Split (2)

train · 33.5k rows

patent_number stringlengths 0 9	section stringclasses 4 values	raw_text stringlengths 0 954k
	claims	1. A method of manufacturing a detector having an integrated scintillator and collimator, the method comprising the steps of:forming a scintillator pack; andmolding a collimator to the scintillator pack to form an integrated scintillator and collimator. 2. The method of claim 1 further comprising the step of milling a top reflector surface of the scintillator pack prior to molding the collimator to the scintillator pack. 3. The method of claim 1 comprising the step of fastening a collimator mold to the scintillator pack prior to the step of molding the collimator mold having a plurality of cavities. 4. The method of claim 3 further comprising the step of filling the mold cavities with a collimator mixture. 5. The method of claim 4 further comprising the step of removing air from the collimator mold using a vacuum pump prior to filling the mold cavities with the collimator mixture. 6. The method of claim 4 wherein the collimator mixture includes a combination of tungsten and epoxy. 7. The method of claim 3 wherein the collimator mold includes a series of parallel-aligned cavities designed to receive a collimator mixture. 8. The method of claim 3 wherein the collimator mold is formed of stainless steel. 9. A method of CT detector manufacture, the method comprising the step of molding a collimator directly to an x-ray reception surface of a scintillator. 10. The method of claim 9 wherein the step of molding includes the steps of:placing a scintillator having an array of scintillator elements on a tooling base;positioning a collimator mold having a plurality of cavities on the scintillator;filling the collimator mold cavities with a collimator composition; andcuring the collimator composition. 11. The method of claim 10 further comprising the step of orienting the scintillator and the collimator mold with respect to a set of pins and bore datums. 12. The method of claim 10 further comprising the step of removing air from the collimator mold cavities by vacuum pumping the air through an evacuation gate before the step of filling. 13. The method of claim 10 wherein the collimator composition includes tungsten and epoxy. 14. The method of claim 13 wherein the tungsten has a powder form.
050154354	abstract	The sleeve (20) for locking the guide tube has an outer surface comprising successivley a cylindrical and a frustoconical part in the axial direction, without any radially protruding part. The upper cylindrical part (25) of the sleeve constitutes a fastening shell of the sleeve (20) in the end fitting of the assembly and the lower frustoconical part (24) a ring for expanding the guide tube. The fastening shell (25) the thickness of which is substantially smaller than the thickness of the ring (24) can be distorted into cavities machined in the end fitting of the assembly. An annular interlocking groove (20) is machined in the upper part of the ring (24).
	description	This application is a national stage filing under 35 U.S.C. 371 of PCT/US2015/027305, filed Apr. 23, 2015, which claims priority to U.S. Provisional Application No. 61/984,538, filed Apr. 25, 2014, the disclosure of which is incorporated by reference in its entirety herein. Generally, in nuclear power generation, thermal energy is generated by the chain fission of a fissionable material (e.g., thorium, uranium, and plutonium), and power necessary for electric power generation is derived from the thermal energy. The fissionable material is typically prepared in the form of a sintered body and contained in a nuclear fuel rod. Nuclear fuel rods are arranged in a bundle to form a nuclear fuel assembly. In a nuclear reactor core, a control rod and a moderator are generally used to control the number and speed of extra neutrons and prevent a chain reaction (reactivity: >1) of fissionable materials. The moderator can include heavy water (D2O), light water (H2O), graphite, and beryllium, for example. Nuclear reactors may be classified into types depending on the nature of the moderator. For example, light-water nuclear reactors (LWR) include pressurized water reactors (PWR) and boiling water reactors (BWR). Other types of nuclear reactors include heavy-water nuclear reactor (HWR), which include a heavy water moderator, and high-temperature gas-cooled reactors (HTGR). Periodically, a portion of the nuclear fuel rods are removed from the reactor core and replaced with new fuel rods. The spent fuel rods are typically stored in racks for several years (e.g., for ten to twenty years) in pools of water deep enough for the water to provide adequate radiation shielding. The water is cooled to control the heat generated by the spent fuel rods. Solid neutron-absorbing materials including 10B atoms (e.g., boron carbide in a metal or polymer matrix) are typically used in the storage racks to absorb neutrons and prevent criticality in the storage pools. Soluble boron from boric acid may also be added to the pool water for this purpose. The use of boric acid in storage pools for nuclear fuel rods poses some problems. Boric acid can cause corrosion, for example, of racking materials or any exposed fuel cladding. Furthermore, the solubility of boric acid in water is typically reported to be about 4.7 grams per 100 grams of solution at 20° C. The low concentration of soluble boron in a storage pool can limit its utility to prevent criticality and/or limit its utility during emergency situations. An aqueous solution including at least one of polyhedral boron hydride anions or carborane anions is provided in the methods and storage pool according to the present disclosure. The polyhedral boron hydride anions or carborane anions absorb neutrons to prevent uncontrolled nuclear fission reactions. The polyhedral boron hydride anions or carborane anions, which in some embodiments comprise at least one of B10H102−, B11H14−, CB11H12−, or B12H122−, have a larger weight percent of boron than boric acid, and at least some of the salts from which they dissociate are more soluble in water than boric acid. As a result, typically, the aqueous solutions comprising at least one of polyhedral boron hydride anions or carborane anions have greater boron availability than boric acid solutions, which can enhance the solution's ability to prevent criticality. Also, the greater boron availability in these solutions may make them useful for movement or storage of active fuel rods during emergency situations or unexpected permanent plant shutdowns. The aqueous solution comprising at least one of polyhedral boron hydride anions or carborane anions is also expected to lead to less system corrosion