate 21 and the reflector 22. Further, a collimator 24 having an opening at its center portion is disposed at the further forward side. Examples of a material for the moderate 21 used include magnesium fluoride (MgF2) and aluminum fluoride (AlF3). Examples of a material for reflector 22 include graphite (C) and lead (Pb). In this regard, however, when lead is used for the reflector 22, the irradiation unit 2 may be heavy. Aside from this disadvantage, lead can exert an effect of shielding γ rays generated in the target section 5. When the above is taken into consideration, lead is more preferable than graphite. As for the neutron absorber 23, used is a material without emitting γ rays during neutron absorption while fast neutrons are theorized by, for example, hydrogen. Examples of the material include boron-containing polyethylene resins. The above filter is made of a material having a function of shielding neutrons and transmission γ rays. Examples of the material used include lead fluoride (PbF2) and bismuth that can prevent γ rays harmful to treatment, such as γ rays generated during nuclear reactions at the target section 5 and γ rays generated during neutron moderation processes, and through which epidermal neutrons can penetrate and can be used to irradiate a treatment tissue. When lead fluoride and bismuth are compared, bismuth is a material with higher neutron penetration and γ ray-shielding performance. However, bismuth is a very expensive material. In view of the above, lead fluoride or bismuth may be selectively used depending on their price and required performance. A material for the collimator 24 may be, for example, lithium fluoride (LiF), which has increased neutron shielding performance and decreased γ ray generation caused by neutron irradiation. (Target Section 5) The following illustrates the structure of the target section 5 by referring to FIGS. 2 to 6D. FIG. 2 outlines the target section. FIGS. 2 and 3 illustrate the target section 5 as follows: two target panels 11A and 11B are used; an end surface 11b of each target panel is joined like a V-shape at their end side (i.e., at a side through which the proton beams 6 travel); each target panel is inclined in respect to the incident direction of the proton beams 6 by, for example, 30 degrees; and each target panel is attached via an electrical insulator 113 to a tip flange part 10a of the collimator 10 installed at the end portion of the beam conduit 4. Further, as shown in FIG. 2, left and right side plates 12L and 12R are each water tightly attached via an electrical insulator 124 to panel side surfaces 11cL and 11cR of the target panels 11A and 11B, respectively. Also, the side plates 12L and 12R are in contact with the tip flange part 10a. Then, a capped cylindrical casing (not shown in FIG. 2) is mounted via a seal member, for example, using screws to the tip flange part 10a from its outside so as to keep the inside of the casing airtight (see FIG. 5 of Patent Literature 3). In addition, the end surfaces 11b are fixed, for example, using screws to a beam stopper 112 so as to prevent the proton beams 6 from passing through the unit as depicted using the imaginary line (two-dot chain line). The beam stopper 112 is a structure to stop the proton beams 6 so as not to irradiate the casing when the proton beams 6 travel through a gap between the end surfaces 11b. Examples of a material used for the beam stopper 112 include low-carbon steel. The target panels 11A and 11B shown in FIG. 2 respectively have coolant passage holes 117L at their left side. In addition, the target panels 11A and 11B respectively have coolant passage holes 117R at their right side. The coolant passage holes 117 L correspond to the upper and lower coolant passage holes 121L of the side plate 12L. While a watertight sealing material (not shown) is used to prevent leakage of a coolant, the coolant can pass through a coolant channel 122L to an upper coolant passage hole 123L. Inside of the above casing (not shown), a first coolant pipe (not shown) is used to connect the coolant passage hole 123L and a first coolant passage hole (not shown) positioned at the tip flange part 10a. The first coolant pipe includes: for example, a resin pipe resistant to neutron irradiation; and watertight metal connectors at both ends. The first metal connector of the first coolant pipe is connected to the first coolant passage hole, and the coolant is distributed using the coolant passage of the collimator 10 (see FIG. 5 of Patent Literature 3). The second metal connector of the first coolant pipe is connected to the coolant passage hole 123L. Likewise, the coolant passage holes 117R (not shown in FIG. 2) each correspond to the upper and lower coolant passage holes 121R of the side plate 12R. While a watertight sealing material (not shown) is used to prevent leakage of the coolant, the coolant can pass through a coolant channel 122R to an upper coolant passage hole 123R. Inside of the above casing (not shown), a second coolant pipe (not shown) is used to connect the coolant passage hole 123R and a second coolant passage hole (not shown) positioned at the tip flange part 10a. The second coolant pipe has the same structure as of the first coolant pipe. The first metal connector of the second coolant pipe is connected to the second coolant passage hole, and the coolant is distributed using the coolant passage of the collimator 10 (see FIG. 5 of Patent Literature 3). The second metal connector of the second coolant pipe is connected to the coolant passage hole 123R. In this way, one of the first and second coolant pipes may supply the coolant to the target panels 11A and 11B. The other one of the first and second coolant pipes may discharge the coolant from the target panels 11A and 11B through the coolant passage of the collimator 10. As used herein, examples of the coolant used include pure water. FIG. 3 illustrates a mounting structure of the target panel. FIG. 4 is an exploded view illustrating the structure of the target panel 11A when viewed from the beam irradiation surface 11a side. FIG. 3 illustrates, as an example, the target panel 11A in FIG. 2. Here, the target panel 11B has the same mounting structure. A mounting bolt 17 is inserted through an insertion hole 115 and is screwed via an electrical insulation piece 18 into a female screw hole (not shown) positioned at the end surface of the tip flange part 10a. Then, a prefabricated assembly including the target panels 11A and 11B and the side plates 12L and 12R is mounted on the tip flange part 10a. Because the insulation piece 18 is interposed, the mounting bolt 17 contacts neither the target panel 11A nor 11B. Before the target panels 11A and 11B have been attached, the targets 51A should be mounted on the beam irradiation surfaces 11a of the target panels 11A and 11B, which surfaces are the side (front side) irradiated with the proton beams 6. However, the target panel and the target are separated for description clarity in FIG. 3. Meanwhile, as described below in the description of FIG. 5, the target 51A includes: a metal substrate 52A; a target material 54 (see FIGS. 4 and 5); a metal thin film 53 for sealing; and a blackboard 55. As used herein, the blackboard 55 is part of each of the target panels 11A and 11B (see FIG. 4). In this connection, examples of a material for the target panels 11A and 11B include carbon steel and copper. Types of a component member for the metal thin film 53 should be used to prevent a chemical reaction such as oxidation of the target material 54. Also, the metal thin film 53 should not be easily corroded by the target material 54. In addition, neither the proton beams 6 should be attenuated nor excessive heat should be generated when the metal thin film 53 is irradiated with the proton beams 6. In view of the above requirement, it is preferable to select the types of the component member through which the proton beams 6 pass easily. Specific examples of the suitable component member for the metal thin film 53 include a stainless steel sheet, titanium sheet, titanium alloy sheet, beryllium sheet, and beryllium alloy sheet. In view of low production cost, a stainless foil at a thickness of 4 μm is herein used for the metal thin film 53 for sealing as an example. When a titanium alloy sheet is used, the sheet preferably has a thickness of 5 μm. When a beryllium alloy sheet is used, the sheet preferably has a thickness of 10 μm. The back surface of the metal substrate 52A has grooved coolant passages 52d as shown in FIGS. 3, 4, and 5. The back surface of the metal substrate 52A is attached to the blackboard 55 at the beam irradiation surface 11a of the target panel 11A as shown in FIG. 4. The blackboard 55 has a recess part that is a little step holding the beam irradiation surface 11a. In FIG. 4, the target panel 11A is viewed from the backside, so that the left-right direction is reversed. The left and right side portions of the blackboard 55 include concave manifolds 116L and 116R used to provide the coolant passages 52d with the coolant and to recover the coolant from the coolant passages 52d. A coolant passage hole 116La that is an opening for the manifold 116L is in communication with the coolant passage hole 117L. Likewise, a coolant passage hole 116Ra that is an opening for the manifold 116R is in communication with the coolant passage hole 117R. The same structure is used for the target panel 11B. In this regard, however, the reference signs denoting the left-right direction in FIG. 4 are changed. Nevertheless, the shape thereof is identical. FIG. 5 is an exploded view illustrating the target. FIG. 5 provides a simplified schematic view of the blackboard 55 as a plate. Like the blackboard 55 of the target panel 11A (11B) shown in FIG. 4, this blackboard also includes the manifolds 116L and 116R that are concave elongated grooves. As shown in FIG. 5, the front surface side (referred to as the “retention surface X” in FIG. 5) of the substantially rectangular metal substrate 52A includes: a circumferential frame portion 52a; discrete island portions 52b that are surrounded by the frame portion 52a and are regularly arranged in the lateral and longitudinal directions as shown in FIG. 6A; and the rest recessed portion 52c where the thickness is decreased. The surface height of the frame portion 52a is equal to the surface height of each island portion 52b. The step height of the recessed portion 52c is equal to the thickness of the target material metal lithium (Li) and is, for example, 50 μm. The structure of these island portions 52b with the rest recessed portion 52c is what is called an “embossed structure”. The structure can be processed using, for example, milling, electric discharge machining, and/or chemical etching. The back surface side (i.e., the surface opposite to the retention surface X) of the metal substrate 52A includes: grooved coolant passages 52d; and the rest cooling fins 52e. Then, this recessed portion 52c is filled with metal lithium. After that, the back surface of the metal substrate 52A is placed on the blackboard 55 as shown in FIG. 4. Further, the metal thin film 53 for sealing is placed on the retention surface X of the metal substrate 52A. Subsequently, HIP bonding is used to attach the metal thin film 53 to the surface of the frame portion 52a and the surfaces of the island portions 52b. At the same time, the blackboard 55 is bonded to the back surface of the metal substrate 52A. Here, the target material metal lithium (Li) has a thickness of 50 μm. The target panels 11A and 11B are inclined by 30 degrees with respect to the irradiation direction of the proton beams 6. Thus, the travel distance of the proton beams 6 passing through the target material 54 is about 110 μm, which is a sufficient thickness. For example, the energy level of the proton beams 6 is decreased from 2.8 MeV to less than 1.889 MeV while the proton beams 6 travel the distance through the metal lithium (i.e., the target material 54). Then, the protons penetrate into the metal substrate 52A. Accordingly, this can prevent γ ray emission caused by inelastic scattering between lithium and the incident protons. Examples of a preferable material for the metal substrate 52A include low-carbon steel (Fe) and tantalum (Ta). The thickness from the bottom of the recessed portion 52c to the groove bottom of the coolant passage 52d is a thickness at which all the rest protons passing through the target material 54 irradiated with the proton beams 6 can be blocked. Iron, like tantalum (Ta), is highly resistant to hydrogen embracement and blistering due to a lattice defect caused by proton collisions, and is a low cost material. In view of heat conductivity, copper (Cu) is preferable as a material for the target panels 11A and 11B. The metal substrate 52A may be attached using HIP (Hot Isostearic Pressing) bonding. When this is taken into account, carbon steel may be suitable. (Method for Manufacturing Target 51A) Next, a method for manufacturing the target 51A will be explained by referring to FIGS. 6A-6D. FIGS. 6A-6D illustrate how to manufacture the target 51A. FIG. 6A illustrates a method including: an embossed structure processing step of producing an embossed structure on the retention surface X side (a front surface side) of the metal substrate 52A of the target 51A; a coolant passage creating step of producing grooves for coolant passages 52d at the side (i.e., a back surface side) opposite to the retention surface of the metal substrate, and thereafter; an attachment-promoting layer formation step of producing an attachment-promoting layer at a bottom of the recessed portion 52c, and thereafter; and a target material filling step of filling the recessed portion 52c with a melted target material in vacuo or under an argon gas atmosphere. FIG. 6B illustrates a condition after the target material filling step. FIG. 6C illustrates a condition after a retention surface smoothing step. FIG. 6D illustrates a condition after a bonding step of subjecting to HIP bonding the blackboard 55, the metal thin film 53 for sealing, and the metal substrate 52A obtained by the last target material filling step. The target 51A is manufactured as follows. (1) Coolant Passage Formation Step The original metal substrate 52A is a rectangular low-carbon steel or tantalum plate. In order to form the coolant passages 52d, many grooves are created using, for example, milling on one surface (i.e., the back side (corresponding to the lower surface in FIG. 6A)) of the metal substrate to produce cooling fins 52e (see FIG. 6A). (2) Embossed Structure Processing Step The front surface side (i.e., corresponding to the upper surface side in FIG. 6A) of the metal substrate 52A includes: the frame portion 52a; and the discrete island portions 52b that are surrounded by the frame portion 52a and are regularly arranged in the lateral and longitudinal directions as shown in FIG. 6A. The rest recessed portion 52c is created by decreasing the thickness by a predetermined length. For example, the thickness is decreased using milling by 50 μm, which is the same thickness as of the target material metal lithium (Li). (3) Attachment-promoting Layer Formation Step After the embossed structure processing step, a very thin layer (i.e., attachment-promoting layer) made of copper, aluminum, magnesium, or zinc is deposited using a film formation process such as vapor deposition and sputtering on the bottom of the recessed portion 52c. The thickness of the layer is, for example, 0.05 μm. This process makes better the attachment (or wearability) between the metal substrate 52A and lithium that is the target material 54. At this time, before the film formation process such as vapor deposition and sputtering, the upper surfaces (in FIG. 6A) of the frame portion 52a and the island portions 52b are masked so as not to form a copper thin layer. After the film formation process such as vapor deposition and sputtering, the mask is ripped off. (4) Target Material Filling Step Next, molten metal lithium that is the target material 54 contained in a crucible 61 is poured in vacuo or under an argon gas atmosphere into the recessed portion 52c (see FIGS. 6A and 6B). Because argon gas contains oxygen and moisture content (H2O) as impurities, the molten metal lithium may be oxidized. Hence, it is preferable to fill the recessed portion 52c with the metal lithium in vacuo. (5) Retention Surface Smoothing Step The metal lithium that is the target material 54 used to fill the recessed portion 52c during the target material filling step (4) is solidified as it is in vacuo or under an argon gas atmosphere. However, as shown in FIG. 6B, the metal lithium is also attached onto the surfaces of the frame portion 52a and the island portions 52b, and the level of the metal lithium is higher than the surfaces of the frame portion 52a and the island portions 52b. Then, the metal lithium is ground and leveled using, for example, milling in vacuo or under an argon gas atmosphere to the height of the surfaces of the frame portion 52a and the island portions 52b. The resulting metal lithium powder is also removed by blowing with argon gas. As a result, the surfaces of the frame portion 52a and the island portions 52b are exposed and kept clean. This makes only the recessed portion 52c filled with the metal lithium (see FIG. 6C). Because argon gas contains oxygen and moisture content (H2O) as impurities, the molten metal lithium may be oxidized. Hence, it is preferable to grind the metal lithium in vacuo. (6) Bonding Step First, the blackboard 55 (e.g., the blackboard 55 is schematically depicted as a rectangular plate for illustration purpose in FIG. 6D) for the target panel 11A (or the target panel 11B) is horizontally placed under an argon gas atmosphere. Next, the back side of the metal substrate 52A is placed on the blackboard 55. Then, the metal thin film 53 for sealing is placed on the retention surface X (see FIG. 5) of the metal substrate 52A. After that, an abutting member that is not bonded to the metal thin film 53 during HIP bonding and that has a flat abutting surface facing the metal thin film 53 is placed on the metal thin film 53. Examples of a material for the abutting member include ceramics. This abutting member has a suitable weight and is to exclude argon gas between the metal thin film 53 and the retention surface X of the metal substrate 52A before the initiation of the HIP bonding. Also, the abutting member makes it possible to keep the flat metal thin film 53 in contact with the retention surface X of the metal substrate 52A during the HIP bonding. This can prevent the metal thin film 53 from being indented into the recessed portion 52c when the metal lithium is melted. Thereafter, the HIP bonding is carried out. According to this bonding step, the metal thin film 53 can be bonded to the surfaces of the frame portion 52a and the island portions 52b of the metal substrate 52A while the blackboard 55 is bonded to the metal substrate 52A. At this time, not only the blackboard 55 is bonded to the lower surfaces of the cooling fins 52e of the metal substrate 52A, but also the corner side portions of the metal substrate 52A are bonded to the frame portion of the blackboard 55 at the beam irradiation surface 11a side of the target panel 11A (or the target panel 11B). Consequently, the manifolds 116L and 116R are water tightly attached at the beam irradiation surface 11a side of the target panel 11A (or the target panel 11B). This bonding step can reduce the number of steps when compared with the bonding step in which the bonding of the metal thin film 53 to the surfaces of the frame portion 52a and the island portions 52b of the metal substrate 52A and the bonding of the blackboard 55 to the metal substrate 52A are separately performed. Then, the above method is used to complete the target 51A. FIGS. 7A and 7B illustrate the structure of a target 51B according to a comparative embodiment. FIG. 7A is a perspective view of the target 51B. FIG. 7B is a cross-sectional view taken along the line Y-Y in FIG. 7A. In the target 51B according to the comparative embodiment, the structure of the front surface side of the metal substrate 52B includes: the circumferential frame portion 52a; and a recessed portion 52c that is surrounded by the frame portion 52a and that is uniformly concave. This recessed portion 52c without an embossed structure is tightly filled with pure metal lithium that is the target material 54. In contrast, according to the target 51A of the present embodiment, the surfaces of the frame portion 52a and the island portions 52b of the metal substrate 52A are bonded to the metal thin film 53 on the metal substrate 52A at the side of the retention surface X irradiated with the proton beams 6. However, according to the comparative embodiment, the metal substrate 52B has no embossed structure at the side of the retention surface X irradiated with the proton beams 6. Thus, when comparing the present embodiment having the embossed structure to the comparative embodiment having no embossed structure, even if the target material 54 metal lithium is heated by the proton beams 6 and becomes melted, the present embodiment can suppress thermal expansion of the metal thin film 53. Further, the present embodiment can prevent occurrence of gravity-mediated dislocation of the molten metal lithium to one side of the plane inside the frame portion 52a. In addition, according to the present embodiment, the collimator 10 is used to collimate the proton beams 6 so as to uniformly irradiate the target materials 54 of the target panels 11A and 11B with the proton beams 6. This configuration helps prevent only part (a spot) of the metal thin film 53 on the target 51A from being irradiated with the proton beams 6. Accordingly, heat damage of the metal thin film 53 can be avoided. This results in a prolonged period until the metal thin film 53 for sealing reaches the end of its service life. Hence, the service life of the target 51A may be extended. By contrast, in the comparative embodiment, the collimator 10 may be used to uniformly irradiate the target material 54 of the target 51B with the proton beams 6. This case, however, results in the gravity-mediated dislocation of the molten metal lithium to one side of the plane inside the frame portion 52a. Consequently, a portion without contacting the molten metal lithium appears at the back side of the metal thin film 53 for sealing. This portion is not cooled with the molten metal lithium. Also, a time until the metal thin film 53 is damaged by excessive heat is shortened. Hence, the service life of the target 51B may be shortened. By contrast, the target 51A according to the present embodiment does not experience such a situation. Thus, the target 51A has a longer service life than the target 51B according to the comparative embodiment. Overall, the target 51A helps reduce cost per patient of boron capture therapy. In addition, the metal lithium of the target material 54 has a thickness of 50 μm. This can prevent the energy of the proton beams 6 from being lost in the metal lithium due to inelastic scattering between the lithium and the proton beams 6. Accordingly, the above can decrease occurrence of inelastic scattering γ rays. Consequently, the γ ray-shielding structure of the irradiation unit 2 can be made to weigh less and the irradiation unit 2 can be made compact. Further, the molten metal lithium of the target material 54 may circulate through the target section 5 of the irradiation unit 2. In this case, the structure of the circulation pipe may be complex. At the same time, the circulation pipe disposed outside the irradiation unit 2 requires a α-ray-shielding structure. The present embodiment does not require such a structure and the target section 5 can be made compact. In this regard, however, examples of a material for the metal substrate 52A include low-carbon steel and tantalum. This material can prevent blistering due to proton (hydrogen) absorption when compared with the case of using copper (Cu) for the metal substrate 52A. This enables the service life of the target 51A to be extended and helps reduce cost per patient of boron capture therapy. Note that when the embossed structure of the metal substrate 52A of the target 51A according to the present embodiment is formed, this embossed structure may be ordered or irregular. The shapes of the concave recessed portion and the rest island portions may be linear or curved. In FIGS. 4 to 6D, rectangular island portions are arranged on the surface of the metal substrate in the longitudinal and lateral directions with equal spacing. In this way, the recessed portion is created by decreasing the thickness of the metal substrate like a grid in a planar view. In FIG. 6A, the island portions 52b are arranged like what is called “a grid” where the island portions 52b have an identical columnar spacing configuration between the adjacent columns. The present invention, however, is not limited to the present embodiment. The island portions 52b may not have an identical columnar spacing configuration between the adjacent columns. That is, the island portions 52b may be arranged like a “zigzag pattern”. <<Modification Embodiment 1>> With reference to FIGS. 8A and 8B, the following illustrates the structure of a target 51C and a method for manufacturing the target 51C. The method differs from that of the target 51A according to the present embodiment. FIGS. 8A and 8B illustrate the structure of the target 51C according to a modification embodiment. FIG. 8A is a schematic perspective view. FIG. 8B is a cross-sectional view taken along the line Z-Z in FIG. 8A. FIG. 9 is an exploded view illustrating the structure of a target panel according to the modification embodiment when viewed from the beam irradiation surface 11a side. FIG. 10 illustrates how to arrange a molten lithium injection inlet and a filled molten lithium outlet in the target panel according to the modification embodiment. The same components as of the target 51A have the same reference signs so as to avoid redundancy. With regard to the target 51C, FIGS. 8A and 8B provide a schematic view of a metal substrate 52C as a plate. The metal thin film 53 for sealing is attached onto the retention surface X of the metal substrate 52C. The blackboard 55 is attached onto the surface opposite to the retention surface X of the metal substrate 52C. The target 51C differs from the target 51A in the following points. (1) As shown in FIGS. 8A and 8B, two areas near the opposing corners of the retention surface X of the metal substrate 52C include relatively wide rectangular recessed portions 52c1 and 52c2 where no island portions 52b are present. (2) The recessed portion 52c1 is in communication with an injection passage 63; the side opposite to the retention surface X of the metal substrate 52C has, for example, a cylindrical protrusion; a penetrate portion 52f1 has an opening of the injection passage 63 at the end of the protrusion; the recessed portion 52c2 is in communication with an injection passage 64; the side opposite to the retention surface X of the metal substrate 52C has a cylindrical protrusion; and a penetrate portion 52f2 has an opening of the injection passage 64 at the end of the protrusion. The penetrate portions 52f1 and 52f2 of the metal substrate 52C are positioned closer to the center so as to avoid the manifolds 116L and 116R as shown in FIGS. 9 and 10. The penetrate portions 52f1 and 52f2 are inserted into through holes 120A and 120B, respectively, that penetrate through the flat surface portion of the blackboard 55. The ends of the penetrate portions 52f1 and 52f2 and the surface opposite to the retention surface X of the blackboard 55 (target panel 11A) should be flush. The injection passages 63 and 64 respectively have an opening at the surface opposite to the retention surface X of the target panel 11A. The same applies to the target panel 11B. To manufacture the target 51C, the following describes a target material filling step of injecting molten metal lithium. The injection passage 63 is connected to a molten lithium inlet pipe 65 depicted using the imaginary line (two-dot chain line) shown in FIG. 8B. The injection passage 64 is connected to a molten lithium-filled outlet pipe 66 depicted using the imaginary line (two-dot chain line). After completion of the filling with and solidification of the molten metal lithium, the molten lithium inlet pipe 65 and the molten lithium outlet pipe 66 are cut. Then, the solidified metal lithium is removed from the injection passages 63 and 64. Subsequently, the injection passages 63 and 64 of the penetrate portions 52f1 and 52f2 are capped (not shown), sealed, and welded. The target 51C is manufactured as follows. (1) Coolant Passage Formation Step The original metal substrate 52C is a rectangular low-carbon steel or tantalum plate. In order to form the coolant passages 52d, many grooves are created using, for example, milling on one surface (i.e., the back side (corresponding to the upper surface in FIG. 10)) of the metal substrate to produce cooling fins 52e (see FIG. 10). (2) Injection Passage Hole-creating Step Next, holes for the injection passages 63 and 64 are created near the lower right corner and the upper left corner of the metal substrate 52C as shown in FIG. 10. (3) Embossed Structure Processing Step The front surface side (corresponding to the upper surface in FIG. 9) of the metal substrate 52C includes: the frame portion 52a; and the plurality of discrete island portions 52b that are surrounded by the frame portion 52a and are regularly arranged in the lateral and longitudinal directions as shown in FIG. 9. The rest recessed portion 52c is created by decreasing the thickness by a predetermined length. For example, the thickness is decreased using milling by 50 μm, which is the same thickness as of the target material metal lithium (Li). At this time, the recessed portion 52c1 is created near the lower left corner by decreasing the thickness by 50 μm in such a manner that the portion invades the frame portion 52a at the lower side as shown in FIG. 9. Further, the recessed portion 52c2 is created near the upper right corner by decreasing the thickness by 50 μm in such a manner that the portion invades the frame portion 52a at the upper side as shown in FIG. 9. Consequently, as shown in FIG. 9, the bottoms of the recessed portion 52c1 and 52c2 have an opening for the injection passages 63 and 64, respectively, which have been created in the injection passage hole-creating step. (4) Penetrate Portion-connecting Step Next, as shown in FIG. 10, the holes for the injection passages 63 and 64 of the metal substrate 52C are welded to the cylindrical penetrate portions 52f1 and 52f2 each having a communication hole for the injection passages 63 and 64. (5) Bonding Step First, the blackboard 55 (e.g., the blackboard 55 is schematically depicted as a rectangular plate for illustration purpose in FIGS. 8A and 8B) for the target panel 11A (or the target panel 11B) is horizontally placed under an argon gas atmosphere. Next, the back side of the metal substrate 52C is placed on the blackboard 55. Then, the metal thin film 53 for sealing is placed on the retention surface X (see FIG. 8A) of the metal substrate 52C. At this time, the penetrate portions 52f1 and 52f2 are inserted into the through holes 120A and 120B, respectively, of the blackboard 55 (see FIGS. 9 and 10) of the target panel 11A (or the target panel 11B). The ends of the penetrate portions 52f1 and 52f2 and the surface opposite to the retention surface X of the blackboard 55 of the target panel 11A (or the target panel 11B) should be flush. After that, an abutting member that is not bonded to the metal thin film 53 during HIP bonding and that has a flat abutting surface facing the metal thin film 53 is placed on the metal thin film 53. Examples of a material for the abutting member include ceramics. This abutting member has a suitable weight and is to exclude argon gas between the metal thin film 53 and the retention surface X of the metal substrate 52C before the initiation of the HIP bonding. Also, the abutting member makes it possible to keep the flat metal thin film 53 in contact with the retention surface X of the metal substrate 52C during the HIP bonding. This can prevent the metal thin film 53 from being indented into the recessed portions 52c, 52c1, and 52c2. Thereafter, the HIP bonding is carried out. According to this bonding step, the metal thin film 53 can be bonded to the surfaces of the frame portion 52a and the island portions 52b of the metal substrate 52C while the blackboard 55 is simultaneously bonded to the metal substrate 52C. At this time, not only the blackboard 55 is bonded to the lower surfaces of the cooling fins 52e of the metal substrate 52C, but also the through holes 120A and 120B of the blackboard 55 are connected to the penetrate portions 52f1 and 52f2, respectively. Further, the circumferential side portions of the metal substrate 52C are also simultaneously bonded to the frame portion of the blackboard 55 at the beam irradiation surface 11a side of the target panel 11A (or the target panel 11B). Consequently, the manifolds 116L and 116R are water tightly attached at the beam irradiation surface 11a side of the target panel 11A (or the target panel 11B). This bonding step can reduce the number of steps when compared with the bonding step in which the bonding of the metal thin film 53 to the surfaces of the frame portion 52a and the island portions 52b of the metal substrate 52C and the bonding of the blackboard 55 to the metal substrate 52C are separately performed. (6) Target Material Filling Step Next, one end of the molten lithium inlet pipe 65 and one end of the molten lithium outlet pipe 66 are welded to the end surfaces of the penetrate portions 52f1 and 52f2 that are exposed at the side opposite to the retention surface X of the blackboard 55 of the target panel 11A (or the target panel 11B). Then, the other end of the molten lithium outlet pipe 66 is connected to a vacuum pump such as an oil diffusion pump. Also, the other end of the molten lithium inlet pipe 65 is connected to a molten metal lithium supplier. At this time, it is preferable to place the target panel 11A (or the target panel 11B) in a sealed chamber including, for example, a welding device, a cutter, and a heating unit such as an induction heater. After that, as shown in FIG. 8B, the molten lithium outlet pipe 66 is arranged at the upper side and the molten lithium inlet pipe 65 is arranged at the lower side. Thereafter, the vacuum pump is actuated to vacuum the inside of the molten lithium inlet pipe 65, the spaces occupied by the recessed portions 52c, 52c1, and 52c2 formed between the blackboard 55 and the metal thin film 53, and the inside of the molten lithium outlet pipe 66. In addition, the target panel 11A (or the target panel 11B) is heated using an induction heating process, etc., to a first predetermined temperature of 200° C. or higher, for example, from 400 to 500° C. The target panel 11A (or the target panel 11B) is provided with a plurality of temperature sensors (not shown). Signals from the temperature sensors are used to check whether or not the target panel has been heated to the first predetermined temperature. Then, the recessed portions 52c, 52c1, and 52c2 are filled via the molten lithium inlet pipe 65 with molten metal lithium that is the target material 54 preheated in vacuo to 200° C. or higher. It is easy to check whether or not the spaces of the recessed portions 52c, 52c1, and 52c2 are sufficiently filled with the molten metal lithium by monitoring the level of the molten metal lithium in the molten lithium outlet pipe 66 by using, for example, X-rays. After the recessed portions 52c, 52c1, and 52c2 are sufficiently filled with the molten metal lithium, the molten metal lithium supplier side is closed. Then, until the metal substrate 52C, the metal thin film 53, and the molten lithium become wet and have sufficient contacts for a predetermined period, the temperature of the target panel 11A (or the target panel 11B) should be kept for a predetermined period (a retention period) at a second predetermined temperature of 200° C. or higher, for example, from 200 to 300° C. This second predetermined temperature and the retention period are defined in preliminary experiments. Here, the first predetermined temperature may be high, but is a temperature where the molten metal lithium invades neither the blackboard 55 nor the metal thin film 53 for sealing. This first predetermined temperature should be defined in preliminary experiments. By the way, the first predetermined temperature may be identical to the second predetermined temperature. (7) Target Material Injection Passage-closing Step The following describes a step of closing the injection passages 63 and 64 after the filling with the molten metal lithium. After the retention period has passed, the target is gradually cooled while the spaces of the recessed portions 52c, 52c1, and 52c2 are still filled with the molten metal lithium. Next, the spaces of the recessed portions 52c, 52c1, and 52c2 are filled with the solidified metal lithium. Then, the temperature sensors installed on the target panel 11A (or the target panel 11B) are used to check whether or not the sufficient cooling has been completed. After that, the molten lithium outlet pipe 66 is closed and the vacuum pump is stopped. Thereafter, the sealed chamber including the target panel 11A (or the target panel 11B) is kept in vacuo or under an argon gas atmosphere. Next, the molten lithium inlet pipe 65 and the molten lithium outlet pipe 66 are cut using the above-mentioned cutter. The metal lithium present in the injection passage 63 of the penetrate portion 52f1 and the injection passage 64 of the penetrate portion 52f2 are cut and removed. Then, caps (not shown), which use the same material as of the metal substrate 52C (not shown), prepared in the sealed chamber are fitted to the injection passages 63 and 64 of the penetrate portions 52f1 and 52f2. After that, the caps are subjected to tight welding such as laser welding and electron beam welding. The above method is used to complete the target 51C. Note that in this modification embodiment, the retention period during the target material filling step (6) may be shortened. For this purpose, the “attachment-promoting layer formation step” (3) during the manufacturing of the target 51A of the present embodiment may be included after the embossed structure processing step (3) and before the bonding step (5). In addition, this modification embodiment includes the target material injection passage-closing step (7) in which the molten lithium inlet pipe 65 and the molten lithium outlet pipe 66 are cut and the injection passages 63 and 64 are capped. The present invention, however, is not limited to this modification embodiment. While the molten lithium inlet pipe 65 and the molten lithium outlet pipe 66 are filled with the molten metal lithium or the solidified metal lithium, the injection passages may be pressed, sealed, and welded. Further, this modification embodiment includes the penetrate portions 52f1 and 52f2 in the metal substrate 52C. The present invention, however, is not limited to this modification embodiment. The penetrate portions 52f1 and 52f2 may not be provided; HIP bonding may be used to attach the end portions of the through holes 120A and 120B of the blackboard 55 to the hole end portions of the injection passages 63 and 64 of the metal substrate 52C; and the through holes 120A and 120B may thus be part of the injection passages 63 and 64. In addition to the effects of the above-described embodiment, this modification embodiment can exert an effect of preventing the metal substrate 52A and the metal thin film 53 from being corroded by the placed molten high-temperature target material 54 during the HIP bonding. As a result, the target 51C of this modification embodiment has a longer service life than the target 51A of the present embodiment. <<Modification Embodiment 2 >> Next, with reference to FIGS. 11A-11C, the following illustrates the structure of a target 51D and a method for manufacturing the target 51D whose embossed structure differs from that of the target 51A of the present embodiment. FIGS. 11A-11C illustrate the structure of the target 51D according to another modification embodiment. FIG. 11A is an exploded view illustrating the target 51D. FIG. 11B is a plan view showing a metal substrate 52D holding the target material 54. FIG. 11C is an enlarged perspective view showing an embossed structure on the metal substrate 52D. The same components as of the target 51A have the same reference signs so as to avoid redundancy. The target 51D includes: the metal substrate 52D; the target material 54; the metal thin film 53 for sealing; and the blackboard 55. FIG. 11A provides a simplified schematic view of the blackboard 55 as a plate. Like the target 51A, the blackboard 55 is part of the target panel 11A or 11B. Like the blackboard 55 of the target panel 11A (11B) shown in FIG. 4, this blackboard also includes the manifolds 116L and 116R that are concave elongated grooves. As shown in FIG. 11A, the metal substrate 52D is a substantially rectangular plate and includes the circumferential frame portion 52a at its front surface side (i.e., the upper side in FIG. 11A). The metal substrate 52D also includes: the discrete island portions 52b that are surrounded by the frame portion 52a and are regularly arranged in the lateral and longitudinal directions; and the rest recessed portion 52c where the thickness is decreased. This recessed portion 52c retains the target material 54. The target 51D differs from the target 51A in the shape of an embossed structure formed on the retention surface of the metal substrate 52D. As shown in FIG. 11B, the embossed structure of the metal substrate 52D includes: a plurality of circular recessed portions that are hexagonally arranged with equal spacing; and communicating recessed portions that are regularly arranged so as to preserve the island portions 52b. Then, the ordered recessed portions hold the target material 54. FIG. 11C is an enlarged perspective view illustrating part of the embossed structure under conditions in which the recessed portions are not filled with the target material 54. In a planar view, the metal substrate 52D includes repeated units of the recessed portion 52c including: a circular recessed portion 52c3 that is circularly created by decreasing the thickness; and rectangular communicating recessed portions 52c4 that are created by decreasing the thickness so as to make communication with the adjacent circular recessed portions 52c3. The island portion 52b, which is a nearly hexagonal cylinder, is positioned at each vertex of a honeycomb structure. Examples of a preferable material for the metal substrate 52D include low-carbon steel (Fe) and tantalum (Ta). Such an embossed structure can be processed using, for example, milling, electric discharge machining, and/or chemical etching. The circular recessed portion 52c3 and the communicating recessed portion 52c4 may have the same depth. The surface height of the frame portion 52a is equal to the surface height of each island portion 52b. The step height of the recessed portion 52c is equal to the thickness of the target material metal lithium (Li) and is, for example, 50 μm. The recessed portion 52c including the circular recessed portions 52c3 and the communicating recessed portions 52c4 is placed beside the rest discrete island portions 52b having a predetermined area. The recessed portion 52c preferably has an area percentage of 70% or more in respect to the area surrounded by the frame portion 52a of the metal substrate 52D. Use of such an area percentage makes it possible to avoid reducing the cross-sectional reaction area of the target material while keeping the surface area of the island portions attached to the metal thin film for sealing. The circular recessed portion 52c3 may be substantially circular and its size may be the same or different. Also, the circular recessed portions 52c3 may be regularly arranged. For example, the centers of the circular recessed portions 52c3 may be hexagonally arranged with equal spacing. In FIG. 11C, R denotes the radius of the circular recessed portion 52c3 and D denotes the distance between the centers of the adjacent circular recessed portions 52c3. The radius R of the circular recessed portion 52c3 is not particularly limited, but may be from 1 to 5 mm and preferably 2 mm. The distance D between the centers of the adjacent circular recessed portions 52c3 is not particularly limited, but may be from R+1 to R+3 mm and preferably R+1 mm. Further, the communicating recessed portion 52c4 is preferably a linear groove in communication with each circular recessed portion 52c3. For example, the axes of the communicating recessed portion 52c4 and the line connecting the centers of the adjacent circular recessed portions 52c3 may be the same, which allows the adjacent centers to be connected using the shortest distance. In a planar view, the communicating recessed portion 52c4 may be substantially rectangular. In FIG. 11C, L1 denotes the width of the communicating recessed portion 52c4 and L2 denotes the length of the communicating recessed portion 52c4. The width L1 of the communicating recessed portion 52c4 is not particularly limited, but may be from ⅕ to ½ of the radius of the circular recessed portion 52c3 and preferably ½. The circular recessed portions 52c3 with a radius of 2 mm may be hexagonally arranged with a 5-mm interval; and the adjacent circular recessed portions 52c3 may then be connected using the communicating recessed portion 52c4 with a length and a width of 1 mm. In this case, the area percentage obtained is about 72% in respect to the area surrounded by the frame portion 52a of the metal substrate 52D. The thickness from the bottom of the recessed portion 52c to the groove bottom of the coolant passage 52d is a thickness at which all the rest protons passing through the target material 54 irradiated with the proton beams 6 can be blocked. As shown in FIG. 11A, in the target 51D, the back side of the metal substrate 52D includes: the coolant passages 52d that are created by grooving in the same manner as in the target 51A; and the rest cooling fins 52e. The recessed portion 52c is filled with metal lithium. Then, the blackboard 55 is placed facing the back side of the metal substrate 52D. Further, the metal thin film 53 for sealing is placed on the upper surface of the metal substrate 52D. After that, HIP bonding is used to attach the metal thin film 53 to the surfaces of the frame portion 52a and the island portions 52b. At the same time, the blackboard 55 is bonded to the back side of the metal substrate 52D. This target 51D can be manufactured in accordance with the method for manufacturing the above mentioned target 51A. According to this modification embodiment, the metal lithium that is the target material 54 present in the recessed portion may be heated and melted by proton beam irradiation. Even in this case, the circular recessed portions 52c3 cause the expansion pressure to scatter. The communicating recessed portion 52c4 distributes the melted metal lithium to the adjacent circular recessed portions 52c3, and the melted metal lithium is leveled. When compared with the case of the target 51A according to the above-described embodiment, the expansion of the metal thin film for sealing is more suppressed. Accordingly, the target material 54 and the metal thin film for sealing are kept tightly attached. Hence, this embodiment can reduce the possible occurrence of heat damage of the metal thin film for sealing. <<Modification Embodiment 3>> With reference to FIGS. 12A and 12B, the following illustrates the structure of a target 51E and a method for manufacturing the target 51E whose material for the embossed structure differs from that of the target 51D of the above modification embodiment. FIGS. 12A and 12B illustrate the structure of the target 51E according to still another modification embodiment. FIG. 12A is an exploded view illustrating the target 51E. FIG. 12B is a plan view showing a metal substrate 52E holding the target material 54. The same components as of the targets 51A and 51D have the same reference signs so as to avoid redundancy. The target 51E includes: the metal substrate 52E; the target material 54; the metal thin film 53 for sealing; and the blackboard 55. FIG. 12A provides a simplified schematic view of the blackboard 55 as a plate. Like the target 51A, the blackboard 55 is part of the target panel 11A or 11B. Like the blackboard 55 of the target panel 11A (11B) shown in FIG. 4, this blackboard also includes the manifolds 116L and 116R that are concave elongated grooves. As shown in FIG. 12A, the front surface side (i.e., the upper side in FIG. 12A) of the substantially rectangular metal substrate 52E includes: the circumferential frame portion 52a; the discrete island portions 52b that are surrounded by the frame portion 52a and are regularly arranged in the lateral and longitudinal directions; and the rest recessed portion 52c where the thickness is decreased. The target 51E has an embossed structure similar to that of the target 51D. As shown in FIG. 12B, the front surface side of the metal substrate 52E includes: the recessed portion 52c including: the circular recessed portions 52c that are surrounded by the frame portion 52a and that are hexagonally arranged with equal spacing by decreasing the thickness; and the communicating recessed portions 52c4 that are created by decreasing the thickness and that connect the adjacent circular recessed portions 52c3; and the rest substantially hexagonal island portions 52b. Then, the front surface side of the metal substrate 52E holds the target material 54. The target 51E differs from the target 51D in the material of the island portions 52b of the embossed structure formed on the retention surface of the metal substrate 52E. In the target 51D, the same material as of the metal substrate 52D is used for the rest island portions 52b while the recessed portion 52c is created by decreasing its thickness. The material may be a non-lithium metal and preferably low-carbon steel (Fe) or tantalum (Ta). By contrast, the island portions 52b of the target 51E are made of a lithium alloy 54a that is the target material 54. Because the material for the island portions 52b s a lithium alloy, the island portions function as a target and are characterized in that they are hard to be melted by heating when compared with the case of using lithium. Examples of the lithium alloy include alloys that are not melted by heat generated by proton beam irradiation, that is, alloys with a melting point of about 300° C. or higher. Preferable examples used include a copper-lithium alloy, an aluminum-lithium alloy, and a magnesium-lithium alloy. In the copper-lithium alloy, Cu content is preferably 1 mass % or more and more preferably from 1 to 20 mass %. In the aluminum-lithium alloy, Al content is preferably 20 mass % or more and more preferably from 20 to 40 mass %. In the magnesium-lithium alloy, Mg content is preferably 45 mass % or more and more preferably from 45 to 60 mass %. This modification embodiment exerts the effect of the target 51D. Further, in this modification embodiment, the proton beam irradiation can generate neutrons in the island portions 52b because the island portions 52b are made of alloy containing lithium as the target material 54. Consequently, this modification embodiment can reduce a decrease in a neutron-generating efficiency, by formation of the island portions 52b at the retention surface side of the metal substrate. As shown in FIG. 12A, in the target 51E, the back side of the metal substrate 52E includes: the coolant passages 52d that are created by grooving in the same manner as in the target 51A; and the rest cooling fins 52e. The recessed portion 52c is filled with metal lithium. Then, the blackboard 55 is placed facing the back side of the metal substrate 52E. Further, the metal thin film 53 for sealing is placed on the retention surface X of the metal substrate 52E. After that, HIP bonding is used to attach the metal thin film 53 to the surfaces of the frame portion 52a and the island portions 52b. At the same time, the blackboard 55 is bonded to the back side of the metal substrate 52E. The following illustrates a method for manufacturing the target 51E by referring to FIGS. 13A-13E. FIGS. 13A-13E illustrate how to manufacture the target 51E. FIG. 13A illustrates a method including: a thickness decreasing step of producing a recessed portion 52c by uniformly reducing the thickness of a metal substrate 52E0 of the target 51E at the retention surface side (i.e., the front surface side); a coolant passage creating step of producing grooves for coolant passages 52d at the side (i.e., the back surface side) opposite to the retention surface of the metal substrate 52E0, and thereafter; an attachment-promoting layer formation step of producing an attachment-promoting layer at the bottom of the recessed portion 52c, and thereafter; and a lithium alloy filling step of filling the recessed portion 52c with a melted lithium alloy 54a in vacuo or under an argon gas atmosphere. FIG. 13B illustrates a condition after the lithium alloy filling step, followed by a retention surface smoothing step. FIG. 13C illustrates a condition after an embossed structure processing step. FIG. 13D illustrates another target material filling step of filling the recessed portion 52c with a melted target material 54 in vacuo or under an argon gas atmosphere. FIG. 13E illustrates a condition after the target material filling step, followed by another retention surface smoothing step. The target 51E is manufactured as follows. (1) Coolant