than boric acid solutions. In one aspect, the present disclosure provides a method of storing nuclear fuel outside of a nuclear reactor core. In some cases, the method includes submerging at least a portion of a nuclear fuel rod in a storage pool containing an aqueous solution including at least one of polyhedral boron hydride anions or carborane anions. In some cases, the method includes adding a salt having a polyhedral boron hydride anion or carborane anion to a storage pool containing water and at least a portion of a nuclear fuel rod submerged in it. In some cases, the method includes both of these. Adding the at least one salt provides an aqueous solution comprising at least one of polyhedral boron hydride anions or carborane anions. The nuclear fuel rod or portion of the nuclear fuel rod is generally outside of a nuclear reactor core. In another aspect, the present disclosure provides a storage pool. The storage pool includes an aqueous solution comprising at least one of polyhedral boron hydride anions or carborane anions and at least a portion of a nuclear fuel rod. The nuclear fuel rod may be a used fuel rod (which may be a spent fuel rod) or a fresh fuel rod. The nuclear fuel rod or portion thereof may be stored in a rack. The storage pool may have at least 20 feet (6.1 meters) of the aqueous solution over the nuclear fuel rod or portion thereof. In one aspect, the present disclosure provides a method of servicing a nuclear reactor. The method includes receiving at least one used fuel rod from a nuclear reactor core into a storage pool containing an aqueous solution including at least one of polyhedral boron hydride anions or carborane anions. The used fuel rod may be a spent fuel rod. In some cases, the method also includes receiving at least one fresh nuclear fuel rod into the storage pool. In this application: Terms such as “a”, “an” and “the” are not intended to refer to only a singular entity, but include the general class of which a specific example may be used for illustration. The terms “a”, “an”, and “the” are used interchangeably with the term “at least one”. The phrase “comprises at least one of” followed by a list refers to comprising any one of the items in the list and any combination of two or more items in the list. The phrase “at least one of” followed by a list refers to any one of the items in the list or any combination of two or more items in the list. The terms “spent”, “used”, and “fresh” herein refer to various degrees of activity of nuclear fuel. “Spent” and “used” nuclear fuel have both been used in a nuclear reactor. “Spent” nuclear fuel has lower activity and may not be considered reusable while “used” nuclear fuel may be reusable. “Fresh” nuclear fuel has not been used in a reactor and has the highest activity. The term “aqueous” refers to including water. The water may be H2O or D2O. The terms “storing” and “storage” are not limited to a certain period of time. Storage can refer to any period time nuclear fuel is present other than inside the reactor core for generating heat. Methods of storing can include storing for several hours, several days, several months, several years, or several decades. All numerical ranges are inclusive of their endpoints and non-integral values between the endpoints unless otherwise stated (e.g., 1 to 5 includes 1, 1.5, 2, 2.75, 3, 3.80, 4, 5, etc.). Aqueous solutions useful for practicing the present disclosure include at least one of polyhedral boron hydride anions or carborane anions. Polyhedral boron hydride anions comprise only boron and hydrogen atoms. Carborane anions comprise only carbon, boron, and hydrogen atoms. In some embodiments, the anions are polyhedral boron hydride anions. In some embodiments, the polyhedral boron hydride anions comprise at least one of B10H102−, B11H14−, or B12H122−. In some embodiments, the polyhedral boron hydride anions comprise at least one of B10H102− or B12H122−. In some embodiments, the polyhedral boron hydride anions comprise B10H102−. In some embodiments, the polyhedral boron hydride anions comprise B11H14−. In some embodiments, the polyhedral boron hydride anions comprise B12H122−. The polyhedral boron hydride anions are typically provided in the aqueous solution by dissolution of Group I salts, Group II salts, ammonium salts, or alkyl ammonium salts, wherein alkyl is ethyl or methyl. The alkyl ammonium salts may be monoalkyl-, dialkyl-, trialkyl-, or tetraalkylammonium salts. In some embodiments, the polyhedral boron hydride anions are provided in the aqueous solution by dissolution of Group I salts, ammonium salts, or tetraalkyl ammonium salts, in some embodiments, Group I salts. Examples of suitable salts include Li2B10H10, Na2B10H10, K2B10H10, (NH4)2B10H10, [(C2H5)3NH]2B10H10, LiB11H14, NaB11H14, KB11H14, NH4B11H14, Li2B12H12, Na2B12H12, K2B12H12, and (NH4)2B12H12. In some embodiments, the anions are carborane anions. In some embodiments, the carborane anions comprise CB11H12−. The carborane anions are typically provided in the aqueous solution by dissolution of Group I salts, Group II salts, ammonium salts, or alkyl ammonium salts, wherein alkyl is ethyl or methyl. The alkyl ammonium salts may be monoalkyl-, dialkyl-, trialkyl-, or tetraalkylammonium salts. In some embodiments, the carborane anions are provided in the aqueous solution by dissolution of Group I salts, ammonium salts, or tetraalkyl ammonium salts, in some embodiments, Group I salts. Examples of suitable salts include LiCB11H12, NaCB11H12, KCB11H12, NH4CB11H12. The aqueous solutions useful for practicing the present disclosure can include combinations of any of the anions or salts described above in any of their embodiments. Also, the aqueous solutions useful for practicing the present disclosure typically are free of organic polymers. Polyhedral boron hydride salts can be prepared by known methods. For example, methods of preparing MB11H14 salts from metal borohydride or MB3H8 starting materials can be found in U.S. Pat. Nos. 4,115,520; 4,115,521; and 4,153,672, each to Dunks et al. Pyrolysis of tetraalkyl ammonium borohydride salts under a variety of conditions has been reported to provide salts of the B10H102− anion. See, for example, (1) W. E. Hill et al, “Boron Chemistry 4.” Pergamon Press, Oxford 1979, p 33; (2) Mongeot et al Bull. Soc. Chim. Fr. 385, 1986; and (3) U.S. Pat. Nos. 4,150,057 and 4,391,993, both issued to Sayles. The tetraalkylammonium borohydride starting materials (R4NBH4) can be prepared by contacting sodium borohydride with one or more molar equivalents of a tetralkylammonium salt (e.g., tetralkylammonium hydrogensulfate) in an aqueous or alcohol solution. By regulating the temperature (e.g., through the use of precise internal temperature readings, methods for cooling the reaction mixture, and particular ramp and isothermal profiles), pyrolysis of tetraalkylammonium borohydride salts can provide salts of the B10H102− and/or B12H122− anion in good yield as reported in U.S. Pat. No. 7,524,477 (Spielvogel et al.). For example, in some methods of preparing B10H102−, B9H9−, B11H14−, and/or B12H122−, the R4NBH4 is dissolved, suspended, or mixed with a solvent having a boiling point of at least about 100° C. and heated. Examples of useful solvents include C8-C18 alkanes or mixtures of C8-C18 alkanes, including n-dodecane and mixtures of n-decane and n-dodecane. In other methods of preparing B10H102−, B9H9−, B11H14−, and/or B12H12−, a mixture of R4NBH4 and a trialkylamine borane adduct is pyrolyzed. A ratio of the borohydride to the trialkylamine borane is typically between about 1:3 to about 3:1, and this ratio can be 1:1. In these methods, pyrolysis at a temperature of about 185° C. typically provides a mixture of tetraalkylammonium B1014102− and tetraalkylammonium B12H122− salts in a ratio of about 1.4:1. Various cations for the polyhedral boron hydride salts can be provided, for example, by ion exchange methods. Further methods for preparing B12H122− salts are reported, for example, in U.S. Pat. No. 7,718,154 (Ivanov et al.), which describes reaction of a metal hydride with an alkyl borate in the presence of a Lewis base to produce a Lewis base-borane complex that is thermally decomposed to form the B12H122− salt, and U.S. Pat. No. 7,563,934 (Banavali et al.), which describes reaction of a metal borohydride with XBH3, where X is a substituted amine, a substituted phosphine, or tetrahydrofuran. Syntheses of CB11H12− salts are also known. See, e.g., Knoth, W. H., Journal of the American Chemical Society, 1967, vol. 89, page 1274; Jelinek, T. et al., Collection of Czechoslovak Chemical Communications, 1986, vol. 51, page 819; and Franken, A., et al., Collection of Czechoslovak Chemical Communications, 2001, vol. 66, pages 1238-1249. Of the two naturally occurring isotopes of boron (11B and 10B), 10B is a better neutron absorber with a thermal neutron absorption cross section of approximately 3800 barns (3.8×10−24 m2). Accordingly, in some embodiments, the polyhedral boron hydride anions, including in any of the aforementioned salts, are enriched in 10B. A variety of procedures are available for the synthesis of 10B enriched polyhedral boron hydride salts. In general, the syntheses begin with 10B enriched boric acid, which can be converted to borohydride salts. Enriched borohydrides can be used with any of the methods described above, for example, to provide salts enriched in 10B. In some embodiments, at least one of the tetraalkylammonium borohydride salts or the trialkylamine borane adduct included in a pyrolysis mixture described above is enriched in 10B. Isotopically enriched B11H14− salts from isotopically enriched boric acid are described in U.S. Pat. No. 7,641,879 (Spielvogel). At least some of the salts (e.g., Li2B10H10, Na2B10H10, K2B10H10, (NH4)2B10H10, LiB11H14, NaB11H14, KB11H14, NH4B11H14, Li2B12H12, Na2B12H12, K2B12H12, and (NH4)2B12H12) including 10B enriched salts are commercially available from Boron Specialties LLC, Valencia, Pa. In some embodiments, the polyhedral boron hydride anions or carborane anions are provided in the aqueous solution by dissolution of Li2B10H10, LiB11H14, LiCB11H12, or Li2B12H12. In some embodiments, the polyhedral boron hydride salt is Li2B10H10. In some embodiments, the polyhedral boron hydride salt is Li2B12H12. In some embodiments, the polyhedral boron hydride salt is LiB11H14. In some embodiments, the carborane salt is LiCB11H12. Because of the low atomic mass of lithium, such salts may have the highest weight percentage of boron in comparison to other polyhedral boron hydride salts or carborane salts. Furthermore, as discussed in greater detail below, the lithium salts may have some of the highest water solubilities of the polyhedral boron hydride salts. 7Li is the most common lithium isotope accounting for 92.5 percent of the atoms. However, 7Li is neutron transparent, and it may be useful in some embodiments for any one of Li2B10H10, LiB11H14, LiCB11H12, or Li2B12H12 to be enriched in 7Li. The enrichment in 7Li can be carried out by treating (Et4N)2B10H10, Et4NB11H14, (Et4N)2B12H12, or a carborane salt prepared according to the methods described above, with commercially available 7LiOH in water. Polyhedral boron hydride and carborane salts are useful in the method and storage pool disclosed herein, for example, because of their generally high boron content. While boric acid is only 17.5% by weight boron, typically, polyhedral boron hydride and carborane salts useful for practicing the present disclosure have at least 25 percent by weight boron, based on the total molecular weight of the salt. For example, Cs2B10H10 is 28% by weight boron. In other examples, Li2B10H10, Na2B10H10, and (NH4)2B10H10 are 81.9%, 65.9%, and 70.1% by weight boron, respectively. In further examples, Li2B12H12, Na2B12H12, and (NH4)2B12H12 are 83.3%, 69.1%, and 72.9% by weight boron, respectively. In yet other examples, LiCB11H12, NaCB11H12, and KCB11H12 are 79.3%, 71.6%, and 65.3% by weight boron, respectively. In some embodiments, the polyhedral boron hydride salts or carborane salts have at least 30, 35, 40, 45, 50, 55, 60, or 65 percent by weight boron, based on the total molecular weight of the salt. Polyhedral boron hydride salts are also useful in the method and storage pool disclosed herein, for example, because of their high solubilities in water. While boric acid is typically reported to have a solubility in water of only about 4.7 grams per 100 grams of solution at 20° C., typically, polyhedral boron hydride salts useful for practicing the present disclosure have solubilities of at least 15 grams per 100 grams of solution at 20° C. or at least three times the water solubility of boric acid. In some embodiments, the polyhedral boron hydride salts useful for practicing the present disclosure have water solubilities of at least 20, 25, 30, 35, 40, 45, or at least 50 grams per 100 grams of solution at 20° C. Certain carborane salts are also expected to have useful water solubilities. CB11H12−, for example, is a very weakly coordinating anion. The water solubilities for many different salts and the method for determining these solubilities are reported in the Examples, below. The storage pool according to the present disclosure is useful, for example, for storing nuclear fuel rods outside of a nuclear reactor core. The storage pool is generally located at the reactor site where electricity is generated and can contain submerged used