Passage Formation Step The original metal substrate 52E is a rectangular low-carbon steel or tantalum plate. In order to form the coolant passages 52d, many grooves are created using, for example, milling on one surface (i.e., the back side (corresponding to the lower surface in FIG. 13A)) of the metal substrate to produce cooling fins 52e (see FIG. 13A). (2) Thickness-decreasing Step The thickness of the plate is decreased by a predetermined depth at the front surface side (corresponding to the upper surface in FIG. 13A) while the frame portion 52a is left intact. By doing so, the processed metal substrate 52E0 has a recessed portion 52c with a flat bottom. For example, the thickness is decreased using milling by 50 μm, which is the same thickness as of the target material metal lithium (Li). (3) Attachment-promoting Layer Formation Step After the thickness-decreasing step, a very thin layer (or attachment-promoting layer) made of copper, aluminum, magnesium, or zinc is deposited using a film formation process such as vapor deposition and sputtering on the bottom of the recessed portion 52c. The thickness of the layer is, for example, 0.05 μm. This process makes better the attachment (or wearability) between the metal substrate 52E0 and the lithium alloy 54a. At this time, before the film formation process such as vapor deposition and sputtering, the surface of the frame portion 52a is masked so as not to form a copper thin layer. After the film formation process such as vapor deposition and sputtering, the mask is ripped off. (4) Lithium Alloy Filling Step Next, a molten lithium alloy 54a contained in a crucible 61 is poured into the recessed portion 52c of the metal substrate 52E0 in vacuo or under an argon gas atmosphere (see FIGS. 13A and 13B). Because argon gas contains oxygen and moisture content (H2O) as impurities, the molten lithium alloy 54a may be oxidized. Hence, it is preferable to fill the recessed portion 52c with the lithium alloy in vacuo. The placed lithium alloy 54a is then solidified as it is in vacuo or under an argon gas atmosphere. (5) Retention Surface Smoothing Step The solidified lithium alloy 54a is attached onto the surface of the frame portion 52a, and the level of the lithium alloy 54a is also higher than the surface of the frame portion 52a. So, the lithium alloy is ground using, for example, milling. The resulting powder of the lithium alloy 54a is then removed by, for example, blowing with argon gas (see FIG. 13B). Because argon gas contains oxygen and moisture content (H2O) as impurities, the molten metal lithium may be oxidized. Hence, it is preferable to grind the surface in vacuo. (6) Embossed Structure Processing Step Next, in a planar view, circular structures with a predetermined depth are created by decreasing the thickness of the lithium alloy 54a with which the recessed portion 52c has been filled. For example, the thickness of the lithium alloy 54a is decreased to produce the structures with a diameter of 4 mm and a depth that reaches the metal substrate at the bottom of the recessed portion 52c . The structures are created using, for example, milling so as to hexagonally arrange the structures in the longitudinal and lateral directions. By doing so, the circular recessed portions 52c3 are formed. Further, communicating recessed portions 52c4 with a predetermined shape are created by decreasing the thickness of the lithium alloy 54a so as to connect the adjacent circular recessed portions 52c3. For example, the thickness of the lithium alloy 54a is decreased to produce the communicating recessed portions 52c4 with a width of 1 mm and a depth that reaches the metal substrate at the bottom of the recessed portion 52c. Then, the communicating recessed portions 52c4 are used to connect all the circular recessed portions 52c3. By doing so, the metal substrate 52E is produced that has an embossed structure including: a plurality of island portions 52b made of the lithium alloy 54a; and the recessed portion 52c (see FIG. 13C). (7) Attachment-Promoting Layer Formation Step After the embossed structure processing step, a very thin layer (or attachment-promoting layer) made of copper, aluminum, magnesium, or zinc is deposited using a film formation process such as vapor deposition and sputtering on the bottom of the recessed portion 52c. The thickness of the layer is, for example, 0.05 μm. This process makes better the attachment (or wearability) between the metal substrate 52E and lithium that is the target material 54. At this time, before the film formation process such as vapor deposition and sputtering, the upper surfaces (in FIG. 13C) of the frame portion 52a and the island portions 52b are masked so as not to form a copper thin layer. After the film formation process such as vapor deposition and sputtering, the mask is ripped off. (8) Target Material Filling Step Next, molten metal lithium, which is the target material 54, contained in a crucible 61 is poured into the recessed portion 52c in vacuo or under an argon gas atmosphere (see FIG. 13D). Because argon gas contains oxygen and moisture content (H2O) as impurities, the molten metal lithium may be oxidized. Hence, it is preferable to fill the recessed portion 52c with the metal lithium in vacuo. The placed metal lithium, which is the target material 54, is solidified as it is in vacuo or under an argon gas atmosphere. (9) Retention Surface Smoothing Step The solidified metal lithium is attached onto the surfaces of the frame portion 52a and the island portions 52b, and the level of the metal lithium is also higher than the surfaces of the frame portion 52a and the island portions 52b. So, the metal lithium is ground using, for example, milling. The resulting metal lithium powder is then removed by, for example, blowing with argon gas. As a result, the surfaces of the frame portion 52a and the island portions 52b are exposed in a clean state. This makes only the recessed portion 52c filled with the metal lithium (see FIG. 13E). Because argon gas contains oxygen and moisture content (H2O) as impurities, the molten metal lithium may be oxidized. Hence, it is preferable to grind the surface in vacuo. (10) Bonding Step Subsequently, in the same manner as in the method for manufacturing the target 51A, the blackboard 55, the metal substrate 52E, and the metal thin film 53 of the target panel 11A (or the target panel 11B) are subjected to HIP bonding under an argon gas atmosphere. The above method is used to complete the target 51C. <<Modification Embodiment 4>> With reference to FIG. 14, the following illustrates the structure of a target 51F and a method for manufacturing the target 51F whose structure of the recessed portion and material for the target material 54 differ from those of the target 51A of the present embodiment. FIG. 14 is an exploded view illustrating the target 51F according to still another modification embodiment. The same components as of the target 51A have the same reference signs so as to avoid redundancy. The target 51F includes: a metal substrate 52F; the target material 54; the metal thin film 53 for sealing; and the blackboard 55. FIG. 14 provides a simplified schematic view of the blackboard 55 as a plate. Like the target 51A, the blackboard 55 is part of the target panel 11A or 11B. Like the blackboard 55 of the target panel 11A (11B) shown in FIG. 4, this blackboard also includes the manifolds 116L and 116R that are concave elongated grooves. As shown in FIG. 14, the front surface side (i.e., the upper side in FIG. 14) of the substantially rectangular metal substrate 52F includes: the circumferential frame portion 52a; and the recessed portion 52c that is surrounded by the frame portion 52a and that is uniformly concave. The recessed portion 52c of the metal substrate 52F has a flat bottom. Like the target 51B of the comparative embodiment, no embossed structure is formed. The target 51F differs from the target 51B in the material for the target material 54 with which the recessed portion 52c is filled. Here, the recessed portion 52c of the target 51B is filled with pure metal lithium, as the target material 54, containing essentially 100 mass % of lithium. By contrast, the recessed portion 52c of the target 51F is filled with the lithium alloy 54a as the target material 54. The lithium alloy 54a is a target material 54 characterized in that the lithium alloy 54a is hard to be melted by heat when compared with metal lithium. Examples of the lithium alloy 54a include lithium alloys that are not melted by heat generated by proton beam irradiation. Namely, a lithium alloy has a melting point of about 300° C. or higher and contains an additional metal at a decreased small % so as not to shorten the travel distance of the proton beams through the lithium alloy. Preferable examples used include a copper-lithium alloy, an aluminum-lithium alloy, and a magnesium-lithium alloy. In the copper-lithium alloy, Cu content is preferably from 1 to 20 mass %. In the aluminum-lithium alloy, Al content is preferably from 20 to 40 mass %. In the magnesium-lithium alloy, Mg content is preferably from 45 to 60 mass %. Examples of a preferable material for the metal substrate 52F include low-carbon steel (Fe) and tantalum (Ta). The recessed portion 52c with a flat bottom can be processed using, for example, milling, electric discharge machining, and/or chemical etching. The step height difference between the frame portion 52a and the recessed portion 52c is the same as the thickness of the target material and is, for example, 50 μm. The thickness from the bottom of the recessed portion 52c to the groove bottom of the coolant passage 52d is a thickness at which all the rest protons passing through the target material 54 irradiated with the proton beams 6 can be blocked. As shown in FIG. 14, in the target 51F, the back side of the metal substrate 52F includes: the coolant passages 52d that are created by grooving in the same manner as in the target 51A; and the rest cooling fins 52e. The recessed portion 52c is filled with the lithium alloy 54a. Then, the blackboard 55 is placed facing the back side of the metal substrate 52D. Further, the metal thin film 53 for sealing is placed on the upper surface of the metal substrate 52F. After that, HIP bonding is used to attach the metal thin film 53 to the surface of the frame portion 52a. At the same time, the blackboard 55 is bonded to the back side of the metal substrate 52F. This target 51F is manufactured as follows: the metal substrate 52Be is filled with the lithium alloy 54a in accordance with the method for manufacturing the above target 51E; the retention surface smoothing step is carried out; and the HIP bonding step is then performed. Alternatively, the metal thin film 53 for sealing is pressed on the lithium alloy 54a that has been subjected to rolling at a predetermined thickness; they are placed on a metal substrate without the recessed portion 52c and further pressed; and the metal thin film 53 for sealing is welded onto the substrate circumference of the metal substrate. This modification embodiment has the advantage compared with the case of using relatively low-melting-point metal lithium as the target material 54. That is, when low-melting-point metal lithium is used as the target material 54, the target material 54 may be heated and melted by proton beam irradiation. The liquefied target material 54 is unevenly distributed at one portion of the metal substrate. By contrast, this modification embodiment using a lithium alloy as the target material 54 can prevent the target material 54 from being melted. Thus, it is possible to prevent the liquefied target material 54 from being unevenly distributed at one portion of the metal substrate, thereby preventing target performance from being deteriorated. 1 Proton beam-generating unit 1a Ion source 1b Accelerator 2 Irradiation unit 3 Treatment unit 4 Beam conduit 5 Target section Proton beams 7 Beam-condensing lens 9 Neutron beams 10 Collimator 10a Tip flange part 11A, 11B Target panel 11a Beam irradiation surface 11b End surface 11cL, 11cR Panel side surface 12L, 12R Side plate 17 Mounting bolt 18 Insulation piece 21 Moderate 22 Reflector 23 Neutron absorber 24 Collimator 51A, 51B, 51C, 51D, 51E, 51F Target 52A, 52B, 52C, 52D, 52E, 52F Metal substrate 52a Frame portion 52b Island portion 52c Recessed portion 52c3 Circular recessed portion 52c4 Communicating recessed portion 52d Coolant passage 52e Cooling fin 53 Metal thin film for sealing 54 Target material 54a Target material (Lithium alloy) 55 Blackboard Crucible 100 Neutron-generating device 112 Beam stopper 113, 124 Insulator 115 Mounting hole 116L, 116R Manifold 116La, 116Ra, 117L, 117R, 121L, 121R, 123L, 123R Coolant passage hole 122L, 122R Coolant channel |
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summary | ||
041347919 | description | The plate-type nuclear reactor fuel assembly shown in FIG. 1 is generally designated by the reference 1. This fuel assembly is mainly composed of a stack of parallel and vertical plates 2 containing in a manner known per se a series of small plates 3 of nuclear fuel material surrounded by a clad which is formed of thin metal foil 4. Said small plates are first stacked together along the plane of each fuel plate 2, then enclosed between two thin cladding sheets 5 and 6 respectively, said sheets being joined together along their lateral sides by means of metallic strips 7 which are welded to the sheets 5 and 6 in order to form a leak-tight cladding with these latter. These fuel plates 2 are preferably designed in accordance with the above-mentioned arrangements which have already been described and claimed in American Patent Application Ser. No. 484,743 of July 1, 1974. The stack of fuel plates 2 is maintained in position with a predetermined spacing between the successive parallel plates by forming notches 8 in the lateral strips 7 which close the cladding, said notches being intended to permit the engagement of spacing combs 9, the teeth 10 of which define the spacing between said plates. Combs of this type advantageously correspond to the arrangements described in French patent Application No 75 30247 of Oct. 2nd, 1975, in accordance with any one of the alternative embodiments contemplated in the cited Application. If so required, the combs 9 which serve to space the fuel plates 2 in the stack can be so arranged that, instead of engaging in notches 8 in order to ensure that they do not project from the apparent contour of the fuel-plate stack, they are more simply mounted on the lateral edges of these latter as illustrated in FIG. 1a; in this case, said combs are designed in the form of substantially rectangular strips having grooves 9a which permit the engagement of the edges of the fuel plates 2 and which are welded against the cladding of these latter by means of weld fillets 9b. In accordance with the invention, at least a number of the parallel plates of the stack which constitutes the fuel assembly is provided with sleeves 11 which are designed in the form of hollow tubular elements of appreciable length and the height of which is substantially greater than the height of the fuel plates 2 in the exemplified embodiment which is illustrated in FIG. 1. Said sleeves 11 are welded at 12 against portions of fuel plates which are designated respectively by the references 2a and 2b for example, said portions being disposed in the same plane so as to constitute the fuel plate 2. The sleeves thus have two additional lengths 13 and 14 at the top and at the bottom of the fuel assembly. Said additional sleeve lengths are in turn rigidly fixed, especially by welding or any other suitable means of attachment, to two parallel end-pieces 15 and 16 respectively which define the total height of the fuel assembly and make it possible in particular to ensure not only the cohesion of the fuel stack but also the positioning or withdrawal of said fuel assembly in or from the reactor core (not shown). The end-plates 15 and 16 are provided in the usual manner with a series of holes 17 in order to permit the reactor core coolant which usually consists of water under pressure to circulate freely and especially upwards through each fuel assembly. After passing through the bottom end-plate 15, the stream of water then circulates between the fuel plates 2 of the stack, then passes out of the fuel assembly through the top end-plate 16. It is clear from the foregoing that the sleeves 11 thus perform the function of tubular tie-rods between the end-plates 15 and 16. In accordance with a final advantageous arrangement which is known per se, at least a certain number of said sleeves are reserved for the sliding motion and guiding of control rods 18 formed of neutron-absorbing material, said rods being necessary for controlling the neutron flux and making reactivity changes during reactor operation. In the example of construction hereinabove described, the stack of fuel plates 2, the lateral coupling combs 9 and the tubular sleeves 11 which are incorporated with a certain number of said fuel plates form a single-unit structure in conjunction with the end-plates 15 and 16. In other alternative embodiments illustrated in FIGS. 2 and 3, the complete array of fuel plates 2 of the stack can be freely mounted so as to be capable of "floating" with respect to a rigid structure which ensures cohesion of the assembly, with the result that the fuel plates are capable of withstanding the expansions which take place during operation without being subjected to any particular mechanical stresses. To this end, at least a certain number of fuel plates 2 of the stack are rigidly fixed to guide sleeves 19 which are similar to the support sleeves 11 of the previous example and designed to permit insertion of tubular tie-rods 20, the ends of which project from said sleeves 19. Said tubular tie-rods are in turn secured to the end-plates 15 and 16, especially by welding or other mechanical means. The guide sleeves 19 are advantageously provided on the end edges of the fuel plates 2 with projecting portions 21 and 22 which make it possible in the case of the portion 21 formed at the lower ends of the plates to apply these latter against the end-plate 15. The projecting portion 22 which is provided on the top edge of each fuel plate between a sufficient clearance space between this latter and the end-plate 16 to permit maximum expansion of the fuel plates. In another alternative embodiment which is illustrated in FIG. 3, the sleeves 19 do not extend to the full length of the corresponding fuel plates 2 but can be subdivided into a plurality of separate sections disposed in the line of extension of each other and designated in the figure by the references 19, 19b, 19c and 19d. As in the previous embodiment, these sections are traversed by tubular tie-rods such as the tie-rod 20 which are rigidly fixed to the end-plates 15 and 16 in order to ensure cohesion of the fuel assembly. FIG. 4 illustrates a detail improvement made in the construction arrangement of the plate-type fuel assembly in any one of the alternative embodiments shown in FIGS. 1 to 3. This improvement is primarily intended to ensure that the fuel plates 2 are braced in a more effective manner in the stack and particularly in the central region of these latter, especially in order to prevent vibrations or deformations of said fuel plates under the action of the flow of coolant. To this end, the fuel plates 2 of the stack are provided in addition to the lateral combs with elongated slots 23 which are located at intervals in the surface of said fuel plates and oriented either parallel or at right angles to the axial direction of the fuel assembly, especially in zones in which there is no fuel material. Said slots 23 permit the engagement of transverse spacers 24 formed of flat lugs 25 which are joined to each other by means of cylindrical-rod elements 26. The spacing width of said lugs corresponds to the desired distance between the fuel plates whilst the rod elements represent the thickness of the fuel plates themselves. As can be seen from FIG. 4, the special shape of said transverse spacers is such as to permit the insertion of these latter in the stack of fuel plates 2 through the elongated slots 23. Once the spacers have been positioned, they can be rotated through an angle of 90.degree. so as to bring the plane of the spacing lugs 25 in a direction which is substantially perpendicular to that of the slots, with the result that the spacers are locked in position. As already mentioned in the foregoing, provision is made for special plates between a certain number of clad fuel plates of a given stack. It is recalled that these special plates have tubular sleeves which serve either to maintain a rigidly spaced relationship between the end-plates of the fuel assembly in the vertical direction or to guide hollow tie-rods which perform a similar function, at least a certain number of said tubular sleeves or tie-rods being intended to permit displacement of reactor control rods in sliding motion. By means of this arrangement, conventional fuel assemblies and especially assemblies of the cylindrical fuel-pencil type can accordingly be replaced in a reactor core by fuel assemblies of the plate type mentioned above without entailing any need to modify the other reactor core structures and in particular the fuel-handling means and control-rod drive mechanisms. In FIG. 5, there have been shown in adjacent relation a fuel assembly 1 comprising fuel plates 2 as described in the foregoing with reference to any one of FIGS. 1 to 3 and a conventional fuel assembly 27 constituted by a cluster of cylindrical fuel pencils 28 which are maintained in position by means of spacer grids 29. In particular, a fuel assembly of this type can be as disclosed and claimed in American Pat. No. 3,954,560 of Dec. 11, 1972 as mentioned earlier. In such a case it is apparent that the coolant which is usually circulated upwards through said fuel assemblies in the direction of the arrows f flows through these latter at a rate which may not be wholly uniform. In particular, the presence of spacer grids 29 in the fuel-pencil assembly 27 causes outward deflection of the flow of fluid and is consequently liable to result in excessive cooling of the fuel plates 2 of the adjacent fuel assembly 1. It is therefore necessary to overcome this disadvantage and to permit substantially identical cooling of both fuel assemblies. In accordance with a particular arrangement of the invention, the plate-type fuel assembly 1 is accordingly provided with sheet-metal strips of suitable height which are intended to form a screen and are designated respectively by the references 30 and 31. Said strips are preferably welded on the external sides of the fuel assembly 1 in the vicinity of the spacer grids of the adjacent fuel-pencil assembly and against the lateral combs 9. In another alternative embodiment which is illustrated in FIG. 6, there is again shown a plate-type fuel assembly 1 placed next to a fuel-pencil assembly 27. In this case, the screen plates 32 are joined to the combs 9 in such a manner as to extend over the entire distance between two successive combs within the fuel assembly in order to ensure that the fuel plates 2 are completely isolated from the coolant flow within the other fuel assembly. Finally, FIGS. 7 to 9 illustrate further arrangements which are advantageously carried into effect in the plate-type assembly under consideration with a view to equalizing the flow between these fuel plates and to ensuring more efficient cooling of this latter. In particular and as illustrated in FIG. 7, the fuel assembly can comprise means for producing turbulence in the fluid flow, these means being constituted by thin metallic cross-strips 33 which extend in a direction parallel to the plane of the fuel plates. Said cross-strips 33 are welded or secured by any suitable mechanical means against the coupling combs 9 which ensure relative spacing and interconnection of the fuel plates 2 of the stack. Vertical slots 34 are formed in at least one edge of each cross-strip and the portions of cross-strips which have thus been cut-out as designated respectively and successively by the references 35 and 36 may or may not be folded-back with respect to the plane of the corresponding cross-strips. In the example illustrated in FIG. 7, the portions 35 thus remain in the plane of said cross-strips whilst the adjacent portions 36 are all bent-back on the same side. On the other hand, in the alternative embodiment which is illustrated in FIG. 8, the successive portions 35 and 36 are all intended to be bent-back alternately on each side of the plane of the cross-strips 23. Finally, in the alternative embodiment illustrated in FIG. 9, the cross-strips which are mounted between the fuel plates of the assembly and designated by the reference 37 have a wavy profile when looking from above, the successive portions 38 and 39 formed by cutting-out one edge of each cross-strip being folded-back on one and the same side of this latter. There is thus formed a plate-type fuel assembly which can be directly substituted within a reactor core for a conventional fuel-pencil assembly without entailing any particular modification of the reactor core structures which are associated with these fuel assemblies. In particular, the control rods can be permitted to pass directly through the fuel assembly itself by means of the sleeves which are added to the fuel plates. It is worthy of note that the construction of the sleeve-type fuel plates can be carried out by means of any suitable method and especially by continuous or non-continuous welding of the sleeves to the flat cladding sheets, either by spot-welding or by mechanical assembly. |
054232198 | summary | BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a device for ultrasonic detection techniques for the inspection of weld defects in a fuel rod weldment. 2. Technical Background In general, a fuel rod for use in a light water pressurized reactor is made by packing fuel pellets inside a fuel pipe, and the ends of the fuel pipe are fitted with end plugs and the end plugs are joined to the ends of the fuel pipe by means of joining techniques such as the tungsten inert gas (TIG) welding. Further, there is a (gas) seal opening disposed on one of the two end plugs for filling the fuel pipe interior with an inert gas under pressure. The gas seal opening is sealed off, by joining methods such as TIG welding, so as to maintain the interior of the fuel pipe at a certain inert gas pressure. Conventionally, the joints of the fuel rod welded as described above have been inspected non-destructively by X-ray transmission. However, the X-ray method is being superseded by the ultrasonic inspection method which is more compact in apparatus design and easier to handle. The ultrasonic inspection apparatuses which have been available to date are based on scanning the entire circumferential periphery of the weld by moving the detection probe linearly in the longitudinal direction while turning the fuel rod. When examining the weld by moving the detection probe in the longitudinal direction while rotating the fuel rod, there are no problems when the examination is being carried out at a rough scanning pitch or at low speeds. However, when it is desired to carry out inspection at a faster operating speed or at a finer scanning pitch, it was necessary to increase the rotational speed of the fuel rod, which lends to high loads on the rod and insufficient processing time for obtaining proper inspection results. SUMMARY OF THE INVENTION The present invention was made in view of the technical background presented above, and the objective of achieving efficient inspection of the weld with an inspection device comprising: a rotating member freely rotatable around its rotation axis having an inspection section formed within for holding said fuel rod in place during inspection; a liquid supplying means for filling said liquid medium in said inspection section; a plurality of ultrasonic probes disposed on said rotating member having said inspection section. According to the device of the above configuration, the fuel rod to be inspected is housed in the inspection section disposed in the rotating member which is filled with liquid, and the rotating member is rotated while ultrasonic inspection is being carried out with the probes disposed on the rotating member. Therefore, there is no need to rotate the fuel rod, and consequently, it is possible to inspect the welded section without imposing loads on the fuel rod, and the inspection process can be carried out more quickly and with higher resolution than with conventional inspection techniques. Furthermore, the inspection apparatus can be made compact, and automation of the inspection process is made easier. The maintenance operation can also be carried out easily. Another aspect of the invention is that the fuel rod is held firmly while being inspected. Still another aspect of the invention is that a transport device is provided to move the rotating member relative to the fuel rod along the rotation axis. Still another aspect of the invention is that the fuel rod is held stably during the inspection by an immobile or more particularly a non-rotating lid member provided opposite to and in sliding contact with an opening section of said rotating member for supporting the fuel rod which passes through a through hole disposed on the immobile on non-rotating lid member. Still another aspect is that the liquid is contained in the inspection section by a through hole provided with: a seal member which envelopes the fuel rod tightly; and a lid member which closes the through hole and is swingable inside the inspection section to open when a fuel rod is inserted through the through hole. Still another aspect is that the inspection is carried out while circulating the liquid from the bottom to the top by liquid supply means disposed on the lower part of the immobile lid member, and a liquid collection means for collecting liquid flowing out of the inspection section is disposed on the upper portion of the inspection section disposed on the upper portion of the immobile lid support member, Still another aspect is that the liquid is supplied to the rotating member through a plurality of liquid flow passages provided on the rotating lid member on the outer periphery; and liquid supply passages are provided opposite to each of the liquid flow passage disposed on the lower part of the immobile lid member for supplying liquid to the inspection section of the rotating member; and liquid collection passages are provided on the upper part of the immobile lid member opposite to each of the liquid flow passages for collecting liquid flowing out of the inspection section of the rotating member; wherein the diameters of each of the liquid supply passages and liquid collection passages are larger than the distance between the two adjacent liquid flow passages. |
041707370 | abstract | A top-entry transmission electron microscope comprises a stage with a changeable cartridge which houses a specimen holder spaced in the magnetic lens field and tiltable about the axis x perpendicular to the microscope optical axis. An executive step motor of the specimen holder's electric drive is mounted on the stage and has a rotor mechanically coupled with the specimen holder for the rotor and holder to be turned synchronously. The microscope comprises also a rocker pivotally mounted in the changeable cartridge and designed to convey the drive to the rotor via a drive transmitting member; a rotor-turning piezoelectrically actuated electro-mechanical means and a rocker-positioning piezoelectrically actuated electromechanical means which are connected, respectively, to a control voltage shaper of the step motor and to a unit for settling the magnitude and sence of specimen holder displacement. The disclosed microscope features a lower level of drift of the tiltable specimen holder, widened up to 360.degree. range of specimen tilt angles, and a greater speed of obtaining stereopair micrograpgs. |
description | The present application claims the benefit of Korean Patent Application No. 10-2016-0089982 filed in the Korean Intellectual Property Office on Jul. 15, 2016, the entire contents of which are incorporated herein by reference. Field The present disclosure relates to an apparatus and system for simulating maintenance of a reactor core protection system including at least two or more channels, the simulation apparatus including a simulation signal generation unit for generating a state signal including a normal state or an abnormal state, a communication unit connected to each of the channels of the reactor core protection system to transmit the state signal to the channel, and a control unit for receiving a result signal output from the channel in response to the input state signal and confirming whether the reactor core protection system normally determines a reactor core state by analyzing the result signal. Background of the Related Art Nuclear power generation is generation of electricity by operating a turbine generator using steam generated by boiling water using energy generated by a fission chain reaction. Since huge energy is generated as the energy needed for generating free particles by completely separating nucleons from atomic nuclei configured of protons and neutrons is emitted, the nuclear power generation is the most desirable power source capable of obtaining a lot of energy using an extremely small amount of fuel, and most countries in the world producing electricity use the nuclear power generation. However, in the case of the nuclear power generation, a great danger is accompanied in using the nuclear energy, and thus a large number of safety devices are necessarily required together with control of highly trained experts. Particularly, in the case of the nuclear power generation, a state of a system for protecting the core of a reactor is most carefully inspected, and even in normal times when an accident of nuclear power generation does not occur, whether or not a nuclear power generator, sensing devices installed in the nuclear power generator and computing devices for analyzing the sensing devices properly operate should be confirmed. Accordingly, a reactor core protection system corresponds to a system for monitoring a degree of nuclear reaction of the reactor core and controlling to shut down the reactor to protect the reactor core when an excessive state occurs. Referring to FIG. 1a, a conventional reactor 110 simultaneously senses various state signals through four different channels including first to fourth channels 121 to 124. At this point, the state signals carry various state data of the reactor of the nuclear power generator, including a temperature, a pressure, a rotation speed, a flow rate and the like. Since safety should be considered above all in the case of nuclear power generation, the conventional reactor transmits one state data to four different computing devices (channels) so that each computing device may determine abnormality of the state data. At this point, it is designed to maintain electrical and physical independence among the channels in order to objectively grasp an abnormal state of the reactor, and if two or more channels simultaneously determine an abnormal situation after receiving the state data and generate a trip signal, countermeasures such as temporarily shutting down the reactor or the like will be taken. This is to cope with occurrence of a failure in the channels themselves, and although the first channel among the first to fourth channels is out of order and determined as an abnormal situation, if the second to fourth channels are determined as a normal situation, the reactor will not be shut down, and unnecessary waste of resources may be prevented. Meanwhile, a control rod of a bar shape covered with a material easily absorbing thermal neutrons exists in the reactor core. In the case of the control rod, reactivity of nuclear fuel is adjusted by inserting and withdrawing the control rod into and out of the reactor core. If the control rod is inserted, reactivity of the reactor is lowered, and if the control rod is removed, reactivity of the reactor is increased. Accordingly, if an abnormal situation occurs in the reactor, the control rod is inserted for emergency shutdown of the reactor, and the reactor can be shut down by fully inserting the control rod. Although a conventional reactor core protection system also confirms the position of the control rod 112 at all times, in the case of a control rod position signal, dozens of different signals should be sensed unlike the state data described above, such as a temperature, a pressure and the like, since one reactor includes a plurality of control rods, and thus control rod position signals are divided to be transmitted over two channels due to the limit of the channels in receiving signals. Accordingly, dozens of the control rod position signals are divided, and first and second channels 121 and 122 receive values of the divided signals, and third and fourth channels 123 and 124 receive values of the divided signals. Then, the first channel and the second channel exchange their values to make a final determination by integrating all the control rod position signals. For example, if there are fifty control rod position signals in total, the first channel may receive thirty control rod position signals, and the second channel may receive twenty control rod position signals. Subsequently, the first channel transmits its thirty control rod position signals to the second channel, and the second channel transmits its twenty control rod position signals to the first channel. In conclusion, the first channel and the second channel respectively receive all the fifty control rod position signals and determine a normal state and an abnormal state. If an abnormal state is determined, a trip signal is generated, and a manager or an expert solves the corresponding abnormal state. Meanwhile, in the case of a reactor, safety should be guaranteed by sensing a variety of state data in real-time as described above, and since huge damage may occur with only a single accident, it should be regularly confirmed whether the channels for sensing an abnormal state of a reactor properly work when an abnormal state occurs in the reactor. Accordingly, a simulation apparatus for simulating a signal generated in the reactor and inputting the signal in a channel and determining whether the channel properly responds is indispensable. Referring to FIG. 1b, a sensing sequence of equipment for sensing a control rod position signal may be confirmed. Conventional response time test equipment (RTTE) 130 is connected to the first to fourth channels 121 to 124 and inputs a simulation state signal into the channels using the simulation apparatus. At this point, the simulation apparatus is connected to each of the channels and generates first to fourth control rod position signals 131 to 134. The simulation apparatus inputs the first control rod position signal into the first channel 121 and the second control rod position signal into the second channel 122. The second channel 122 transfers the input second control rod position signal to the first channel 121, and the first channel 121 integrates the first control rod position signal and the second control rod position signal and finally determines an abnormal state. If it is determined as an abnormal state, the first channel 121 generates a trip signal 135 and transmits the trip signal to the simulation apparatus 130. However, in the case of the conventional reactor core protection system, if a response time is measured for a situation of generating a trip signal by the first channel based on the control rod position signal transferred to the first channel 121 by way of the second channel 122, since the conventional simulation apparatus has a disadvantage of connecting only one simulation apparatus to one channel, the simulation apparatus itself cannot measure the response time, and the response time test equipment 130 should be used. Furthermore, there is a problem in that one simulation apparatus may simulate a state signal input into one channel. Therefore, a simulation apparatus for inspecting the conventional reactor core protection system should use additional equipment to test a response time while connecting four channels and should connect hundreds of different resistors to a terminal block. In addition, the simulation should be conducted by connecting the simulation apparatus to a channel which will be tested mainly, using the response time test equipment for a control rod position signal which needs a signal change among the other channels and connecting resistors for the remaining control rod position signals. Accordingly, the simulation apparatus for inspecting the conventional reactor core protection system may not conduct all the needed tests within an inspection time since a lot of time is consumed to set a test environment, and since existing external wires should be separated when the resistors are connected and wired again after the test is finished, this may induce a human error or a failure of the terminal block. Furthermore, there are restrictions in simulating various dynamic signals. Furthermore, the simulation apparatus for inspecting the conventional reactor core protection system may change a simulation signal to a type such as a step signal, a ramp signal or the like only once, and a communication signal may delay a corresponding signal, and there is a problem in that a pump speed signal that should be simulated using a pulse signal cannot be dynamically simulated together with other signals and can be changed only individually. Therefore, the present disclosure has been made in view of the above problem of delaying a response time that a conventional simulation apparatus has, and it is an object of the present disclosure to provide an apparatus for simulating maintenance of a reactor core protection system, which improves the response time by supplying a simulation signal to all channels. The technical problems to be accomplished by the present disclosure are not limited to the technical problems mentioned above, and various technical problems may be included within a scope apparent to those skilled in the art. To accomplish the above object, according to one aspect of the present disclosure, there is provided an apparatus for simulating a reactor core protection system including at least two or more channels, the apparatus including: a simulation signal generation unit for generating a simulation state signal including a normal state or an abnormal state, a communication unit connected to each of the channels of the reactor core protection system to transmit the state signal to the channel, and a control unit for receiving a result signal output from the channel in response to the input simulation state signal and confirming whether the reactor core protection system normally determines a reactor core state by analyzing the result signal. In addition, the apparatus for simulating a reactor core protection system according to an embodiment of the present disclosure is characterized in that the simulation signal generation unit generates the simulation state signal including at least any one of a reactor temperature, a reactor pressure, a hot leg temperature, a pump rotation speed, a neutron level, a flow rate and a reactor control rod position. At this point, the apparatus for simulating a reactor core protection system according to an embodiment of the present disclosure is characterized in that the simulation signal generation unit generates first to fourth simulation state signals for the reactor control rod position, and the communication unit transmits the first simulation state signal to a first channel, the second simulation state signal to a second channel, the third simulation state signal to a third channel and the fourth simulation state signal to a fourth channel. In addition, the apparatus for simulating a reactor core protection system according to an embodiment of the present disclosure is characterized in that the first simulation state signal includes twenty-three signals, and the second simulation state signal includes seventy signals. In addition, the apparatus for simulating a reactor core protection system according to an embodiment of the present disclosure is characterized in that the simulation signal generation unit generates a simulation state signal of a form including at least any one of a ramp signal, a step signal, an impulse signal, a pulse signal and a sinusoidal signal. In addition, the apparatus for simulating a reactor core protection system according to an embodiment of the present disclosure is characterized in that the communication unit transmits the simulation state signal to all the first to fourth channels of the reactor core protection system. In addition, the apparatus for simulating a reactor core protection system according to an embodiment of the present disclosure is characterized in that the communication unit is connected to the reactor core protection system through a connector. In addition, the apparatus for simulating a reactor core protection system according to an embodiment of the present disclosure may further include a response time test unit for measuring a time taken from transmission of the simulation state signal and reception of the result signal. At this point, the apparatus for simulating a reactor core protection system according to an embodiment of the present disclosure is characterized in that if the response time is delayed longer than a preset standard response time after the response time test unit measures the response time, the control unit analyzes corresponding content. In addition, the apparatus for simulating a reactor core protection system according to an embodiment of the present disclosure may further include a control rod position determination unit for receiving a control rod position signal of the reactor core protection system. In addition, the apparatus for simulating a reactor core protection system according to an embodiment of the present disclosure may further include a control rod drop time test unit for measuring a drop time of a control rod when the control rod of the reactor core protection system is shut down according to a simulation abnormal state signal generated by the simulation signal generation unit. At this point, the apparatus for simulating a reactor core protection system according to an embodiment of the present disclosure is characterized in that the control rod drop time test unit measures and stores all of the drop time of the control rod for each of the channels. In addition, the apparatus for simulating a reactor core protection system according to an embodiment of the present disclosure is characterized in that the control unit determines whether the reactor core protection system normally determines a reactor core state according to the measured drop time of the control rod. Meanwhile, according to another aspect of the present disclosure, there is provided a system for simulating maintenance of a reactor core protection system, the simulation system including: a simulation apparatus for generating a simulation state signal including a normal state or an abnormal state, and first to n-th channels included in the reactor core protection system and respectively connected to the simulation apparatus, in which the first to n-th channels receive the generated simulation state signal, output a result signal, and transmit the result signal to the simulation apparatus, and the simulation apparatus confirms whether the reactor core protection system normally determines a reactor core state by analyzing the result signal. Meanwhile, according to another aspect of the present disclosure, there is provided a method of simulating maintenance of a reactor core protection system, the method including the steps of: generating a simulation state signal including a normal state or an abnormal state; transmitting the simulation state signal to at least two or more channels respectively connected to the reactor core protection system; receiving a result signal output from each of the channels in response to the input simulation state signal; and confirming whether the reactor core protection system normally determines a reactor core state by analyzing the result signal. 