fuel rods, removed after use in a reactor core and which may be spent fuel rods, submerged fresh fuel rods yet to be used in the nuclear reactor core, other submerged reactor components, or any combination thereof. The aqueous solution including at least one of polyhedral boron hydride anions or carborane anions, which are neutron absorbers, can prevent uncontrolled nuclear fission reactions in the storage pool. The aqueous solution in the storage pool also serves as a radiation shield from the radioactive fuel rods and as a coolant to absorb the heat of the radioactively decaying isotopes in the fuel. The aqueous solution useful for practicing the present disclosure may include dissolved salts according to any of the embodiments described above at any useful concentration up to the solubility limit of the salt(s). In some embodiments, the polyhedral boron hydride salt or carborane salt is present at a concentration of at least 15, 20, 25, 30, 35, 40, 45, or at least 50 grams per 100 grams of the aqueous solution. The storage pool may have at least about 20 feet (6.1 meters) of aqueous solution over the submerged fuel rods to provide a safety margin and allow fuel assembly manipulation without special shielding protecting the operators. Although other depths of at least 20 feet (6.1 meters) are possible, in some embodiments, the storage pool is at least about 30 or 40 feet (9.1 or 12.2 meters) in depth. In some embodiments, the storage pool is made of concrete. It should be understood that the storage pool is a collection of standing water and is not itself a nuclear reactor core. In some embodiments, the storage pool includes storage racks designed to hold fuel rods or fuel assemblies from the nuclear reactor core. The storage racks may include boron carbide in a metal or polymer matrix. The storage racks may be located in approximately the bottom 14 feet (4.3 meters) of the pool. The fuel rods may be stored in racks in a configuration similar to their configuration when they were in use in a nuclear reactor core although other configurations may be useful. The method and storage pool according to the present disclosure are also useful when the fuel rods are not stored in racks. For example, after a natural disaster or accident, fuel rods may be disordered at the bottom of the pool. At least some of the fuel rods may be crushed or broken or may have lost a portion of their cladding. In the method of storing nuclear fuel outside of a nuclear reactor core disclosed herein, dissolved salts in any of their embodiments described above may be present in the storage pool before any nuclear fuel rod or portion thereof is submerged in it. Alternatively or additionally, at least one polyhedral boron hydride salt or carborane salt can be added to a storage pool of water having at least a portion of a nuclear fuel rod already submerged in it. Adding the polyhedral boron hydride salt or carborane salt provides the aqueous solution of at least one of polyhedral boron hydride anions or carborane anions. Adding the polyhedral boron hydride salt or carborane salt to existing pools may be useful after a natural disaster, nuclear emergency, or other situations presenting the threat of criticality (e.g., additional nuclear fuel, either spent or fresh, needs to be added to the pool). The present disclosure also provides a method of servicing a nuclear reactor that includes receiving at least one used fuel rod from a nuclear reactor core into a storage pool comprising an aqueous solution comprising at least one of polyhedral boron hydride anions or carborane anions. The servicing can be part of a shutdown or refueling operation, for example. In some cases, used fuel assemblies are racked and moved from the reactor core to the storage pool along the bottom of water canals. In embodiments in which the nuclear reactor is refueled, the used fuel rod is typically spent, and the method can also include receiving at least one fresh nuclear fuel rod into the storage pool. However, the fresh fuel and the spent fuel need not be in the same storage pool. Typically when the nuclear reactor core is refueled, the fresh fuel replaces a portion of the spent fuel in the reactor core and the spent fuel from the core is stored in the spent fuel storage pool. Fresh fuel can be delivered from a fresh fuel transportation cask into a fresh fuel pool, from which it is transferred to the nuclear reactor core. Certain characteristics of boric acid limit its utility in a spent fuel pool and/or fresh fuel pool. As described above, the solubility of boric acid in water is typically reported to be about 4.7 grams per 100 grams of solution at 20° C. The low concentration of soluble boron in a storage pool can limit its utility to prevent criticality when a large amount of fuel is present. Also, boric acid corrosion due to deposits can compromise the integrity of the racks and related systems. Also, the use of boric acid provides a slightly acidic pH, which can lead to corrosion of the fuel rod cladding. To bring the pH to acceptable levels, 7LiOH can be added to the water. However, the presence of too much LiOH can also lead to corrosion of nuclear fuel rod cladding. To further protect the cladding from corrosion, depleted zinc oxide, which interacts with the fuel cladding material, can be added. Due to increased solubility of the polyhedral boron hydride salts and certain polyhedral carborane salts, higher concentrations of soluble boron can be present in storage pools than when boric acid is used, providing better control over fission reactions and allowing for the presence of higher amounts of fuel. Also, because of this increased solubility, the polyhedral boron hydride salts and certain polyhedral carborane salts will not be as prone to deposition, and if deposits do occur they are not expected to have the same corrosiveness. The polyhedral boron hydride and carborane salts are pH neutral, which may reduce or eliminate the need for the expensive LiOH and depleted zinc oxide in the methods and storage pool according to the present disclosure. Furthermore, polyhedral boron hydride and carborane anions are typically thermally stable and non-toxic. The cage structure of polyhedral boron hydride and carborane anions renders them highly chemically stable, which allows for long term storage. The aqueous solutions containing these salts are then ready to use when needed. Also, the use of polyhedral boron hydride salts in aqueous solutions will not introduce any additional atoms or subsequent decay species to the general water chemistry that are conventionally not present. The fuel rods that can be stored or received according to the methods disclosed herein and/or present in the storage pool of the present disclosure can be from any type of nuclear reactor core. In some embodiments, the nuclear reactor core is a component of a light water reactor, a boiling water reactor, a pressurized water reactor, a small modular reactor, or a heavy water reactor. In some embodiments, the nuclear reactor core is a component of a light water reactor, which may be a boiling water reactor or a pressurized water reactor. In some embodiments, the fuel rods that can be stored or received according to the methods disclosed herein and/or present in the storage pool of the present disclosure are from a light water reactor. In a light water reactor, the primary coolant is H2O, which flows through the reactor core to extract heat to generate steam or for some other useful purpose. For electrical power generation, the steam is used to drive a generator turbine. In thermal nuclear reactors, the primary coolant water also serves as a neutron moderator that thermalizes neutrons, which enhances reactivity of the fissionable material. Various reactivity control mechanisms, such as mechanically operated control rods and chemical treatment of the primary coolant with a soluble neutron poison are employed to regulate the reactivity and resultant heat generation. In some embodiments, the fuel rods that can be stored or received according to the methods disclosed herein and/or present in the storage pool of the present disclosure are from a boiling water reactor (BWR). A BWR is a type of light water reactor, described above, in which the primary coolant water boils to generate the steam. The primary coolant water is typically maintained in a reactor pressure vessel that also contains the reactor core. In some embodiments, the fuel rods that can be stored or received according to the methods disclosed herein and/or present in the storage pool of the present disclosure are from a pressurized water reactor (PWR). A PWR is a type of light water reactor, described above, with the primary coolant water maintained in a superheated state in a sealed pressure vessel that also contains the reactor core. This hot water, which does not boil, then exchanges heat with a secondary, lower pressure water system, which turns to steam and drives the turbine. In the PWR, both pressure and temperature of the primary coolant water are controlled. In some embodiments, the fuel rods that can be stored according to the method and/or in the storage pool of the present disclosure are from a heavy water reactor (HWR). A HWR operates like a PWR, but the primary cooling water is D2O instead of H2O. In some embodiments, the fuel rods that can be stored or received according to the methods disclosed herein and/or present in the storage pool of the present disclosure are from a small modular reactor. Such reactors typically have an electricity output of less than 500 megawatts (MW). Modular reactors are designed to be manufactured and assembled at a central factory location and then sent to their new location for installation. The small modular reactors may be light water cooled or heavy water cooled and may be boiling water reactors or pressurized water reactors. In a first embodiment, the present disclosure provides a method of storing nuclear fuel outside of a nuclear reactor core, the method comprising at least one of: submerging at least a portion of a nuclear fuel rod in a storage pool comprising an aqueous solution comprising at least one of polyhedral boron hydride anions or carborane anions; or adding a salt comprising a polyhedral boron hydride anion or carborane anion to a storage pool comprising water and at least a portion of a nuclear fuel rod submerged therein, wherein adding the salt provides an aqueous solution comprising at least one of polyhedral boron hydride anions or carborane anions. In a second embodiment, the present disclosure provides the method of the first embodiment, wherein the method comprises submerging at least a portion of a nuclear fuel rod in a pool comprising an aqueous solution comprising at least one of polyhedral boron hydride anions or carborane anions. In a third embodiment, the present disclosure provides the method of the first embodiment, wherein the method comprises adding at least one salt comprising a polyhedral boron hydride anion or carborane anion to a pool comprising water and at least a portion of a nuclear fuel rod submerged therein. In a fourth embodiment, the present disclosure provides a storage pool comprising: an aqueous solution comprising at least one of polyhedral boron hydride anions or carborane anions; and at least a portion of a nuclear fuel rod submerged in the aqueous solution. In a fifth embodiment, the present disclosure provides the method or storage pool of any one of the first to fourth embodiments, wherein the nuclear fuel rod or the portion thereof is a spent fuel rod or a portion thereof. In a sixth embodiment, the present disclosure provides the method or storage pool of any one of the first to fourth embodiments, wherein the nuclear fuel rod or the portion thereof is a fresh fuel rod or a portion thereof. In a seventh embodiment, the present disclosure provides the method or storage pool of any one of the first to fourth embodiments, wherein the nuclear fuel rod or the portion thereof is a used fuel rod or a portion thereof. In an eighth embodiment, the present disclosure provides the method or storage pool of any one of the first to seventh embodiments, wherein the at least one of polyhedral boron hydride anions or carborane anions are enriched in 10B. In a ninth embodiment, the present disclosure provides the method or storage pool of any one of the first to eighth embodiments, wherein the at least one of polyhedral boron hydride anions or carborane anions are provided by a dissolved Group I salt or ammonium salt. In a tenth embodiment, the present disclosure provides the method or storage pool of the ninth embodiment, wherein the Group I salt or ammonium salt has at least 25 percent by weight boron. In an eleventh embodiment, the present disclosure provides the method or storage pool of the ninth or tenth embodiment, wherein the Group I salt or ammonium salt has a water solubility of at least 15 grams per 100 grams of solution at 20° C. In a twelfth embodiment, the present disclosure provides the method or storage pool of any one of the first to eleventh embodiments, wherein the anions are polyhedral boron hydride anions comprising at least one of B10H102−, B11H14−, or B12H122−. In a thirteenth embodiment, the present disclosure provides the method or storage pool of the twelfth embodiment, wherein the polyhedral boron hydride anions comprise at least one of B10H102− or B12H12−. In a fourteenth