110: Conventional nuclear power generator 111: Conventional sensing device 112: Conventional reactor core 121: Conventional first channel 122: Conventional second channel 123: Conventional third channel 124: Conventional fourth channel 130: Conventional response time test equipment 131, 132, 133, 134: Conventional simulation apparatus 135: Trip signal generated by channel 200: Apparatus for simulating maintenance of reactor core protection system 210: Simulation signal generation unit 220: Communication unit 230: Control unit 240: Response time test unit 250: Control rod position determination unit 260: Control rod drop time test unit 310: First channel 320: Second channel 330: Third channel 340: Fourth channel 400: Nuclear power generator including reactor Hereinafter, ‘an apparatus for simulating maintenance of a reactor core protection system’ according to the present disclosure will be described in detail with reference to the accompanying drawings. The disclosed embodiments are provided to enable those skilled in the art to easily understand the scope of the present disclosure, and the present disclosure is not limited by such embodiments. Moreover, matters illustrated in the drawings are schematized in order to describe or explain the embodiments of the present disclosure more easily and hence may be different from actually embodied forms. Meanwhile, the constitutional components expressed below are merely examples for implementing the present disclosure. Accordingly, other constitutional components may be used in other implementations of the present disclosure without departing from the spirit and scope of the present invention. In addition, the expression of ‘including’ a component is an expression of an ‘open type’ which merely refers to existence of a corresponding component, and it should not be construed as precluding additional components. In addition, the expressions such as “first”, “second” and the like are expressions used only to distinguish a plurality of constitutions and do not limit the sequence or other features of the constitutions. In describing the embodiments, a description of forming a layer (film), region, pattern or structure “on” or “under” another substrate, layer (film), region, pad or pattern includes directly forming or interposing another layer. The reference of “on” or “under” of each layer is defined with respect to the drawings. When an element is connected to another element, it includes a case of indirectly connecting the elements interposing another member therebetween, as well as a case of directly connecting the elements. In addition, when an element includes a component, it means further including another component, not excluding another component, as far as an opposed description is not specially specified. FIG. 2a is a view showing the configuration of a system for simulating maintenance of a reactor core protection system of the present disclosure, and FIG. 2b is a view showing the configuration of an apparatus for simulating maintenance of a reactor core protection system of the present disclosure. Referring to FIG. 2b, a nuclear power generator 400 including a reactor of the present disclosure may include at least two or more channels and preferably include a first channel 310, a second channel 320, a third channel 330 and a fourth channel 340. When the nuclear power generator 400 is in operation, the first to fourth channels are connected to the nuclear power generator, receive state data generated by the nuclear power generator, and output a result signal. At this point, if the result signal is determined as an abnormal situation, the channels may generate a trip signal to inform a user or a manger of the abnormal situation and shut down the nuclear power generator by dropping a control rod. The first to fourth channels may be implemented using a computing device and output a result signal for the state signal generated by the nuclear power generator. In addition, although a process signal input into the first to fourth channels is quadrupled 1, 2, 3 and 4 to input one signal into each of the four channels, a control rod position signal may be duplicated RSPT1 and RSPT2. In addition, the first to fourth channels may include a core protection processor for executing a main algorithm of the reactor core protection system, such as calculation of DNBR, LPD or the like, a control rod assembly processor for collecting control rod assembly position signals and calculating a position signal deviation in each group or sub-group, a channel communication processor for collecting control rod position signals and transferring the control rod position signals to other channels, and transferring an overall signal including signals received from other channels to the control rod assembly processor, an interface test processor for transmitting various process variables received from other racks in a channel to the Qualified Indication and Alarm System-Non safety (QIAS-N), an operator module capable of monitoring major variables and changing set values, and a maintenance and test panel for performing periodic surveillance test and monitoring major variables. At this point, the channels are physically and electrically separated, and each of the channels independently derive its own result signal, and thus if two or more channels determine an abnormal situation, it is finally determined as an abnormal situation of the nuclear power generator. More specifically, the first to fourth channels may confirm an abnormal situation by exchanging inputted control rod position signals with each other, and an abnormal situation determination unit of each channel may receive a control rod position signal and a state signal, confirm deviation of a state in each group, calculate a penalty factor based on the deviation, and transmit the penalty factor to all the channels through HR-SDL communication. The apparatus 200 for simulating maintenance of a reactor core protection system of the present disclosure is connected to the first to fourth channels during the maintenance period and operates to maintain the first to fourth channels connected to the nuclear power generator 400 to sense an abnormal situation of the reactor. Details of the configuration and technical content of the apparatus for simulating maintenance of a reactor core protection system will be described with reference to FIG. 2a. Referring to FIG. 2a, the apparatus 200 is for simulating maintenance of a reactor core protection system of the present disclosure, the reactor core protection system including at least two or more channels. The simulation apparatus 200 is an electronic control unit that includes a central processing unit (CPU), read only memory (ROM), random access memory (RAM), and the like. The apparatus 200 executes various controls by loading programs stored in the ROM on the RAM and causing the CPU to execute the programs. The simulation apparatus 200 may be configured from a plurality of electronic control units. For example the simulation apparatus 200 may include a simulation signal generation unit 210, a communication unit 220, a control unit 230, a response time test unit 240, a control rod position determination unit 250 and a control rod drop time test unit 260. The simulation signal generation unit 210 may generate a simulation state signal including a normal state or an abnormal state. At this point, the simulation signal generation unit may generate a simulation state signal including at least any one of a reactor temperature, a reactor pressure, a hot leg temperature, a pump rotation speed, a neutron level, a flow rate and a reactor control rod position. In addition, the communication unit 220 is connected to each of the channels of the reactor core protection system and may transmit the simulation state signal to the channels. At this point, the communication unit may transmit the simulation state signal to all the first to fourth channels of the reactor core protection system. Unlike the conventional disclosure of connecting one simulation apparatus to only one channel, since the simulation apparatus of the present disclosure may transmit the simulation state signal to a plurality of channels, the simulation can be conducted without separate equipment. In addition, the simulation signal generation unit of the present disclosure may generate first to fourth simulation state signals for the reactor control rod position. Since a system for simulating maintenance of a reactor core protection system of the present disclosure may include first to fourth channels, the simulation signal generation unit of the present disclosure may individually generate a signal that can be input into each channel and input the signal into the channel. At this point, the communication unit may transmit the first simulation state signal to the first channel, the second simulation state signal to the second channel, the third simulation state signal to the third channel and the fourth simulation state signal to the fourth channel. Since the communication unit transmits the simulation state signal generated by the simulation signal generation unit to a relevant channel, the channel determines an abnormal situation by outputting a result signal for a corresponding simulation state signal. Particularly, of the simulation state signal generated by the simulation signal generation unit of the present disclosure, the first simulation state signal may include twenty-three signals, and the second simulation state signal may include seventy signals. The first to fourth simulation state signals correspond to a simulation state signal for a control rod position, and since a plurality of control rods may be included in one reactor of a nuclear power generator, the simulation signal generation unit generates ninety-three different simulation state signals, appropriately distributes the simulation state signals among the channels to be processed by each channel, and separately inputs twenty-three signals and seventy signals into each channel. In addition, the simulation signal generation unit of the present disclosure may generate a simulation state signal of a form including at least any one of a ramp signal, a step signal, an impulse signal, a pulse signal and a sinusoidal signal. Since a simulation can be properly conducted only when the simulation signal generation unit of the present disclosure generates a state signal of a form the same as that of a state signal generated by the nuclear power generator, the simulation signal generation unit is able to generate a state signal of all possible forms. More specifically, the simulation signal generation unit of the present disclosure may generate a simulation signal of a form that can be generally used in a signal, such as a sinusoidal signal of a sinusoidal waveform of a trigonometric function, a ramp signal proportionally increasing after a predetermined time, a step signal outputting a constant value after a predetermined time, an impulse signal inputting an infinite value at a specific time, and a pulse signal. Particularly, unlike the disadvantage of the conventional simulation apparatus capable of changing a signal only once and incapable of dynamic simulation together with another signal at the same time, since the simulation signal generation unit of the present disclosure may simulate various forms of signals, including a hard wire signal and a communication signal, an unlimited number of times at a desired time, it may generate all forms of state signals generated by the nuclear power generator. In addition, the communication unit of the present disclosure may be connected to the reactor core protection system through a connector. Since the apparatus for simulating maintenance of a reactor core protection system of the present disclosure may generate all kinds of responses using only a simulator, it may progress a simulation by connecting a hard wire to the system through a connector without the need of separate equipment such as response time test equipment (RTTE) or resistors of the terminal block. The control unit 230 may receive a result signal output from the channel in response to the input simulation state signal and confirm whether the reactor core protection system normally determines a reactor core state by analyzing the result signal. Since the object of the apparatus for simulating a reactor core protection system of the present disclosure is to confirm whether the first to fourth channels properly operate, the control unit confirms whether an output signal corresponding to the input simulation state signal is properly output from each of the channels. For example, after the simulation signal generation unit of the present disclosure inputs an abnormal state simulation signal into the first channel and a normal state simulation signal into the second to fourth channels, a normal state output signal may be received from all of the channels. After receiving corresponding content, the control unit of the present disclosure may determine that the first channel is out of order and inform a manager or a maintenance technician of the corresponding content using an e-mail or a text message. In addition, the control unit of the present disclosure may confirm whether the reactor core protection system suspends output of the trip signal. For example, if the simulation signal generation unit simulates twelve single control rod drops and a Reactor Power Cutback (RPC) request signal is output from the reactor core protection system, the control unit may confirm whether the reactor core protection system suspends the trip signal by subsequently inserting the control rod for reactor power cutback. The response time test unit 240 may measure a time taken from transmission of the simulation state signal to reception of the result signal. Since the apparatus for simulating maintenance of a reactor core protection system of the present disclosure performs a function of confirming how fast a result signal is output in response to the simulation state signal input from each channel, the response time is measured through the response time test unit. At this point, if the response time test unit measures the response time and the response time is delayed longer than a preset standard response time, the control unit may analyze corresponding content. For example, if the time taken from transmission to reception and measured by the response time test unit of the present disclosure is 3500 ms when the preset standard response time is 5000 ms, the control unit of the present disclosure determines that the first to fourth channels operate normally. In addition, if the time taken from transmission to reception and measured by the response time test unit is 7000 ms, the control unit of the present disclosure confirms a channel of the delayed response time and determines that the third channel, which is the delayed channel, is out of order and informs a manager or a technical expert of corresponding content through an e-mail or a text message. FIG. 3 is a view showing the configuration of a simulation method of an apparatus for simulating maintenance of a reactor core protection system of the present disclosure. Referring to FIG. 3, this is an exemplary view showing a sequence of a simulation conducted by the apparatus for simulating maintenance of a reactor core protection system of the present disclosure. The simulation apparatus 200 may generate a simulation state signal that can be input into a first channel 310, a second channel 320, a third channel 330 and a fourth channel 340. At this point, the simulation state signal may include a first simulation state signal 211 for the position of a reactor control rod, a second simulation state signal 212 for the position of a reactor control rod, a third simulation state signal 213 for the position of a reactor control rod, and a fourth simulation state signal 214 for the position of a reactor control rod and may include a first simulation state signal 215, a second simulation state signal 216, a third simulation state signal 217 and a fourth simulation state signal 218 including general information such as a temperature, a pressure, a neutron level, a flow rate and the like. The simulation apparatus 200 may generate twenty-three of the first simulation state signal 211 for the position of a reactor control rod and transmit the first simulation state signals to the first channel 310 and may generate seventy of the second simulation state signal 212 for the position of a reactor control rod and transmit the second simulation state signals to the second channel 320. At this point, the first channel 310 may transmit twenty-three received first simulation state signals to the second channel 320, and the second channel 320 may transmit seventy received second simulation state signals to the first channel 310. At this point, communication between the first channel and the second channel may be accomplished through HR-SDL signals, and signal exchange can be conducted in a speedy way since communication between PCs is allowed. The first channel 310 and the second channel 320 analyze the first simulation state signal for the position of a reactor control rod and the second simulation state signal for the position of a reactor control rod received from each other and respectively generate a result signal. At this point, if the first simulation state signal for the position of a reactor control rod is determined as an abnormal state, each of the channels generates a trip signal 351 and 352 and transmits the trip signal to the simulation apparatus 200. The third channel 330 and the fourth channel 340 also determine a simulation state signal received from the simulation apparatus in a method the same as the signal exchange method of the first channel 310 and the second channel 320. In addition, a method of communicating between the channels includes a link method, a network method, a HR-SDL method, a HR-SDN method or the like, and communication between the channels may be accomplished in the various methods. The link or HR-SDL method performs peer-to-peer communication and may be used for an important data link for transmitting a control signal related to safety, such as a trip signal. At this point, a self-diagnosis, a variety of set values and constant values, a trip, a preliminary trip and the like may be transmitted to a processor, and whether or not the signals meet safety requirements may be determined. The network or HR-SDN method performs computer network communication and corresponds to one-to-many communication for controlling a plurality of apparatuses connected to a network by one central control apparatus. In addition, the apparatus for simulating maintenance of a reactor core protection system of the present disclosure may be used to train beginner operators or trainees of the reactor core protection system, in addition to conducting a maintenance simulation. Only experienced operators may operate the reactor core protection system, and verification on the channels may be performed using the simulation apparatus of the present disclosure before using the reactor core in order to perfectly guarantee a safety system of the reactor core. In addition, a beginner operator or a trainee, who operates the reactor core protection system for the first time, as well as an experienced operator, may confirm how the reactor core protection system operates the safety system, and the simulation apparatus may be used as a training material for confirming the types of information collected from the reactor and the types of logic for shutting down the reactor. FIG. 4 is a view showing the configuration of measuring a control rod position drop response time of an apparatus for simulating maintenance of a reactor core protection system of the present disclosure, and FIG. 5 is a view showing a graph measuring a control rod position drop response time of an apparatus for simulating maintenance of a reactor core protection system of the present invention. The apparatus for simulating maintenance of a reactor core protection system of the present disclosure may further include a control rod position determination unit 250 and a control rod drop time test unit 260. The control rod position determination unit 250 may receive a control rod position signal of the reactor core protection system, and the control rod drop time test unit 260 may measure a drop time of the control rod when the control rod of the reactor core protection system is shut down according to a simulation abnormal state signal generated by the simulation signal generation unit. At this point, in order to sense movement of the control rod, the control rod position determination unit may configure a 1 kΩ resistor, one hundred of 10Ω resistors and a 1 kΩ resistor in series and configure the resistors so that the total resistance may vary among the one hundred of 10Ω resistors according to the movement of the control rod. Accordingly, since the total resistance value varies according to the position of the control rod, determination of the position of the control rod may be efficiently performed by adjusting the applied voltage out of the supply voltage of 15V to have a value between 5 and 10V. At this point, the control rod drop time test unit may measure and store all of the drop time of the control rod for each of the channels. In addition, the control unit may determine whether the reactor core protection system normally determines a reactor core state according to the measured drop time of the control rod. A control rod of a bar shape covered with a material easily absorbing thermal neutrons exists in the reactor core. In the case of the control rod, reactivity of nuclear fuel is adjusted by inserting and withdrawing the control rod into and out of the reactor core, and if the control rod is inserted, reactivity of the reactor is lowered, and if the control rod is removed, reactivity of the reactor is increased. Accordingly, if an abnormal situation occurs in the reactor, the control rod is inserted for emergency shutdown of the reactor, and the reactor may be shut down by fully inserting the control rod. Accordingly, the apparatus for simulating maintenance of a reactor core protection system of the present disclosure may determine the current position of the control rod placed in the reactor core and measure performance of the reactor core protection system by measuring drop time of the control rod for fast shutdown of the reactor when an abnormal situation occurs in the reactor. In addition, whether a time counted from the time point of generating the trip signal of the reactor core protection system (PPS) until 90% of the control rod is inserted is in a permitted range can be confirmed. At this point, one-to-one communication signals between controllers in the reactor core protection system are connected to the simulation apparatus to measure the time. Referring to FIG. 4, the configuration of measuring a control rod position drop response time of the apparatus for simulating maintenance of a reactor core protection system may be confirmed. A system for receiving a control rod position signal from a RSPT signal corresponds to the reactor core protection system, and the apparatus for simulating a reactor core protection system should receive information on the control rod position signal from the reactor core protection system to perform a control rod drop test. The internal structure of the reactor core protection system is a structure in which the CCP transfers total ninety-three pieces of information on the control rod position of RSPT1 and RSPT2 to the CEAP, and since the transmission port of the HR-SDL card of the controller is duplicated, the apparatus for simulating maintenance of a reactor core protection system may receive a signal the same as the control rod position signal transferred to the CEAP through an unused port. The apparatus for simulating maintenance of a reactor core protection system of the present disclosure applies a HR-SDL card for PC to directly receive the signal, records all the ninety-three RSPT1 signals and ninety-three RSPT2 signals every 50 ms, and determines whether the control rod has dropped within the permitted range of time. Referring to FIG. 4, first, the simulation apparatus artificially generates an abnormal state signal and inputs the signal into the PPS apparatus connected to two or more channels {circle around (1)} and {circle around (2)}, and the apparatus for simulating maintenance of a reactor core protection system of the present disclosure generates a trip signal. Subsequently, since an abnormal situation has been occurred in two or more channels, the RTSS apparatus connected to the PPS apparatus transmits the trip signal to shut down the reactor by dropping the control rod in the reactor {circle around (3)}. Subsequently, a control rod position signal RSPT is transmitted to the first to fourth channels 310 to 340 {circle around (4)}, and the first to fourth channels sense a corresponding control rod position signal and transmit values measuring the current position and the drop time of the control rod to the simulation apparatus {circle around (5)}. Referring to FIG. 5, when the control rod of the reactor core protection system of the present disclosure is shut down, a value measuring the drop time of the control rod can be confirmed. The control rod gradually drops as the control rod is shut down, and finally, the control rod is completely dropped to the bottom after about 5500 ms. In addition, the control rod position determination unit of the present disclosure may receive a control rod position signal from one of two channels among the first to fourth channels and receive a control rod position signal from one of two other channels. Since the first and second channels receive a control rod position signal and the third and fourth channels receive another control rod position signal, the control rod position determination unit of the present disclosure may receive two different control rod position signals. Meanwhile, a system for simulating maintenance of a reactor core protection system of the present disclosure includes a simulation apparatus for generating a simulation state signal including a normal state or an abnormal state, and first to n-th channels included in the reactor core protection system and respectively connected to the simulation apparatus, in which the first to n-th channels receive the generated simulation state signal, output a result signal, and transmit the result signal to the simulation apparatus, and the simulation apparatus confirms whether the reactor core protection system normally determines a reactor core state by analyzing the result signal. FIG. 6 is a flowchart illustrating a method of simulating maintenance of a reactor core protection system of the present disclosure. Referring to FIG. 6, a method of simulating maintenance of a reactor core protection system according to an embodiment of the present disclosure may include the steps of generating a simulation state signal including a normal state or an abnormal state, transmitting the simulation state signal to at least two or more channels respectively connected to the reactor core protection system, receiving a result signal output from each of the channels in response to the input simulation state signal, and confirming whether the reactor core protection system normally determines a reactor core state by analyzing the result signal. At this point, diverse components that can be applied to the apparatus for simulating maintenance of a reactor core protection system described above can be applied to the system for simulating maintenance of a reactor core protection system and the method of simulating maintenance of a reactor core protection system of the present disclosure. Meanwhile, the system for simulating maintenance of a reactor core protection system of the present disclosure may perform an additional function for a configuration of inputting a simulation situation in the form of a power graph by a user or a manager and a behavior of the simulation apparatus conducted according to a virtual power input pattern. The control rod may be dropped or maintain its position according to a value of the power applied to the simulation system, and such a power value may be changed to an arbitrary value with respect to time. For example, it may be controlled to apply 5V between zero and one seconds, 10V between one and two seconds, and 0V between two and three seconds so that a simulation situation may be implemented using the system in each situation. In addition, when the reactor of the present disclosure includes twelve control rods, there may be an occasion of performing a simulation of dropping all the twelve control rods. However, since the reactor will be shut down even when only one control rod is dropped and wasted time and cost will be great if the reactor is really shut down, a simulation of shutting down the reactor when a few number of control rods are dropped may be configured through the simulation system. Since the apparatus for simulating maintenance of a reactor core protection system of the present disclosure may support input and output signals for all the four channels, as well as one channel, of the reactor core protection system, a rapid simulation can be conducted by reducing a response time between the input of a simulation state signal and the output of a result signal. In addition, since the apparatus for simulating maintenance of a reactor core protection system of the present disclosure may simulate both a hard wire signal and a communication signal among input and output signals, two hundred or more different state signals of four channels may be input. In addition, the apparatus for simulating maintenance of a reactor core protection system of the present disclosure may conveniently progress a simulation since all simulations can be conducted only with the simulation apparatus without the need of an additional work of using response time test equipment (RTTE) or the like or inserting resistors in a terminal block. In addition, the apparatus for simulating maintenance of a reactor core protection system of the present disclosure may simulate various forms of signals (a ramp signal, a step signal and the like), including a hard wire signal or a communication signal, an unlimited number of times at a desired time. In addition, the apparatus for simulating maintenance of a reactor core protection system of the present disclosure may simulate various design basis accidents or various movements of a control rod may and conduct a variety of tests while all the channels are connected. In addition, the apparatus for simulating maintenance of a reactor core protection system of the present disclosure may reduce overall control rod drop test time and minimize the probability of malfunction at the site of a reactor by adding various test functions. In addition, the apparatus for simulating maintenance of a reactor core protection system of the present disclosure may greatly reduce the total test time including a time for setting a test environment and immediately display a control rod position signal received through measurement of a control rod drop time on a test screen. In addition, the apparatus for simulating maintenance of a reactor core protection system of the present disclosure may be used to construct a reactor core protection system by measuring a position and a drop speed of a control rod using a method of confirming a position of a control rod when a state of the reactor is confirmed. The embodiments of the present disclosure described above are disclosed for illustrative purposes, and the present invention is not limited thereto. In addition, those skilled in the art may make diverse modifications and changes within the spirit and scope of the present invention, and all the modifications and changes should be regarded as belonging to the scope of the present invention. |
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abstract | Passive emergency cooling in response to a loss of coolant accident (LOCA) in a PWR, having an integral reactor pressure vessel incorporating the steam generators and housed in a small high pressure containment vessel, is provided by circulating cooling water through the steam generators and heat exchangers in an external tank to cool the reactor vessel at a rate sufficient to lower the pressure in the reactor vessel below that in containment to reverse mass flow out of the reactor vessel and keep the reactor core covered without the addition of makeup water. Suppression tanks inside the small high pressure containment structure limit peak blowdown pressure in containment and provide flood-up water and gravity fed makeup water to cool the core. Diverse cooling is provided by natural circulation of air, and if needed, water, over the spherical containment structure. |
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abstract | The invention relates to the field of nuclear technology, and specifically to a method for the in situ passivation of steel surfaces. The method consists in installing, in a position intended for a regular core, a core simulator in the form of a model of the core, which models the shape thereof, the relative position of the core components, and also the mass characteristics thereof; next, the reactor is filled with a heavy liquid metal heat transfer medium, the heat transfer medium is heated to a temperature which provides for the conditions of passivation, and in situ passivation is carried out in two stages, the first of which includes an isothermal passivation mode in conformity with the conditions determined for this stage, and the second mode includes non-isothermal passivation, which is carried out under different conditions, after which the core simulator is removed and the regular core is installed in the place thereof. The method provides for the corrosion-resistance of steel elements in a heavy liquid metal heat transfer medium environment and permits a decrease in the maximum rate of oxygen consumption during the initial period of operation of a nuclear actor. |
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abstract | Radiation therapy systems and their components, including secondary radiation shields. At least some versions of the disclosed systems combine a radiation delivery device, a primary radiation shielding device, and a secondary shielding layer into an integrated, modular unit. This is accomplished by using a small direct beam shield capable of blocking a primary beam from a radiation delivery device. In turn, a thinner shielding layer can be used to surround the radiation delivery device and primary shielding device, enabling a single modular unit to be delivered to an installation site. In some embodiments, a bed may be disposed within the secondary shielding layer. In some embodiments, the system is configured to provide up to 4-pi (4π) steradians of radiation coverage to the bed from the radiation delivery device. |
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06041099& | claims | 1. An x-ray directing system comprising: a Kirkpatrick-Baez side-by-side optic which redirects x-rays, wherein said Kirkpatrick-Baez side-by-side optic has multi-layer Bragg x-ray reflective surfaces. a unitary x-ray reflector having at least two reflective surfaces pre-aligned and bonded together; wherein said x-ray reflector is a multi-layer Bragg x-ray reflector; and wherein said x-ray reflector reflects an incident beam in two directions independently. a Kirkpatrick-Baez side-by-side optic which redirects x-rays, wherein said Kirkpatrick-Baez side-by-side optic has multi-layer Bragg x-ray reflective surfaces, and wherein said Kirkpatrick-Baez side-by-side optic is radiationally coupled to a microfocused x-ray source. 2. The x-ray directing system of claim 1, wherein said multi-layer Bragg x-ray reflective surfaces have graded-d spacing. 3. The x-ray directing system of claim 2 wherein said graded-d spacing is lateral grading. 4. The x-ray directing system of claim 2 wherein said graded-d spacing is depth grading. 5. The x-ray directing system of claim 1, wherein said multi-layer Bragg x-ray reflective surfaces have an elliptical surface. 6. The x-ray directing system of claim 1, wherein said multi-layer Bragg x-ray reflective surfaces have a parabolic surface. 7. The x-ray directing system of claim 1, wherein said multi-layer Bragg x-ray reflective surfaces are a parabolic surface and an elliptical surface. 8. The x-ray directing system of claim 1 further including at least one x-ray aperture assembly, wherein said assembly occludes a portion of said x-rays. 9. An x-ray reflecting system comprising: 10. The x-ray reflecting system of claim 9, wherein said multi-layer Bragg x-ray reflector has graded-d spacing. 11. The x-ray reflecting system of claim 10, wherein said graded-d spacing is lateral graded. 12. The x-ray reflecting system of claim 10, wherein said graded-d spacing is depth graded. 13. The x-ray reflecting system of claim 9, wherein said multi-layer Bragg x-ray reflector has an elliptical surface. 14. The x-ray reflecting system of claim 9, wherein said multi-layer Bragg x-ray reflector has a parabolic surface. 15. The x-ray reflecting system of claim 9, wherein said multi-layer Bragg x-ray reflector has a parabolic surface and an elliptical surface. 16. The x-ray reflecting system of claim 9 further including at least one x-ray aperture assembly, wherein said assembly occludes a portion of said x-rays. 17. An x-ray directing system comprising: 18. The x-ray directing system of claim 17, wherein said multi-layer Bragg x-ray reflective surfaces have graded-d spacing. 19. The x-ray directing system of claim 17, wherein said multi-layer Bragg x-ray reflective surfaces have an elliptical surface. 20. The x-ray directing system of claim 17, wherein said multi-layer Bragg x-ray reflective surfaces have a parabolic surface. |
claims | 1. A discharge apparatus usable in a nuclear reactor environment for determining neutron flux at a plurality of locations and being structured to be connected with a number of inputs of a detection device, the discharge apparatus comprising:an elongated emitter apparatus comprising a plurality of emitters spaced apart from one another in a predetermined fashion along the longitudinal extent of the emitter apparatus, the plurality of emitters each being structured to emit a number of electrons via beta decay responsive to absorption of neutrons;a collector situated in proximity to the emitter apparatus and being structured to collect from the plurality of emitters the number of electrons;an insulator apparatus interposed between the emitter apparatus and the collector, the insulator apparatus electrically insulating from one another at least some of the emitters of the plurality of emitters;the emitter apparatus and the collector being electrically insulated from one another due at least in part to the insulator apparatus; andat least some of the emitters of the plurality of emitters each being structured to undergo an electrostatic discharge event with the collector when an imbalance in electrical charge between the emitter and the collector is sufficient to exceed the dielectric properties of the insulator apparatus. 2. The discharge apparatus of claim 1 wherein the plurality of emitters comprise a plurality of pieces of wire of known length. 3. The discharge apparatus of claim 1 wherein the collector comprises an elongated tube, and wherein the emitter apparatus further comprises a first detector situated at a first end of the tube and a second detector situated at a second end of the tube opposite the first end, the first detector being structured to be electrically connected with a first input of the number of inputs and to generate an output signal responsive to detecting the electrostatic discharge event, the second detector being structured to be electrically connected with a second input of the number of inputs and to generate another output signal responsive to detecting the electrostatic discharge event. 4. The discharge apparatus of claim 3 wherein the first and second detectors are acoustic detectors that are structured to acoustically detect the occurrence of the electrostatic discharge event and to responsively generate electrical signals as the output signal and the another output signal. 5. The discharge apparatus of claim 1 wherein the collector comprises an elongated tube, and wherein the emitter apparatus further comprises another tube, a first detector, and a second detector, the emitter apparatus being situated within an interior region of the tube, the another tube being elongated and being in communication with the tube, the first detector being situated at a first end of the another tube, the second detector being situated one of at the first end and at a second end of the tube opposite the first end, the first detector being structured to be electrically connected with a first input of the number of inputs and to generate an output signal responsive to detecting the electrostatic discharge event, the second detector being structured to be electrically connected with a second input of the number of inputs and to generate another output signal responsive to detecting the electrostatic discharge event. 6. The discharge apparatus of claim 5 wherein the first and second detectors are acoustic detectors that are structured to acoustically detect the occurrence of the electrostatic discharge event via communication of sound from the electrostatic discharge through the another tube and to responsively generate electrical signals as the output signal and the another output signal. 7. The discharge apparatus of claim 1 wherein the collector comprises an elongated tube, and wherein the emitter apparatus further comprises a first detector situated at a first end of the tube and a second detector situated one of at the first end and at a second end of the tube opposite the first end, the first detector being an acoustic detector that is structured to be electrically connected with a first input of the number of inputs, the first detector being structured to acoustically detect through a first medium of the discharge apparatus the occurrence of the electrostatic discharge event and to responsively generate an output signal, the second detector being an acoustic detector that is structured to be electrically connected with a second input of the number of inputs, the second detector being structured to acoustically detect through a second medium of the discharge apparatus the occurrence of the electrostatic discharge event and to responsively generate another output signal, the first medium being a material that transmits a particular acoustic energy therethrough at a first velocity, the second medium being a material that transmits the particular acoustic energy therethrough at a second velocity different than the first velocity. 8. The discharge apparatus of claim 7 wherein the first detector is structured to detect the occurrence of the electrostatic discharge event through the material of the tube as the first medium. 9. The discharge apparatus of claim 8 wherein the second medium is one of a material situated within the tube and a material situated at least in part external to the tube. 10. The discharge apparatus of claim 1 wherein the collector comprises an elongated tube, and wherein the emitter apparatus further comprises a detector situated at an end of the tube, the detector being structured to be electrically connected with an input of the number of inputs, the detector being structured to detect through a medium of the discharge apparatus acoustic energy generated as a result of the occurrence of the electrostatic discharge event and to responsively generate output signals, the medium being a material that transmits the acoustic energy therethrough at a velocity that varies with the frequency of the acoustic energy, the detector being structured to detect at a first time a first acoustic aspect of the electrostatic discharge event and to generate a first output signal, and the detector being structured to detect at a second time different from the first time a second acoustic aspect of the electrostatic discharge event that is of a different frequency than the first acoustic aspect and to generate a second output signal. 11. The discharge apparatus of claim 10 wherein the medium is the material of the tube. 12. A method of employing the discharge apparatus of claim 1 in determining neutron flux at a plurality of locations in a nuclear reactor environment, the method comprising:connecting the discharge apparatus with a number of inputs of a detection device;detecting an input signal at the number of inputs as being representative of an electrostatic discharge event;determining with the detection device a time differential between a portion of the input signal and another portion of the input signal;employing the time differential to identify a position along the longitudinal extent of the emitter apparatus as being the site where the electrostatic discharge event occurred; anddetermining a neutron flux at a location that includes the position and that is based at least in part upon the occurrence of the electrostatic discharge event. 13. The method of claim 12, further comprising:employing the position to identify a particular emitter of the plurality of emitters that experienced the electrostatic discharge event; andstoring in a storage a record representative of the occurrence of the electrostatic discharge event experienced at the particular emitter. 14. The method of claim 12, wherein the collector comprises an elongated tube, and wherein the emitter apparatus further comprises a first detector situated at a first end of the tube and a second detector situated at a second end of the tube opposite the first end, and further comprising:electrically connecting the first detector with a first input of the number of inputs;detecting the electrostatic discharge event with the first detector and responsively generating an output signal;receiving the output signal at the first input as the portion of the input signal;electrically connecting the second detector with a second input of the number of inputs;detecting the electrostatic discharge event with the second detector and responsively generating another output signal; andreceiving the another output signal at the second input as the another portion of the input signal. 15. The method of claim 14 wherein the first and second detectors are acoustic detectors, and further comprising:acoustically detecting the occurrence of electrostatic discharge event and responsively generating electrical signals as the output signal and the another output signal. 16. The method of claim 12 wherein the collector comprises an elongated tube, and wherein the emitter apparatus further comprises another tube, a first detector, and a second detector, the emitter apparatus being situated within an interior region of the tube, the another tube being elongated and being in communication with the tube, the first detector being situated at a first end of the another tube, the second detector being situated one of at the first end and at a second end of the tube opposite the first end, and further comprising:electrically connecting the first detector with a first input of the number of inputs;generating with the first detector an output signal responsive to detecting the electrostatic discharge event;receiving the output signal at the first input as the portion of the input signal;electrically connecting the second detector with a second input of the number of inputs;generating with the second detector another output signal responsive to detecting the electrostatic discharge event; andreceiving the another output signal at the second input as the another portion of the input signal. 17. The method of claim 16 wherein the first and second detectors are acoustic detectors, and further comprising acoustically detecting the occurrence of the electrostatic discharge event via communication of sound from the electrostatic discharge through the another tube and responsively generating electrical signals as the output signal and the another output signal. 18. The method of claim 12 wherein the collector comprises an elongated tube, and wherein the emitter apparatus further comprises a first detector situated at a first end of the tube and a second detector situated one of at the first end and at a second end of the tube opposite the first end, the first and second detectors being acoustic detectors, the discharge apparatus comprising a first medium and a second medium, the first medium being a material that transmits a particular acoustic energy therethrough at a first velocity, the second medium being a material that transmits the particular acoustic energy therethrough at a second velocity different than the first velocity, and further comprising:electrically connecting the first detector with a first input of the number of inputs;acoustically detecting with the first detector through the first medium the occurrence of the electrostatic discharge event and responsively generating an output signal;receiving the output signal at the first input as the portion of the input signal;electrically connecting the second detector with a second input of the number of inputs;acoustically detecting with the second detector through the second medium the occurrence of the electrostatic discharge event and responsively generating another output signal; andreceiving the another output signal at the second input as the another portion of the input signal. 19. The method of claim 12 wherein the collector comprises an elongated tube, and wherein the emitter apparatus further comprises a detector situated at an end of the tube, the discharge apparatus comprising a medium that is a material that transmits acoustic energy therethrough at a velocity that varies with the frequency of the acoustic energy, and further comprising:electrically connecting the detector with an input of the number of inputs;detecting through the medium with the detector at a first time a first acoustic aspect of the acoustic energy generated as a result of the occurrence of the electrostatic discharge event and responsively generating a first output signal;receiving the first output signal at the input as one of the portion of the input signal and the another portion of the input signal;detecting through the medium with the detector at a second time different from the first time a second acoustic aspect of the acoustic energy generated as a result of the occurrence of the electrostatic discharge event that is of a different frequency than the first acoustic aspect and responsively generating a second output signal; andreceiving the second output signal at the input as the other of the portion of the input signal and the another portion of the input signal. 20. A detection assembly comprising the discharge apparatus of claim 1, the detection assembly being usable in a nuclear reactor environment for determining neutron flux at a plurality of locations, and further comprising a detection device having a number of inputs, the discharge apparatus being electrically connected with the number of inputs. |
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047160110 | claims | 1. In a nuclear reactor having a flow of coolant/moderator fluid therein, at least one fuel assembly installed in the fluid flow, said fuel assembly comprising in combination: a bundle of elongated fuel rods disposed in side-by-side relationship so as to form an array of spaced fuel rods; an outer tubular flow channel surrounding said fuel rods so as to direct the flow of coolant/moderator fluid along said fuel rods; bottom and top nozzles mounted at opposite ends of said flow channel and having an inlet and outlet respectively for allowing entry and exit of the flow of coolant/moderator fluid into and from said flow channel and along said fuel rods therein, said bottom nozzle having an annular surface defined therein so as to surround said inlet thereof, said annular surface having circumferentially spaced sectors and circumferentially spaced segments which alternate with said spaced sectors; and a coolant flow direction control device operatively disposed in said bottom nozzle so as to open said inlet thereof to the flow of coolant/moderator fluid in an inflow direction into said flow channel through said bottom nozzle inlet but close said inlet to the flow of coolant/moderator fluid from said flow channel through said bottom nozzle inlet upon reversal of coolant/moderator fluid flow from the inflow direction; said coolant flow direction control device being a unidirectional flow check valve positioned across said inlet of said bottom nozzle for sensing the direction of coolant/moderator fluid flow and automatically opening when the flow direction sensed is into said bottom nozzle and closing when the flow direction sensed is out of said bottom nozzle; said flow check valve including a plurality of outer portions mounted to said respective circumferentially spaced sectors of said bottom nozzle annular surface surrounding said inlet thereof, and a plurality of inner portions being pivotably connected to said respective outer portions for pivotal movement toward and away from one another between lowered and closed and raised open positions; said inner valve portions, when in their raised positions, extending toward said bottom nozzle in the direction of coolant flow into said bottom nozzle, said inner valve portions being configured to extend in close fitting relationship adjacent to one another and coplanarly across said inlet so as to close said inlet when disposed in their respective lowered positions and to extend in generally parallel relationship to the direction of coolant flow and be located remote from one another so as to open said inlet when disposed in their respective raised positions; each of said inner valve portions, when in its lowered position, has opposite lateral edge portions that seat on respective surface portions of the two segments located on opposite ends of said sector to which the respective outer portion of said valve is mounted, said inner valve portions in seating on said spaced segments of said bottom nozzle annular surface being stopped by said surface from pivoting past their lowered positions in which they would extend away from said bottom nozzle and allow reverse flow of coolant therefrom; said inner valve portions being arranged in first and second pairs which are angularly displaced about ninety degrees from one another wherein said inner valve portions of each pair are placed in opposing relation to one another such that one is a mirror image of the other, said inner valve portions located directly opposite to one another in said respective pairs thereof extending generally parallel to one another when in said raised positions. |