embodiment, the present disclosure provides the method or storage pool of the thirteenth embodiment, wherein the polyhedral boron hydride anions are from a dissolved salt selected from the group consisting of Li2B10H10, Na2B10H10, K2B10H10, (NH4)2B10H10, Li2B12H12, Na2B12H12, K2B12H12, (NH4)2B12H12, and combinations thereof. In a fifteenth embodiment, the present disclosure provides the method or storage pool of the fourteenth embodiment, wherein the Li2B10H10 or Li2B12H12 is enriched in 7Li. In a sixteenth embodiment, the present disclosure provides the method or storage pool of the twelfth embodiment, wherein the polyhedral boron hydride anions comprise B11H14−, wherein the polyhedral boron hydride anions are from a dissolved salt selected from the group consisting of LiBi11H14, NaB11H14, KB11H14, (NH4)B11H14, and combinations thereof, and optionally wherein the LiB11H14 is enriched in 7Li. In a seventeenth embodiment, the present disclosure provides the method or storage pool of any one of the first to eleventh embodiments, wherein the anions are carborane anions, wherein the carborane anions comprise CB11H12−, wherein the carborane anions are from a dissolved salt selected from the group consisting of LiCB11H12, NaCB11H12, KCB11H12, NH4CB11H12, and combinations thereof, and optionally wherein the LiCB11H12 is enriched in 7Li. In an eighteenth embodiment, the present disclosure provides the method or storage pool of any one of the first to seventeenth embodiments, wherein the storage pool further comprises a rack on which the nuclear fuel rod or portion thereof is stored. In a nineteenth embodiment, the present disclosure provides the method or storage pool of any one of the first to eighteenth embodiments, wherein the storage pool has at least 20 feet (6.1 meters) of the aqueous solution over the nuclear fuel rod or portion thereof. In a twentieth embodiment, the present disclosure provides the method or storage pool of any one of the first to nineteenth embodiments, wherein the storage pool is located on a site that further comprises at least one of a light water reactor, a boiling water reactor, a pressure water reactor, a small modular reactor, or a heavy water reactor. In a twenty-first embodiment, the present disclosure provides a method of servicing a nuclear reactor core, the method comprising receiving at least one used fuel rod from a nuclear reactor core into a storage pool comprising an aqueous solution comprising at least one of polyhedral boron hydride anions or carborane anions. In a twenty-second embodiment, the present disclosure provides the method of the twenty-first embodiment, wherein the used nuclear fuel rod is a spent fuel rod. In a twenty-third embodiment, the present disclosure provides the method of the twenty-first or twenty-second embodiment, further comprising receiving at least one fresh nuclear fuel rod into the storage pool. In a twenty-fourth embodiment, the present disclosure provides the method of any one of the twenty-first to twenty-third embodiments, wherein the storage pool further comprises a rack onto which the at least one used nuclear fuel rod is placed. In a twenty-fifth embodiment, the present disclosure provides the method of any one of the twenty-first to twenty-fourth embodiments, wherein the storage pool has at least 20 feet (6.1 meters) of the aqueous solution over the at least one used nuclear fuel rod. In a twenty-sixth embodiment, the present disclosure provides the method of any one of the twenty-first to twenty-fifth embodiments, wherein the nuclear reactor core is a component of a light water reactor, a boiling water reactor, a pressure water reactor, a small modular reactor, or a heavy water reactor. In a twenty-seventh embodiment, the present disclosure provides the method of any one of the twenty-first to twenty-sixth embodiments, wherein servicing the nuclear reactor core comprises refueling the nuclear reactor core. In a twenty-eighth embodiment, the present disclosure provides the method of any one of the twenty-first to twenty-sixth embodiments, wherein servicing the nuclear reactor core comprises shutting down the nuclear reactor core. In a twenty-ninth embodiment, the present disclosure provides the method of any one of the twenty-first to twenty-eighth embodiments, wherein the at least one of polyhedral boron hydride anions or carborane anions are enriched in 10B. In a thirtieth embodiment, the present disclosure provides the method of any one of the twenty-first to twenty-ninth embodiments, wherein the at least one of polyhedral boron hydride anions or carborane anions are provided by a dissolved Group I salt or ammonium salt. In a thirty-first embodiment, the present disclosure provides the method of the thirtieth embodiment, wherein the Group I salt or ammonium salt has at least 25 percent by weight boron. In a thirty-second embodiment, the present disclosure provides the method of the thirtieth or thirty-first embodiment, wherein the Group I salt or ammonium salt has a water solubility of at least 15 grams per 100 grams of solution at 20° C. In a thirty-third embodiment, the present disclosure provides the method of any one of the twenty-first to thirty-second embodiments, wherein the anions are polyhedral boron hydride anions comprising at least one of B10H102−, B11H14−, or B12H12−. In a thirty-fourth embodiment, the present disclosure provides the method of the thirty-third embodiment, wherein the polyhedral boron hydride anions comprise at least one of B10H102− or B12H122−. In a thirty-fifth embodiment, the present disclosure provides the method of the thirty-fourth embodiment, wherein the polyhedral boron hydride anions are from a dissolved salt selected from the group consisting of Li2B10H10, Na2B10H10, K2B10H10, (NH4)2B10H10, Li2B12H12, Na2B12H12, K2B12H12, (NH4)2B12H12, and combinations thereof. In a thirty-sixth embodiment, the present disclosure provides the method of the thirty-fifth embodiment, wherein the Li2B10H10 or Li2B12H12 is enriched in 7Li. In a thirty-ninth embodiment, the present disclosure provides the method of the thirty-third embodiment, wherein the polyhedral boron hydride anions comprise B11H14−, wherein the polyhedral boron hydride anions are from a dissolved salt selected from the group consisting of LiB11H14, NaB11H14, KB11H14, (NH4)B11H14, and combinations thereof, and optionally wherein the LiB11H14 is enriched in 7Li. In a thirty-eighth embodiment, the present disclosure provides the method of any one of the twenty-first to thirty-second embodiments, wherein the anions are carborane anions, wherein the carborane anions comprise CB11H12−, wherein the carborane anions are from a dissolved salt selected from the group consisting of LiCB11H12, NaCB11H12, KCB11H12, NH4CB11H12, and combinations thereof, and optionally wherein the LiCB11H12 is enriched in 7Li. The following specific, but non-limiting, examples will serve to illustrate the present disclosure. The salts in the Table, below, can be useful in the method and storage pool according to the present disclosure in any of the above embodiments. Salt solubilities indicated in the Table, below, were determined by the following procedure. A known quantity of water (either 25 grams or 50 grams) was added to a 2-necked round bottomed flask with thermometer and stir bar on a magnetic stir plate. The solute (salt) was analytically weighed and added to the solvent in approximately 0.1-g increments while measuring the temperature of the solution. Solute was added until turbidity was observed in the solution after addition and agitation. Solubility in grams per 100 grams solution was then calculated and provided the Table, below. The temperature range measured was 18° C. to 21° C. TABLESalt solubilities in grams per 100 grams of solutionLiNaKCs(C2H5)3NHB12H122− salts54.750.440.72.3 1.6B10H102− salts58.456.938.04.215.7 Various modifications and alterations of this disclosure may be made by those skilled the art without departing from the scope and spirit of the disclosure, and it should be understood that this invention is not to be unduly limited to the illustrative embodiments set forth herein.
	summary
052290689	summary	This invention relates to nuclear fuel bundles utilized in boiling water nuclear reactors having part length rods. More particularly, the combination of a fuel bundle having part length rods is disclosed wherein pressure reduction obtained by the introduction of part length rods in the upper two phase region of a fuel assembly is reclaimed by the introduction of spacers causing substantial recapture of the reduced pressure drop. Improved critical power results. For example, spacer pitch can be changed to add spacers to the upper two phase region of the fuel bundle. Alternately, so-called vanes, especially swirl vanes can be added. Other expedients are introduced for causing pressure drop with the spacers including increased spacer height and constructing the spacers of thicker metallic materials. This invention also includes the addition of separation devices overlying the part length rods. BACKGROUND OF THE INVENTION In Dix et al. U.S. Pat. No. 5,112,570 issued May 12, 1992, entitled TWO-PHASE PRESSURE DROP REDUCTION BWR ASSEMBLY DESIGN (formerly U.S. patent application Ser. No. 07/176,975 filed Apr. 4, 1988), a fuel bundle having a plurality of part length rods was illustrated. A summary of that construction and the advantages set forth in this reference can be instructive. Construction of the fuel bundle in Dix et al. is conventional with the exception of the addition of less than full length fuel rods. The conventional portion of the disclosed fuel assembly in the Dix et al. Patent is easy to understand. This assembly includes a channel having vertically extending walls for extending around a fuel bundle assembly volume. The channel is open at the bottom for receipt of water moderator and open at the top for the discharge of water and steam. The fuel bundle includes a matrix of vertically upstanding fuel rods--these rods being sealed tubes containing fissionable materials. The fuel rods are supported on a lower tie plate which permits the entry of the water moderator to the fuel bundle. The fuel rods typically extend to an upper tie plate which maintains the fuel rods in their side by side vertical relation and permits the generated steam and remaining water to escape. The Dix et al. disclosure adds to the conventional fuel assembly, a plurality of less than full length spaced apart so-called "part length (fuel) rods" (PLRs). These fuel rods are supported on the lower tie plate, extend upwardly to and toward the upper tie plate, but terminate short of the upper tie plate. Between the point of part length fuel rod termination and the upper tie plate, the part length fuel rod defines in the upper two phase region of the fuel bundle a vent volume. This vent volume preferentially receives vapor from the liquid vapor two phase mixture in the upper two phase region of the fuel bundle during power producing operation. Numerous advantages result from the part length rod construction. Improved cold shut down margin enables fuel to be designed with reduced amounts of burnable absorbers such as gadolinium. The tendency of the fuel bundle in the reactor to produce plutonium at the top of the bundle from resonance neutron capture in uranium 238 is reduced. The void overlying the part length rod has an increased vapor fraction with the result that the full length rods adjacent the voids have an increased liquid fraction. Further, the pressure drop in the upper two phase region of the fuel bundle is reduced. This being the case, the fuel bundle enjoys increased stability from thermal hydraulic and nuclear instabilities. The fuel bundles are elongate. Further, the fuel rods contained within the fuel bundle are flexible. These fuel rods can flex out of their designed side-by-side spacing--and even into interfering contact with one another--due to flow induced vibration and rod bow. Therefore, spacers are utilized throughout the length of the fuel bundle. Fuel bundle spacers have the function of maintaining the individual fuel rods at given elevations in their designed side-by-side relationship. Such spacers usually define a matrix of individual fuel rod containing cells. These cells fit around each and every fuel rod at their particular elevation in a fuel bundle. The fuel bundle spacers maintain the fuel rods in their designed side-by-side relationship and prevent interfering contact between the individual fuel rods. In the case of the part length rods where the fuel rods do not extend to the upper tie plate, the spacers maintain the fuel rods in their designed upstanding relation. All fuel bundles--including those having part length rods--must be designed to operate within thermal limits. Specifically, that thermal limit in boiling water reactors known as critical power has always been a limitation. Critical power originates from rupture of the coolant liquid film on the exterior surface of the fuel rod in a phenomena known as "transition boiling." In this transition boiling condition a liquid film no longer coats the exterior surface of the fuel rod. The rod on the exterior surface is exposed to coolant vapor only. Heat transfer from the fuel interior of the fuel rod undergoing fission reaction to the coolant is reduced. The fuel rod cladding becomes overheated. Naturally, as any fuel rod within a fuel bundle even