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055966152 | summary | BACKGROUND OF THE INVENTION The present invention relates to a method of manufacturing a fuel assembly applicable for a core of a nuclear reactor using a fuel containing Pu.sup.239, members constituting the fuel assembly (sometimes referred to herein as "fuel assembly elements"), and alloys used for the members. In particular, the present invention concerns a method of manufacturing a fuel assembly applicable for a reactor core in which a water-uranium fuel volume ratio is 1.5 or less and the conversion ratio from U.sup.238 to Pu.sup.239 is high, members constituting the fuel assembly, and alloys used for the members. As for members constituting a fuel assembly used for nuclear power generation, those for a light water reactor use a zirconium alloy; and those for a fast breeder reactor use a stainless steel. A high conversion reactor acts as a bridge between a light water reactor and a fast breeder reactor, and has a feature of effectively converting non-fissionable U.sup.238 contained in natural uranium to fissionable Pu.sup.239 usable for power generation. The non-fissionable U.sup.238, which has been not used in a light water reactor, can be used by the high conversion reactor, resulting in the effective utilization of uranium resource. The stored Pu.sup.239 can be effectively used as a fuel for a fast breeder reactor, or a fuel for a high conversion reactor and a general breeder reactor. In a conventional light water reactor and a high conversion reactor, the reduction in the exhaust amount of a spent fuel by increasing an operation cycle and the burn-up of fuel contributes to an economic merit, for example in reducing a power generation cost. However, when the operation cycle is increased and the burn-up of fuel is enhanced, the staying period of a fuel assembly in a reactor is increased. This further accelerates the corrosion of the surfaces of members constituting the fuel assembly in water at a high temperature/high pressure. Moreover, the effective conversion from U.sup.238 to fissionable Pu.sup.239 is mainly due to resonance neutrons having an energy higher than that of thermal neutrons. As a result, neutron spectrum in a reactor core is hardened (a large number of neutrons having high energy exist), thus accelerating the damage of the material due to neutrons. A further problem is that the zirconium alloy (normally used as a high corrosion resisting alloy) has a tendency to become brittle by fast neutron irradiation. Further, in the environment of a BWR (Boiling Water Reactor), a member constituting a ZIRCALOY fuel assembly generates a local oxidization called the nodular corrosion, and the corrosion portion propagates with time. A method of reducing this corrosion has been known, wherein a heat-treatment of heating a zirconium alloy for a short period of time in a temperature range of (.alpha.+.beta.) phase or .alpha. phase and quenching the alloy is inserted in the downstream step in a member manufacturing process (for example, Unexamined Japanese Patent Publications Nos. SHO 51-110411 and SHO 51-110412, and Examined Japanese Patent Publications Nos. SHO 60-59983 and SHO 63-31543). This known technique is called (.alpha.+.beta.) quenching or .beta. quenching, which is applied to alloys used for the existing light water reactor: ZIRCALOY-2 (Sn: 1.2-1.7 wt %, Fe: 0.10-1.20 wt %, Cr: 0.05-0.15 wt %, Ni: 0.03-0.08 wt %, O: 0.06-0.14 wt %, and the balance: Zr); and ZIRCALOY-4 (Sn: 1.2-1.7 wt %, Fe: 0.15-1.24 wt %, Cr: 0.05-0.15 wt %, O: 0.06-0.14 wt %, and the balance: Zr). Of the above alloy components, Fe, Cr and Ni are elements for improving corrosion resistance, and Sn is an element of improving strength. Fe, Cr, Ni precipitate as intermetallic compounds within crystal grains and crystal boundaries. These intermetallic compounds are refined by the (.alpha.+.beta.) quenching or .alpha. quenching; and further when the cooling rate is sufficiently large, they are dissolved in solid even in the matrix. The mechanism of enhancing the corrosion resistance is not fully understood, but it is generally considered that the refining of precipitations and the increase in the concentration of solid-solution of Fe, Ni, and Cr contribute to the increase in the corrosion resistance. The improvement of the alloy composition and alloy components leads to the enhancement of the corrosion resistance. Various improved alloys have been known as follows: an alloy improved in corrosion resistance which has the same composition of that of the existing ZIRCALOY but is optimized in the added amounts of the alloy elements (Unexamined Japanese Patent Publication No. SHO 62-228442); an alloy having the composition of ZIRCALOY which is further added with the fifth element such as Nb, Mo, W, V, Te, Ta, Si, Ru, Rh, Pd, Pt, or An (Unexamined Japanese Patent Publication Nos. SHO 60-36640, SHO 63-33535, SHO 64-73037, SHO 64-73038, and HEI 1-242747); an alloy having the composition of Zr--Nb alloy which is further added with elements of Sn, Mo, Cr, Ni, Fe, V, W, and Cu in a slight amount (Unexamined Japanese Patent Publication Nos. SHO 50-148213, SHO 51-134404, SHO 61-170552, SHO 62-207835, and HEI 1-119650); a Zr--Bi alloy (Unexamined Japanese Patent Publication No. SHO 63-290234); and a Zr--Sn--Te, Mo alloy (Unexamined Japanese Patent Publication No. SHO 63-290233). These zirconium alloys are intended to be used for a light water reactor, and thereby they are difficult to be used as they are for a high conversion type future reactor in which neutron spectrum is shifted on a high energy side as compared with the existing light water reactor. As described above, in the high conversion type future reactor, non-fissionable U.sup.238 is effectively convened into fissionable Pu.sup.239 and is used for power generation. The nuclear transformation is generated by allowing resonance neutrons (energy: 10.sup.0 to 10.sup.4 eV) to absorb U.sup.238. In such a reactor core, it is required to lower a water-uranium fuel ratio and to shift neutron spectrum on a high energy side (spectrum is hardened). As a result, the damage ratio of a member constituting a fuel assembly due to neutrons is increased. Accordingly, to significantly increase the burn-up of a light water reactor and to realize a high conversion type future reactor, it becomes important to improve the neutron damage resistance and the corrosion resistance of a member constituting a fuel assembly and to reduce the capture amount of neutrons of the member. An object of the present invention, therefore, is to provide a Zr alloy for use with a fuel assembly element, which has a high neutron damage resistance and a high corrosion resistance, and further has a small resonance neutron capture cross-section. Another object of the present invention is to provide a method of manufacturing a member such as a fuel sheath tube constituting a fuel assembly usable for a high conversion type future reactor which is capable of keeping an excellent performance for a long period of time. SUMMARY OF THE INVENTION For improving a neutron damage resistance, reduction in crystal gains has been found to be very effective. This is because a pair of an interstitial atom and a vacancy produced by neutron irradiation rapidly disappear at crystal grain boundaries, thus preventing the generation of irradiation defect in the crystal grains. Even if the irradiation defect is generated, the density thereof is significantly lowered. According to one embodiment of the invention, therefore, crystal grain size of 1000 nm or less gives the most reduction in irradiation defect. According to a further embodiment of the invention, significant reductions in the radiation defect occur with crystal grain sizes below 100 nm, as explained with regard to other embodiments, below. According to one more specific embodiment of the invention, there is provided a fuel assembly for a nuclear reactor comprising fuel assembly elements, said fuel assembly elements comprising: a fuel pellet made of uranium containing plutonium; a fuel sheath tube for sheathing said pellet; a spacer for holding said fuel sheath tube; and a channel box for containing a plurality of said sheath tubes, wherein at least one fuel assembly element comprises a Zr-containing metal, and an average crystal grain size of said Zr-containing metal is in the range of 1000 nm or less. According to further embodiments, said average crystal grain size is in the range of 100 nm or less; at least one of said fuel assembly elements comprises a Zr alloy having a random crystal orientation; and at least one fuel assembly element comprises a Zr alloy which comprises at least about 0.02 wt % of Fe. In some embodiments, at least one fuel assembly element comprises a Zr alloy comprising at least about 0.05 to 30 wt % of Fe, and an average crystal grain size of said Zr alloy is in the range of 100 nm or less. According to still further embodiments, at least one fuel assembly element comprises a ZrFe.sub.2 intermetallic compound containing at least about 33 atomic percent Zr. According to another embodiment, at least one fuel assembly element comprises a ZrFe.sub.2 intermetallic compound containing at least about 66 atomic percent Fe. Alternatively, there are embodiments in which at least one fuel assembly element comprises a Zr(Fe, Ni, Cr, Sn).sub.2 intermetallic compound containing a range of Zr between about 30 and about 35 atomic percent, and in other embodiments, at least one fuel assembly element comprises a Zr(Fe, Ni, Cr, Sn).sub.2 intermetallic compound containing a range of (Fe, Ni, Cr, Sn) of between about 65 and about 70 atomic percent. According to still another embodiment, there is provided a fuel assembly element for a nuclear reactor comprising a Zr-containing metal having an average crystal grain size of 1000 nm or less. Still further, in one embodiment of the invention, there is provided a fuel assembly element manufacturing method of a Zr alloy or compound, said fuel assembly element being chosen from a group consisting of: a fuel sheath tube for sheathing a fuel pellet made of uranium containing plutonium, a spacer for holding said sheath tube, or a channel box for containing a plurality of said sheath tubes, which constitute a fuel assembly used for a core of a nuclear reactor, said method comprising: mechanically mixing a Zr-containing metal and an alloying element, the alloying element being chosen from a group consisting of: Fe, Cr, Ni, Nb, Mo, Te, Bi, and Sn, whereby a Zr alloy is produced; crystallizing the pressure-treated Zr alloy in a temperature range of between the crystallization temperature of the pressure-treated Zr alloy and a maximum crystallization temperature, said maximum crystallization temperature being 200 degrees C. above the crystallization temperature of the pressure-treated Zr alloy; subjecting the Zr alloy to an isostatic pressure, whereby a pressure-treated Zr alloy is produced; and forming the pressure-treated alloy into a shape of the fuel assembly element. Further, in some embodiments, said crystallizing occurs during said subjecting, wherein said subjecting comprises subjecting the Zr alloy to an isostatic pressure at a temperature lower than a crystallization temperature of the Zr alloy, and in other embodiments, said crystallizing comprises working the pressure-treated Zr alloy at a temperature range between about 100 degrees C. and about 200 degrees C. According to still further embodiments, said subjecting occurs at a temperature above the crystallizing temperature for said Zr alloy, while according to other embodiments, said mechanically mixing comprises: hydrogenation of the Zr-containing metal; crushing of the Zr-containing metal into a powder, and; dehydrogenation of the powder. According to even further embodiments, said dehydrogenation comprises heating in a vacuum atmosphere. According two to alternate embodiments of the method, said Zr-containing metal comprises a powder of pure Zr or a Zr alloy. According to still a further embodiment of the method, the temperature is never allowed above about 650 degrees C., and in another embodiment, there is further provided hot-working, performed below about 650 degrees C. According to some embodiments of the invention, annealing is performed at a temperature higher than about 530 degrees C. According to still a further embodiment, for improving the corrosion resistance, it is effective to dissolve in solid a corrosion resistance improving element such as Fe, Ni, or Cr in a matrix. The super-saturated solid-solution with ultra-fine crystals can be obtained by a means of realizing a non-equilibrium crystal structure, for example, mechanical alloying, molten metal quenching, or splat cooling. The neutron capture cross-section of Fe is about 1/3 that of Zr in an energy range (of resonance neutron) of 10.sup.0 to 10.sup.4 eV. The reduction in the capture mount of resonance neutrons of a member constituting a fuel assembly is achieved by the methods of: (a) reducing the resonance neutron capture cross-section by increasing the added amount of Fe, and (b) thinning the member by increasing the strength of the Zr alloy. By increasing the added mount of Fe in a zirconium alloy, the above-described precipitations are coarsened, thereby leading to the embrittlement of the material. In particular, the precipitations produced upon melting are significantly coarsened, so that the zirconium alloy cannot be manufactured by a conventional manufacturing process. Accordingly, even in this case, the above-described means of realizing a non-equilibrium crystal structure is effective. According to even further embodiments of the present invention, there is provided a fuel assembly for a nuclear reactor comprising: a fuel pellet made of uranium containing plutonium; a fuel sheath tube for sheathing the pellet; a spacer for holding the fuel sheath tube; and a channel box for containing a plurality of the sheath tubes, wherein at least one member of the fuel sheath tube, the spacer and the channel box is made of a Zr alloy containing 0.05 to 30 wt % of Fe, and an average crystal grain size of the Zr alloy is in the range of 1000 nm or less. In the above fuel assembly, at least one member of the fuel sheath tube, the spacer and the channel box may be made of a Zr alloy, and an average crystal grain size of the Zr alloy may be in the range of 1000 nm or less. Also in the above fuel assembly, at least one member of the fuel sheath tube, the spacer and the channel box may be made of a Zr alloy containing an alloy element forcibly dissolved in solid in an amount of 2 wt % or more. Further in the above fuel assembly, at least one member of the fuel sheath tube, the spacer and the channel box may be made of a Zr alloy containing 0.5-30 wt % of Fe, 0-5 wt % of Ni, 0-5 wt % of Cr, 0-5 wt % of Nb, 0-1 wt % of Mo, 0-1 wt % of Te, 0-5 wt % of Sn, 0-2 wt % of Bi, 0-1 wt % of O, and 0-0.5 wt % of Si. According to still a further embodiment of the present invention, there is provided a Zr alloy containing 0.5-30 wt % of Fe, 0-5 wt % of Ni, 0-5 wt % of Cr, 0-5 wt % of Nb, 0-1 wt % of Mo, 0-1 wt % of Te, 0-5 wt % of Sn, 0-2 wt % of Bi, and 0-0.5 wt % of Si. And, according to one aspect of such an embodiment, there is provided a Zr alloy containing an alloy element forcibly dissolved in an mount of 2 wt % or more. According to an even further embodiment of the present invention, there is provided a Zr alloy powder made of an amorphous Zr alloy containing crystal grains having a crystal grain size of 1000 nm or less In still a further embodiment, there is provided a Zr alloy powder made of a Zr alloy containing 0.5-30 wt % of Fe, 0-5 wt % of Ni, 0-5 wt % of Cr, 0-5 wt % of Nb, 0-1 wt % of Mo, 0-1 wt % of Te, 0-5 wt % of Sn, 0-2 wt % of Bi, and 0-0.5 wt % of Si, and the Zr alloy powder made of a Zr alloy containing an alloy element forcibly dissolved in solid in an amount of 2 wt % or more. Moreover, according yet another embodiment of the present invention, there is provided a fuel assembly manufacturing method of manufacturing either of a fuel sheath tube for sheathing a fuel pellet made of uranium containing plutonium, a spacer for holding the sheath tube, and a channel box for containing a plurality of the sheath tubes, which constitute a fuel assembly used for a core of a nuclear reactor, the method comprising: a) a process of mechanically mixing pure metal powders including Zr powder or a crystalline Zr alloy powder for alloying, thereby manufacturing an amorphous alloy powder made of a Zr alloy being mostly amorphous; b) a process of solidifying the amorphous alloy powder under an isostatic pressure at a temperature lower than a re-crystallization temperature of the amorphous alloy powder; c) a process of forming the solidified block into the shape of either of the member by hot-working or cold-working; and d) a process of crystallizing the metal structure of the formed product by heat-treatment. In the above-described process of manufacturing a pure Zr powder or a crystalline Zr alloy powder, preferably, sponge-like pure Zr or an ingot of a Zr alloy is hydrogenated and crushed into a powder having a specified particle size, and the powder is dehydrogenated by heating in a vacuum atmosphere. In the above-described process of forming the solidified block into a specified shape by hot-working or cold-working, preferably, the hot-working is performed at 650 degrees C., followed by cold-working. In the above-described process of crystallizing the metal structure by heat-treatment, preferably, the final crystallization annealing is performed at a temperature higher than 530 degrees C. |
abstract | A photolithographic mask for patterning a photosensitive material, in particular on a wafer, has at least one structure region for imaging a structure on the photosensitive material, and an absorber structure for absorbing incident radiation. At least one structure region is provided and has at least one thin protective coating of only a few atomic layers made of chemically and mechanically resistive material selected from Al2O3, Ta2O5, ZrO2, and HfO2formed by atomic layer chemical vapor deposition (ALCVD) so that the protective coating constitutes a negligible alteration of nominal or critical dimensions for the structure region, and in which additional absorption or reflection losses are negligibly low. In this way, the photolithographic mask can be cleaned chemically and/or mechanically, without the structure regions being attacked and damaged by the chemical and/or mechanical cleaning media. Furthermore, a plurality of methods are possible for fabricating this photolithographic mask. |
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abstract | Methods and systems for providing illumination of a specimen for a process performed on the specimen are provided. One system configured to provide illumination of a specimen for a process performed on the specimen includes a laser configured to generate excitation light. The system also includes focusing optics configured to focus the excitation light to a plasma in an electrodeless lamp such that the plasma generates light. The system is also configured such that the light illuminates the specimen during the process. |
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description | The invention relates to a method and device for loading a fuel assembly into the core of a nuclear reactor and in particular into the core of a pressurised water-cooled nuclear reactor. Pressurised water-cooled nuclear reactors comprise a nuclear reactor core within a reactor vessel, the core of the nuclear reactor comprising fuel assemblies, generally of straight prismatic shape, which are placed with their longitudinal axes in the vertical direction and along which the pressurised cooling water of the nuclear reactor circulates in an upward direction. The fuel assemblies in the reactor core are positioned within the lower internal equipment of the nuclear reactor vessel comprising in particular a core supporting plate, or lower core plate, and a surrounding wall comprising vertical plates holding the peripheral assemblies of the core. The fuel assemblies in the core rest on the core supporting plate through their lower members, or bottom nozzles, which incorporate openings which engage vertical axis positioning pins fixed to the core supporting plate. The juxtaposed fuel assemblies comprise a dense group in which each of the fuel assemblies is in contact with adjacent assemblies within a location of right prismatic shape whose position is perfectly defined within the core, the location for one fuel assembly being bounded by vertical planes constituting the geometrical envelope of the fuel assembly of right prismatic shape. The virtual vertical plane surfaces of each of the fuel assemblies in the core are also contact surfaces between the fuel assembly and the adjacent assemblies in the core, or again with the inner surfaces of one or more vertical surrounding walls. The right transverse cross-sections of the fuel assembly locations within the core, in transverse planes perpendicular to the vertical axis of the core, form a regular system throughout the cross-section of the core. The fuel assemblies generally have a right cross-section of square shape and their locations comprise a square grid arrangement throughout the cross-section of the core within the surrounding wall. The fuel assemblies, which are generally of square cross-section, incorporate struts/grids which hold a bundle of fuel rods parallel to the axial direction, and at the extremities of the assembly an upper nozzle and a lower nozzle through which the assembly rests on the core supporting plate. Within the core the fuel assemblies are in contact with adjacent fuel assemblies through their struts/grids and nozzles. The fissile fuel material present within the fuel assembly rods is progressively consumed within the nuclear reactor when it is in service, so the fuel assemblies become progressively impoverished in fissile fuel material and undergo some wear. Operations for reloading the core of the nuclear reactor have to be performed at intervals. These operations, which require shutdown and cooling of the nuclear reactor, comprise replacing some of the fuel assemblies positioned within a zone of the core with new assemblies, the other assemblies in the core which are not replaced by new assemblies being moved from one zone of the core to another. When the nuclear reactor is first placed in service the core must be loaded with new fuel assemblies comprising the first charge for the nuclear reactor. The operations of loading and unloading a nuclear reactor are performed under water, the head of the vessel being taken apart from the top level of the reactor pool, into the bottom of which the reactor pit opens. A machine for lifting and handling the fuel assemblies, known as a loading machine, which incorporates means for movement and guidance in horizontal directions, located above the upper level of the pool, in such a way that gripping and lifting means of the loading machine can be positioned immediately above each of the fuel assembly locations in the core of the reactor, is used to carry out the operations of loading and unloading. In order to load a fuel assembly into a location within the core, the assembly which is to be loaded and is fixed in a vertical position through the gripping means of the loading machine is positioned and then the fuel assembly is inserted into its loading position by movements of the loading machine and its gripping and lifting means. When the reactor is in operation, the fuel assemblies, which are subjected to irradiation and which are the source of an intense release of heat, may undergo deformation. Because the fuel assemblies are of a very slender shape, their transverse cross-section having very much smaller dimensions than their axial length, they may undergo deformation, for example by buckling, resulting in a relatively large displacement of the nozzles at their extremities in relation to the theoretical positions of those nozzles centred on the axis of the fuel assembly. Because of this, the upper parts of fuel assemblies adjacent to a location in which a fuel assembly has to be loaded may be displaced into the theoretical location into which the fuel assembly will be loaded, as a result of their deformation through buckling. As a consequence it may in some case be very difficult to insert the fuel assembly into its location in order to load it. In particular the locations of the peripheral assemblies are bounded in one or two vertical surfaces by the surrounding wall and on the other sides by the adjacent fuel assemblies of peripheral assemblies. Deformation of the upper parts of the fuel assemblies adjacent to the peripheral assemblies in the direction of the surrounding wall may restrict the space for inserting the peripheral fuel assembly in the core, so that loading becomes very difficult or impossible. In general, deformation of the fuel assemblies used for reloading the core of a nuclear reactor may complicate and considerably lengthen loading operations, which causes the loss of a great deal of time in the critical path for the shutdown of that unit of the nuclear power station. In order to assist the insertion of a fuel assembly into its location within a core it has been proposed that dummy assemblies or dummy fuel assembly nozzles should be used, placed on the supporting plate of the core around a location in which the fuel assembly which is to be reloaded is inserted. These devices bring about a substantial improvement in the positioning of deformed fuel assemblies within the core, but their use is complex because of the fact that these devices must be fitted in the bottom of the reactor pool and recovered therefrom before and after the fuel assembly is positioned. In addition to this, with these devices it is not possible for continuous loading to take place through the successive positioning of fuel assemblies in the core of the nuclear reactor, or again for fuel assemblies within the core in locations bounded by other fuel assemblies which might be deformed to be replaced. A device for loading a fuel assembly through which the lower nozzle openings of the fuel assembly are engaged on the positioning pins of the core supporting plate in the location intended for the fuel assembly have also been proposed, in FR 99 00457. Such devices also fail to assist the insertion of a fuel assembly into a location bounded by adjacent fuel assemblies which have been deformed. The object of the invention is therefore to provide a method for the loading of fuel assemblies into a loading location in the core of a nuclear reactor comprising fuel assemblies of generally straight prismatic shape located within a surrounding wall, in adjacent right prismatic locations having vertical axes, the transverse cross-sections of which in a horizontal plane form a regular grid, the location for loading the fuel assembly comprising at least one lateral vertical surface along which a lateral surface of a fuel assembly adjacent to the fuel assembly being loaded is positioned, this process rendering loading of the fuel assembly easier and reducing the time required for loading in those circumstances where at least one of the fuel assemblies adjacent to the fuel assembly being loaded is deformed in such a way as to be displaced into the loading location. With this object: a dummy assembly having substantially the shape and dimensions of the location and having smooth side walls, substantially over the full height of the loading location, is inserted into the loading location, the position of the at least one adjacent assembly is fixed, with the dummy assembly present, in relation to at least one second assembly in the core, at least in the upper part of the adjacent assembly, the dummy assembly is removed from the loading location and, the fuel assembly which is to be loaded into the loading location is inserted. The invention also relates to a loading device for a fuel assembly in a loading location in the core of a nuclear reactor comprising fuel assemblies of general straight prismatic shape located within a surrounding wall in adjacent right prismatic locations having vertical axes, whose transverse cross-sections in a horizontal plane form a regular pattern, the loading location for the fuel assembly comprising at least one vertical lateral surface along which a lateral surface of a fuel assembly adjacent to the fuel assembly being loaded is positioned, characterised in that it comprises a tool for aligning the fuel assemblies in the form of a dummy assembly having the general right prismatic shape of a fuel assembly location within the core and bounded laterally by smooth walls, and at least one tool for holding fuel assemblies comprising a supporting plate and positioning pins designed to engage the positioning openings of the upper nozzles of the fuel assemblies of the core, and at least one handling means for gripping and handling the fuel assembly alignment tool and at least one tool holding the fuel assemblies through suspension and holding means. Preferably: the means suspending and holding the alignment tool for the fuel assemblies and the tool holding the fuel assemblies is similar to a part suspending and holding an upper nozzle of a fuel assembly in the core, and the fuel assembly alignment tool handling device and the fuel assembly holding tool is a gripper of a machine for loading the nuclear reactor, the fuel assembly alignment tool comprises a central body, an upper end member and a lower end member having a common longitudinal axis and a transverse cross-section in a plane perpendicular to the axis which has the shape of the transverse cross-section of a location for a fuel assembly in the core of the nuclear reactor, the central body and the lower end member of the fuel assembly alignment tool of right prismatic shape have a transverse cross-section of dimensions smaller than the dimensions of the transverse cross-section of a fuel assembly location in the core, an upper end member whose transverse cross-section has the dimensions of the transverse cross-section of a location for a fuel assembly in the reactor core, and an intermediate part between the central body and the upper end member bounded by side walls which are inclined with respect to the axis of the fuel assembly alignment tool which has a transverse cross-section of a size which generally increases between the central body and the upper end member, the fuel assembly alignment tool comprises a central body of right prismatic shape whose transverse cross-section has the dimensions of the transverse cross-section of a location for a fuel assembly in the core of the reactor, and a lower end member having side walls which are inclined with respect to the axis of the fuel assembly alignment tool in such a way that the transverse cross-section of the lower end member has dimensions which decrease between the central body and its lower extremity which engages in a location in the core of the nuclear reactor, the lower end member of the alignment tool comprises lateral openings for the passage of positioning pins at a location in the reactor core and two posts which engage in the water holes of the location when the alignment tool is positioned on the supporting plate for the reactor core, the lower end member of the alignment tool has a cross-section such that it can be engaged between the positioning pins of a location for a fuel assembly in the reactor core and two posts engaging the water holes of the location when the alignment tool is positioned on the supporting plate for the reactor core, the walls which are inclined with respect to the axis of the intermediary part or lower end member of the fuel assembly alignment tool have successive portions in the direction of the axis which are inclined with respect to the axis and substantially parallel thereto, the fuel assembly holding tool comprises a supporting plate, a first set of positioning fingers and a second set of positioning fingers which are parallel to each other and secured in positions perpendicular to the supporting plate, the positioning fingers of the second set having a length in the direction perpendicular to the supporting plate which is shorter than the lengths of the fingers in the first set, the positioning fingers of the first set or long fingers comprise a shank having a first longitudinal axis and an end tip in an extension of the shank having a longitudinal axis which is offset in relation to the axis of the shank in a direction perpendicular to the axis of the shank, the long fingers of the fuel assembly holding tool are fixed to the supporting plate by mechanical fixing means through which the orientation of the finger about its longitudinal axis and thus the direction of the offset between the axis of the finger's shank and the end tip of the long finger can be adjusted, for loading fuel assemblies of square transverse cross-section in right prismatic locations of square cross-section within the core of a nuclear reactor the fuel assembly holding tool comprises a supporting plate having the shape of a square whose side is substantially equal to twice the size of the transverse cross-section of a location for a fuel assembly within the core of the nuclear reactor, four long fingers in the positions of the positioning holes for four adjacent fuel assemblies within the core of the nuclear reactor and four short fingers of shorter length than the long fingers in a direction perpendicular to the supporting plate in positions corresponding to the positions in transverse cross-section of four positioning holes for the four adjacent fuel assemblies located diagonally in each of the upper end members of the fuel assemblies in relation to the positioning holes in the positions of the long fingers, in the case of a nuclear reactor core comprising fuel assemblies of square transverse cross-section located within locations in the core of right prismatic shape having square transverse cross-sections arranged in a square grid arrangement, the fuel assembly holding tool comprises a supporting plate in the form of a square having dimensions corresponding to the dimensions of the transverse cross-sections of the three adjacent fuel assembly locations in the core, three long pins and three short pins designed to engage in positioning openings for the three adjacent fuel assemblies arranged in a square in the core of the nuclear reactor respectively, the long pins being inserted into first openings of each of the fuel assemblies and the three short pins respectively being inserted into three second positioning openings for the three fuel assemblies arranged in a square located diagonally with respect to the first openings receiving the long pins, the tool holding the fuel assemblies comprises a suspension and holding device similar to a suspension and holding device for an upper end member of a fuel assembly which is integral with the supporting plate on one surface of the supporting plate opposite a surface of the supporting plate on which the positioning pins are projectingly fixed. The cross-sections of the locations 3 for the fuel assemblies of right prismatic shape of square cross-section are shown in FIG. 1. The square cross-sections of the locations 3 for fuel assemblies in core 1 form a square grid arrangement within boundary wall 2. In FIG. 1 the core 1 of the nuclear reactor is shown while it is being loaded, the locations 3 for fuel assemblies into which an assembly has already been placed in the course of loading being identified by crosses. Loading is carried out along successive diagonals of the square grid arrangement of core loading locations. The orientations of the axial planes of symmetry of the core through the angles 0°, 90°, 180° and 270° clockwise are also shown in FIG. 1. The positions of the locations 3 for fuel assemblies within the core are identified by indicating successive letters A, B, . . . , R for rows of locations parallel to the 0°-180° axial plane, and FIGS. 1, 2, . . . , 15 for rows parallel to the 90°-270° axial plane. The loading of a fuel assembly into location C14, which is bounded by the enclosing wall on two sides and by an adjacent fuel assembly located in C13 on one side and having one side free not bounded by a fuel assembly or by the enclosing wall, will be described below, in particular with reference to FIGS. 1 and 12. It will be assumed that the fuel assembly located in C13 which was previously loaded into core 1 of the nuclear reactor has deformed through buckling so that part of the assembly and in particular an upper part of the assembly is displaced into the location C14 into which it is desired to load a fuel assembly. Because of the displacement of the fuel assembly positioned in C13 into location C14, the remaining cross-section of location C14 will not allow the fuel assembly which is intended to be loaded in it to pass and be inserted. In a first stage the method according to the invention comprises inserting a dummy assembly 4 into location C14 to push the displaced part of the fuel assembly located in C13 back out of location C14. A dummy fuel assembly 4, which can reposition the upper part of fuel assembly 5 in C13 so as to free a passage for a replacement fuel assembly in the upper part of location 3 in C14 is illustrated in FIG. 2A. The dummy assembly, which has the function of aligning the fuel assemblies adjacent to the loading location, will subsequently be referred to as the fuel assembly alignment tool (FAAT). Dummy assembly or FAAT 4 has the general right prismatic shape of a location 3 for the positioning of a fuel assembly in the core. Central body 4a of FAAT 4 is a sheet metal envelope having flat lateral surfaces arranged in the manner of the faces of a right prism of square cross-section, that is to say a parallelepiped of square cross-section. Axis 6 of the right prismatic envelope which is connected at the bottom to a lower dummy end member 7 of square cross-section and openings 7a engaging two vertical positioning pins projecting from the upper surface of the core supporting plate in the loading location are also shown. Central body 4a and lower end member 7 of the FAAT have a transverse cross-section whose side is slightly shorter than the side of the square cross-section of the lower end member or strut/grid of a fuel assembly 5 of the core which has standard dimensions. FAAT 4 also has an upper end member 8 which is identical to the upper end member of a standard fuel assembly 5 in the core 1 of the nuclear reactor. End member 8 has in particular gripping parts 8a through which the upper end member 8 can be gripped by the gripper of the nuclear reactor loading machine illustrated in FIG. 9, which will be described below. Upper end member 8 of the FAAT is connected to central body 4a by an envelope 9 of pyramidal shape whose lateral surfaces are slightly inclined with respect to the axis 6 of the FAAT. As can be seen in FIG. 2C, the inclined surfaces of the connecting part 9 of the generally planar FAAT comprise successive parts 9a, which are substantially parallel to the axis 6 of the FAAT, and 9b, which are inclined with respect to the axis 6 through a small angle of the order of 0.5 to 6° and preferably from 1 to approximately 3.5°. FAAT 4, which is used in a first stage of the process of reloading a fuel assembly, is picked up by the handling gripper of the nuclear reactor loading machine vertically above the reloading location, i.e. in the case in point vertically above location C14. The weight of the FAAT is not greater than the weight of a fuel assembly in which a moderating cluster is engaged. The FAAT supported from the gripper in a vertical position, i.e. with its axis 6 vertical, is lowered towards location C14 into which assembly 5 present in C13 is slightly displaced. The cross-section of lower end member 7 of FAAT 4, which is smaller than the maximum cross-section of a fuel assembly, i.e. the cross-section of a location 3, allows the lower part of FAAT 4 to be inserted readily. While the FAAT is being inserted into loading location 3 in position C14, the smooth lateral walls of lower end member 7 and then central body 4a can come into contact with the upper part of adjacent fuel assembly 5 in position 13 which has been displaced into location 3 in position C14. The fact that the FAAT has smooth lateral walls means that it can be inserted without any risk of becoming hooked onto adjacent assemblies and, in the case described, onto assembly 5 in position C13. In the case where a fuel assembly is inserted in order to be loaded directly into a location between adjacent fuel assemblies, the end members and above all the grids of the fuel assembly projecting on the lateral sides of the fuel assembly are likely to become hooked onto components of adjacent fuel assemblies. Once the FAAT has been inserted in location 3, the intermediate part 9 of the FAAT which has surfaces inclined with respect to axis 6 comes into contact with the upper part of fuel assembly 5 in position C13 which has become displaced into loading location 3. FIG. 2C shows a portion of the lateral wall of intermediate part 9 of the FAAT in contact with the upper end member 10 of a fuel assembly 5 in position C13. The inclination of the side wall of intermediate part 9 with respect to axis 6 of the FAAT along which movement in the vertical direction takes place is not constant, so that this inclined wall comes into contact with the edge of upper member 10 of fuel assembly 5 through its inclined parts 9b, and thus as it moves downwards brings about displacement of the upper end member 10 of adjacent assembly 5 in a direction away from the loading location, that is it brings about some realignment of the fuel assembly in relation to its theoretical longitudinal axis. FIG. 2C shows part of the lateral edge of upper end member 10 of adjacent assembly 5 on which flat springs 10′ are fixed along one side of end member 10. The presence of sections 9a of the lateral surface of intermediate part 9 of the FAAT in the form of planar surfaces substantially parallel to axis 6 of the FAAT between two successive inclined parts 9b prevents springs 10′ from coming into contact with the inclined wall of intermediate part 9 while it is being moved downwards. In the event of contact with springs 10′, the side wall of intermediate part 9 of the FAAT would risk deformation and damage to springs 10′ while the latter is moving downwards. The presence of inclined parts and parts parallel to the axis of movement of the FAAT on the lateral surface of intermediate part 9 makes it possible to realign adjacent fuel assembly 5 to move it away from loading location 3 in successive stages, springs 10′ of the upper end member of adjacent assembly 5 being always at a distance from the lateral surface of intermediate part 9 of the FAAT. When the FAAT has been fully inserted into loading location 3 for the fuel assembly in position C14, over substantially the full height of the location, openings 7a in lower end member 7 have engaged the positioning pins in the fuel assembly location and the adjacent assembly in position C13 is wholly replaced so as to completely free the upper part of the loading location. FIG. 2B illustrates a different embodiment of the dummy assembly or FAAT 4′, this embodiment of the FAAT making it possible to restraighten and realign the fuel assembly or assemblies adjacent to the loading location over their entire height. According to the variant embodiment, FAAT 4′ comprises a dummy assembly having smooth lateral walls and its transverse cross-section has the maximum dimension of the transverse cross-section of a fuel assembly, i.e. the dimension of upper end member 8′ and the struts/grids of the fuel assembly. Lower end member 7′ of the FAAT has a lateral surface of pyramidal shape, the lateral sides of end member 7′ being inclined with respect to axis 6′ of the FAAT in such a way that the cross-section of the end member increases from a section of dimensions smaller than the maximum cross-section of the fuel assembly and loading location 3 up to a cross-section which is equal to the maximum cross-section of the fuel assembly also corresponding to the cross-section of upper end member 8′. Furthermore, the lateral surfaces of lower end member 7′ of the FAAT have a shape such as shown in FIG. 4 and described above in relation to the lateral walls of intermediate part 9. The lateral walls of end member 7′, which are generally inclined in relation to the axis 6′ of the FAAT, have inclined parts similar to parts 9b of the lateral surfaces of intermediate part 9 and parts substantially parallel to axis 6′ similar to portions 9a of the inclined surfaces of intermediate part 9. Thus contact between the lateral surfaces of end member 7′ and springs 10′ of the upper end member of adjacent assembly 5 in position C13 is avoided when the FAAT engages within loading location 3 in position C14. End member 7′ is easily inserted into the upper part of location 3 in position C13 because of its smaller cross-section, and downwards movement of the FAAT in the direction of its axis 6′ brings about progressive realignment of assembly 5 in position C13. As previously the smooth walls of the FAAT allow the FAAT to be inserted without any risk of becoming hooked onto the assembly or assemblies adjacent to loading location 3 in position C14. FIGS. 3A and 3B and 4A and 4B show two variant embodiments of a lower end member 7 (or 7′) of a FAAT which enable FAAT 4 to rest and remain on the supporting plate for the core of the nuclear reactor in a perfectly stable manner. In each of the locations 3 for a fuel assembly, as indicated above the supporting plate for the core comprises two upwardly projecting positioning pins along a first diagonal of the location and large diameter through openings for the passage of water, or water holes, arranged in particular along a second diagonal of location 3 perpendicular to the first diagonal. In accordance with a first embodiment of the FAAT illustrated in FIGS. 3A and 3B, lower end member 7 (or 7′) incorporating the engaging openings 7a for the positioning pins at two corners also has two studs 26 located on a second diagonal of the end member projecting in the axial direction above the lower surface of the end member, the diameter of which is substantially equal to or slightly less than the diameter of the water hole in the plate supporting the core. According to a second variant embodiment illustrated in FIGS. 4A and 4B, the lower end member of the FAAT of square cross-section has smaller dimensions in comparison with the end member illustrated in FIGS. 3A and 3B in such a way that it can rest on the supporting plate for the core between the positioning pins of a location 3 for a fuel assembly without interfering with the positioning pins; in this case the lower end member 7 of the FAAT only has large diameter studs 26′ projecting beneath its lower surface to engage in the water holes and has no openings such as 7a for passage of the positioning pins. In all situations, studs 26 or 26′ which are engaged in the water holes of the plate supporting the core can be used to achieve very stable positioning of the FAAT in the core of the nuclear reactor. When the FAAT is in position, the assembly or assemblies adjacent to the loading location will be realigned into positions which provide full access to the loading location. However the assembly or assemblies adjacent to the loading location must be held in their realigned position, at least at the top, independently of the FAAT, so that a further fuel assembly can be loaded into the loading location. One or more tools such as illustrated in FIGS. 5, 6A, 6B and 7 may be used in order to hold the fuel assemblies adjacent to the loading location in place. The fuel assembly holding tool (FAHT), indicated in general by reference 11, comprises a supporting plate 12 of square shape whose cross-section corresponds to the cross-section of four locations fitted with fuel assemblies 5, a suspension and holding device 13 integral with an upper surface of plate 12 and positioning and holding pins 14 attached to and projecting beneath plate 12 opposite suspension and holding device 13. Suspension and holding device 13 is similar to an upper end member of a fuel assembly which can be picked up by the gripper of the fuel loading machine illustrated in FIG. 9. Suspension and holding device 13 comprises a square frame similar to the upper extremity of a fuel assembly end member comprising positioning holes 13a, 13b in two diagonal corners and a hole 13c for engaging a finger of the gripper of the loading machine, comprising an element ensuring proper positioning, in a third corner on a second diagonal. In fact the gripper of the loading machine must always be placed in the same orientation in relation to the FAHT, which must itself be placed in a fixed orientation above the four adjacent fuel assemblies inserted into the core of the nuclear reactor. As may be seen in FIG. 9, the fuel assembly handling gripper used for handling FAHT 11 and in general indicated by reference 15 comprises a support 16 on which finger 17 ensuring correct orientation and four gripping fingers 18 pivotally mounted about an axis 18a at right angles to axis 19 of the handling device are mounted on support 16 which is integral with a mast 20 of the loading machine. An operating tube 21 slidably mounted within mast 20 of the loading machine is used to move fingers 18 between a projecting position illustrated by solid lines in FIG. 9 and a retracted position shown by dotted and dashed lines for one of fingers 18. Gripper 15 with fingers 18 in the retracted position is inserted into the inner space of the square frame of suspension device 13 of FAHT 11 and then the fingers are manoeuvred into the projecting position by operating tube 21. It should be noted that in their retracted and operating positions fingers 18 bear against corresponding stops 25a and 25b. Fingers 18 of the gripper bear against the frame of suspension device 13 of the FAHT in the median zones of the four sides of the frame of suspension device 13. In orientation the position of the FAHT beneath the gripper is determined by orientating finger 17 which is inserted into orientating hole 13c of suspension device 13. As may be seen in FIGS. 5, 6A and 7, the pins engaging and holding the FAHT comprise four long pins 14a which may be seen in particular in FIG. 6A and four short pins 14b, two of which are visible in FIG. 7. FIG. 5 shows the directions of the axial planes of the reactor vessel at 90°-270° and 0°-180° in the plane of plate 12, as illustrated in FIG. 1 and FIG. 12, when the FAHT is in the operating position above assemblies in the core of the nuclear reactor. Long pins 14a of the FAHT are located at the corners of fuel assembly cross-sections and adjacent and on either side of the 90°-270° axial plane of the reactor vessel and the reactor core. The short pins are placed diagonally opposite the long pins in each of the fuel assembly cross-sections on which the FAHT is positioned. When the FAHT is positioned above four fuel assemblies, for example above the fuel assemblies in locations C12, C13, B12 and B13 illustrated in FIG. 12, the FAHT has a long pin and a short pin in diagonal positions for each of the fuel assemblies. As may be seen in particular in FIG. 6B, long pins 14a have a shank and lower extremity portion of smaller diameter produced by a positioning tip 22 whose axis 22a is offset in an axial direction of the core in relation to the axis 14′a of the shank of the long pin. The offset between axis 22a of positioning tip 22 and the axis 14′a of the shank of a long finger 14a may for example be 5 mm in a direction which may be the horizontal direction of the FAHT which is intended to be positioned along the 90°-270° axial direction of the core of the nuclear reactor on which loading is being carried out. The offset between the axis of positioning tip 22 and the axis of the shank of the long pin may also be provided in the 0°-180° direction of the core and reactor vessel of the nuclear reactor, in either direction. The orientation of the offset of the axis of the positioning tips of the long fingers of the FAHT is selected on the basis of the observed offset in the position of the assembly or assemblies adjacent to the loading location, so as to ensure that the long fingers of the FAHT are centred and easily positioned when it is positioned above the four fuel assemblies in positions as shown in B12, B13, C12 and C13 in FIG. 12. The FAHT picked up by the handling gripper of the loading machine is placed above the assemblies in positions B12, B13, C12, C13 and lowered, as shown in FIG. 10A, in such a way that for each of fuel assemblies 5 in positions B12, B13, C12, C13 the positioning tip 22 of a corresponding long finger 14a is positioned above a positioning hole 24a of the upper end member 10 of fuel assembly 5. By lowering the FAHT in the vertical direction, the tips 22 of long fingers 14a of the FAHT ensure that the end members of the fuel assemblies are put back into position by acting together with holes 24a, 24b of the end members of the fuel assemblies through an inclined ramp 22a on tip 22, in a direction ensuring centering with respect to the axis of positioning fingers 14a and 14b of holes 24a and 24b in which these positioning fingers are engaged. As may be seen in FIG. 10C, fingers 14a and 14b in a centred position are then engaged in corresponding positioning holes 24a and 24b of upper end member 10 of the fuel assembly shown. Positioning fingers 14a and 14b of the three other fuel assemblies are simultaneously engaged in the positioning holes of the upper end members of these fuel assemblies. The engagement of fingers 14a and 14b in positioning holes 24a and 24b of the fuel assembly upper end members with virtually no play ensures that the four upper end members of the fuel assemblies in positions B12, B13, C12, C13 are kept in relative position and in particular that the end member and the upper part of the fuel assembly in position C13 adjacent to loading position C14 are held in position. The FAAT can then be removed from loading location 3 in position C14 without the end member and the upper part of fuel assembly 5 in position C13 again becoming displaced in the direction of the loading location. The fuel assembly can then be loaded into loading location C14, as the upper part of the adjacent fuel assembly in position C13 is no longer out of position within location C14. In the situation where an assembly is loaded into location C14 as illustrated in FIG. 12, a single FAHT device 11 placed on four fuel assemblies can realign the adjacent fuel assembly in position C13, the other sides of the fuel assembly being loaded coming into contact with the surrounding wall or facing an empty fuel assembly location. In other cases, the loading location will be surrounded by at least two adjacent fuel assemblies which may be displaced towards the interior of the loading location. In this case two or more FAHT may be used in such a way as to ensure that the adjacent fuel assemblies surrounding the loading location are held in position once they have been realigned by fitting the FAHT. Up to four FAHT devices 11 may be used for example, as illustrated in FIGS. 5 to 7, to ensure that four fuel assemblies surrounding a loading location are held in position in the situation where a fuel assembly is inserted into the core, for example on completing loading or after loading. As may be seen in FIG. 11, a FAHT device 11′ constructed in accordance with a variant and designed to ensure that three fuel assemblies surrounding a loading location are held in position may be used. In this case it may be possible to use only two FAHT devices 11′ positioned on two out of three fuel assemblies surrounding a loading location within the core. A FAHT device as illustrated in FIG. 11 comprises six centering pins 14′, three of which are long pins and three are short pins. As explained above, the FAHT device must be attached to the loading machine in such a way that its two horizontal axes are located in the axial planes of the core and reactor vessel respectively, at 0-180° and 90°-270°. Depending upon the direction of the offset of the positioning holes in the upper end members of the fuel assemblies on which the FAHT is placed, it will then be necessary to select one of the four FAHT tools having long fingers whose positioning tips are offset in one of directions 25a, 25b, 25c and 25d illustrated in FIG. 5. Appropriate FAHT tools must therefore be available for each of the directions in which the fuel assemblies are realigned at the time when the FAAT is fitted. As may be seen from FIG. 8, the construction of a FAHT tool comprising long fingers 14a attached to plate 12 of the FAHT in such a way that they can be orientated about their axes 14′a and fixed in any desired orientation depending upon the direction in which the fuel assemblies have to be realigned may be envisaged. It is possible for example to construct the upper part of the lining of the long finger in the form of a threaded rod which engages an opening in plate 12 and is immobilised by a fixing nut. After the fuel assembly has been loaded the FAHT or FAHTs are withdrawn and removed from the pool. The method and device according to the invention may be adapted to the situation of loading fuel assemblies of right prismatic shape having a transverse cross-section which is not square and placed in locations of corresponding shape in a grid arrangement of any type. |
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claims | 1. A method of determining an operating margin to a given operating limit in a nuclear reactor, comprising:accessing operational plant data during a current operating cycle from an on-line nuclear reactor plant to be evaluated,simulating reactor operation off-line using the operational plant data to generate simulation results including predicted dependent variable data representative of the given operating limit,normalizing the predicted dependent variable data for evaluation with normalized historical dependent variable data stored from each of a plurality of operating cycles of nuclear reactor plants having a similar plant configuration to the reactor plant being evaluated,determining a time-dependent average bias value for the predicted dependent variable data using the normalized historical dependent variable data,determining a time-dependent uncertainty value for the predicted dependent variable data using the normalized historical dependent variable data,obtaining a risk-tolerance level for the plant being evaluated related to a probability of an event not occurring during a given period in the current operating cycle, andcalculating an operating margin to the given operating limit based on the determined time-dependent average bias value and time-dependent uncertainty value so as to satisfy the risk-tolerance level of the evaluated plant. 2. The method of claim 1, wherein accessing operational data further includesretrieving plant operating conditions representing independent variables and monitored thermal limit data representing actual dependent variable data at one or more exposure points in the current operating cycle, andstoring the independent variables and actual dependent variable data in a database. 3. The method of claim 2, wherein the independent variables are selected from the group consisting of reactor power level, core flow rate, rod pattern, control blade sequence, mechanical conditions, cycle exposure, enrichment properties, and gadolinium properties. 4. The method of claim 1, wherein the given operating limit is one of a thermal limit selected from the group consisting of a Maximum Fraction of Limiting Power Density (MFLPD) limit, a Maximum Average Planar Linear Heat Generation Rate (MAPLHGR) limit, a Maximum Fraction of Limiting Critical Power Ratio (MFLCPR) limit, a power-related limit such as an eigenvalue for the evaluated plant, and other industry-standard, power-related plant limits or thermal limits on nuclear fuel. 5. The method of claim 2, wherein simulating reactor operation off-line includescreating a simulator input file which models the plant being evaluated using the independent variables for simulating reactor operation in an off-line simulation program, andexecuting the off-line simulation program to generate the predicted dependent variable data representing the given operating limit. 6. The method of claim 1, whereina bias value for the historical dependent variable data stored from each of the operating cycles at a plurality of exposure points in each of the respective operating cycles has been calculated in advance, the bias value at a given exposure point in a given stored operating cycle representing a difference between the measured and the predicted operating limit at that exposure point for a given historical cycle, anddetermining the time-dependent average bias value for the predicted dependent variable data includes:calibrating the normalized historical dependent variable data to force the bias values for the historical dependent variable data to a current exposure point in the operating cycle of the reactor plant being evaluated, anddetermining the time-dependent average bias value as an average of all the bias values of the normalized historical dependent variable data at each of the exposure points in each of the stored operating cycles, as calibrated from the current exposure point in the operating cycle of the reactor plant being evaluated. 7. The method of claim 6, wherein determining the time-dependent uncertainty value for the predicted dependent variable data includes determining a standard deviation of each of the bias values of the historical dependent variable data at each of the exposure. 8. The method of claim 1, further comprising:determining revised plant operating parameters based on the calculated operating margin for the given operating limit, andchanging plant operational conditions of the on-line reactor based on the revised plant operating parameters. 9. The method of claim 8, wherein the revised plant operating parameters are determined using a method selected from the group consisting of manually and using an optimization algorithm using the calculated operating margin. 10. The method of claim 1, wherein the calculation of the operating margin for the given operating limit is repeated continuously or at a given periodicity. 11. The method of claim 1, wherein the historical dependent variable data is filtered to incorporate historical dependent variable data from similar plant operation styles to the plant being evaluated. 12. The method of claim 1, wherein the historical dependent variable data is correlated by a method selected from the group consisting of least squares and neural networks. |
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058621954 | description | DETAILED DESCRIPTION OF THE INVENTION After service in power plant nuclear reactor spent fuel rods 1 which can no longer heat to efficiently make steam are put into the power plants water storage pool 2 for about five years or more of further radioactive decay or heat reduction. After time, clusters of the typically fourteen foot long spent fuel rods 1 are put into cylindrical canisters 3, "MPC"s 3, for transport and dry storage. Fuel rods 1 are typically loaded into "MPC"s 3 under the pool water 2 where the canister 3 loading has the shielding of the water 2 during this operation. "MPC" 3 is a term or name for a popular design called a multi-purpose-canister 3 where the "MPC" 3 is used for both the transport of the fuel rods 1 and storage of the fuel rods 1. A proposed "MPC" 3 has shielding on its top to shield operators making its closure. "MPC"s 3 are usually standing vertical, an exception is when they lay horizontal during transport. For interplant transfer from the wet to the dry storage the inventors preferred design is to keep the "MPC" 3 vertical. Loaded and sealed "MPC"s 3 are crane 4 lifted from the plant's water storage pool 2, carried through a shielded corridor 6, placed into a transporter 7 which rides on a RR-track 8 or roadway. The transporter 7 has walls and floor with radiation shielding 9 to confine radiation when the transporter 7 is outside in the open 11 between the wet pool 2 storage and dry-pool 12 storage. The "MPC" 3 containing transporter 7 enters the storage field area 13 which has radiation shielding 14 by either strategically placed panels 14, or storage casks 16 themselves, or the building 17 over the dry-pool which may be the primary shield for the entire storage site 13. The transporter 7 enters on tracks 8 extending from the load out at the plant water pool 2. At the field 13 or in the building 17 other tracks 18 carry a bridge crane 19 which picks an "MPC" 3 from the transporter 7. Doors 21 in the transporter 7 shielding 9 allows a horizontal exodus of the "MPC" through a shielded corridor 22 to an entrance 23 of the dry-pool 24. Walls 26 of an on plane dry-pool 27 provide shielding to move the "MPC" to the its storage spot 28. Once in position a seismic brace 29 hinged to the wall 26 secures the "MPC" 3 standing vertical. In a submerged dry-pool 31 a vertical chase 32 provides a falling floor 33 so as the "MPC" 3 is lowered to the dry-pool 31 floor 34 should the "MPC" 3 be dropped, it would fall less than eighteen inches to an impact. The falling floor 33 is a mechanically moving device which would move with the "MPC" 3. A most simple form of a hydraulic device is simply a pool of water 36 confined by water lock gates 37. The lock water 36 surface would provide a cushioned fall and only an obvious and massive leak would foil the safety process. When the "MPC" 3 gets to the dry-pool 31 floor 34 the water lock gates 37 are opened and the bridge crane 19 then carries the "MPC" 3 to its selected storage spot 28. As described before, again, a hinged seismic brace 29 secures the top of the "MPC" 3 to the dry-pool 31 walls 26. At the storage spot 28 around the perimeter of the standing "MPC" 3 vertical holes 38 communicated with a horizontal pipe 39 which brings in outside air 41 for cooling the surface of the standing "MPC" 3. In the on plane dry-pool 27 configuration the horizontal pipe 39 may extend directly out to the outside air atmosphere 41 without a basin 42. In the submerged dry-pool configuration 31 an outside basin 42 extends down from the ground surface 43 where the sub-floor 34 horizontal pipe 39 extends horizontally to into the outside air entrance basin 42 so outside air 41 can sink into the basin 42, then proceed under the dry-pool 31 floor 34, then proceed up the circumferential holes 38 to cool surface of the "MPC" 3. The cooling air 41 would then be vented back to the atmosphere 41 by exiting to the outside of the building 17. In the submerged dry-pool configuration 31, if additional shielding should be desired, then the dry-pool 31 could be filled with water 44 which would then provide shielding typical of the wet pool 2 configuration. Then, again, by draining the water 44 out the dry-pool 31 it would return to its dry configuration. After such an exercise, it would be well to check the "MPC"s 3 for water leakage from the pool into the vessels. A building 17 having a thick concrete roof 46 and thick concrete walls 47 combined with vertical shielding 14 will shield the ambient atmosphere 48 from outward radiation 49 but still allow a transporter 7 and the servicing bridge crane 19 to freely enter and exit the storage field 13 or storage building 17. The field 13 and storage building 17 are un-manned and the storage operation is orchestrated from an off-site control center 51. |
summary | ||
048760579 | description | FIG. 1 shows a sectional view of a pressurized nuclear reactor vessel 2. The core of said nuclear reactor comprises: (a) Nuclear fuel (fissile materials) contained in jacketing and referred to as fuel rods 6, which are positioned vertically. (b) Sometimes, neutron-absorbing rods, often called consumable poison rods. The absorbing or fuel rods are maintained in mechanical structures, called assemblies. The core is constituted by assemblies and the network formed by the rods is generally regular. (c) A cooling fluid supplied by a feed pipe 8 and discharged by a discharge pipe 10 connected to a pump. This fluid flows vertically from top to bottom in the core and is constituted by water in the form .sub.1.sup.1 H.sub.2 8.sup.16 O having the property of slowing down the neutrons. In the case of a pressurized water system, the water can contain, in solution, neutron-absorbing nuclei and in particular boron nuclei .sub.5.sup.10 B. (d) Control rods 12 containing materials absorbing the neutrons which can be vertically displaced in the core during reactor operation. These control rods are used for the rapid control of the power in the core. A description will now be given of the inventive process with reference to the flowchart of FIGS. 2a and 2b. In order not to overburden the description, the simplified case will be assumed in which the neutron sources consist solely of fast fission neutrons. At the end of the description reference will be made to the general or kinetic case, in which the neutron sources also have delayed neutrons. This process involves a stage of determining the neutron flux .phi.(j,g), the power P(j) and the source S(j) in each mesh j by an iterative calculation, as well as a stage of using given physical quantities for controlling the core regulating means. The inventive process starts with an operation of initializing the values of the sources S(j), the neutron fluxes .phi.(j,g) and powers P(j). The initial value of the sources S(j) can be fixed in arbitrary manner, e.g. at 1. More advantageously they can be considered as equal, for the calculation of the neutron fluxes and powers at an instant t, to the value calculated according to the inventive process at a prior instant t' (t'<t). In the first case, it is experimentally found that the first stage of the inventive process requires a number of iterations n of approximately 100, whereas in the second case n is approximately a few units. In the same way, the neutron fluxes .phi.(j,g) can be initially fixed at the value zero, but can be advantageously fixed at values determined at a preceding instant by the process of the invention. Finally, the powers P(j) are preferably preset to a value: ##EQU5## in which P is the total power of the core, which is known by measurements carried out thereon and v.sub.j is the volume of mesh j. Operation 16 in FIG. 2a notes the incrementation of the iteration index n. Each iteration consists of a sequence of operations 18-30 and ends by a convergence test 32. Operation 18 relates to the calculation of a first neutron flux component .phi..sup.0 (j,g) of the real neutron flux .phi.(j,g). Each first component .phi..sup.0 (j,g).sup.(n) at the nth iteration is expressed as a function of a predetermined coupling matrix [.psi.g] and sources S(j).sup.(n-1) calculated during the preceding iteration n-1. There are in all G coupling matrixes, one per velocity group g and each having a size K.times.K, in which K is the number of adjacent matrixes to a random matrix. The coupling matrixes [.psi.g] are associated with the influence field of neutron exchanges between meshes k, 1.ltoreq.k.ltoreq.K, adjacent to a mesh j (and including the latter) and mesh j. These predetermined coupling matrixes are calculated for a predetermined state of the core (also called reference medium), i.e. for predetermined interaction probabilities of the neutrons in the core. The terms .psi.g(j,k), 1.ltoreq.j.ltoreq.J and 1.ltoreq.k.ltoreq.K of the coupling matrixes [.psi.g] are defined by the following relation: ##EQU6## are the volumes of the meshes j and k and r=d(x.sub.j,x.sub.k) is the distance between a point x.sub.j of mesh j and a point x.sub.k of mesh k. The term .psi.g(r) represents the neutron flux in cm.sup.-2 at a point x.sub.j of mesh j at distance r=d(x.sub.j,x.sub.k) created by a source located at point x.sub.k of mesh k and emitting one neutron/second in accordance with a fission spectrum .chi..sub.g. The term .psi.g(j,k) represents the mean flux in mesh j produced by a source uniformly distributed in mesh k and emitting one neutron/second in accordance with the fission spectrum .chi..sub.g in the velocity group g. For a fission spectrum .chi..sub.g, the term .psi.g(r) can e.g. be determined in known manner on the basis of the ANISN transport code. The terms .psi.g(j,k) are then obtained by integration, which can introduce a certain imprecision in the values of terms .psi.g(j,k). It is possible to ensure that the values found are correct by proving that the equation: ##EQU7## is satisfied, which means that in the area formed by the K meshes, there is an absorption of one neutron (in the equation .SIGMA.a.sup.0,g is the effective macroscopic absorption section of the reference medium for group g). The first components of the neutron fluxes .phi..sup.0 (j,g).sup.(n) can be calculated on the basis of the coupling matrixes ].psi.g], notably according to the equation: ##EQU8## in which v.sub.k is the volume of mesh k. The predetermined interaction probabilities, i.e. associated with the reference medium are e.g. defined by predetermined values of the effective macroscopic sections .SIGMA.a.sup.0 (j,g), .SIGMA.s.sup.0 (j,g.fwdarw.g'), .SIGMA.t.sup.0 (j,g) and .SIGMA.f.sup.0 (j,g). Preferably .SIGMA.f.sup.0 (j,g) is chosen equal to zero. Each coefficient .psi.g(j,k) represents the flux in group g and mesh j, when one neutron is emitted per volume unit and time unit, in a homogeneous manner in mesh k in accordance with the fission spectrum, in a core for which the interaction probabilities of the neutrons are said predetermined interaction probabilities. The values are defined for each assembly type and are preferably chosen in such a way that the predetermined effective macroscopic sections are close to the real effective macroscopic sections in the core under normal operating conditions. This makes it possible to have a higher precision in the calculation of the neutron fluxes .phi.(j,g) and powers P(j). It is e.g. possible to choose a value for each predetermined effective macroscopic section equal to the mean value of the possible amplitude range for said effective macroscopic section. The following operation 20 of the process consists of evaluating second neutron flux components .phi..sup.1 (j,g).sup.(n) as a function of the real interaction probabilities of the neutrons in the core. In known manner, they are deduced from values of physical parameters describing the state of the core, the values of said physical parameters being in known manner either directly detectable by sensors, or evaluatable on the basis of indirect measurements. The generally known physical parameters are: (a) the position PBCq of each control rod q, 1.ltoreq.q.ltoreq.Q, in which Q is the total number of control rods, (b) the intake temperature .theta..sub.E of the cooling fluid into the core, (c) the pressure PR of the cooling fluid in the core, (d) the boron concentration C.sub.B in the core, (e) the total power P supplied by the core, (f) the description of the position of the assemblies of each type in the core and (g) the neutron fluxes .phi.(j,g).sup.(n-1) and the powers P(j).sup.(n-1) calculated at the preceding iteration instant n-1. On the basis of these physical parameters, it is possible to evaluate for each mesh j, a group of local parameters, such as: (a) the temperature of the fuel Tu(j), (b) the temperature of the cooling fluid .theta.(j), (c) the density of the cooling fluid (j), (d) the concentration Xe(j) in nuclei of .sub.54.sup.135 Xe, (e) the irradiation rate or the wear of the fuel I(j), (f) the state x.sub.m (j) (presence or absence) of a control rod of type m in mesh j, (g) a parameter p(j) characterizing the assemblies from the standpoint of their equivalent neutron properties (presence or absence of consumable poisons, initial .sub.92.sup.235 U enrichment, initial plutonium content, initial plutonium isotope composition, etc.). More specifically, the parameters Tu(j), .theta.(j) and (j) are calculated by relations expressing the thermal aspects of the fuel nucleus and the thermohydraulic aspects of the water in the rods on the basis of the physical parameters .theta..sub.E, PR, PBCq, P and powers P(j). The parameter Xe(j) is calculated on the basis of the neutron fluxes .phi.(j,g) by relations expressing the formation and disappearance of .sub.54.sup.135 Xe nuclei. The parameter I(j) is calculated by a time-based wear relationship. Reference can be made to the work "Nuclear Reactor Theory" by George I. Bell and Samuel Glasstone, Van Nostrand Reinhold Company for a description of methods for obtaining local parameters on the basis of physical parameters. The interaction probabilities of neutrons in the core, which can e.g. be defined by the effective macroscopic sections .SIGMA.s(j,g.fwdarw.g'), .SIGMA.a(j,g), .SIGMA.t(j,g) and .SIGMA.f(j,g), are then deduced in known manner from local parameters and the boron concentration C.sub.B. A method of calculating the effective macroscopic sections as a function of local parameters and C.sub.B is e.g. given in the document "Homogenization methods in reactor physics" issued by the International Atomic Energy Agency, Vienna, 1980. Following operation 20 relating to the evaluation of the effective real macroscopic sections, i.e. those corresponding to the effective values of the physical parameters of the core, in operation 22 second neutron flux components .phi..sup.1 (j,g).sup.(n) are calculated. The latter are expressed as a function of the first neutron flux component .phi..sup.0 (j,g).sup.(n), predetermined interaction probabilities of the neutrons in the core and real interaction probabilities of the neutrons in the core. For each mesh j, 1.ltoreq.j.ltoreq.J, this relation can be expressed by a linear system with G equations: ##EQU9## For each mesh, it is consequently a question of resolving a system of G equations with G unknowns .phi..sup.1 (j,g).sup.(n), 1.ltoreq.g.ltoreq.G. The number G of velocity groups is in general a few units. Thus, the linear system can be simply resolved by reversing the associated matrix of size G.times.G. Operations 18 and 22 respectively supply the first neutron flux components .phi..sup.0 (j,g).sup.(n) and the second neutron flux components .phi..sup.1 (j,g).sup.(n). The neutron fluxes .phi.(j,g).sup.(n) are then calculated as the sum of the first and second components by operation 24. In the particular case, which frequently occurs in practice, where the number of velocity groups is equal to 2 (G=2) and in which there is no rise of neutrons of group 2 (slow velocities) into group 1 (fast velocities) during a diffusion, the neutron fluxes .phi.(j,g).sup.(n) for velocities g=1 and g=2 can be more rapidly calculated in direct manner on the basis of first neutron flux components .phi..sup.0 (j,g).sup.(n) by the following expressions: ##EQU10## In the particular case where G=2, it is consequently not necessary to explicitly calculate the second neutron flux components .phi..sup.1 (j,g).sup.(n), so that operation 22 is eliminated. The knowledge of the neutron fluxes .phi.(j,g).sup.(n) makes it possible to evaluate th new values S(j).sup.(n) of the sources. Initially, operation 26 is used for determining new sources NS(j).sup.(n) as a function of the neutron fluxes .phi.(j,g).sup.(n) and effective fission section .SIGMA.f(j,g), according to relation: ##EQU11## in which .nu. is the mean number of new neutrons produced by one fission. Secondly (operation 28), an updated value is calculated of sources S(j) by: ##EQU12## From this is deduced by operation 30 the value of the power given off by each mesh j in accordance with relation: ##EQU13## Thus, at the end of operation 30, the neutron flux .phi.(j,g).sup.(n), the source S(j).sup.(n) and the power given off P(j).sup.(n) are obtained for each mesh j 1.ltoreq.j.ltoreq.J. A test 32 is then performed to determine whether there is convergence of the calculated values, or whether it is necessary to perform a new iteration. The test can e.g. apply to sources S(j) and to the multiplication rates of the neutrons in the core, said rate being defined by .lambda..sup.(n) =NS.sup.(n) /S.sup.(n-1). For the sources S(j), there is a comparison for each mesh j, of the relative increase .vertline.S(j).sup.(n) -S(j).sup.(n-1) /S(j).sup.(n-1) .vertline. with a constant factor .epsilon. having a value equal to e.g. 10.sup.-4. In the same way, there is a comparison of the increase of the multiplication rate .vertline.(.lambda..sup.(n) -.lambda..sup.(n-1))/.lambda..sup.(n-1) .vertline. with a constant factor .eta. having a value e.g. equal to 10.sup.-5. If the two comparisons indicate that there is convergence, the process is continued by operation 34. In the opposite case, operation 16 is repeated to start a new iteration. If convergence occurs, the values P(j).sup.(n) and .phi.(j,g).sup.(n) are respectively allocated to parameters P(j) and .phi.(j,g) (operation 34). These values are then used for controlling the core by acting on the position of the control rods and/or on the boron concentration. More specifically, the values P(j) and .phi.(j,g) make it possible to accurately evaluate the physical limits of the core and to compare them in conventional manner with thresholds respecting the safety criteria of the reactor. This comparison leads to an action on the control rods and/or the boron concentration and/or the transmission of an alarm signal. In the preceding description, the neutron sources only had neutrons directly resulting from fission. In practice, account can also be taken of sources formed from delayed neutrons. This only slightly modifies the equations defining the fluxes .phi..sup.0 (h,g), .phi..sup.1 (j,g) and the new sources NS(j). Thus, the kinetic case consists of taking into account the sources S.sub.k.sup.PREC linked with delayed neutron precursors and the flux variation term ##EQU14## in which v is the mean neutron velocity. In order to take account of delayed neutrons, it is necessary to introduce a time index m, the calculations being performed iteratively (n being the iteration index) at each time t equal to t.sub.0 +m..DELTA.t. The first flux component .phi..sup.0 (j,g).sup.(n,m) is defined by ##EQU15## in which .psi.g(j,k).sup.PREC represents the mean flux in mesh j for the velocity group g, associated with a source uniformly distributed in mesh k and emitting one neutron per second in accordance with the emission spectrum of the delayed neutron .chi..sub.g.sup.PREC. Thus, the first flux component appears as the sum of two fluxes, each produced by a particular neutron source. These sources are calculated by the following equations: ##EQU16## in which .beta. is the total number of delayed neutrons per fission neutron and ##EQU17## in which .lambda.i is the radioactive decay constant of the precursor and Ci(j).sup.(n,m) is the concentration of the precursor i in mesh j at instant t.sub.0 +m..DELTA.t and at iteration n. The second neutron flux component .phi..sup.1 (j,g).sup.(n,m) is obtained as in the preceding description by the resolution of a linear system: ##EQU18## in which .phi.(j,g).sup.(m-1) is the neutron flux obtained on time iteration m-1 and v.sub.g is the mean neutron velocity of the velocity group g. Finally, the new sources Nw(j).sup.(n,m) are defined by ##EQU19## |
043307116 | summary | BACKGROUND OF THE INVENTION The invention is directed to a container combination for the transportation and storage of irradiated fuel elements of nuclear reactors consisting of a removable inner container which also is usable by itself for the storage in correspondingly laid out fuel element storehouses and an outer container wherein the two containers in each case have their own cover. The previous practice is to store spent fuel elements in water basins. In this case the water has the task of shielding the radiocative radiation set free in the decay and to reliably transfer to the outside the simultaneously set free heat of decay. In this case there are expensive and costly precautions required to guarantee dependable cooling. Therefore there was also considered the dry storage of fuel elements. Thus, e.g. it has been proposed to tightly pack spent fuel elements in steel boxes, place the boxes individually in shielded cells in layered shafts and lead off the residual heat of the fuel elements from the surface of the box with ambient air by free convection. A disadvantage of this conception of storage is that the spent fuel elements must be unloaded at the storage place from the transportation container into the storage boxes. During the unloading the fuel elements are not protected, besides defective fuel rods must be reckoned with so that there is an increased risk of setting free activity and nuclear fuels. Therefore the reload operation must be remotely controlled and take place in a hot cell. The closing of the boxes and the control of the sealing likewise can only be carried out by remote control. An additional storage concept is described in Boldt U.S. Pat. No. 3,828,197. Here there are stored in the free air containers with high-level radioactive waste in thick walled metal containers having shielding covers. In this case also for unloading the container from the transportation container into the storage shielding a hot cell is required. This concept thus also has the same disadvantage as the previously described concept. A further concept therefore provides for further storage of the spent fuel elements in the container employed for the transportation. In this case an unloading of the fuel element at the storage place is not required. However, a disadvantage in this container storage is that the costly and expensive transportation container during the entire storage time cannot be employed for further transportation. This storage concept consequently is very capital expensive. Therefore there have also been described many times two part transporation containers consisting of an outer and an inner container, thus, e.g. in Blum German OS 2147133 a container combination of an inner container with shielding walls and cover for gamma rays and an outer container laid out as a pressure container. The annular gap between outer and inner container is filled with water as a medium for neutron shielding and for heat transfer. This combination container, however, has various disadvantages. Thus, e.g. in the loading in the nuclear power plant the inner container cannot remain in the outer container so that there exists the danger of contamination. Also the handling therefore deviates substantially from the loading of customary transportation containers which leads to difficulties with the loading devices and the loading personnel. The pressure container surrounds the thick walled .gamma. shielding and the neutron shielding. The thick walled gamma shielding does not contribute to the strength but in an accident acts as an additional load factor on the outer container. Water is necessary for the transfer of heat from the inner container to the outer container. In case of the loss of this water due to an accident the safety of the combination container is no longer guaranteed. There also exists the danger of the formation of radioactive hydrogen. In inserting the inner container as storage container the entire .gamma. shielding remains on the storage container. This places an additional load on the storage structure and increases the cost of the storage concept. Likewise in Lindsay U.S. Pat. No. 3,575,601 there is described a combination container consisting of an outer, shock resistant steel container and a plurality of shielding inserts. This container besides the previously described disadvantages has the further disadvantage that the inner insert as storage container additionally must be made tight at all places of connection of the shielding parts. Also in Smith, Jr. U.S. Pat. No. 2,935,616 there is described a multi-part container. It consists of outer shielding segments screwed together and a thin walled inner container. Since the inner container does not have a cover of its own, the insertion as storage container is not possible. Therefore it was the problem of the present invention to provide a combination container for the transportation and the storage of spent fuel elements from nuclear reactors, consisting of a removable inner container which is also usable for its own in correspondingly laid out fuel element storehouses, and an outer container, whereby both containers in each case has its own cover. This combination container should not have the above described disadvantages, especially the inner container should make possible a dry storage of spent fuel elememts without changing the fuel elements at the storage place in a storage box and without unnecessary squandoring of space and weight load. SUMMARY OF THE INVENTION This problem was solved according to the invention by providing a combination container in which (a) the bottom and the jacket of the outer container are so dimensioned in their thickness that they completely or preponderantly take care of the shielding function against gamma and neutron radiation, (b) the inner container is axially fixed in the outer container in such manner that the cover of the inner container and the cover of the outer container do not touch, (c) the radial position of the inner container in the outer container is fixed by a narrowing of the cross section of the inner space of the outer container proceeding downwardly to the bottom and (d) the outer wall of the inner container is made tight against the inner wall of the outer container through sealing elements. |
description | This application is a continuation-in-part of U.S. patent application Ser. No. 15/167,617 filed May 27, 2016, which is: a continuation-in-part of U.S. patent application Ser. No. 15/152,479 filed May 11, 2016, which: is a continuation-in-part of U.S. patent application Ser. No. 14/216,788 filed Mar. 17, 2014, which is a continuation-in-part of U.S. patent application Ser. No. 13/087,096 filed Apr. 14, 2011, which claims benefit of U.S. provisional patent application No. 61/324,776 filed Apr. 16, 2010; and is a continuation-in-part of U.S. patent application Ser. No. 13/788,890 filed Mar. 7, 2013; is a continuation-in-part of U.S. patent application Ser. No. 14/952,817 filed Nov. 25, 2015, which is a continuation-in-part of U.S. patent application Ser. No. 14/293,861 filed Jun. 2, 2014, which is a continuation-in-part of U.S. patent application Ser. No. 12/985,039 filed Jan. 5, 2011, which claims the benefit of U.S. provisional patent application No. 61/324,776, filed Apr. 16, 2010; is a continuation-in-part of U.S. patent application Ser. No. 14/860,577 filed Sep. 21, 2015, which is a continuation of U.S. patent application Ser. No. 14/223,289 filed Mar. 24, 2014, which is a continuation-in-part of U.S. patent application Ser. No. 14/216,788 filed Mar. 17, 2014, which is a continuation-in-part of U.S. patent application Ser. No. 12/985,039 filed Jan. 5, 2011, which claims the benefit of U.S. provisional patent application No. 61/324,776, filed Apr. 16, 2010; and is a continuation-in-part U.S. patent application Ser. No. 15/073,471 filed Mar. 17, 2016, which claims benefit of U.S. provisional patent application No. 62/304,839 filed Mar. 7, 2016, is a continuation-in-part of U.S. patent application Ser. No. 14/860,577 filed Sep. 21, 2015, which is a continuation of U.S. patent application Ser. No. 14/223,289 filed Mar. 24, 2014, which is a continuation-in-part of U.S. patent application Ser. No. 14/216,788 filed Mar. 17, 2014, which is a continuation-in-part of U.S. patent application Ser. No. 13/572,542 filed Aug. 10, 2012, which is a continuation-in-part of U.S. patent application Ser. No. 12/425,683 filed Apr. 17, 2009, which claims the benefit of U.S. provisional patent application No. 61/055,395 filed May 22, 2008, now U.S. Pat. No. 7,939,809 B2; all of which are incorporated herein in their entirety by this reference thereto. Field of the Invention The invention relates generally to extraction of an ion beam from an ion source. Discussion of the Prior Art Cancer Treatment Proton therapy works by aiming energetic ionizing particles, such as protons accelerated with a particle accelerator, onto a target tumor. These particles damage the DNA of cells, ultimately causing their death. Cancerous cells, because of their high rate of division and their reduced ability to repair damaged DNA, are particularly vulnerable to attack on their DNA. Patents related to the current invention are summarized here. Proton Beam Therapy System F. Cole, et. al. of Loma Linda University Medical Center “Multi-Station Proton Beam Therapy System”, U.S. Pat. No. 4,870,287 (Sep. 26, 1989) describe a proton beam therapy system for selectively generating and transporting proton beams from a single proton source and accelerator to a selected treatment room of a plurality of patient treatment rooms. Imaging P. Adamee, et. al. “Charged Particle Beam Apparatus and Method for Operating the Same”, U.S. Pat. No. 7,274,018 (Sep. 25, 2007) and P. Adamee, et. al. “Charged Particle Beam Apparatus and Method for Operating the Same”, U.S. Pat. No. 7,045,781 (May 16, 2006) describe a charged particle beam apparatus configured for serial and/or parallel imaging of an object. K. Hiramoto, et. al. “Ion Beam Therapy System and its Couch Positioning System”, U.S. Pat. No. 7,193,227 (Mar. 20, 2007) describe an ion beam therapy system having an X-ray imaging system moving in conjunction with a rotating gantry. C. Maurer, et. al. “Apparatus and Method for Registration of Images to Physical Space Using a Weighted Combination of Points and Surfaces”, U.S. Pat. No. 6,560,354 (May 6, 2003) described a process of X-ray computed tomography registered to physical measurements taken on the patient's body, where different body parts are given different weights. Weights are used in an iterative registration process to determine a rigid body transformation process, where the transformation function is used to assist surgical or stereotactic procedures. M. Blair, et. al. “Proton Beam Digital Imaging System”, U.S. Pat. No. 5,825,845 (Oct. 20, 1998) describe a proton beam digital imaging system having an X-ray source that is movable into a treatment beam line that can produce an X-ray beam through a region of the body. By comparison of the relative positions of the center of the beam in the patient orientation image and the isocentre in the master prescription image with respect to selected monuments, the amount and direction of movement of the patient to make the best beam center correspond to the target isocentre is determined. S. Nishihara, et. al. “Therapeutic Apparatus”, U.S. Pat. No. 5,039,867 (Aug. 13, 1991) describe a method and apparatus for positioning a therapeutic beam in which a first distance is determined on the basis of a first image, a second distance is determined on the basis of a second image, and the patient is moved to a therapy beam irradiation position on the basis of the first and second distances. Problem There exists in the art a need for reduced emittance in extraction of charged particles from an ion source, such as for increased precision of treatment of a tumor of a patient. The invention comprises an extraction of charged particles from an ion source apparatus and method of use thereof, such as for tumor therapy or tomographic imaging. Elements and steps in the figures are illustrated for simplicity and clarity and have not necessarily been rendered according to any particular sequence. For example, steps that are performed concurrently or in different order are illustrated in the figures to help improve understanding of embodiments of the present invention. The invention relates generally to extraction of charged particles from an ion source. The ion source extraction system facilitates on demand extraction of charged particles at relatively low voltage levels and from a stable ion source. For example, a triode extraction system allows extraction of charged particles, such as protons, from a maintained temperature plasma source, which reduces emittance of the extracted particles and allows use of lower, more maintainable downstream potentials to control an ion beam path of the extracted ions. The reduced emittance facilitates ion beam precision in applications, such as in imaging, tumor imaging, tomographic imaging, and/or cancer treatment. In another embodiment, a state of a charged particle beam is monitored and/or checked, such as against a previously established radiation plan, in a position just prior to the beam entering the patient. In one example, the charged particle beam state is measured after a final manipulation of intensity, energy, shape, and/or position, such as via use of an insert, a range filter, a collimator, an aperture, and/or a compensator. In one case, one or more beam crossing elements, sheets, coatings, or layers, configured to emit photons upon passage therethrough by the charged particle beam, are positioned between the final manipulation apparatus, such as the insert, and prior to entry into the patient. In another embodiment, a patient specific tray insert is inserted into a tray frame to form a beam control tray assembly, the beam control tray assembly is inserted into a slot of a tray receiver assembly, and the tray assembly is positioned relative to a gantry nozzle. Optionally, multiple tray inserts, each used to control a beam state parameter, are inserted into slots of the tray receiver assembly. The beam control tray assembling includes an identifier, such as an electromechanical identifier, of the particular insert type, which is communicated to a main controller, such as via the tray receiver assembly. Optionally and preferably, a hand control pendant is used in loading and/or positioning the tray receiver assembly. In another embodiment, a gantry positions both: (1) a section of a beam transport system, such as a terminal section, used to transport and direct positively charged particles to a tumor and (2) at least one imaging system. In one case, the imaging system is orientated on a same axis as the positively charged particle, such as at a different time through rotation of the gantry. In another case, the imaging system uses at least two crossing beamlines, each beamline coupled to a respective detector, to yield multiple views of the patient. In another case, one or more imaging subsystem yields a two-dimensional image of the patient, such as for position confirmation and/or as part of a set of images used to develop a three-dimensional image of the patient. In still another embodiment, multiple linked control stations are used to control position of elements of a beam transport system, nozzle, and/or patient specific beam shaping element relative to a dynamically controlled patient position and/or an imaging surface, element, or system. In yet another embodiment, a tomography system is optionally used in combination with a charged particle cancer therapy system. Optionally and preferably, a common injector, accelerator, and beam transport system is used for both charged particle based tomographic imaging and charged particle cancer therapy. In one case, an output nozzle of the beam transport system is positioned with a gantry system while the gantry system and/or a patient support maintains a scintillation plate of the tomography system on the opposite side of the patient from the output nozzle. In another example, a charged particle state determination system, of a cancer therapy system or tomographic imaging system, uses one or more coated layers in conjunction with a scintillation detector or a tomographic imaging system at time of tumor and surrounding tissue sample mapping and/or at time of tumor treatment, such as to determine an input vector of the charged particle beam into a patient and/or an output vector of the charged particle beam from the patient. In another example, the charged particle tomography apparatus is used in combination with a charged particle cancer therapy system. For example, tomographic imaging of a cancerous tumor is performed using charged particles generated with an injector, accelerator, and guided with a delivery system. The cancer therapy system uses the same injector, accelerator, and guided delivery system in delivering charged particles to the cancerous tumor. For example, the tomography apparatus and cancer therapy system use a common raster beam method and apparatus for treatment of solid cancers. More particularly, the invention comprises a multi-axis and/or multi-field raster beam charged particle accelerator used in: (1) tomography and (2) cancer therapy. Optionally, the system independently controls patient translation position, patient rotation position, two-dimensional beam trajectory, delivered radiation beam energy, delivered radiation beam intensity, beam velocity, timing of charged particle delivery, and/or distribution of radiation striking healthy tissue. The system operates in conjunction with a negative ion beam source, synchrotron, patient positioning, imaging, and/or targeting method and apparatus to deliver an effective and uniform dose of radiation to a tumor while distributing radiation striking healthy tissue. In another embodiment, a treatment delivery control system (TDCS) or main controller is used to control multiple aspects of the cancer therapy system, including one or more of: an imaging system, such as a CT or PET; a positioner, such as a couch or patient interface module; an injector or injection system; a radio-frequency quadrupole system; a ring accelerator or synchrotron; an extraction system; an irradiation plan; and a display system. The TDCS is preferably a control system for automated cancer therapy once the patient is positioned. The TDCS integrates output of one or more of the below described cancer therapy system elements with inputs of one or more of the below described cancer therapy system elements. More generally, the TDCS controls or manages input and/or output of imaging, an irradiation plan, and charged particle delivery. In yet another embodiment, one or more trays are inserted into the positively charged particle beam path, such as at or near the exit port of a gantry nozzle in close proximity to the patient. Each tray holds an insert, such as a patient specific insert for controlling the energy, focus depth, and/or shape of the charged particle beam. Examples of inserts include a range shifter, a compensator, an aperture, a ridge filter, and a blank. Optionally and preferably, each tray communicates a held and positioned insert to a main controller of the charged particle cancer therapy system. The trays optionally hold one or more of the imaging sheets configured to emit light upon transmission of the charged particle beam through a corresponding localized position of the one or more imaging sheets. Charged Particle Beam Therapy Throughout this document, a charged particle beam therapy system, such as a proton beam, hydrogen ion beam, or carbon ion beam, is described. Herein, the charged particle beam therapy system is described using a proton beam. However, the aspects taught and described in terms of a proton beam are not intended to be limiting to that of a proton beam and are illustrative of a charged particle beam system, a positively charged beam system, and/or a multiply charged particle beam system, such as C4+ or C6+. Any of the techniques described herein are equally applicable to any charged particle beam system. Referring now to FIG. 1A, a charged particle beam system 100 is illustrated. The charged particle beam preferably comprises a number of subsystems including any of: a main controller 110; an injection system 120; a synchrotron 130 that typically includes: (1) an accelerator system 131 and (2) an internal or connected extraction system 134; a beam transport system 135; a scanning/targeting/delivery system 140; a patient interface module 150; a display system 160; and/or an imaging system 170. An exemplary method of use of the charged particle beam system 100 is provided. The main controller 110 controls one or more of the subsystems to accurately and precisely deliver protons to a tumor of a patient. For example, the main controller 110 obtains an image, such as a portion of a body and/or of a tumor, from the imaging system 170. The main controller 110 also obtains position and/or timing information from the patient interface module 150. The main controller 110 optionally controls the injection system 120 to inject a proton into a synchrotron 130. The synchrotron typically contains at least an accelerator system 131 and an extraction system 134. The main controller 110 preferably controls the proton beam within the accelerator system, such as by controlling speed, trajectory, and timing of the proton beam. The main controller then controls extraction of a proton beam from the accelerator through the extraction system 134. For example, the controller controls timing, energy, and/or intensity of the extracted beam. The controller 110 also preferably controls targeting of the proton beam through the scanning/targeting/delivery system 140 to the patient interface module 150. One or more components of the patient interface module 150, such as translational and rotational position of the patient, are preferably controlled by the main controller 110. Further, display elements of the display system 160 are preferably controlled via the main controller 110. Displays, such as display screens, are typically provided to one or more operators and/or to one or more patients. In one embodiment, the main controller 110 times the delivery of the proton beam from all systems, such that protons are delivered in an optimal therapeutic manner to the tumor of the patient. Herein, the main controller 110 refers to a single system controlling the charged particle beam system 100, to a single controller controlling a plurality of subsystems controlling the charged particle beam system 100, or to a plurality of individual controllers controlling one or more sub-systems of the charged particle beam system 100. Referring now to FIG. 13A, a first example of an integrated cancer treatment—imaging system 1300 is illustrated. In this example, the charged particle beam system 100 is illustrated with a treatment beam 269 directed to the tumor 720 of the patient 730 along the z-axis. Also illustrated is a set of imaging sources 1310, imaging system elements, and/or paths therefrom and a set of detectors 1320 corresponding to a respective element of the set of imaging sources 1310. Herein, the set of imaging sources 1310 are referred to as sources, but are optionally any point or element of the beam train prior to the tumor or a center point about which the gantry rotates. Hence, a given imaging source is optionally a dispersion element used to for cone beam. As illustrated, a first imaging source 1312 yields a first beam path 1332 and a second imaging source 1314 yields a second beam path 1334, where each path passes at least into the tumor 720 and optionally and preferably to a first detector array 1322 and a second detector array 1324, respectively, of the set of detectors 1320. Herein, the first beam path 1332 and the second beam path 1334 are illustrated as forming a ninety degree angle, which yields complementary images of the tumor 720 and/or the patient 730. However, the formed angle is optionally any angle from ten to three hundred fifty degrees. Herein, for clarity of presentation, the first beam path 1332 and the second beam path 1334 are illustrated as single lines, which optionally is an expanding, uniform diameter, or focusing beam. Herein, the first beam path 1332 and the second beam path 1334 are illustrated in transmission mode with their respective sources and detectors on opposite sides of the patient 730. However, a beam path from a source to a detector is optionally a scattered path and/or a diffuse reflectance path. Optionally, one or more detectors of the set of detectors 1320 are a single detector element, a line of detector elements, or preferably a two-dimensional detector array. Use of two two-dimensional detector arrays is referred to herein as a two-dimensional—two-dimensional imaging system or a 2D-2D imaging system. Still referring to FIG. 13A, the first imaging source 1312 and the second imaging source 1314 are illustrated at a first position and a second position, respectively. Each of the first imaging source 1312 and the second imaging source 1322 optionally: (1) maintain a fixed position; (2) provide the first beam path 1332 and the second beam path 1334, respectively, through the gantry 960, such as through a set of one or more holes or slits; (3) provide the first beam path 1332 and the second beam path 1334, respectively, off axis to a plane of movement of the nozzle system 760; (4) move with the gantry 960 as the gantry 960 rotates about at least a first axis; and/or (5) represent a narrow cross-diameter section of an expanding cone beam path. Still referring to FIG. 13A, the set of detectors 1320 are illustrated as coupling with respective elements of the set of sources 1310. Each member of the set of detectors 1320 optionally and preferably co-moves/and/or co-rotates with a respective member of the set of sources 1310. Thus, if the first imaging source 1312 is statically positioned, then the first detector 1322 is optionally and preferably statically positioned. Similarly, to facilitate imaging, if the first imaging source 1312 moves along a first arc as the gantry 960 moves, then the first detector 1322 optionally and preferably moves along the first arc or a second arc as the gantry 960 moves, where relative positions of the first imaging source 1312 on the first arc, a point that the gantry 960 moves about, and relative positions of the first detector 1322 along the second arc are constant. To facilitate the process, the detectors are optionally mechanically linked, such as with a first mechanical support 1342 to the gantry 960 in a manner that when the gantry 960 moves, the gantry moves both the source and the corresponding detector. Optionally, the source moves and a series of detectors, such as along the second arc, capture a set of images. Still referring to FIG. 13A, optionally and preferably, elements of the set of sources 1310 combined with elements of the set of detectors 1320 are used to collect a series of responses, such as one source and one detector yielding a detected intensity and preferably a set of detected intensities to form an image. For instance, the first imaging source 1312, such as a first X-ray source or first cone beam X-ray source, and the first detector 1322, such as an X-ray film, digital X-ray detector, or two-dimensional detector, yield a first X-ray image of the patient at a first time and a second X-ray image of the patient at a second time, such as to confirm a maintained location of a tumor or after movement of the gantry 760 or rotation of the patient 730. A set of n images using the first imaging source 1312 and the first detector 1322 collected as a function of movement of the gantry 760 and/or as a function of movement and/or rotation of the patient 730 are optionally and preferably combined to yield a three-dimensional image of the patient 730, such as a three-dimensional X-ray image of the patient 730, where n is a positive integer, such as greater than 1, 2, 3, 4, 5, 10, 15, 25, 50, or 100. The set of n images is optionally gathered as described in combination with images gathered using the second imaging source 1314, such as a second X-ray source or second cone beam X-ray source, and the second detector 1324, such as a second X-ray detector, where the use of two, or multiple, source/detector combinations are combined to yield images where the patient 730 has not moved between images as the two, or the multiple, images are optionally and preferably collected at the same time, such as with a difference in time of less than 0.01, 0.1, 1, or 5 seconds. Longer time differences are optionally used. Preferably the n two-dimensional images are collected as a function of rotation of the gantry 960 about the tumor and/or the patient and/or as a function of rotation of the patient 730 and the two-dimensional images of the X-ray cone beam are mathematically combined to form a three-dimensional image of the tumor 720 and/or the patient 730. Optionally, the first X-ray source and/or the second X-ray source is the source of X-rays that are divergent forming a cone through the tumor. A set of images collected as a function of rotation of the divergent X-ray cone around the tumor with a two-dimensional detector that detects the divergent X-rays transmitted through the tumor is used to form a three-dimensional X-ray of the tumor and of a portion of the patient, such as in X-ray computed tomography. Still referring to FIG. 13A, use of two imaging sources and two detectors set at ninety degrees to one another allows the gantry 960 or the patient 730 to rotate through half an angle required using only one imaging source and detector combination. A third imaging source/detector combination allows the three imaging source/detector combination to be set at sixty degree intervals allowing the imaging time to be cut to that of one-third that gantry 960 or patient 730 rotation required using a single imaging source-detector combination. Generally, n source-detector combinations reduces the time and/or the rotation requirements to 1/n. Further reduction is possible if the patient 730 and the gantry 960 rotate in opposite directions. Generally, the used of multiple source-detector combination of a given technology allow for a gantry that need not rotate through as large of an angle, with dramatic engineering benefits. Still referring to FIG. 13A, the set of sources 1310 and set of detectors 1320 optionally use more than one imaging technology. For example, a first imaging technology uses X-rays, a second used fluoroscopy, a third detects fluorescence, a fourth uses cone beam computed tomography or cone beam CT, and a fifth uses other electromagnetic waves. Optionally, the set of sources 1310 and the set of detectors 1320 use two or more sources and/or two or more detectors of a given imaging technology, such as described supra with two X-ray sources to n X-ray sources. Still referring to FIG. 13A, use of one or more of the set of sources 1310 and use of one or more of the set of detectors 1320 is optionally coupled with use of the positively charged particle tomography system described supra. As illustrated in FIG. 13A, the positively charged particle tomography system uses a second mechanical support 1343 to co-rotate the scintillation plate 710 with the gantry 960, as well as to co-rotate an optional sheet, such as the first sheet 760 and/or the fourth sheet 790. Referring now to FIG. 1B, an example of a charged particle cancer therapy system 100 is provided. A main controller receives input from one, two, three, or four of a respiration monitoring and/or controlling controller 180, a beam controller 185, a rotation controller 147, and/or a timing to a time period in a respiration cycle controller 148. The beam controller 185 preferably includes one or more or a beam energy controller 182, the beam intensity controller 340, a beam velocity controller 186, and/or a horizontal/vertical beam positioning controller 188. The main controller 110 controls any element of the injection system 120; the synchrotron 130; the scanning/targeting/delivery system 140; the patient interface module 150; the display system 160; and/or the imaging system 170. For example, the respiration monitoring/controlling controller 180 controls any element or method associated with the respiration of the patient; the beam controller 185 controls any of the elements controlling acceleration and/or extraction of the charged particle beam; the rotation controller 147 controls any element associated with rotation of the patient 830 or gantry; and the timing to a period in respiration cycle controller 148 controls any aspects affecting delivery time of the charged particle beam to the patient. As a further example, the beam controller 185 optionally controls any magnetic and/or electric field about any magnet in the charged particle cancer therapy system 100. One or more beam state sensors 190 sense position, direction, intensity, and/or energy of the charged particles at one or more positions in the charged particle beam path. A tomography system 700, described infra, is optionally used to monitor intensity and/or position of the charged particle beam. Referring now to FIG. 1C, an illustrative exemplary embodiment of one version of the charged particle beam system 100 is provided. The number, position, and described type of components is illustrative and non-limiting in nature. In the illustrated embodiment, the injection system 120 or ion source or charged particle beam source generates protons. The injection system 120 optionally includes one or more of: a negative ion beam source, an ion beam focusing lens, and a tandem accelerator. The protons are delivered into a vacuum tube that runs into, through, and out of the synchrotron. The generated protons are delivered along an initial path 262. Optionally, focusing magnets 127, such as quadrupole magnets or injection quadrupole magnets, are used to focus the proton beam path. A quadrupole magnet is a focusing magnet. An injector bending magnet 128 bends the proton beam toward a plane of the synchrotron 130. The focused protons having an initial energy are introduced into an injector magnet 129, which is preferably an injection Lamberson magnet. Typically, the initial beam path 262 is along an axis off of, such as above, a circulating plane of the synchrotron 130. The injector bending magnet 128 and injector magnet 129 combine to move the protons into the synchrotron 130. Main bending magnets, dipole magnets, turning magnets, or circulating magnets 132 are used to turn the protons along a circulating beam path 264. A dipole magnet is a bending magnet. The main bending magnets 132 bend the initial beam path 262 into a circulating beam path 264. In this example, the main bending magnets 132 or circulating magnets are represented as four sets of four magnets to maintain the circulating beam path 264 into a stable circulating beam path. However, any number of magnets or sets of magnets are optionally used to move the protons around a single orbit in the circulation process. The protons pass through an accelerator 133. The accelerator accelerates the protons in the circulating beam path 264. As the protons are accelerated, the fields applied by the magnets are increased. Particularly, the speed of the protons achieved by the accelerator 133 are synchronized with magnetic fields of the main bending magnets 132 or circulating magnets to maintain stable circulation of the protons about a central point or region 136 of the synchrotron. At separate points in time the accelerator 133/main bending magnet 132 combination is used to accelerate and/or decelerate the circulating protons while maintaining the protons in the circulating path or orbit. An extraction element of an inflector/deflector system is used in combination with a Lamberson extraction magnet 137 to remove protons from their circulating beam path 264 within the synchrotron 130. One example of a deflector component is a Lamberson magnet. Typically the deflector moves the protons from the circulating plane to an axis off of the circulating plane, such as above the circulating plane. Extracted protons are preferably directed and/or focused using an extraction bending magnet 142 and optional extraction focusing magnets 141, such as quadrupole magnets, and optional bending magnets along a positively charged particle beam transport path 268 in a beam transport system 135, such as a beam path or proton beam path, into the scanning/targeting/delivery system 140. Two components of a scanning system 140 or targeting system typically include a first axis control 143, such as a vertical control, and a second axis control 144, such as a horizontal control. In one embodiment, the first axis control 143 allows for about 100 mm of vertical or y-axis scanning of the proton beam 268 and the second axis control 144 allows for about 700 mm of horizontal or x-axis scanning of the proton beam 268. A nozzle system 146 is used for imaging the proton beam, for defining shape of the proton beam, and/or as a vacuum barrier between the low pressure beam path of the synchrotron and the atmosphere. Protons are delivered with control to the patient interface module 150 and to a tumor of a patient. All of the above listed elements are optional and may be used in various permutations and combinations. Ion Extraction from Ion Source A method and apparatus are described for extraction of ions from an ion source. For clarity of presentation and without loss of generality, examples focus on extraction of protons from the ion source. However, more generally cations of any charge are optionally extracted from a corresponding ion source with the techniques described herein. For instance, C4+ or C6+ are optionally extracted using the ion extraction methods and apparatus described herein. Further, by reversing polarity of the system, anions are optionally extracted from an anion source, where the anion is of any charge. Herein, for clarity of presentation and without loss of generality, ion extraction is coupled with tumor treatment and/or tumor imaging. However, the ion extraction is optional used in any method or apparatus using a stream or time discrete bunches of ions. Diode Extraction Referring now to FIG. 2A and FIG. 2B, a first ion extraction system is illustrated. The first ion extraction system uses a diode extraction system 200, where a first element of the diode extraction system is an ion source 122 or first electrode at a first potential and a second element 202 of the diode extraction system is at a second potential. Generally, the first potential is raised or lowered relative to the second potential to extract ions from the ion source 122 along the z-axis or the second potential is raised or lowered relative to the first potential to extract ions from the ion source 122 along the z-axis, where polarity of the potential difference determines if anions or cations are extracted from the ion source 122. Still referring to FIG. 2A and FIG. 2B, an example of ion extraction from the ion source 122 is described. As illustrated in FIG. 2A, in a non-extraction time period, a non-extraction diode potential, A1, of the ion source 122 is held at a potential equal to a potential, B1, of the second element 202. Referring now to FIG. 2B, during an extraction time period, a diode extraction potential, A2, of the ion source 122 is raised, causing a positively charged cation, such as the proton, to be drawn out of the ion chamber toward the lower potential of the second element 202. Similarly, if the diode extraction potential, A2, of the ion source is lowered relative a potential, B1, then an anion is extracted from the ion source 122 toward a higher potential of the second element 202. In the diode extraction system 200, the voltage of a large mass and corresponding large capacitance of the ion source 122 is raised or lowered, which takes time, has an RC time constant, and results in a range of temperatures of the plasma during the extraction time period, which is typically pulsed on and off with time. Particularly, as the potential of the ion source 122 is cycled with time, the ion source 122 temperature cycles, which results in a range of emittance values, resultant from conservation of momentum, and a corresponding less precise extraction beam. Alternatively, potential of the second element 202 is varied, altered, pulsed, or cycled, which reduces a range of emittance values during the extraction process. Triode Extraction Referring now to FIG. 2C and FIG. 2D, a second ion extraction system is illustrated. The second ion extraction system uses a triode extraction system 210. The triode extraction system 210 uses: (1) an ion source 122, (2) a gating electrode 204 also referred to as a suppression electrode, and (3) an extraction electrode 206. Optionally, a first electrode of the triode extraction system 210 is positioned proximate the ion source 122 and is maintained at a potential as described, infra, using the ion source as the first electrode of the triode extraction system. Generally, potential of the gating electrode 204 is raised and lowered to, as illustrated, stop and start extraction of a positive ion. Varying the potential of the gating electrode 204 has the advantages of altering the potential of a small mass with a correspondingly small capacitance and small RC time constant, which via conservation of momentum, reduces emittance of the extracted ions. Optionally, a first electrode maintained at the first potential of the ion source is used as the first element of the triode extraction system in place of the ion source 122 while also optionally further accelerating and/or focusing the extracted ions or set of ions using the extraction electrode 206. Several example further describe the triode extraction system 210. Referring now to FIG. 13B, a second example of the integrated cancer treatment—imaging system 1300 is illustrated using greater than three imagers. Still referring to FIG. 13B, two pairs of imaging systems are illustrated. Particularly, the first and second imaging source 1312, 1314 coupled to the first and second detectors 1322, 1324 are as described supra. For clarity of presentation and without loss of generality, the first and second imaging systems are referred to as a first X-ray imaging system and a second X-ray imaging system. The second pair of imaging systems uses a third imaging source 1316 coupled to a third detector 1326 and a fourth imaging source 1318 coupled to a fourth detector 1328 in a manner similar to the first and second imaging systems described in the previous example. Here, the second pair of imaging systems optionally and preferably uses a second imaging technology, such as fluoroscopy. Optionally, the second pair of imaging systems is a single unit, such as the third imaging source 1318 couple to the third detector 1328, and not a pair of units. Optionally, one or more of the set of imaging sources 1310 are statically positioned while one of more of the set of imaging sources 1310 co-rotate with the gantry 960. Pairs of imaging sources/detector optionally have common and distinct distances, such as a first distance, d1, such as for a first source-detector pair and a second distance, d2, such as for a second source-detector or second source-detector pair. As illustrated, the tomography detector or the scintillation plate 710 is at a third distance, d3. The distinct differences allow the source-detector elements to rotate on a separate rotation system at a rate different from rotation of the gantry 960, which allows collection of a full three-dimensional image while tumor treatment is proceeding with the positively charged particles. For clarity of presentation, referring now to FIG. 13C, any of the beams or beam paths described herein is optionally a cone beam 1390 as illustrated. The patient support 152 is an mechanical and/or electromechanical device used to position, rotate, and/or constrain any portion of the tumor 720 and/or the patient 730 relative to any axis. Still yet another embodiment includes any combination and/or permutation of any of the elements described herein. The main controller, a localized communication apparatus, and/or a system for communication of information optionally comprises one or more subsystems stored on a client. The client is a computing platform configured to act as a client device or other computing device, such as a computer, personal computer, a digital media device, and/or a personal digital assistant. The client comprises a processor that is optionally coupled to one or more internal or external input device, such as a mouse, a keyboard, a display device, a voice recognition system, a motion recognition system, or the like. The processor is also communicatively coupled to an output device, such as a display screen or data link to display or send data and/or processed information, respectively. In one embodiment, the communication apparatus is the processor. In another embodiment, the communication apparatus is a set of instructions stored in memory that is carried out by the processor. The client includes a computer-readable storage medium, such as memory. The memory includes, but is not limited to, an electronic, optical, magnetic, or another storage or transmission data storage medium capable of coupling to a processor, such as a processor in communication with a touch-sensitive input device linked to computer-readable instructions. Other examples of suitable media include, for example, a flash drive, a CD-ROM, read only memory (ROM), random access memory (RAM), an application-specific integrated circuit (ASIC), a DVD, magnetic disk, an optical disk, and/or a memory chip. The processor executes a set of computer-executable program code instructions stored in the memory. The instructions may comprise code from any computer-programming language, including, for example, C originally of Bell Laboratories, C++, C#, Visual Basic® (Microsoft, Redmond, Wash.), Matlab® (MathWorks, Natick, Mass.), Java® (Oracle Corporation, Redwood City, Calif.), and JavaScript® (Oracle Corporation, Redwood City, Calif.). Herein, any number, such as 1, 2, 3, 4, 5, is optionally more than the number, less than the number, or within 1, 2, 5, 10, 20, or 50 percent of the number. The particular implementations shown and described are illustrative of the invention and its best mode and are not intended to otherwise limit the scope of the present invention in any way. Indeed, for the sake of brevity, conventional manufacturing, connection, preparation, and other functional aspects of the system may not be described in detail. Furthermore, the connecting lines shown in the various figures are intended to represent exemplary functional relationships and/or physical couplings between the various elements. Many alternative or additional functional relationships or physical connections may be present in a practical system. In the foregoing description, the invention has been described with reference to specific exemplary embodiments; however, it will be appreciated that various modifications and changes may be made without departing from the scope of the present invention as set forth herein. The description and figures are to be regarded in an illustrative manner, rather than a restrictive one and all such modifications are intended to be included within the scope of the present invention. Accordingly, the scope of the invention should be determined by the generic embodiments described herein and their legal equivalents rather than by merely the specific examples described above. For example, the steps recited in any method or process embodiment may be executed in any order and are not limited to the explicit order presented in the specific examples. Additionally, the components and/or elements recited in any apparatus embodiment may be assembled or otherwise operationally configured in a variety of permutations to produce substantially the same result as the present invention and are accordingly not limited to the specific configuration recited in the specific examples. Benefits, other advantages and solutions to problems have been described above with regard to particular embodiments; however, any benefit, advantage, solution to problems or any element that may cause any particular benefit, advantage or solution to occur or to become more pronounced are not to be construed as critical, required or essential features or components. As used herein, the terms “comprises”, “comprising”, or any variation thereof, are intended to reference a non-exclusive inclusion, such that a process, method, article, composition or apparatus that comprises a list of elements does not include only those elements recited, but may also include other elements not expressly listed or inherent to such process, method, article, composition or apparatus. Other combinations and/or modifications of the above-described structures, arrangements, applications, proportions, elements, materials or components used in the practice of the present invention, in addition to those not specifically recited, may be varied or otherwise particularly adapted to specific environments, manufacturing specifications, design parameters or other operating requirements without departing from the general principles of the same. Although the invention has been described herein with reference to certain preferred embodiments, one skilled in the art will readily appreciate that other applications may be substituted for those set forth herein without departing from the spirit and scope of the present invention. Accordingly, the invention should only be limited by the Claims included below. In a fourth example, the gantry comprises at least two imaging devices, where each imaging device moves with rotation of the gantry and where the two imaging devices view the patient 730 along two axes forming an angle of ninety degrees, in the range of eighty-five to ninety-five degrees, and/or in the range of seventy-five to one hundred five degrees. Pendant Referring still to FIG. 12A and referring now to FIG. 12B, a pendant system 1250, such as a system using the external pendant 1216 and/or internal pendent 1218 is described. In a first case, the external pendant 1216 and internal pendant 1218 have identical controls. In a second case, controls and/or functions of the external pendant 1216 intersect with controls and/or function of the internal pendant 1218. Particular processes and functions of the internal pendant 1218 are provided below, without loss of generality, to facilitate description of the external and internal pendants 1216, 1218. The internal pendant 1218 optionally comprises any number of input buttons, screens, tabs, switches, or the like. The pendant system 1250 is further described, infra. Still referring to FIG. 2C and FIG. 2D, a fifth example of using the triode extraction system 210 with varying types of ion sources is provided. The triode extraction system 210 is optionally used with an electron cyclotron resonance (ECR) ion source, a dual plasmatron ion source, an indirectly heated cathode ion source, a Freeman type ion source, or a Bernas type ion source. Herein, for clarity of presentation and without loss of generality, the triode extraction system 210 is integrated with an electron cyclotron resonance source. Generally, the electron resonance source generates an ionized plasma by heating or superimposing a static magnetic field and a high-frequency electromagnetic field at an electron cyclotron resonance frequency, which functions to form a localized plasma, where the heating power is optionally varied to yield differing initial energy levels of the ions. As the electron resonance source: (1) moves ions in an arc in a given direction and (2) is tunable in temperature, described infra, emittance of the electron resonance source is low and has an initial beam in a same mean cycling or arc following direction. The temperature of the electron cyclotron resonance ion source is optionally controlled through an external input, such as a tunable or adjustable microwave power, a controllable and variable gas pressure, and/or a controllable and alterable arc voltage. The external input allows the plasma density in the electron cyclotron resonance source to be controlled. In a sixth example, an electron resonance source is the ion source 122 of the triode extraction system 210. Optionally and preferably, the gating electrode 204 of the triode extraction system is oscillated, such as from about the ion source potential toward the extraction electrode potential, which is preferably grounded. In this manner, the extracted electron beam along the initial path 262 is bunches of ions that have peak intensities alternating with low or zero intensities, such as in an AC wave as opposed to a continuous beam, such as a DC wave. Still referring to FIG. 2C and FIG. 2D, optionally and preferably geometries of the gating electrode 204 and/or the extraction electrode 206 are used to focus the extracted ions along the initial ion beam path 262. Still referring to FIG. 2C and FIG. 2D, the lower emittance of the electron cyclotron resonance triode extraction system is optionally and preferably coupled with a downbeam or downstream radio-frequency quadrupole, used to focus the beam, and/or a synchrotron, used to accelerate the beam. Still referring to FIG. 2C and FIG. 2D, the lower emittance of the electron cyclotron resonance triode extraction system is maintained through the synchrotron 130 and to the tumor of the patient resulting in a more accurate, precise, smaller, and/or tighter treatment voxel of the charged particle beam or charged particle pulse striking the tumor. Still referring to FIG. 2C and FIG. 2D, the lower emittance of the electron cyclotron resonance triode extraction system reduces total beam spread through the synchrotron 130 and the tumor to one or more imaging elements, such as an optical imaging sheet or scintillation plate emitting photons upon passage of the charged particle beam or striking of the charged particle beam, respectively. The lower emittance of the charged particle beam, optionally and preferably maintained through the accelerator system 134 and beam transport system yields a tighter, more accurate, more precise, and/or smaller particle beam or particle burst diameter at the imaging surfaces and/or imaging elements, which facilitates more accurate and precise tumor imaging, such as for subsequent tumor treatment or to adjust, while the patient waits in a treatment position, the charged particle treatment beam position. Any feature or features of any of the above provided examples are optionally and preferably combined with any feature described in other examples provided, supra, or herein. Ion Extraction from Accelerator Referring now to FIG. 3, both: (1) an exemplary proton beam extraction system 300 from the synchrotron 130 and (2) a charged particle beam intensity control system 305 are illustrated. For clarity, FIG. 3 removes elements represented in FIG. 1C, such as the turning magnets, which allows for greater clarity of presentation of the proton beam path as a function of time. Generally, protons are extracted from the synchrotron 130 by slowing the protons. As described, supra, the protons were initially accelerated in a circulating path, which is maintained with a plurality of main bending magnets 132. The circulating path is referred to herein as an original central beamline 264. The protons repeatedly cycle around a central point in the synchrotron 136. The proton path traverses through a radio frequency (RF) cavity system 310. To initiate extraction, an RF field is applied across a first blade 312 and a second blade 314, in the RF cavity system 310. The first blade 312 and second blade 314 are referred to herein as a first pair of blades. In the proton extraction process, an RF voltage is applied across the first pair of blades, where the first blade 312 of the first pair of blades is on one side of the circulating proton beam path 264 and the second blade 314 of the first pair of blades is on an opposite side of the circulating proton beam path 264. The applied RF field applies energy to the circulating charged-particle beam. The applied RF field alters the orbiting or circulating beam path slightly of the protons from the original central beamline 264 to an altered circulating beam path 265. Upon a second pass of the protons through the RF cavity system, the RF field further moves the protons off of the original proton beamline 264. For example, if the original beamline is considered as a circular path, then the altered beamline is slightly elliptical. The frequency of the applied RF field is timed to apply outward or inward movement to a given band of protons circulating in the synchrotron accelerator. Orbits of the protons are slightly more off axis compared to the original circulating beam path 264. Successive passes of the protons through the RF cavity system are forced further and further from the original central beamline 264 by altering the direction and/or intensity of the RF field with each successive pass of the proton beam through the RF field. Timing of application of the RF field and/or frequency of the RF field is related to the circulating charged particles circulation pathlength in the synchrotron 130 and the velocity of the charged particles so that the applied RF field has a period, with a peak-to-peak time period, equal to a period of time of beam circulation in the synchrotron 130 about the center 136 or an integer multiple of the time period of beam circulation about the center 136 of the synchrotron 130. Alternatively, the time period of beam circulation about the center 136 of the synchrotron 130 is an integer multiple of the RF period time. The RF period is optionally used to calculated the velocity of the charged particles, which relates directly to the energy of the circulating charged particles. The RF voltage is frequency modulated at a frequency about equal to the period of one proton cycling around the synchrotron for one revolution or at a frequency than is an integral multiplier of the period of one proton cycling about the synchrotron. The applied RF frequency modulated voltage excites a betatron oscillation. For example, the oscillation is a sine wave motion of the protons. The process of timing the RF field to a given proton beam within the RF cavity system is repeated thousands of times with each successive pass of the protons being moved approximately one micrometer further off of the original central beamline 264. For clarity, the approximately 1000 changing beam paths with each successive path of a given band of protons through the RF field are illustrated as the altered beam path 265. The RF time period is process is known, thus energy of the charged particles at time of hitting the extraction material or material 330, described infra, is known. With a sufficient sine wave betatron amplitude, the altered circulating beam path 265 touches and/or traverses a material 330, such as a foil or a sheet of foil. The foil is preferably a lightweight material, such as beryllium, a lithium hydride, a carbon sheet, or a material having low nuclear charge components. Herein, a material of low nuclear charge is a material composed of atoms consisting essentially of atoms having six or fewer protons. The foil is preferably about 10 to 150 microns thick, is more preferably about 30 to 100 microns thick, and is still more preferably about 40 to 60 microns thick. In one example, the foil is beryllium with a thickness of about 50 microns. When the protons traverse through the foil, energy of the protons is lost and the speed of the protons is reduced. Typically, a current is also generated, described infra. Protons moving at the slower speed travel in the synchrotron with a reduced radius of curvature 266 compared to either the original central beamline 264 or the altered circulating path 265. The reduced radius of curvature 266 path is also referred to herein as a path having a smaller diameter of trajectory or a path having protons with reduced energy. The reduced radius of curvature 266 is typically about two millimeters less than a radius of curvature of the last pass of the protons along the altered proton beam path 265. The thickness of the material 330 is optionally adjusted to create a change in the radius of curvature, such as about ½, 1, 2, 3, or 4 mm less than the last pass of the protons 265 or original radius of curvature 264. The reduction in velocity of the charged particles transmitting through the material 330 is calculable, such as by using the pathlength of the betatron oscillating charged particle beam through the material 330 and/or using the density of the material 330. Protons moving with the smaller radius of curvature travel between a second pair of blades. In one case, the second pair of blades is physically distinct and/or is separated from the first pair of blades. In a second case, one of the first pair of blades is also a member of the second pair of blades. For example, the second pair of blades is the second blade 314 and a third blade 316 in the RF cavity system 310. A high voltage DC signal, such as about 1 to 5 kV, is then applied across the second pair of blades, which directs the protons out of the synchrotron through an extraction magnet 137, such as a Lamberson extraction magnet, into a transport path 268. Control of acceleration of the charged particle beam path in the synchrotron with the accelerator and/or applied fields of the turning magnets in combination with the above described extraction system allows for control of the intensity of the extracted proton beam, where intensity is a proton flux per unit time or the number of protons extracted as a function of time. For example, when a current is measured beyond a threshold, the RF field modulation in the RF cavity system is terminated or reinitiated to establish a subsequent cycle of proton beam extraction. This process is repeated to yield many cycles of proton beam extraction from the synchrotron accelerator. In another embodiment, instead of moving the charged particles to the material 330, the material 330 is mechanically moved to the circulating charged particles. Particularly, the material 330 is mechanically or electromechanically translated into the path of the circulating charged particles to induce the extraction process, described supra. In this case, the velocity or energy of the circulating charged particle beam is calculable using the pathlength of the beam path about the center 136 of the synchrotron 130 and from the force applied by the bending magnets 132. In either case, because the extraction system does not depend on any change in magnetic field properties, it allows the synchrotron to continue to operate in acceleration or deceleration mode during the extraction process. Stated differently, the extraction process does not interfere with synchrotron acceleration. In stark contrast, traditional extraction systems introduce a new magnetic field, such as via a hexapole, during the extraction process. More particularly, traditional synchrotrons have a magnet, such as a hexapole magnet, that is off during an acceleration stage. During the extraction phase, the hexapole magnetic field is introduced to the circulating path of the synchrotron. The introduction of the magnetic field necessitates two distinct modes, an acceleration mode and an extraction mode, which are mutually exclusive in time. The herein described system allows for acceleration and/or deceleration of the proton during the extraction step and tumor treatment without the use of a newly introduced magnetic field, such as by a hexapole magnet. Charged Particle Beam Intensity Control Control of applied field, such as a radio-frequency (RF) field, frequency and magnitude in the RF cavity system 310 allows for intensity control of the extracted proton beam, where intensity is extracted proton flux per unit time or the number of protons extracted as a function of time. Still referring FIG. 3, the intensity control system 305 is further described. In this example, an intensity control feedback loop is added to the extraction system, described supra. When protons in the proton beam hit the material 330 electrons are given off from the material 330 resulting in a current. The resulting current is converted to a voltage and is used as part of an ion beam intensity monitoring system or as part of an ion beam feedback loop for controlling beam intensity. The voltage is optionally measured and sent to the main controller 110 or to an intensity controller subsystem 340, which is preferably in communication or under the direction of the main controller 110. More particularly, when protons in the charged particle beam path pass through the material 330, some of the protons lose a small fraction of their energy, such as about one-tenth of a percent, which results in a secondary electron. That is, protons in the charged particle beam push some electrons when passing through material 330 giving the electrons enough energy to cause secondary emission. The resulting electron flow results in a current or signal that is proportional to the number of protons going through the target or extraction material 330. The resulting current is preferably converted to voltage and amplified. The resulting signal is referred to as a measured intensity signal. The amplified signal or measured intensity signal resulting from the protons passing through the material 330 is optionally used in monitoring the intensity of the extracted protons and is preferably used in controlling the intensity of the extracted protons. For example, the measured intensity signal is compared to a goal signal, which is predetermined in an irradiation of the tumor plan. The difference between the measured intensity signal and the planned for goal signal is calculated. The difference is used as a control to the RF generator. Hence, the measured flow of current resulting from the protons passing through the material 330 is used as a control in the RF generator to increase or decrease the number of protons undergoing betatron oscillation and striking the material 330. Hence, the voltage determined off of the material 330 is used as a measure of the orbital path and is used as a feedback control to control the RF cavity system. In one example, the intensity controller subsystem 340 preferably additionally receives input from: (1) a detector 350, which provides a reading of the actual intensity of the proton beam and/or (2) an irradiation plan 360. The irradiation plan provides the desired intensity of the proton beam for each x, y, energy, and/or rotational position of the patient/tumor as a function of time. Thus, the intensity controller 340 receives the desired intensity from the irradiation plan 350, the actual intensity from the detector 350 and/or a measure of intensity from the material 330, and adjusts the amplitude and/or the duration of application of the applied radio-frequency field in the RF cavity system 310 to yield an intensity of the proton beam that matches the desired intensity from the irradiation plan 360. As described, supra, the protons striking the material 330 is a step in the extraction of the protons from the synchrotron 130. Hence, the measured intensity signal is used to change the number of protons per unit time being extracted, which is referred to as intensity of the proton beam. The intensity of the proton beam is thus under algorithm control. Further, the intensity of the proton beam is controlled separately from the velocity of the protons in the synchrotron 130. Hence, intensity of the protons extracted and the energy of the protons extracted are independently variable. Still further, the intensity of the extracted protons is controllably variable while scanning the charged particles beam in the tumor from one voxel to an adjacent voxel as a separate hexapole and separated time period from acceleration and/or treatment is not required, as described supra. For example, protons initially move at an equilibrium trajectory in the synchrotron 130. An RF field is used to excite or move the protons into a betatron oscillation. In one case, the frequency of the protons orbit is about 10 MHz. In one example, in about one millisecond or after about 10,000 orbits, the first protons hit an outer edge of the target material 130. The specific frequency is dependent upon the period of the orbit. Upon hitting the material 130, the protons push electrons through the foil to produce a current. The current is converted to voltage and amplified to yield a measured intensity signal. The measured intensity signal is used as a feedback input to control the applied RF magnitude or RF field. An energy beam sensor, described infra, is optionally used as a feedback control to the RF field frequency or RF field of the RF field extraction system 310 to dynamically control, modify, and/or alter the delivered charge particle beam energy, such as in a continuous pencil beam scanning system operating to treat tumor voxels without alternating between an extraction phase and a treatment phase. Preferably, the measured intensity signal is compared to a target signal and a measure of the difference between the measured intensity signal and target signal is used to adjust the applied RF field in the RF cavity system 310 in the extraction system to control the intensity of the protons in the extraction step. Stated again, the signal resulting from the protons striking and/or passing through the material 130 is used as an input in RF field modulation. An increase in the magnitude of the RF modulation results in protons hitting the foil or material 130 sooner. By increasing the RF, more protons are pushed into the foil, which results in an increased intensity, or more protons per unit time, of protons extracted from the synchrotron 130. In another example, a detector 350 external to the synchrotron 130 is used to determine the flux of protons extracted from the synchrotron and a signal from the external detector is used to alter the RF field, RF intensity, RF amplitude, and/or RF modulation in the RF cavity system 310. Here the external detector generates an external signal, which is used in a manner similar to the measured intensity signal, described in the preceding paragraphs. Preferably, an algorithm or irradiation plan 360 is used as an input to the intensity controller 340, which controls the RF field modulation by directing the RF signal in the betatron oscillation generation in the RF cavity system 310. The irradiation plan 360 preferably includes the desired intensity of the charged particle beam as a function of time and/or energy of the charged particle beam as a function of time, for each patient rotation position, and/or for each x-, y-position of the charged particle beam. In yet another example, when a current from material 330 resulting from protons passing through or hitting material is measured beyond a threshold, the RF field modulation in the RF cavity system is terminated or reinitiated to establish a subsequent cycle of proton beam extraction. This process is repeated to yield many cycles of proton beam extraction from the synchrotron accelerator. In still yet another embodiment, intensity modulation of the extracted proton beam is controlled by the main controller 110. The main controller 110 optionally and/or additionally controls timing of extraction of the charged particle beam and energy of the extracted proton beam. The benefits of the system include a multi-dimensional scanning system. Particularly, the system allows independence in: (1) energy of the protons extracted and (2) intensity of the protons extracted. That is, energy of the protons extracted is controlled by an energy control system and an intensity control system controls the intensity of the extracted protons. The energy control system and intensity control system are optionally independently controlled. Preferably, the main controller 110 controls the energy control system and the main controller 110 simultaneously controls the intensity control system to yield an extracted proton beam with controlled energy and controlled intensity where the controlled energy and controlled intensity are independently variable and/or continually available as a separate extraction phase and acceleration phase are not required, as described supra. Thus the irradiation spot hitting the tumor is under independent control of: time; energy; intensity; x-axis position, where the x-axis represents horizontal movement of the proton beam relative to the patient, and y-axis position, where the y-axis represents vertical movement of the proton beam relative to the patient. In addition, the patient is optionally independently translated and/or rotated relative to a translational axis of the proton beam at the same time. Beam Transport The beam transport system 135 is used to move the charged particles from the accelerator to the patient, such as via a nozzle in a gantry, described infra. Charged Particle Energy The beam transport system 135 optionally includes means for determining an energy of the charged particles in the charged particle beam. For example, an energy of the charged particle beam is determined via calculation, such as via equation 1, using knowledge of a magnet geometry and applied magnetic field to determine mass and/or energy. Referring now to equation 1, for a known magnet geometry, charge, q, and magnetic field, B, the Larmor radius, ρL, or magnet bend radius is defined as: ρ L = v ⊥ Ω c = 2 Em qB ( eq . 1 ) where: ν⊥ is the ion velocity perpendicular to the magnetic field, Ωc is the cyclotron frequency, q is the charge of the ion, B is the magnetic field, m is the mass of the charge particle, and E is the charged particle energy. Solving for the charged particle energy yields equation 2. E = ( ρ L qB ) 2 2 m ( eq . 2 ) Thus, an energy of the charged particle in the charged particle beam in the beam transport system 135 is calculable from the know magnet geometry, known or measured magnetic field, charged particle mass, charged particle charge, and the known magnet bend radius, which is proportional to and/or equivalent to the Larmor radius. Nozzle After extraction from the synchrotron 130 and transport of the charged particle beam along the proton beam path 268 in the beam transport system 135, the charged particle beam exits through the nozzle system 146. In one example, the nozzle system includes a nozzle foil covering an end of the nozzle system 146 or a cross-sectional area within the nozzle system forming a vacuum seal. The nozzle system includes a nozzle that expands in x/y-cross-sectional area along the z-axis of the proton beam path 268 to allow the proton beam 268 to be scanned along the x-axis and y-axis by the vertical control element and horizontal control element, respectively. The nozzle foil is preferably mechanically supported by the outer edges of an exit port of the nozzle 146. An example of a nozzle foil is a sheet of about 0.1 inch thick aluminum foil. Generally, the nozzle foil separates atmosphere pressures on the patient side of the nozzle foil from the low pressure region, such as about 10−5 to 10−7 torr region, on the synchrotron 130 side of the nozzle foil. The low pressure region is maintained to reduce scattering of the circulating charged particle beam in the synchrotron. Herein, the exit foil of the nozzle is optionally the first sheet 760 of the charged particle beam state determination system 750, described infra. Charged Particle Control Referring now to FIG. 4A, FIG. 4B, FIG. 5, FIG. 6A, and FIG. 6B, a charged particle beam control system is described where one or more patient specific beam control assemblies are removably inserted into the charged particle beam path proximate the nozzle of the charged particle cancer therapy system 100, where the patient specific beam control assemblies adjust the beam energy, diameter, cross-sectional shape, focal point, and/or beam state of the charged particle beam to properly couple energy of the charged particle beam to the individual's specific tumor. Beam Control Tray Referring now to FIG. 4A and FIG. 4B, a beam control tray assembly 400 is illustrated in a top view and side view, respectively. The beam control tray assembly 400 optionally comprises any of a tray frame 410, a tray aperture 412, a tray handle 420, a tray connector/communicator 430, and means for holding a patient specific tray insert 510, described infra. Generally, the beam control tray assembly 400 is used to: (1) hold the patient specific tray insert 510 in a rigid location relative to the beam control tray 400, (2) electronically identify the held patient specific tray insert 510 to the main controller 110, and (3) removably insert the patient specific tray insert 510 into an accurate and precise fixed location relative to the charged particle beam, such as the proton beam path 268 at the nozzle of the charged particle cancer therapy system 100. For clarity of presentation and without loss of generality, the means for holding the patient specific tray insert 510 in the tray frame 410 of the beam control tray assembly 400 is illustrated as a set of recessed set screws 415. However, the means for holding the patient specific tray insert 510 relative to the rest of the beam control tray assembly 400 is optionally any mechanical and/or electromechanical positioning element, such as a latch, clamp, fastener, clip, slide, strap, or the like. Generally, the means for holding the patient specific tray insert 510 in the beam control tray 400 fixes the tray insert and tray frame relative to one another even when rotated along and/or around multiple axes, such as when attached to a charged particle cancer therapy system 100 dynamic gantry nozzle 610 or gantry nozzle, which is an optional element of the nozzle system 146, that moves in three-dimensional space relative to a fixed point in the beamline, proton beam path 268, and/or a given patient position. As illustrated in FIG. 4A and FIG. 4B, the recessed set screws 415 fix the patient specific tray insert 510 into the aperture 412 of the tray frame 410. The tray frame 410 is illustrated as circumferentially surrounding the patient specific tray insert 510, which aids in structural stability of the beam control tray assembly 400. However, generally the tray frame 410 is of any geometry that forms a stable beam control tray assembly 400. Still referring to FIG. 4A and now referring to FIG. 5 and FIG. 6A, the optional tray handle 420 is used to manually insert/retract the beam control tray assembly 400 into a receiving element of the gantry nozzle or dynamic gantry nozzle 610. While the beam control tray assembly 400 is optionally inserted into the charged particle beam path 268 at any point after extraction from the synchrotron 130, the beam control tray assembly 400 is preferably inserted into the positively charged particle beam proximate the dynamic gantry nozzle 610 as control of the beam shape is preferably done with little space for the beam shape to defocus before striking the tumor. Optionally, insertion and/or retraction of the beam control tray assembly 400 is semi-automated, such as in a manner of a digital-video disk player receiving a digital-video disk, with a selected auto load and/or a selected auto unload feature. Patient Specific Tray Insert Referring again to FIG. 5, a system of assembling trays 500 is described. The beam control tray assembly 400 optionally and preferably has interchangeable patient specific tray inserts 510, such as a range shifter insert 511, a patient specific ridge filter insert 512, an aperture insert 513, a compensator insert 514, or a blank insert 515. As described, supra, any of the range shifter insert 511, the patient specific ridge filter insert 512, the aperture insert 513, the compensator insert 514, or the blank insert 515 after insertion into the tray frame 410 are inserted as the beam control tray assembly 400 into the positively charged particle beam path 268, such as proximate the dynamic gantry nozzle 610. Still referring to FIG. 5, the patient specific tray inserts 510 are further described. The patient specific tray inserts comprise a combination of any of: (1) a standardized beam control insert and (2) a patient specific beam control insert. For example, the range shifter insert or 511 or compensator insert 514 used to control the depth of penetration of the charged particle beam into the patient is optionally: (a) a standard thickness of a beam slowing material, such as a first thickness of Lucite, an acrylic, a clear plastic, and/or a thermoplastic material, (b) one member of a set of members of varying thicknesses and/or densities where each member of the set of members slows the charged particles in the beam path by a known amount, or (c) is a material with a density and thickness designed to slow the charged particles by a customized amount for the individual patient being treated, based on the depth of the individual's tumor in the tissue, the thickness of intervening tissue, and/or the density of intervening bone/tissue. Similarly, the ridge filter insert 512 used to change the focal point or shape of the beam as a function of depth is optionally: (1) selected from a set of ridge filters where different members of the set of ridge filters yield different focal depths or (2) customized for treatment of the individual's tumor based on position of the tumor in the tissue of the individual. Similarly, the aperture insert is: (1) optionally selected from a set of aperture shapes or (2) is a customized individual aperture insert 513 designed for the specific shape of the individual's tumor. The blank insert 515 is an open slot, but serves the purpose of identifying slot occupancy, as described infra. Slot Occupancy/Identification Referring again to FIG. 4A, FIG. 4B, and FIG. 5, occupancy and identification of the particular patient specific tray insert 510 into the beam control tray assembly 400 is described. Generally, the beam control tray assembly 400 optionally contains means for identifying, to the main controller 110 and/or a treatment delivery control system described infra, the specific patient tray insert 510 and its location in the charged particle beam path 268. First, the particular tray insert is optionally labeled and/or communicated to the beam control tray assembly 400 or directly to the main controller 110. Second, the beam control tray assembly 400 optionally communicates the tray type and/or tray insert to the main controller 110. In various embodiments, communication of the particular tray insert to the main controller 110 is performed: (1) directly from the tray insert, (2) from the tray insert 510 to the tray assembly 400 and subsequently to the main controller 110, and/or (3) directly from the tray assembly 400. Generally, communication is performed wirelessly and/or via an established electromechanical link. Identification is optionally performed using a radio-frequency identification label, use of a barcode, or the like, and/or via operator input. Examples are provided to further clarify identification of the patient specific tray insert 510 in a given beam control tray assembly 400 to the main controller. In a first example, one or more of the patient specific tray inserts 510, such as the range shifter insert 511, the patient specific ridge filter insert 512, the aperture insert 513, the compensator insert 514, or the blank insert 515 include an identifier 520 and/or and a first electromechanical identifier plug 530. The identifier 520 is optionally a label, a radio-frequency identification tag, a barcode, a 2-dimensional bar-code, a matrix-code, or the like. The first electromechanical identifier plug 530 optionally includes memory programmed with the particular patient specific tray insert information and a connector used to communicate the information to the beam control tray assembly 400 and/or to the main controller 110. As illustrated in FIG. 5, the first electromechanical identifier plug 530 affixed to the patient specific tray insert 510 plugs into a second electromechanical identifier plug, such as the tray connector/communicator 430, of the beam control tray assembly 400, which is described infra. In a second example, the beam control tray assembly 400 uses the second electromechanical identifier plug to send occupancy, position, and/or identification information related to the type of tray insert or the patient specific tray insert 510 associated with the beam control tray assembly to the main controller 110. For example, a first tray assembly is configured with a first tray insert and a second tray assembly is configured with a second tray insert. The first tray assembly sends information to the main controller 110 that the first tray assembly holds the first tray insert, such as a range shifter, and the second tray assembly sends information to the main controller 110 that the second tray assembly holds the second tray insert, such as an aperture. The second electromechanical identifier plug optionally contains programmable memory for the operator to input the specific tray insert type, a selection switch for the operator to select the tray insert type, and/or an electromechanical connection to the main controller. The second electromechanical identifier plug associated with the beam control tray assembly 400 is optionally used without use of the first electromechanical identifier plug 530 associated with the tray insert 510. In a third example, one type of tray connector/communicator 430 is used for each type of patient specific tray insert 510. For example, a first connector/communicator type is used for holding a range shifter insert 511, while a second, third, fourth, and fifth connector/communicator type is used for trays respectively holding a patient specific ridge filter insert 512, an aperture insert 513, a compensator insert 514, or a blank insert 515. In one case, the tray communicates tray type with the main controller. In a second case, the tray communicates patient specific tray insert information with the main controller, such as an aperture identifier custom built for the individual patient being treated. Tray Insertion/Coupling Referring now to FIG. 6A and FIG. 6B a beam control insertion process 600 is described. The beam control insertion process 600 comprises: (1) insertion of the beam control tray assembly 400 and the associated patient specific tray insert 510 into the charged particle beam path 268 and/or dynamic gantry nozzle 610, such as into a tray assembly receiver 620 and (2) an optional partial or total retraction of beam of the tray assembly receiver 620 into the dynamic gantry nozzle 610. Referring now to FIG. 6A, insertion of one or more of the beam control tray assemblies 400 and the associated patient specific tray inserts 510 into the dynamic gantry nozzle 610 is further described. In FIG. 6A, three beam control tray assemblies, of a possible n tray assemblies, are illustrated, a first tray assembly 402, a second tray assembly 404, and a third tray assembly 406, where n is a positive integer of 1, 2, 3, 4, 5 or more. As illustrated, the first tray assembly 402 slides into a first receiving slot 403, the second tray assembly 404 slides into a second receiving slot 405, and the third tray assembly 406 slides into a third receiving slot 407. Generally, any tray optionally inserts into any slot or tray types are limited to particular slots through use of a mechanical, physical, positional, and/or steric constraints, such as a first tray type configured for a first insert type having a first size and a second tray type configured for a second insert type having a second distinct size at least ten percent different from the first size. Still referring to FIG. 6A, identification of individual tray inserts inserted into individual receiving slots is further described. As illustrated, sliding the first tray assembly 402 into the first receiving slot 403 connects the associated electromechanical connector/communicator 430 of the first tray assembly 402 to a first receptor 626. The electromechanical connector/communicator 430 of the first tray assembly communicates tray insert information of the first beam control tray assembly to the main controller 110 via the first receptor 626. Similarly, sliding the second tray assembly 404 into the second receiving slot 405 connects the associated electromechanical connector/communicator 430 of the second tray assembly 404 into a second receptor 627, which links communication of the associated electromechanical connector/communicator 430 with the main controller 110 via the second receptor 627, while a third receptor 628 connects to the electromechanical connected placed into the third slot 407. The non-wireless/direct connection is preferred due to the high radiation levels within the treatment room and the high shielding of the treatment room, which both hinder wireless communication. The connection of the communicator and the receptor is optionally of any configuration and/or orientation. Tray Receiver Assembly Retraction Referring again to FIG. 6A and FIG. 6B, retraction of the tray receiver assembly 620 relative to a nozzle end 612 of the dynamic gantry nozzle 610 is described. The tray receiver assembly 620 comprises a framework to hold one or more of the beam control tray assemblies 400 in one or more slots, such as through use of a first tray receiver assembly side 622 through which the beam control tray assemblies 400 are inserted and/or through use of a second tray receiver assembly side 624 used as a backstop, as illustrated holding the plugin receptors configured to receive associated tray connector/communicators 430, such as the first, second, and third receptors 626, 627, 628. Optionally, the tray receiver assembly 620 retracts partially or completely into the dynamic gantry nozzle 610 using a retraction mechanism 660 configured to alternatingly retract and extend the tray receiver assembly 620 relative to a nozzle end 612 of the gantry nozzle 610, such as along a first retraction track 662 and a second retraction track 664 using one or more motors and computer control. Optionally the tray receiver assembly 620 is partially or fully retracted when moving the gantry, nozzle, and/or gantry nozzle 610 to avoid physical constraints of movement, such as potential collision with another object in the patient treatment room. For clarity of presentation and without loss of generality, several examples of loading patient specific tray inserts into tray assemblies with subsequent insertion into an positively charged particle beam path proximate a gantry nozzle 610 are provided. In a first example, a single beam control tray assembly 400 is used to control the charged particle beam 268 in the charged particle cancer therapy system 100. In this example, a patient specific range shifter insert 511, which is custom fabricated for a patient, is loaded into a patient specific tray insert 510 to form a first tray assembly 402, where the first tray assembly 402 is loaded into the third receptor 628, which is fully retracted into the gantry nozzle 610. In a second example, two beam control assemblies 400 are used to control the charged particle beam 268 in the charged particle cancer therapy system 100. In this example, a patient specific ridge filter 512 is loaded into a first tray assembly 402, which is loaded into the second receptor 627 and a patient specific aperture 513 is loaded into a second tray assembly 404, which is loaded into the first receptor 626 and the two associated tray connector/communicators 430 using the first receptor 626 and second receptor 627 communicate to the main controller 110 the patient specific tray inserts 510. The tray receiver assembly 620 is subsequently retracted one slot so that the patient specific ridge filter 512 and the patient specific aperture reside outside of and at the nozzle end 612 of the gantry nozzle 610. In a third example, three beam control tray assemblies 400 are used, such as a range shifter 511 in a first tray inserted into the first receiving slot 403, a compensator in a second tray inserted into the second receiving slot 405, and an aperture in a third tray inserted into the third receiving slot 407. Generally, any patient specific tray insert 510 is inserted into a tray frame 410 to form a beam control tray assembly 400 inserted into any slot of the tray receiver assembly 620 and the tray assembly is not retracted or retracted any distance into the gantry nozzle 610. Tomography/Beam State In one embodiment, the charged particle tomography apparatus is used to image a tumor in a patient. As current beam position determination/verification is used in both tomography and cancer therapy treatment, for clarity of presentation and without limitation beam state determination is also addressed in this section. However, beam state determination is optionally used separately and without tomography. In another example, the charged particle tomography apparatus is used in combination with a charged particle cancer therapy system using common elements. For example, tomographic imaging of a cancerous tumor is performed using charged particles generated with an injector, accelerator, and guided with a delivery system that are part of the cancer therapy system, described supra. In various examples, the tomography imaging system is optionally simultaneously operational with a charged particle cancer therapy system using common elements, allows tomographic imaging with rotation of the patient, is operational on a patient in an upright, semi-upright, and/or horizontal position, is simultaneously operational with X-ray imaging, and/or allows use of adaptive charged particle cancer therapy. Further, the common tomography and cancer therapy apparatus elements are optionally operational in a multi-axis and/or multi-field raster beam mode. In conventional medical X-ray tomography, a sectional image through a body is made by moving one or both of an X-ray source and the X-ray film in opposite directions during the exposure. By modifying the direction and extent of the movement, operators can select different focal planes, which contain the structures of interest. More modern variations of tomography involve gathering projection data from multiple directions by moving the X-ray source and feeding the data into a tomographic reconstruction software algorithm processed by a computer. Herein, in stark contrast to known methods, the radiation source is a charged particle, such as a proton ion beam or a carbon ion beam. A proton beam is used herein to describe the tomography system, but the description applies to a heavier ion beam, such as a carbon ion beam. Further, in stark contrast to known techniques, herein the radiation source is preferably stationary while the patient is rotated. Referring now to FIG. 7, an example of a tomography apparatus is described and an example of a beam state determination is described. In this example, the tomography system 700 uses elements in common with the charged particle beam system 100, including elements of one or more of the injection system 120, accelerator 130, targeting/delivery system 140, patient interface module 150, display system 160, and/or imaging system 170, such as the X-ray imaging system. One or more scintillation plates, such as a scintillating plastic, are used to measure energy, intensity, and/or position of the charged particle beam. For instance, a scintillation plate 710 is positioned behind the patient 730 relative to the targeting/delivery system 140 elements, which is optionally used to measure intensity and/or position of the charged particle beam after transmitting through the patient. Optionally, a second scintillation plate or a charged particle induced photon emitting sheet, described infra, is positioned prior to the patient 730 relative to the targeting/delivery system 140 elements, which is optionally used to measure incident intensity and/or position of the charged particle beam prior to transmitting through the patient. The charged particle beam system 100 as described has proven operation at up to and including 330 MeV, which is sufficient to send protons through the body and into contact with the scintillation material. Particularly, 250 MeV to 330 MeV are used to pass the beam through a standard sized patient with a standard sized pathlength, such as through the chest. The intensity or count of protons hitting the plate as a function of position is used to create an image. The velocity or energy of the proton hitting the scintillation plate is also used in creation of an image of the tumor 720 and/or an image of the patient 730. The patient 730 is rotated about the y-axis and a new image is collected. Preferably, a new image is collected with about every one degree of rotation of the patient resulting in about 360 images that are combined into a tomogram using tomographic reconstruction software. The tomographic reconstruction software uses overlapping rotationally varied images in the reconstruction. Optionally, a new image is collected at about every 2, 3, 4, 5, 10, 15, 30, or 45 degrees of rotation of the patient. In one embodiment, a tomogram or an individual tomogram section image is collected at about the same time as cancer therapy occurs using the charged particle beam system 100. For example, a tomogram is collected and cancer therapy is subsequently performed: without the patient moving from the positioning systems, such as in a semi-vertical partial immobilization system, a sitting partial immobilization system, or the a laying position. In a second example, an individual tomogram slice is collected using a first cycle of the accelerator 130 and using a following cycle of the accelerator 130, the tumor 720 is irradiated, such as within about 1, 2, 5, 10, 15 or 30 seconds. In a third case, about 2, 3, 4, or 5 tomogram slices are collected using 1, 2, 3, 4, or more rotation positions of the patient 730 within about 5, 10, 15, 30, or 60 seconds of subsequent tumor irradiation therapy. In another embodiment, the independent control of the tomographic imaging process and X-ray collection process allows simultaneous single and/or multi-field collection of X-ray images and tomographic images easing interpretation of multiple images. Indeed, the X-ray and tomographic images are optionally overlaid to from a hybrid X-ray/proton beam tomographic image as the patient 730 is optionally in the same position for each image. In still another embodiment, the tomogram is collected with the patient 730 in the about the same position as when the patient's tumor is treated using subsequent irradiation therapy. For some tumors, the patient being positioned in the same upright or semi-upright position allows the tumor 720 to be separated from surrounding organs or tissue of the patient 730 better than in a laying position. Positioning of the scintillation plate 710 behind the patient 730 allows the tomographic imaging to occur while the patient is in the same upright or semi-upright position. The use of common elements in the tomographic imaging and in the charged particle cancer therapy allows benefits of the cancer therapy, described supra, to optionally be used with the tomographic imaging, such as proton beam x-axis control, proton beam y-axis control, control of proton beam energy, control of proton beam intensity, timing control of beam delivery to the patient, rotation control of the patient, and control of patient translation all in a raster beam mode of proton energy delivery. The use of a single proton or cation beamline for both imaging and treatment facilitates eases patient setup, reduces alignment uncertainties, reduces beam sate uncertainties, and eases quality assurance. In yet still another embodiment, initially a three-dimensional tomographic proton based reference image is collected, such as with hundreds of individual rotation images of the tumor 720 and patient 730. Subsequently, just prior to proton treatment of the cancer, just a few 2-dimensional control tomographic images of the patient are collected, such as with a stationary patient or at just a few rotation positions, such as an image straight on to the patient, with the patient rotated about 45 degrees each way, and/or the patient rotated about 90 degrees each way about the y-axis. The individual control images are compared with the 3-dimensional reference image. An adaptive proton therapy is subsequently performed where: (1) the proton cancer therapy is not used for a given position based on the differences between the 3-dimensional reference image and one or more of the 2-dimensional control images and/or (2) the proton cancer therapy is modified in real time based on the differences between the 3-dimensional reference image and one or more of the 2-dimensional control images. Charged Particle State Determination/Verification/Photonic Monitoring Still referring to FIG. 7, the tomography system 700 is optionally used with a charged particle beam state determination system 750, optionally used as a charged particle verification system. The charged particle state determination system 750 optionally measures, determines, and/or verifies one of more of: (1) position of the charged particle beam, (2) direction of the charged particle beam, (3) intensity of the charged particle beam, (4) energy of the charged particle beam, and (5) a history of the charged particle beam. For clarity of presentation and without loss of generality, a description of the charged particle beam state determination system 750 is described and illustrated separately in FIG. 8 and FIG. 9A; however, as described herein elements of the charged particle beam state determination system 750 are optionally and preferably integrated into the nozzle system 146 and/or the tomography system 700 of the charged particle treatment system 100. More particularly, any element of the charged particle beam state determination system 750 is integrated into the nozzle system 146, the dynamic gantry nozzle 610, and/or tomography system 700, such as a surface of the scintillation plate 710 or a surface of a scintillation detector, plate, or system. The nozzle system 146 or the dynamic gantry nozzle 610 provides an outlet of the charged particle beam from the vacuum tube initiating at the injection system 120 and passing through the synchrotron 130 and beam transport system 135. Any plate, sheet, fluorophore, or detector of the charged particle beam state determination system is optionally integrated into the nozzle system 146. For example, an exit foil of the nozzle 610 is optionally a first sheet 760 of the charged particle beam state determination system 750 and a first coating 762 is optionally coated onto the exit foil, as illustrated in FIG. 7. Similarly, optionally a surface of the scintillation plate 710 is a support surface for a fourth coating 792, as illustrated in FIG. 7. The charged particle beam state determination system 750 is further described, infra. Referring now to FIG. 7, FIG. 8, and FIG. 9A, four sheets, a first sheet 760, a second sheet 770, a third sheet 780, and a fourth sheet 790 are used to illustrated detection sheets and/or photon emitting sheets upon transmittance of a charged particle beam. Each sheet is optionally coated with a photon emitter, such as a fluorophore, such as the first sheet 760 is optionally coated with a first coating 762. Without loss of generality and for clarity of presentation, the four sheets are each illustrated as units, where the light emitting layer is not illustrated. Thus, for example, the second sheet 770 optionally refers to a support sheet, a light emitting sheet, and/or a support sheet coated by a light emitting element. The four sheets are representative of n sheets, where n is a positive integer. Referring now to FIG. 7 and FIG. 8, the charged particle beam state verification system 750 is a system that allows for monitoring of the actual charged particle beam position in real-time without destruction of the charged particle beam. The charged particle beam state verification system 750 preferably includes a first position element or first beam verification layer, which is also referred to herein as a coating, luminescent, fluorescent, phosphorescent, radiance, or viewing layer. The first position element optionally and preferably includes a coating or thin layer substantially in contact with a sheet, such as an inside surface of the nozzle foil, where the inside surface is on the synchrotron side of the nozzle foil. Less preferably, the verification layer or coating layer is substantially in contact with an outer surface of the nozzle foil, where the outer surface is on the patient treatment side of the nozzle foil. Preferably, the nozzle foil provides a substrate surface for coating by the coating layer. Optionally, a binding layer is located between the coating layer and the nozzle foil, substrate, or support sheet. Optionally, the position element is placed anywhere in the charged particle beam path. Optionally, more than one position element on more than one sheet, respectively, is used in the charged particle beam path and is used to determine a state property of the charged particle beam, as described infra. Still referring to FIG. 7 and FIG. 8, the coating, referred to as a fluorophore, yields a measurable spectroscopic response, spatially viewable by a detector or camera, as a result of transmission by the proton beam. The coating is preferably a phosphor, but is optionally any material that is viewable or imaged by a detector where the material changes spectroscopically as a result of the charged particle beam hitting or transmitting through the coating or coating layer. A detector or camera views secondary photons emitted from the coating layer and determines a position of a treatment beam 269, which is also referred to as a current position of the charged particle beam or final treatment vector of the charged particle beam, by the spectroscopic differences resulting from protons and/or charged particle beam passing through the coating layer. For example, the camera views a surface of the coating surface as the proton beam or positively charged cation beam is being scanned by the first axis control 143, vertical control, and the second axis control 144, horizontal control, beam position control elements during treatment of the tumor 720. The camera views the current position of the charged particle beam or treatment beam 269 as measured by spectroscopic response. The coating layer is preferably a phosphor or luminescent material that glows and/or emits photons for a short period of time, such as less than 5 seconds for a 50% intensity, as a result of excitation by the charged particle beam. The detector observes the temperature change and/or observe photons emitted from the charged particle beam traversed spot. Optionally, a plurality of cameras or detectors are used, where each detector views all or a portion of the coating layer. For example, two detectors are used where a first detector views a first half of the coating layer and the second detector views a second half of the coating layer. Preferably, at least a portion of the detector is mounted into the nozzle system to view the proton beam position after passing through the first axis and second axis controllers 143, 144. Preferably, the coating layer is positioned in the proton beam path 268 in a position prior to the protons striking the patient 730. Referring now to FIG. 1 and FIG. 7, the main controller 110, connected to the camera or detector output, optionally and preferably compares the final proton beam position or position of the treatment beam 269 with the planned proton beam position and/or a calibration reference to determine if the actual proton beam position or position of the treatment beam 269 is within tolerance. The charged particle beam state determination system 750 preferably is used in one or more phases, such as a calibration phase, a mapping phase, a beam position verification phase, a treatment phase, and a treatment plan modification phase. The calibration phase is used to correlate, as a function of x-, y-position of the glowing response the actual x-, y-position of the proton beam at the patient interface. During the treatment phase, the charged particle beam position is monitored and compared to the calibration and/or treatment plan to verify accurate proton delivery to the tumor 720 and/or as a charged particle beam shutoff safety indicator. Referring now to FIG. 10, the position verification system 172 and/or the treatment delivery control system 112, upon determination of a tumor shift, an unpredicted tumor distortion upon treatment, and/or a treatment anomaly optionally generates and or provides a recommended treatment change 1070. The treatment change 1070 is optionally sent out while the patient 730 is still in the treatment position, such as to a proximate physician or over the internet to a remote physician, for physician approval 1072, receipt of which allows continuation of the now modified and approved treatment plan. |
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summary | ||
abstract | The scintillator panel includes a support, a reflective layer on the support, and a scintillator layer formed on the reflective layer by deposition. The reflective layer includes light-scattering particles and a binder resin. A specific region of the reflective layer is defined by a resin or includes light-scattering particles having a specific area average particle diameter, or the reflective layer has a specific arithmetic average roughness. |
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abstract | A method for suppressing a pyrophoric metal fire may include arranging a suppression system above a containment structure. The suppression system includes a first extinguishing agent. The containment structure is configured to contain and isolate a pyrophoric metal from ambient air. The suppression system is configured to activate upon a leak and ignition of the pyrophoric metal so as to release the first extinguishing agent to suppress the pyrophoric metal fire. |
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048511838 | claims | 1. A nuclear power generating facility, comprising: a substantially vertical borehole in the surface of the earth which is at least 600 feet deep and has a substantially constant diameter; a casing, extending from the surface of the earth down to at least 600 feet deep, lining the borehole and wherein the casing is completely within the borehole; a self regulating nuclear reactor, of a diameter less than the diameter of the borehole, within the casing at least 600 feet below the surface of the earth, wherein the reactor generates heat; means for converting the heat generated by the reactor to electricity, wherein the conversion means is located at or above the surface of the earth; means for transferring the heat generated by the reactor from the reactor to the conversion means; and a means for completely and permanently closing all access between the surface of the earth and the reactor through the borehole, wherein said means is located between the reactor and the surface of the earth, and wherein the casing and the borehole have no opening below the closing means sealing the reactor within the casing. a first acting, high explosive actuated pipe closure; and a plurality of later acting mechanical valves located between the first acting closure and the surface of the earth. 2. A nuclear power generating facility, as cited in claim 1, wherein the means for completely and permanently closing access is able to completely close access in less than 0.5 seconds after actuation to prevent the accidental upward movement of radioactive materials within the casing after actuation. 3. A nuclear power generating facility, as cited in claim 2, wherein the means for completely and permanently closing access comprises gas driven doors which move from a fully open to fully closed positions in less than or equal to substantially 40 milliseconds against a pressure differential as high as substantially 1600 psi to prevent the accidental upward movement of radioactive materials within the casing after actuation. 4. A nuclear power generating facility, as cited in claim 2, wherein the means for completely and permanently closing access, comprises: 5. A nuclear power generating facility, as cited in claim 1, wherein the means for transferring the heat comprises a heat pipe array. 6. A nuclear power generating facility, as cited in claim 5, wherein the heat pipe array comprises a plurality of thermally coupled heat pipe stages. 7. A nuclear power generating facility, as cited in claim 5, wherein the heat pipe array comprises a first heat exchanger, and a first plurality of heat pipes, which have first ends which are located in the reactor and which have second ends which are located in the first heat exchanger. 8. A nuclear power generating facility, as cited in claim 7, wherein the first ends of the first plurality of heat pipes are conical with the apex of each cone located on the part of the first ends furthest from the second ends, and wherein the second ends of the first plurality of heat pipes are conical with the apex of each cone located on the part of the second ends furthest from the first ends, and wherein the second ends comprise semi-helical baffles. 9. A nuclear power generating facility, as cited in claim 8, wherein the heat pipe array further comprises, a second heat exchanger and a second plurality of heat pipes, which have first ends which are located in the first heat exchanger and second ends located in the second heat exchanger. 10. A nuclear power generating facility, as cited in claim 7, wherein the self regulating nuclear reactor is a self regulating heat pipe controlled nuclear reactor. 11. A nuclear power generating facility, as cited in claim 10, wherein the self regulating nuclear reactor is a self regulating heat pipe controlled, reflector critical nuclear reactor. 12. A nuclear power generating facility, as cited in claim 1, wherein the self regulating nuclear reactor is a fast breeder reactor. 13. A nuclear power generating facility, as cited in claim 1, wherein the diameter of the borehole is less than 6 meters. |
045029873 | abstract | Improved spherules for making enhanced forms of nuclear-reactor fuels are prepared by internal gelation procedures within a sol-gel operation and are accomplished by first boiling the concentrated HMTA-urea feed solution before engaging in the spherule-forming operation thereby effectively controlling crystallite size in the product spherules. |
051924927 | summary | FIELD OF THE INVENTION The invention relates to a method and apparatus for sealing communicating co-axial tubes containing a fluid so that the fluid level in one of the tubes can be higher than the fluid level in the other of the tubes and will permit operations intermediate the tubes without being encumbered by fluid intermediate the tubes. The invention relates particularly to a method and apparatus for permitting repair operations between the inner and outer shells of a steam generator which is supplied with a heated fluid from a nuclear reactor vessel. BACKGROUND OF THE INVENTION Known types of steam generators supplied with heated fluid from a nuclear reactor vessel have an outer shell or tube and an inner shell or tube with heat exchanger tubes within the inner shell for circulating the heated fluid within the steam generator. A liquid, such as water, is contained within the shells, which are interconnected for liquid flow, so that the upper level of the liquid is the same both in the inner shell and the outer shell and covers the heat exchanger tubes during operation of the steam generator. At times, it can be necessary to perform repair operations within the space intermediate the inner and outer shells, e.g. repair of the girth weld in the outer shell which is adjacent the upper level of at least one of said heat exchanger tubes. It would appear to be a simple matter merely to suspend operation of the steam generator and the reactor and lower the fluid water level in the generator to permit such repairs, but radiation is still omitted from inside the inner shell to which workmen in the space between the inner and outer shells are exposed which is undesirable. In the past, under such conditions, lead sheathing has been applied to the outer surface of the inner shell to reduce such exposure. However, the application of such sheathing is time consuming, resulting in high radiation exposure of the workmen, and is not as effective as keeping the tubes immersed in water within the inner shell. Since the spaces within the shells are interconnected for water flow, the water level between the shells ordinarily would be the same as the water level within the inner shell so that merely raising, or permitting, the water level within the inner shell to be high enough to provide the desired shielding would be unsatisfactory because the areas on which repairs are to be performed would be immersed in the water. The problem then arises as to how to maintain a water upper level between the shells which is low enough to permit such repairs while permitting a water level within the inner shell which is higher than the water level between the shells and which will cause said heat exchanger tubes to be immersed. With steam generators of the type which have been installed in pressurized water, reactor power plants, the steam generator cannot, as a practical matter, be opened up to provide easy access to the space between the shells where repairs are to be made. Access to such space is normally limited to relatively small access openings in the outer shell which are above such space. SUMMARY OF THE INVENTION In accordance with the preferred embodiment of the invention, the water level within the inner shell, and hence, in the space between the inner and outer shell, is adjusted so that the water covers said heat exchanger tubes within the inner shell, yet is at a small distance below the area where the repairs are to be made so that during the installation steps described hereinafter, which can be accomplished within a relatively short time, the workers are protected by the water within the inner shell as well as the water in the space between the shells. In this case, desirably, the workmen wear wet suits because the subsequent steps require that parts of the bodies of the workmen be immersed in the water between the inner and outer shells. However, if desired, with less safety, the water level in the inner shell may be temporarily reduced below the installation positions for the equipment hereinafter described, and after such equipment is installed, the water level within the inner shell can be raised to a level at which the heated fluid tubes within the inner shell are totally immersed in water. In the area of concern, the outer shell and the lower part of the inner shell usually have the shape of truncated cones with the lower ends having the smaller diameter. At its upper part, the inner shell can have the shape of a cylindrical annulus. Thus, the shells are nearer each other at the lower ends of the truncated cones. A resilient, flexible tube of a diameter which will fill the space between the inner and outer shells at the lower ends of the truncated cones is inserted between the inner and outer shells to provide a support for workmen and to restrain debris and dropped tools. Thereafter, a plurality of arcuate, metal, seal support sections of a size which can be passed through the access openings in the outer shell are inserted between the shells above the flexible tube and below the level where the workmen will stand while making repairs and are clamped against the surfaces of the inner and outer shells to provide a seal support deck encircling the inner shell. Then, two sections of uninflated, but inflatable tubing, the combined length of the sections being substantially equal to the peripheral size of the inner shell, are passed through an access opening and applied over the seal support sections with flexible sealing blocks between the adjacent ends thereof. After the inflatable sealing tubes are installed, a plurality of arcuate, metal, seal retention sections which can be passed through said access openings are installed over the sealing tubes, clamped together and, by means of jack screws engaging the outer surface of the inner shell, positioned within the space between the shells to provide a ring of sections encircling the inner shell. The inflatable tube sections are then inflated, e.g. by air under pressure, to provide a water-tight seal between the inner and outer shells. Preferably, after the tube sections are inflated, but optionally, before they are inflated, a plurality of arcuate metal sections which can pass through an access opening are applied on top of the seal retention sections to provide a work platform encircling the inner shell on which workmen can stand during the making of repairs. If water is between the shells and above the work platform after the steps described, preferably, such water is pumped out from between the shells so that the space between the shells and above the work platform is free of water. However, because of the seal provided by the sealing tube sections, the water level within the inner shell will not be lowered by the pumping operation. |
043409709 | summary | SUMMARY OF THE INVENTION This invention relates to a power drive activated through several expansion valves which are installed around a drive shaft. The expansion valves consisting of hollow cylinders made of a good heat transmitting material such as stainless steel joined in a ceramic body with push rod and pushrod cylinder at the very end. The inside of the expansion valve is completely filled with expansible liquid, so any temperature difference penetrating the heat collector from the inside or outside of the valve will expand or contract. Inside the valve the liquid which will in return push the pushrod in or out the valve unit. The pushrod is connected to a spindle drive and ratched gear in such a way that the downstroke will push the spindle through a spindle thread and drive a pinion gear. Inside the pinion gear is a ratched gear installed which will disengage the spindle drive on the back stroke. The pinion gear is connected to the spindle drive through a stud sliding bushing and key inside the spindle drive. The pinion gear will drive the big wheel around a side gear which is fastened against the stand. A second side gear called satellite gear which runs free are connected to the driveshaft. The functioning of the satellite gear is to keep the pinion gear against the side gears, the pinion gear is also secured through a sliding collar on the very end. A pressure spring between the pinion gear and the spindle will push the spindle back together with the contraction of the liquid. The ratched gear inside the pinion gear will disconnect the drive from the spindle on the back stroke, so only the down stroke of each expansion valve will drive the big wheel around the side gear. In this fashion a very powerful hydraulic drive is created through a low temperature difference between the inside and outside of the expansion valve. Conventional heat sources are usually in the form of hot or cold water on the bottom of the wheel in which the valve dips. Solar heat can also be used through reflectors on top of the wheel. When nuclear heat elements are installed inside the expansion valve, the entire wheel has to be submerged into water. Nuclear Heat Expansion valve, the same expansion valves as explained above will have nuclear heat elements installed inside the valve in the form of highly concentrated uranium 235 and plutonium, kept in separate parts. The isotopes are divided through a cadmium plunger which can be pulled in or out of the heat element. The movement of the cadmium stick is controlled through the position of the big wheel, meaning, when in upward position the weight of the cadmium plunger will move down and so neutralize the heat elements. In the upside down position the cadmium plunger will move out of the nuclear heat elements through its own weight and so activate a nuclear reaction which is only introduced for a second or so. Liquid like toluene is a very good moderator in connection with graphite. The benefit of this design is that because of the small amount of heat needed to expand the small amount of liquid, a powerful drive from nuclear direct into mechanical power is achieved without any electronic devices or sophisticated cooling systems. This kind of power conversion needs almost no expertise or service. In this fashion the nuclear power wheel can operate completely on its own. To stop the machine, contact screws on the extreme outside have to be screwed inward, which moves the cadmium stick inward and so stops all reactions. The nuclear power wheel is designed to operate on a permanent speed till the nuclear heat elements are used up, which then can be replaced. The machine, because of its slow motion and heavy mass, is ideal for driving a water pump on the bottom of the ocean in order to harvest precious metal dust and sediments. To install this machine on the ocean floor, it has to be assembled on land and then put in motion before submergence in the water. The drive of the big wheel has to be disconnected from the pump drive through a clutch with a timing device. The drive from the machine to the pump cannot be engaged until the machine is installed on the ocean floor and the water hose connected to a float on the surface, FIG. 8 (54). Now the clutches can be released and the machine will drive the pump in a continuous manner. The waterhose, FIG. 8 (45) should be constructed of a flexible material, strong enough to lower the machine into the water and flexible enough to be folded together and upon the drum of a winch during the lowering of the machine to the ocean floor. Air pillows have to be installed around the hose to keep the weight of it up, FIG. 8 (46). Under the pillows, air jets are installed in such a way that they penetrate the hose with a nozzle so that compressed air can be injected in an upward direction, FIG. 9 (45 & 49). Once the machine is in position on the ocean floor, the pump, FIG. 8 (38) will suck up the seawater and mud through a drill and suction stud, FIG. 10 (39-56-58). Hooks under the fundament will give it a better hold in the sand, FIGS. 8 & 10 (44). Wheel covers FIG. 8 (42) will prevent the wheel from getting tangled up with the hose. The massive weight and the steady suction of the pump as well as the digging action of the drill, FIGS. 10 & 11 (56) will lower the machine until solid ground is reached. The machine, with the help of the hose, can be moved to any location. The Advantage of this Design is, that water, sand and mud can be pumped up from the ocean floor into a boat or onto land. It is known that below the depth of 3000 feet there is very little or no oxygen and therefore almost no plant or micro life possible, so all substances and minerals are dissolved into liquid substance which is loaded with nutritious fertilizer, which is seldom found at higher levels except in case of earthquakes or tidal waves. This substance is unknown to man and could answer the question of creation of ocean life. Since the creation of the earth the seas have scraped the crust of the earth with sand, salt and water and so ground the earthcrust into a fine powder. Corrosion resisting minerals like gold and platinum can be traced in almost any salt water, but as long as the sea water is in motion, these precious metals cannot settle to the floor and if they do, corals and plant life will bury them. Only in the depth of the sea where there is no vegetation or coral life possible and where there is no current, has the precious metal dust been able to settle on the floor over millions of years. Only sand and mud covers it. So far no one has been able to collect these treasures. With the help of the nuclear heat expansion machine, these treasures can be reached without polluting the environment. Of course the exact location has to be discovered through detectors which I have already designed under the name "Digger". With this machine the deepest ocean floor can be explored with all its secrets which is far more profitable and a greater accomplishment than the exploration of space. The nuclear power wheel machine can be built in a matter of months. The location of gold layers could also be detected at about the same time. So giving this project one year and success should be on hand. INDEX 1. Heat Collector PA1 2. Expansion Cylinder PA1 3. Spindle Drive Cylinder PA1 4. Pinion Gear Stud PA1 5. Pinion Gear PA1 6. Side Gear PA1 7. Sliding Collar PA1 8. Drive Shaft PA1 9. Lock Screw PA1 10. Spring PA1 11. Spindle Bushing PA1 12. Heat Expansion Valve PA1 13. Big Wheel PA1 14. Bearings PA1 15. Stud PA1 16. Drive Gear PA1 17. Sliding Bushing PA1 18. Cadmium Plunger PA1 19. Cadmium Stick PA1 20. Heat Element (Uranium 235) PA1 21. Lead Crystal Glass Shield PA1 22. Air Hose PA1 23. Push Rod PA1 24. Push Rod Joint PA1 25. Key PA1 26. Ratched Gear Pressure Plate PA1 27. Ratched Pins PA1 28. Springs PA1 29. Ratched Teeth PA1 30. Ratched Gear PA1 31. Side Gear PA1 32. Satellite Gear PA1 33. Rubber Cap PA1 34. Spindle Thread Cylinder PA1 35. Pinion Stud Cylinder PA1 36. Lead Crystal Reflector PA1 37. Stopper for Cadmium Stick PA1 38. Water Pump PA1 39. Suction Stud PA1 40. Bottom Plate PA1 41. Nuclear Power Wheel PA1 42. Wheel Guard PA1 43. Suction Channel PA1 44. Anker Brushes PA1 45. Water Hose PA1 46. Air Pillow PA1 47. Air Hose Joint PA1 48. Air Pressure Hose PA1 49. Air Jets PA1 50. Air Jet Stream PA1 51. Air Compressor PA1 52. Water Hose Outlet PA1 53. Float Collar PA1 54. Float PA1 55. Bearing Bushings PA1 56. Drill Head PA1 57. First Drill Extension PA1 58. Second Drill Extension PA1 59. Side Gear PA1 60. Power Drive for Drill PA1 61. Pump Bracket |
summary | ||
abstract | An x-ray generating system includes a source of x-ray radiation, a waveguide bundle optic for collimating the x-ray radiation produced by the source, a focusing optic for focusing the collimated x-ray radiation to a focal point. |
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description | This application is a National Stage Application of International Application No. PCT/JP2005/000294 filed Jan. 13, 2005, which application published in Japanese on Jul. 28, 2005 as WO 2005/068019 A1 under PCT Article 21 (2). The International Application PCT/JP2005/000294 is based upon and claims the benefit of priority from Japanese Patent application No. 2004-005922, filed on Jan. 13, 2004, the entire contents of which are incorporated herein by reference. The present invention relates to an irradiation field limiting device which forms an irradiation field corresponding to the shape of the lesion of a radiotherapy target subject. When applying radiation to the lesion of a radiotherapy target subject, an irradiation field limiting device has been widely used which forms an irradiation field corresponding to the shape of the lesion by limiting the irradiation range. Japanese (unexamined) Patent Application, No. H06-300896 (hereinafter called “patent document 1”) discloses an irradiation field limiting device which includes an aperture block (hereinafter called “aperture leaf”) of which the surface of the aperture operation which limits the irradiation range forms a cylindrical surface and which is provided with a rack in the inner circumferential surface, and a pinion which engages the aperture leaf, in which the aperture leaf is driven by transmitting rotation of a motor to the rack and the pinion through a chain or the like. Japanese Examined Patent Application, No. H07-10282 (hereinafter called “patent document 2”) discloses an irradiation field limiting device which includes a plurality of aperture leaves in which grooves and protrusions are formed on the sliding surface, in which the aperture leaves are slidably arranged in the side surface direction to shield radiation passing through the opening between the sliding surfaces. The irradiation field limiting device disclosed in the patent document 1 has a problem in which the positional accuracy of the aperture leaf decreases due to wear of the rack and the pinion. Therefore, it is difficult to accurately form the irradiation field. The widths of the rack and the pinion cannot be reduced to a large extent taking durability and the like into consideration (for example, durability significantly decreases when reducing the width to 2 mm or less). This makes it difficult to form an aperture leaf with a reduced thickness. As a result, a large number of aperture leaves cannot be disposed in a limited installation space. When the shape of the aperture leaf is linear, the aperture leaf operates linearly. Therefore, the aperture leaf can be driven with high accuracy in comparison with the irradiation field limiting device disclosed in the patent document 1 which uses the rack and the pinion by forming a female thread portion in the aperture leaf and forming a male thread portion on a drive shaft connected to a motor. In this case, when reducing the thickness of the aperture leaf, the diameters of the female thread portion and the male thread portion must be correspondingly reduced. As a result, the female thread portion and the male thread portion exhibit reduced ridge strength. Therefore, it is difficult to ensure stable operation over a long period of time since the ridges easily wear and exhibit poor lubricity. The irradiation field limiting device disclosed in the patent document 2 has a problem in which it is difficult to form a thin aperture leaf because the groove is formed in the sliding surface of the aperture leaf. An object of the present invention is to provide an irradiation field limiting device which allows arrangement of a plurality of thin aperture leaves and can accurately form an irradiation field by accurately driving the aperture leaves. A first invention provides an irradiation field limiting device which shields radiation from a radiation source by driving a plurality of aperture leaves, arranged in a thickness direction, a specific amount to limit an irradiation field to a desired range, the irradiation field limiting device comprising: a flexible linear member secured to a thick portion of the aperture leaf; and a driver section which drives the linear member. A second invention provides the irradiation field limiting device according to the first invention, wherein the driver section includes: a base; a drive shaft connected with a driving source through a connection portion and inserted into the base; and a slider which moves along an axial direction of the drive shaft accompanying rotation of the drive shaft and is connected with the linear member. A third invention provides the irradiation field limiting device according to the second invention, wherein the connection portion includes a torque limiter section which limits transmission of torque equal to or greater than a specific torque. A fourth invention provides the irradiation field limiting device according to the third invention, wherein the connection portion includes a clutch mechanism which transmits a driving force to the drive shaft or disconnects the driving force from the drive shaft; and wherein the irradiation field limiting device includes a control section which prevents the driving force from being transmitted to the drive shaft using the clutch mechanism when the torque limiter section has operated for a specific period of time. A fifth invention provides the irradiation field limiting device according to the second invention, wherein the connection portion includes: a clutch mechanism which transmits a driving force to the drive shaft or disconnects the driving force from the drive shaft; and wherein the irradiation field limiting device includes a position detection section which detects a position of the aperture leaf; and a control section which prevents the driving force from being transmitted to the drive shaft using the clutch mechanism to stop movement of the aperture leaf when the position detection section has detected that the aperture leaf has moved to a target position. A sixth invention provides the irradiation field limiting device according to the second invention, comprising: a driving force transmission section which transmits a driving force of the driving source to a plurality of the drive shafts; a plurality of clutch mechanisms which transmit the driving force to the drive shafts or disconnect the driving force from the drive shafts; and a control section which can drive each of the aperture leaves by transmitting the driving force of the driving source in units of the drive shafts by controlling each of the clutch mechanisms. A seventh invention provides the irradiation field limiting device according to the second invention, wherein the slider has a female thread portion; and wherein the drive shaft has a male thread portion which engages the female thread portion and moves the slider in the axial direction of the drive shaft by being rotated. An eighth invention provides the irradiation field limiting device according to the first invention, wherein the aperture leaf is fan-shaped or approximately rectangular. A ninth invention provides the irradiation field limiting device according to the first invention, wherein the linear member is a continuous metal wire, a wire rope formed by twisting the metal wires, or a hollow pipe. A tenth invention provides the irradiation field limiting device according to the second invention, comprising: a support shaft provided in the base and disposed approximately in parallel with the drive shaft at a specific interval from the drive shaft; at least one guide which is supported on the support shaft so that the guide can move in an axial direction of the support shaft and maintains a shape of the linear member; and an elastic member which is disposed between the guides and maintains an approximately identical interval between the guides. An eleventh invention provides the irradiation field limiting device according to the second invention, comprising: an absolute position sensor which measures an absolute position of the aperture leaf and/or the slider; and a high-resolution relative position sensor which measures an amount of movement from a specific position of the aperture leaf and/or the slider measured using the absolute position sensor. A twelfth invention provides the irradiation field limiting device according to the first invention, wherein the aperture leaves are arranged in a thickness direction so that the aperture leaves can freely move through rolling elements, and a side surface of the aperture leaf protrudes in the thickness direction to form a holding portion which holds the rolling element. A thirteenth invention provides the irradiation field limiting device according to the twelfth invention, wherein the holding portion forms a straight line and/or a curve to hold the rolling element. A fourteenth invention provides the irradiation field limiting device according to the twelfth invention, wherein one of the adjacent rolling elements provided on either side of the aperture leaf is disposed at a position close to the radiation source, and the other is disposed at a position away from the radiation source. A fifteenth invention provides the irradiation field limiting device according to the twelfth invention, wherein the holding portions are disposed at different positions with respect to the irradiation direction, and are repeatedly disposed at an identical position in units of a specific number of the aperture leaves. A sixteenth invention provides the irradiation field limiting device according to the twelfth invention, wherein the holding portion is a shielding portion which prevents radiation from passing through a space between the aperture leaves adjacent to each other. A seventeenth invention provides the irradiation field limiting device according to the first invention, comprising a shielding portion which shields radiation in an opening between the aperture leaves adjacent to each other. An eighteenth invention provides the irradiation field limiting device according to the first invention, wherein the linear members respectively secured to the aperture leaves adjacent in the thickness direction differ in axial direction. A nineteenth invention provides the irradiation field limiting device according to the eighteenth invention, wherein the driver section drives the aperture leaf of which the axial direction of the linear member is set to be identical in units of a specific number of the linear members. A twentieth invention provides the irradiation field limiting device according to the first invention, wherein the linear members respectively secured to the aperture leaves adjacent in the thickness direction differ in axial direction and are identical in axial direction in units of a specific number of the linear members; and wherein the irradiation field limiting device includes a plurality of driver units each of which includes a plurality of the driver sections which respectively drive the linear members of which the axial directions are set to be identical in units of a specific number of the linear members. A twenty first invention provides the irradiation field limiting device according to the first invention, comprising a linear member holding portion which holds the linear member between the aperture leaf and the driver section so that the linear member can move in the axial direction to prevent the linear member from buckling. A twenty second invention provides the irradiation field limiting device according to the first invention, wherein the linear member drives the aperture leaf while contacting the thick portion, is preliminarily bent in a direction away from a contact portion between the linear member and the thick portion, and presses a portion in contact with the contact portion so that the linear member is prevented from buckling. The following effects are obtained by the present invention. (1) In the irradiation field limiting device according to the present invention, the flexible linear member is secured to the thick portion of each of the aperture leaves arranged in the thickness direction and which shield radiation from the radiation source, and the driver section drives the linear member a specific amount. According to this irradiation field limiting device, since it suffices that the aperture leaf have such a thickness that the linear member can be secured to the aperture leaf, the thickness of the aperture leaf can be sufficiently reduced. (2) In the irradiation field limiting device according to the present invention, the driver section includes the slider which moves along the axial direction of the drive shaft accompanying rotation of the drive shaft inserted into the base, and the flexible linear member is connected with the slider. According to this irradiation field limiting device, since the aperture leaf to which the linear member is secured can be driven due to the movement of the slider accompanying the rotation of the drive shaft, the irradiation field can be accurately formed. (3) In the irradiation field limiting device according to the present invention, the connection portion includes the torque limiter section (driving force limiting section) which limits transmission of torque (driving force) equal to or greater than a specific torque. According to this irradiation field limiting device, the torque limiter (torque limiter section) limits the transmission of torque from the motor (driving source) when the oppositely disposed aperture leaves contact the inner side surfaces during the opening/closing operation so that a load equal to or greater than a specific load is applied to the drive shaft, whereby breakage of the motor and the like can be prevented. (4) In the irradiation field limiting device according to the present invention, the connection portion includes the clutch mechanism which transmits the driving force to the drive shaft or disconnects the driving force from the drive shaft. The control section prevents the driving force from being transmitted to the drive shaft using the clutch mechanism when the torque limiter section has operated for a specific period of time. According to this irradiation field limiting device, excess wear of the contact surface can be prevented when using a mechanical torque limiter (torque limiter section), for example. Moreover, excess operation of the motor (driving source) in a high load state can be prevented, whereby breakage of the motor can be prevented. (5) In the irradiation field limiting device according to the present invention, the connection portion includes the clutch mechanism which transmits the driving force to the drive shaft or disconnects the driving force from the drive shaft, and the position detection section which detects the position of the aperture leaf is provided. When the position detection section has detected that the aperture leaf has moved to the target position, the control section prevents the driving force from being transmitted to the drive shaft using the clutch mechanism to stop movement of the aperture leaf. According to this irradiation field limiting device, since the aperture leaf can be prevented from moving across (i.e. (overrunning)) the target position, the aperture leaf can be stopped in a short time. Specifically, the aperture leaf can be stably controlled and driven. (6) The irradiation field limiting device according to the present invention includes the driving force transmission section which transmits the driving force of the driving source to the drive shafts, and the clutch mechanisms which transmit the driving force to the drive shafts or disconnect the driving force from the drive shafts The control section controls driving of the aperture leaves by transmitting the driving force of the driving source in units of the drive shafts by controlling the clutch mechanisms. According to this irradiation field limiting device, the driving force of one driving source can be transmitted to the drive shafts using a pulley, gear, and the like (driving force transmission section), and the drive shaft provided in each base can be driven, for example. The irradiation field limiting device can control and drive the aperture leaves by controlling the clutch mechanisms in units of the drive shafts using the control section. Moreover, since one driving source drives the drive shafts, the space required for the driving source can be reduced, whereby the size of the driver section can be reduced. (7) In the irradiation field limiting device according to the present invention, the drive shaft has a male thread portion which engages a female thread portion and moves the slider in the axial direction of the drive shaft by being rotated. This allows the irradiation field limiting device to accurately drive the aperture leaf. (8) In the irradiation field limiting device according to the present invention, the fan-shaped or approximately rectangular aperture leaf can be accurately driven along a path by securing the flexible linear member to the aperture leaf. (9) In the irradiation field limiting device according to the present invention, since the linear member is a continuous metal wire, a wire rope formed by twisting the wires, or a hollow pipe, the linear member exhibits flexibility. (10) In the irradiation field limiting device according to the present invention, the support shaft is provided in the base approximately in parallel with the drive shaft at a specific interval from the drive shaft, and at least one guide maintains the shape of the linear member and can move in the axial direction of the support shaft. The elastic member is disposed to maintain an approximately identical interval between the guides. According to this irradiation field limiting device, when a load is applied to the linear member in the axial direction when driving the aperture leaf, the linear member can be prevented from buckling in the base. (11) In the irradiation field limiting device according to the present invention, the absolute position sensor measures the absolute position of the aperture leaf and/or the slider. The high-resolution relative position sensor measures the amount of movement from a specific position of the aperture leaf and/or the slider utilizing the absolute position sensor. According to this irradiation field limiting device, the reference position (specific position) of the oppositely disposed aperture leaves is measured using the absolute position sensor in a state in which an opening is not formed between the aperture leaves, and the amount of movement of the aperture leaf from the specific position is measured using the relative position sensor, whereby the position of the aperture leaf can be more accurately measured. Moreover, since the position of the aperture leaf is always monitored using the absolute position sensor, an alarm signal can be output to the control section when the absolute position information obtained using the absolute position sensor differs from the amount of movement of the aperture leaf from the specific position measured using the relative position sensor. (12) In the irradiation field limiting device according to the present invention, the aperture leaves are arranged in the thickness direction so that the aperture leaves can freely move through rolling elements, and the side surface of the aperture leaf protrudes in the thickness direction to form the holding portion which holds the rolling element. According to this irradiation field limiting device, even if an opening is formed between the aperture leaves, strong radiation can be prevented from passing through the opening. Moreover, the strength of the aperture leaf can be maintained to be equal to or greater than a specific value. (13) In the irradiation field limiting device according to the present invention, the holding portion forms a straight line and/or a curve to hold the rolling element. According to this irradiation field limiting device, even when using a thin aperture leaf, the holding portion can be formed by bending or cutting the aperture leaf. (14) In the irradiation field limiting device according to the present invention, one of the adjacent rolling elements provided on either side of the aperture leaf is disposed at a position close to the radiation source, and the other is disposed at a position away from the radiation source. According to this irradiation field limiting device, a situation can be prevented in which the total thickness of the aperture leaves arranged in the thickness direction changes due to the rolling element. Since the opening between the aperture leaves is uniformly maintained by the adjacent rolling elements, a situation can be prevented in which the adjacent aperture leaves provided on either side of the rolling element come in contact to increase the frictional resistance, whereby a large amount of load is applied to the linear member, the driver section, and the like. (15) In the irradiation field limiting device according to the present invention, the holding portions are disposed at different positions with respect to the irradiation direction, and are repeatedly disposed at an identical position in units of a specific number of the aperture leaves. According to this irradiation field limiting device, since the shape of the aperture leaf can be made identical in units of a specific number of aperture leaves, the holding portions can be formed by repeatedly arranging a specific number of aperture leaves. (16) In the irradiation field limiting device according to the present invention, the holding portion holds the rolling element and also serves as the shielding portion which prevents radiation from passing through the space between adjacent aperture leaves. According to this irradiation field limiting device, the holding portion of the rolling element can prevent radiation from leaking through the space between adjacent aperture leaves. (17) The irradiation field limiting device according to the present invention includes the shielding portion which shields radiation in the opening between adjacent aperture leaves. According to this irradiation field limiting device, radiation can be prevented from leaking through the space between adjacent aperture leaves. (18) In the irradiation field limiting device according to the present invention, the linear members respectively secured to the aperture leaves adjacent in the thickness direction differ in axial direction. According to this irradiation field limiting device, a space sufficient to accommodate the driver section can be provided. Moreover, a driver section of a necessary size can be provided. (19) In the irradiation field limiting device according to the present invention, the driver section drives the aperture leaf of which the axial direction of the linear member is set to be identical in units of a specific number of the linear members. According to this irradiation field limiting device, the driver sections can be disposed at specific intervals in units of the axial directions of the linear members. Moreover, since adjacent aperture leaves need not be driven using one driver section, the size of the driver section can be increased to a certain extent. As a result, cost can be reduced, and the durability of the driver section can be maintained. (20) In the irradiation field limiting device according to the present invention, the linear members respectively secured to the aperture leaves adjacent in the thickness direction differ in axial direction and are identical in axial direction in units of a specific number of the linear members. Each driver unit includes a plurality of driver sections which respectively drive the linear members of which the axial directions are set to be identical in units of a specific number of the linear members. This allows the irradiation field limiting device to simply contain the driver sections by disposing the driver sections in units of the axial directions of the linear members and providing the driver units containing the driver sections in units of the axial directions of the linear members. (21) The irradiation field limiting device according to the present invention includes the linear member holding portion which holds the linear member between the aperture leaf and the driver section so that the linear member can move in the axial direction to prevent the linear member from buckling. This allows the irradiation field limiting device to stably drive the aperture leaf, whereby reliability can be improved. (22) In the irradiation field limiting device according to the present invention, the linear member drives the aperture leaf while coming in contact with the thick portion of the aperture leaf. The linear member is preliminarily bent in the direction away from the contact portion between the linear member and the thick portion of the aperture leaf, and presses the contact portion between the linear member and the thick portion after being assembled. According to this irradiation field limiting device, since the linear member can be prevented from buckling in the contact portion between the linear member and the thick portion of the aperture leaf, the aperture leaf can be stably driven, whereby the reliability can be improved. 1: radiation source 3: linear member 5: potentiometer 10 and 10-1: driver section 10A, 10B, and 10C: driver unit 11: base 12: driving source 14: drive shaft 15 and 15-1: slider 16: support shaft 17: potentiometer 19: encoder 20 and 40: aperture leaf 21 to 28: rolling element 31: guide 32: elastic member R1 to R9: roller 100, 100A, and 100B: irradiation field limiting device A: irradiation field The present invention achieves the object of providing an irradiation field limiting device which allows arrangement of a plurality of thin aperture leaves and can accurately form an irradiation field by accurately driving the aperture leaves by securing a flexible linear member to a thick portion of the aperture leaf and driving the linear member a specific amount using a driver section. Embodiments of the present invention are described below in detail with reference to the drawings. FIG. 1 is a view showing an irradiation field limiting device 100 according to a first embodiment of the present invention. The irradiation field limiting device 100 is a device for shielding radiation from a radiation source 1 to limit an irradiation field A to a desired range, the device including an aperture leaf 20, a flexible linear member 3 secured to the thick portion of the aperture leaf 20, a driver section 10 which drives the linear member 3 a specific amount, and the like. The aperture leaf 20 is formed of an appropriate material (e.g. tungsten) which shields the radiation from the radiation source 1, for example. A plurality of aperture leaves 20 are arranged in the thickness direction. Each aperture leaf 20 includes fan-shaped aperture leaves 20A and 20B oppositely disposed. Members disposed for the aperture leaf 20A are described below for convenience of description. Note that these members are similarly disposed for the aperture leaf 20B. One end of the linear member 3 is secured to the aperture leaf 20A through a connection section 4 tangentially to the outer arc of the aperture leaf 20A. The other end of the linear member 3 is connected with the driver section 10. When the driver section 10 applies a load to the linear member 3, the linear member 3 is easily warped along the arc of the aperture leaf 20A without buckling. The linear member 3 may be formed using an appropriate material (e.g., continuous metal wire, wire rope formed by twisting such wires, or hollow pipe) insofar as the material exhibits flexibility. The linear member 3 drives the aperture leaf 20A while contacting the thick portion of the aperture leaf 20A. The linear member 3 is preliminarily bent in the direction away from the contact portion between the linear member 3 and the thick portion, as indicated by the dash-dot-dot line in FIG. 1, before being secured to the connection section 4, and presses the contact portion between the linear member 3 and the thick portion with a large force after being assembled. This allows the irradiation field limiting device 100 to prevent the linear member 3 from buckling in the contact portion between the linear member 3 and the thick portion of the aperture leaf 20A. The driver section 10 includes a base 11, a driving source 12, a connection portion 13, a drive shaft 14, a slider 15 connected with the linear member 3, a support axis 16, and the like. The drive shaft 14 is connected with the driving source 12 through the connection portion 13, and inserted into the base 11. The connection portion 13 includes a clutch mechanism and a torque limiter mechanism (torque limiter section). The clutch mechanism of the connection portion 13 transmits the driving force of the driving source 12 to the drive shaft 14 through mechanical contact, or disconnects the driving force from the drive shaft 14. When a control section (not shown) moves the aperture leaf 20A to the target position and detects that the aperture leaf 20A has moved to the target position from location information of a potentiometer 5, an encoder 19, and the like (position detection section) described later, the control section prevents the driving force from being transmitted to the drive shaft 14 using the clutch mechanism to stop the movement of the aperture leaf 20A. This allows the irradiation field limiting device 100 to prevent the aperture leaf 20A from moving across (i.e. (overrunning)) the target position. Specifically, the irradiation field limiting device 100 allows the movement of the aperture leaf 20A to be completed within a short time to ensure stable control and drive of the aperture leaf 20A. In the irradiation field limiting device 100, since the drive shaft 14 engages the slider 15, as described later, the position of the slider 15 can be maintained after the clutch mechanism has disconnected the driving force from the drive shaft 14. The torque limiter mechanism of the connection portion 13 is an overload protection mechanism of which the spring force is adjusted so that the mechanical contact of the clutch mechanism is effected by the spring and the mechanical contact surfaces slide when a load equal to or greater than a specific load has been applied to the drive shaft 14. In the irradiation field limiting device 100, when a load equal to or greater than a specific load has been applied to the drive shaft 14 due to contact between inner side surfaces 20A-a and 20B-a of the aperture leaves 20A and 20B, breakage of the driving source 12 can be prevented by operating the torque limiter mechanism, for example. The drive shaft 14 has a male thread portion 14A and engages a female thread portion 15A formed in the slider 15. The slider 15 moves along the axial direction of the drive shaft 14 accompanying rotation of the drive shaft 14. The slider 15 is supported on a support shaft 16 which is disposed approximately in parallel with the drive shaft 14 at a specific interval from the drive shaft 14, whereby rotation around the drive shaft 14 is limited. Rollers R1 to R6 (linear member holding portions) hold the linear member 3 positioned outside the base 11 and prevent the linear member 3 from buckling. The rollers R1 to R6 specify the path of the linear member 3. Specifically, the irradiation field limiting device 100 according to this embodiment prevents the linear member 3 from buckling by allowing the rollers R1 to R6 to hold the linear member 3 positioned between the aperture leaf 20A and the driver section 10 so that the linear member 3 can move in the axial direction. Rollers R7 to R9 are disposed along the outer circumferential surface of the aperture leaf 20A to hold the aperture leaf 20A. Since the linear member 3 is connected with the slider 15 which moves in the axial direction of the drive shaft 14 through engagement between the male thread portion 14A and the female thread portion 15A, the load due to the movement of the slider 15 is directly transmitted to the linear member 3, whereby the aperture leaf 20 is driven a specific amount (see FIG. 2). In more detail, FIG. 1 illustrates a state in which the linear member 3 is pulled into the base 11 by the slider 15 so that the aperture leaf 20A is pulled in the direction in which the irradiation field A is enlarged. On the other hand, FIG. 2 illustrates a state in which the linear member 3 is pushed out from the base 11 by the slider 15 so that the aperture leaf 20A is pushed in the direction in which the irradiation field A is reduced (seen the arrow in FIG. 2). Since the amount of movement of the linear member 3 connected with the slider 15 and the rotation angle of the drive shaft 14 have a proportional relationship, the amount that the aperture leaf 20 is driven can be accurately controlled through accurate control of the rotation angle. Means for accurately detecting the position of the aperture leaf 20 in order to accurately control the amount that the aperture leaf 20 is driven is described below. The irradiation field limiting device 100 includes a potentiometer 5 (absolute position sensor) and an encoder 19 (relative position sensor) for detecting the position of the aperture leaf 20. The potentiometer 5 is a linear potentiometer and includes a detection spring 5a and a meter body 5b. The detection spring 5a is a plate spring formed of phosphorus bronze or the like and secured to the side surface of the aperture leaf 20A. One end of the detection spring 5a contacts the meter body 5b described later. The meter body 5b is a member formed of a material with a specific electric resistance. The surface 5c of the meter body 5b on the side of the radiation source 1 forms a circumferential surface around the radiation source 1. The surface 5c of the meter body 5b contacts the end of the detection spring 5a which moves to follow the movement of the aperture leaf 20A. This causes the electric resistance of the plate spring 5a and the meter body 5b to change. The potentiometer 5 measures the electric resistance to detect the position of the plate spring 5a. Since the outer circumferential surface of the aperture leaf 20A and the surface 5c of the meter body 5b are circumferential surfaces around the radiation source 1, the position of the aperture leaf 20A can be detected from the diameters of the circumferential surfaces and the position of the plate spring 5a. The encoder 19 is a detection section which measures the amount of movement from the position of the slider 15, and is provided on the end of the drive shaft 14 opposite to the driving source 12 through a connection portion 18 The encoder 19 measures the amount of movement of the slider 15 by counting the number of pulses generated through the rotation of the drive shaft 14. For example, when the encoder 19 counts 256 pulses during one rotation of the drive shaft 14 and the slider 15 is set to move in an amount of 1 mm by one rotation of the drive shaft 14, the encoder 19 can measure the amount of movement of the slider 15 in units of 1/256 mm (i.e. 3.9 microns). This allows the irradiation field limiting device 100 to drive the linear member 3 and accurately control and drive the aperture leaf 20A. An example of the process of detecting and controlling the position of the aperture leaf 20A using the potentiometer 5, the encoder 19, and the like is described below. The control section (not shown) directs that the inner side surfaces 20A-a and 20B-a of the aperture leaves 20A and 20B come in contact, detects the reference position of the aperture leaf 20A using the potentiometer 5 in a state in which the opening is not formed between the inner side surfaces 20A-a and 20B-a, and stores the reference positions (specific positions) of the aperture leaf 20A and the slider 15. The control section calculates the amount of movement of the aperture leaf 20A and the number of rotations of the drive shaft 14 from the target position of the aperture leaf 20A input from an operation section (not shown), and calculates a specific number of pulses of the encoder 19 corresponding to the number of rotations. The control section drives the driving source 12 to rotate the drive shaft 14, and stops the driving source 12 after the specific number of pulse has been reached. In the above example, when the user has set the target position at a position of 10 mm from the reference position (i.e. the amount of movement is 10 mm), the control section rotates the drive shaft 14 ten times. Therefore, the control section drives the driving source 12 until the encoder 19 counts 2560 pulses (=256 pulses×10). This allows the irradiation field limiting device 100 to accurately detect the current position of the aperture leaf 20A based on the absolute location information of the aperture leaf 20A and the relative position information of the slider 15. Specifically, the control section can accurately form the irradiation field A by calculating the difference between the position of the aperture leaf 20A detected using the potentiometer 5 and the target position, controlling the rotation of the drive shaft 14 in order to drive the aperture leaf 20A to the target position, and driving the aperture leaf 20A a specific amount. In the above operation, the control section can prevent the aperture leaf 20A from overrunning the target position by disconnecting the driving force from the drive shaft 14 using the clutch mechanism of the connection portion 13 when the control section has recognized that the aperture leaf 20A has reached the target position. The irradiation field limiting device 100 can monitor the position of the aperture leaf 20A in two ways from the absolute position information of the aperture leaf 20A detected using the potentiometer 5 and the position information measured based on the amount of movement from the position of the aperture leaf 20A detected using the encoder 19. This allows the irradiation field limiting device 100 to output an alarm signal to the control section when the two pieces of position information differ in an amount equal to or greater than a specific amount. FIG. 3 is a perspective view showing an irradiation field limiting device 100A according to a second embodiment of the present invention. FIG. 4A is a front view and FIG. 4B is a sectional view taken along line B-B of FIG. 4A, showing the irradiation field limiting device 100A according to the second embodiment of the present invention. Note that the same members as those of the above-described irradiation field limiting device 100 are indicated by the same symbols for convenience of description. Description of the functions and the like of these members are appropriately omitted. The irradiation field limiting device 100A includes a plurality of thin aperture leaves 20A-1 to 20A-12 (about 3 to 5 mm) arranged in the thickness direction, flexible linear members 3 secured to the thick portions of the aperture leaves 20A-1 to 20A-12, a plurality of driver units 10A to 10C which drive the linear members 3 in specific amounts, and the like. A plurality of sliders 15 (see FIG. 1) are contained in the driver unit 10A, in which the driver sections which respectively drive the linear members 3A-1 to 3A-4 are provided. Likewise, the driver sections which respectively drive the linear members 3B-1 to 3B-4 and 3C-1 to 3C-4 are provided in the driver units 10B and 10C. As shown in the drawings, the linear members 3A-1 to 3A-4 are almost identical in axial direction. Likewise, the linear members 3B-1 to 3B-4 and the linear members 3C-1 to 3C-4 are almost identical in axial direction, respectively. On the other hand, the linear members 3A-1 to 3A-4, the linear members 3B-1 to 3B-4, and the linear members 3C-1 to 3C-4 differ in axial direction. As shown the drawings, the linear members 3A-1 to 3A-4 are connected with the driver unit 10A on one end, and are respectively connected with the aperture leaves 20A-1, 20A-4, 20A-7, and 20A-10 on the other end. The linear members 3B-1 to 3B-4 are connected with the driver unit 10B on one end, and are respectively connected with the aperture leaves 20A-2, 20A-5, 20A-8, and 20A-11 on the other end. The linear members 3C-1 to 3C-4 are connected with the driver unit 10C on one end, and are respectively connected with the aperture leaves 20A-3, 20A-6, 20A-9, and 20A-12 on the other end. As shown the drawings, the linear members 3A-1 and 3B-1 respectively secured to the aperture leaves (e.g., aperture leaves 20A-1 and 20A-2) adjacent in the thickness direction differ in axial direction. Therefore, since the irradiation field limiting device 100A can drive the aperture leaves adjacent in the thickness direction using different driver sections, a plurality of sliders 15 can be provided in the driver sections 10A to 10C of which the size is increased to a certain extent. In more detail, when the aperture leaf 20A-1 to 20A-12 have a thickness of 5 mm, since one slider 15 must have a thickness of 15 mm, the linear members 3 connected with the sliders 15 are connected with the aperture leaves every three aperture leaves. Specifically, since the irradiation field limiting device 100A allows the driver units 10A to 10C to be disposed at specific intervals, as described above, even if the thicknesses of the aperture leaves 20A-1 to 20A-12 are reduced, the aperture leaves adjacent in the thickness direction can be driven using the driver sections with durability. Therefore, the irradiation field limiting device 100A allows the driver units 10A to 10C to be disposed at specific intervals in units of the axial directions of the linear members 3A-1 to 3A-4, 3B-1 to 3B-4, and 3C-1 to 3C-4. Moreover, since one driver unit (e.g. driver unit 10A) need not drive the aperture leaves (e.g., aperture leaves 20A-1 and 20A-2) adjacent in the thickness direction, the size of the driver units 10A to 10C can be increased to a certain extent. This reduces cost and maintains the durability of the driver units 10A to 10C. In the irradiation field limiting device 100A according to this embodiment, the linear members 3 (3A-1 to 3A-4, 3B-1 to 3B-4, and 3C-1 to 3C-4) respectively secured to the aperture leaves 20A (aperture leaves 20A-1, 20A-4, 20A-7, and 20A-10, aperture leaves 20A-2, 20A-5, 20A-8, and 20A-11, and aperture leaves 20A-3, 20A-6, 20A-9, and 20A-12) adjacent in the thickness direction differ in axial direction, and the axial directions are set to be identical in units of a specific number (three in this embodiment) of linear members. The driver units 10A, 10B, and 10C contain the driver sections which respectively drive the linear members of which the axial directions are set to be identical in units of a specific number of linear members. This allows the irradiation field limiting device 100 to simply contain the driver sections by disposing the driver sections in units of the axial directions of the linear members 3 and providing the driver units 10A, 10B, and 10C containing the driver sections in units of the axial directions of the linear members 3. FIG. 5 is a view showing an aperture leaf 20A according to a third embodiment of the present invention (corresponding to the cross-sectional view along the line D-D in FIG. 1 showing the first embodiment). The aperture leaf 20A includes aperture leaves which are arranged in the thickness direction so that the aperture leaves can freely move through rolling elements. The aperture leaves 20A-1 to 20A-4 are described below. As shown in FIG. 5, when the shape of the aperture leaves 20A-1 to 20A-4 is considered as one pattern, the aperture leaf 20A is formed by repeatedly arranging the aperture leaves 20A-1 to 20A-4 in the thickness direction (described later). The aperture leaves 20A-1 to 20A-4 are arranged in the thickness direction so that the aperture leaves 20A-1 to 20A-4 can freely move through rolling elements 21 to 28. As shown in FIG. 5, the side surfaces of the aperture leaves 20A-1 to 20A-4 protrude in the thickness direction to form holding portions which hold the rolling elements 21 to 28. Therefore, even when the aperture leaves 20A-1 to 20A-4 are driven and an opening occurs between the aperture leaves, strong radiation can be prevented from passing through the space between the aperture leaves 20A-1 to 20A-4. Specifically, the holding portions hold the rolling elements 21 to 28 and function as shielding portions which shield radiation. The strength of the aperture leaves 20A-1 to 20A-4 can be maintained at a value equal to or higher than a specific value by adjusting the thicknesses of the aperture leaves 20A-1 to 20A-4 forming the holding portions and the size of the rolling elements 21 to 28 to values equal to or higher than specific values. The rolling elements 21 to 28 may have an appropriate shape (e.g., ball shape, cylindrical, or conical trapezoidal) insofar as the rolling elements 21 to 28 function as bearings when the aperture leaves 20A-1 to 20A-4 are respectively driven using the linear members 3A-1, 3B-1, 3C-1, and 3A-2. The rolling elements 21 to 24 are disposed at a position closer to the radiation source 1 than the rolling elements 25 to 28, and have a diameter smaller than that of the rolling elements 25 to 28. The aperture leaves 20A-1 to 20A-4 are smoothly driven using the linear members 3A-1, 3B-1, 3C-1, and 3A-2. The arrangement of the rolling elements 23 and 24 and the rolling elements 27 and 28 adjacent on either side of one aperture leaf (e.g. aperture leaf 20A-1) is described below. The rolling element 23 is disposed at a position close to the radiation source 1, and the rolling element 24 is disposed at a position away from the radiation source 1. Likewise, the rolling element 27 is disposed at a position close to the radiation source 1, and the rolling element 28 is disposed at a position away from the radiation source 1. Therefore, the thickness of the entire aperture leaf 20A does not change depending on the size of the rolling elements 21 to 28. For example, a rolling element having a diameter almost equal to the thickness of the aperture leaf 20A-1 may be held using the holding portion. Since the opening between the aperture leaves 20A-1 and 20A-2 is uniformly maintained by the rolling elements 23 and 27, a situation can be prevented in which the frictional resistance increases due to contact between the aperture leaves 20A-1 and 20A-2, whereby a large amount of load is applied to the linear member 3, the driver section 10, and the like. The holding portions are formed of a straight line and/or a curve formed by bending or cutting the aperture leaves 20A-1 to 20A-4. As a result, the holding portions can be formed even if the thicknesses of the aperture leaves 20A-1 to 20A-4 are reduced. As shown in FIG. 5, the holding portions are disposed at different positions with respect to the irradiation direction (see FIG. 1). The holding portions are repeatedly disposed at an identical position in units of a specific number (four in this embodiment) of aperture leaves 20A-1 to 20A-4. Therefore, the aperture leaf 20A allows the holding portions to be formed by repeatedly arranging the aperture leaves of the same shape in units of a specific number. As a result, the number of types of bending or cutting can be set at a specific value when forming the aperture leaf 20A, whereby the aperture leaf 20A can be quickly formed at reduced cost. FIGS. 6A to 6C are view showing a driver section 10-1 according to a fourth embodiment of the present invention. FIG. 6C is a view as seen from the direction of C-C in FIG. 6A. Note that description of the functions and the like of the same members as those of the above-described driver section 10 is appropriately omitted. The driver section 10-1 differs from the driver section 10 in that the driver section 10-1 includes a slider 15-1, a guide 31, an elastic member 32 (coil spring in FIG. 6A or 6B), and the like which are provided in the base 11, for example. The slider 15-1 can move in the axial direction of the drive shaft 14 accompanying the rotation of the drive shaft 14, and includes a pedestal portion 15-1a and an engagement portion 15-1b connected with the pedestal section 15-1a. The pedestal section 15-1a includes a female thread portion 15A which engages the male thread portion 14A of the drive shaft 14, a support hole 15B through which the support shaft 16 passes, and a joint portion 15C connected with the linear member 3. The guide 31 is supported on the support shaft 16, can move in the axial direction of the support shaft 16, and maintains the shape of the linear member 3. The elastic member 32 supported on the support shaft 16 is disposed between the guides 31. In FIG. 6A, illustrates a state in which the linear member 3 is pulled into the base 11 by the slider 15-1 (i.e. a state in which the aperture leaf 20A is pulled out in the direction in which the irradiation field A is enlarged). In this case, since the linear member 3 can freely move in the base 11 in the driver section 10 (see FIG. 1), the linear member 3 may buckle when the slider 15 pushes the linear member 3 out of the base 11. In order to prevent the linear member 3 from buckling in the base 11, the driver section 10-1 according to this embodiment includes the guides 31 supported on the support shaft 16 and the elastic member 32 disposed between the guides 31. The elastic member 32 can maintain the interval between the guides 31 approximately identical, even if the guides 31 have moved in the axial direction of the support shaft 16. The interval between the guides 31 is determined by the length of the elastic member 32. As the elastic member 32, an appropriate elastic member other than the coil spring may be used insofar as the interval between the guides 31 can be maintained approximately identical. In FIG. 6B, illustrates a state in which the linear member 3 is pushed out from the base 11 by the slider 15-1 (i.e. a state in which the aperture leaf 20A is pushed in the direction in which the irradiation field A is reduced). In this case, since only a small portion of the linear member 3 freely moves in the base 11 and the elastic member 32 provided between the guides 31 shrinks, the interval between the guides 31 is reduced, whereby the linear member 3 can be reliably prevented from buckling. FIG. 7 is a view showing an irradiation field limiting device 100B according to a fifth embodiment of the present invention. The irradiation field limiting device 100B differs from the irradiation field limiting device 100 according to the first embodiment in that one end of the linear member 3 is secured to an approximately rectangular aperture leaf 40 (aperture leaf 40A in FIG. 7) through the connection section 4 tangentially to the shape on the outer circumference of the aperture leaf 40. The other end of the linear member 3 is connected with the slider 15 provided in the driver section 10. The approximately rectangular aperture leaf 40A is driven a specific amount along a path guided by the rollers R5, R7, and R8 along with the movement of the slider 15. According to the irradiation field limiting device 100B, even if the aperture leaf 40A is approximately rectangular, the aperture leaf 40A can be accurately driven along the path by securing the flexible linear member 3 to the aperture leaf 40A. (Modification) The present invention is not limited to the above-described embodiments, and various modifications and variations may be made. Such modifications and variations are also within the scope of the equivalence of the present invention. (1) In the driver sections 10 and 10-1, the slider 15 is driven in the axial direction of the drive shaft 14 by causing the male thread portion 14A formed in the drive shaft 14 connected with the driving source 12 to engage the female thread portion 15A of the slider 15. Note that the present invention is not limited thereto. An appropriate drive method (e.g. method of driving the slider 15 using a hydraulic mechanism or a pneumatic mechanism) may be used insofar as the driving force of the driving source 12 can be transmitted to the slider 15. (2) In the driver sections 10 and 10-1, one drive shaft 14 is driven using one driving source 12. Note that the present invention is not limited thereto. A plurality of drive shafts 14 may be driven using one driving source. In more detail, a pulley (or a gear) or the like corresponding to the position of each drive shaft 14 is provided to the drive shaft connected with one driving source, and a belt (or a gear which engages the gear provided to the drive shaft) or the like connected with the pulley is provided on one end of each drive shaft 14. This allows the driving force of one driving source to be transmitted to each drive shaft 14 through the pulley, the gear, and the like. When applying radiation to the lesion of a radiotherapy target subject, it is necessary to accurately form an irradiation field corresponding to the shape of the lesion in a short time. Accordingly, the required driving amount differs for each of the arranged aperture leaves 20 and 40. Therefore, a control section is provided which controls the clutch mechanism of the connection portion 13 of each of the aperture leaves 20 and 40, and the control section calculates the driving amount of each drive shaft 14 required for each of the aperture leaves 20 and 40 and the transmission time of the driving force of one driving source using the clutch mechanism corresponding to the driving amount based on the absolute position information of the aperture leaves 20 and 40 and/or the slider 15 and the relative position information of the slider 15. According to this control section, the driving force of one driving source can be transmitted for a period of time necessary for each drive shaft 14 corresponding to the driving amount of each drive shaft 14 corresponding to the arranged aperture leaves 20 and 40, whereby the drive shafts 14 can be accurately controlled using one driving source, and the irradiation field can be accurately formed in a short time. Moreover, since a different driving source 12 need not be disposed for each drive shaft 14, the installation space can be reduced, whereby a driving source with a certain size (e.g. driving source exhibiting high abrasion resistance and a large torque, such as a servomotor, pulse motor, or brushless DC motor) can be applied. (3) In the aperture leaf 20A, the rolling elements 21 to 24 are disposed at positions on the aperture leaf 20A closer to the radiation source 1, and the rolling elements 25 to 28 are disposed at positions away from the radiation source 1. Note that the number and the positions of the rolling elements are not limited thereto insofar as the aperture leaf 20A can be arranged to freely move. An appropriate number of rolling elements may be provided. Another rolling element may be disposed at a position approximately between the rolling elements 21 to 24 and the rolling elements 25 to 28. (4) In the irradiation field limiting device 100, the driver section 10 is disposed so that one end of the linear member 3 is secured to the outer circumference of the aperture leaf 20A. Note that the driver section 10 may be disposed so that one end of the linear member 3 is secured to the inner circumference of the aperture leaf 20A insofar as the aperture leaf 20A can be driven. (5) The aperture leaves 20 and 40 respectively have a fan shape and an approximately rectangular shape. Note that the aperture leaves 20 and 40 may have an appropriate shape insofar as the aperture leaf can be connected with the linear member 3 and radiation from the radiation source 1 can be shielded along with the movement of the linear member 3. (6) In the first embodiment, the potentiometer 5 directly measures the absolute position of the outer circumference of the aperture leaf 20A. Note that the invention is not limited thereto. For example, the potentiometer 17 (indicated by the dash-dot-dot line) may be provided in the driver section 10, as shown in FIGS. 1 and 2. The displacement of the slider 15 may be measured, and the position of the aperture leaf 20A may be determined from the amount of movement of the linear member 3. If the driver sections are provided in units of the axial directions of the linear members 3 as in the second embodiment, the irradiation field limiting device can have a thickness necessary for the potentiometer (e.g. when the thickness of the aperture leaf 20A is 3 mm and the number of axial directions of the linear members 3 is three, the thickness of the potentiometer 17 may be 9 mm or less). Even if the thickness of the aperture leaf 20A is reduced, the potentiometer 17 can have a necessary thickness (e.g., when the thickness of the aperture leaf 20A is set at 1 mm, the thickness of the potentiometer 17 may be set at 3 mm or less). (7) In the first embodiment, the irradiation field limiting device 100 measures the amount of movement of the slider 15 using the encoder 19 (relative position sensor) to accurately control and drive the aperture leaf 20A. Note that the invention is not limited thereto. For example, the amount of movement of the aperture leaf 20A from the reference position (specific position) may be measured using a linear encoder. This also allows the irradiation field limiting device 100 to accurately control and drive the aperture leaf 20A. (8) In the second embodiment, the driver section includes the slider 15. Note that the invention is not limited thereto. Since it suffices that a thickness required for the driver section be provided and the linear member 3 be driven in the axial direction, the irradiation field limiting device may include a mechanism such as a rack and a pinion gear. In this case, the driver section can accurately drive the aperture leaf, even if a gap is formed between the rack and the pinion gear, by using the potentiometer or the like. Moreover, the driver section can prevent breakage of the driving source or the like by providing a driving force limiting section (e.g. ball torque limiter) in the drive shaft of the pinion gear. (9) In each embodiment, the driver section drives the aperture leaf by causing the drive shaft 14 to engage the slider 15. Note that the invention is not limited thereto. For example, when the aperture leaf 20 has a large thickness and weight, the drive shaft 14 and the slider 15 may be connected using a ball screw. This allows the driver section to smoothly rotate the drive shaft 14, whereby the aperture leaf 20 can be stably driven, even if the aperture leaf 20 has a large weight. (10) In the first embodiment, only the encoder 19 for measuring the number of rotations of the drive shaft 14 is provided. Note that the invention is not limited thereto. For example, a driving source measurement encoder may be provided to measure the number of rotations of the driving source 12 in addition to the encoder 19. Since the number of rotations of the drive shaft 14 differs from the number of rotations of the driving source in a state in which the torque limiter mechanism operates, the control section may be allowed to monitor the output from the driving source measurement encoder with the encoder 19, and the driving source may be stopped when a difference has been monitored between the number of rotations of the drive shaft 14 and the number of rotations of the driving source. As a result, when using a mechanical torque limiter (torque limiter section), excess wear of the contact surface can be prevented. The irradiation field limiting device can prevent extended operation of a motor (driving source) at a high load, whereby breakage of the motor can be prevented. |
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abstract | A container for holding radioactive waste has a side wall, a floor connected to a lower end of the side wall, and a cover. A set of side-wall formations is provided at an upper end of the side wall and on an inner surface of the side wall, and a set of cover-edge formations is distributed around an outer edge of the cover and fittable with the side-wall formations. Thus, as a result of the interfitting of cover-edge formations with the side-wall formations, the cover can be or is fixedly connected to the side wall without welds. |
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