approaches such a boiling condition anywhere along its length, power is restricted to avoid violation of this "critical power" limitation. Past experimentation has been directed to the critical power limitation. It is known that by decreasing the spacer pitch in the upper two phase region of the fuel bundle, that critical power can be improved. Unfortunately, the additional spacers caused additional pressure loss. This additional pressure loss causes additional tendencies for instabilities at certain power rates of the reactor. These instabilities include local and core wide thermal hydraulic and nuclear thermal hydraulic instabilities. For these reasons, the experimentally determined improvement of critical power could not be implemented by decreasing the spacer pitch in the upper two phase region of boiling water nuclear reactor fuel bundles. It is also known to incorporate so-called "swirl vanes" to both boiling water nuclear reactors and the spacers in boiling water nuclear reactors. These devices can be simply summarized and easily understood. In summary, so-called swirl vanes are placed interstitially of fuel rods. The vanes themselves comprise pieces of metal twisted in a helical pattern. In the earliest known cases, these so-called swirl vanes were the same length as the fuel rods in the reactor. In a later case, a spacer constructed from such swirl vanes was constructed. See Johansson, U.S. Pat. No. 4,913,895 issued Apr. 3, 1990 entitled SWIRL VANES INTEGRAL WITH SPACER GRID. These swirl vanes when added to reactors had a beneficial effect and a detrimental effect. The beneficial effect was the classification of water from upwardly flowing water and steam. Specifically, upwardly flowing water and steam. Simply stated, and despite the helical pattern of the twisted metal strips, steam tended to upwardly flow about the swirl vanes. Water, however, did not tend to join this upward flow. Instead the heavier water received a horizontal velocity component from the swirl vanes. As the swirl vanes were placed interstitially of the fuel rods, the heavier water when thrown horizontally by the momentum of the swirl vanes has the beneficial effect of impacting the adjacent fuel rods. Consequently, the critical power limit is increased. The detrimental effect of such swirl vanes is increased pressure drop. The swirl vanes themselves raise the pressure drop in the upper two phase region of the boiling water reactor. This increase in pressure drop will increase the possibility of instabilities including thermal hydraulic instabilities and nuclear, thermal hydraulic instabilities at high power/low flow conditions of the boiling water nuclear reactor. This being the case, the swirl vanes have not been in large measure introduced into the boiling water nuclear reactors. Any physical explanation of spacer relative thermal hydraulic performance should depend on the flow regimes that the coolant experiences in flowing up the channel as well as how the flow interacts with the spacer. Single phase water enters the bottom of the fuel assembly and is heated until sub cooled boiling occurs. Bubbles are formed at the surface of the fuel rod but quickly condense as they contact the bulk sub cooled flow. At the 100% power/100% flow condition bundle average bulk boiling will begin somewhere between the bottom spacer and the second spacer from the bottom of the fuel assembly. Now bubbles in the main flow stream will grow and the flow regime will progress from bubble flow to a type of slug or froth flow where individual small bubbles are starting to combine to make larger slugs of vapor. During these processes the vapor is flowing as bubbles or slugs in a continuous liquid medium. Depending on conditions somewhere around the middle of the bundle a flow regime transformation takes place. Now there is so much vapor that it becomes the continuous medium and the liquid is either found as a thin film flowing on all the solid surfaces of the bundle or as droplets entrained in the continuous vapor. This is the annular flow regime which is important because it is where dry out or boiling transition will commonly take place in a BWR. The limiting critical power condition in a BWR has been referred to in the literature alternately as dry out, boiling crisis, critical heat flux, burnout and boiling transition, the term which will be used here. Boiling transition is defined as the first condition of degraded heat transfer in the fuel bundle. This occurs in the annular flow regime as a result of the thin liquid film which covers all the fuel rod surfaces going to zero film thickness. A critical power problem results. DISCOVERY We have discovered that there can be a deficiency in fuel bundles having part length rods. Specifically, such fuel bundles have a tendency to have critical power limitations in the upper two phase region of the fuel bundle. This critical power limitation occurs in the full length rods in the upper two phase region of the fuel bundle. It has been determined by experiment that flow rates around and adjacent the full length rods may be below average. This apparently has the tendency to generate transition boiling and the critical power limitations. The reader will understand that this discovery is not prior art. In so far that discovery can constitute invention, our invention incorporates this discovery. SUMMARY OF THE INVENTION In a fuel bundle for use in the core of a boiling water nuclear reactor, part length rods having a tendency to reduce pressure drop are used in combination with spacers and spacer attached devices tending to restore pressure drop to improve critical power. The fuel bundle includes a preferred 9 by 9 matrix of upstanding vertically disposed fuel rods surrounded by a fuel channel between upper and lower tie plates. The tie plates support the fuel rods and permit the entry of water coolant at the lower tie plate and the exit of water and generated steam at the upper tie plate. Part length rods are distributed in the fuel rod matrix and combined with increased spacer pitch. The addition of the part length rods has the advantage of lowering the pressure drop. Spacer additions (such as the increase in spacer pitch in the upper two phase region of the bundle) or spacer attachments (such as vanes and especially so-called swirl vanes) are utilized to restore the pressure drop removed by the insertion of the part length rods. There results a serendipitous improved critical power performance in the upper two phase region of the fuel assembly. One method of achieving the disclosed result is the increase in total number of spacers in the upper two phase region of the fuel bundle to increase pressure drop. The spacers are distributed in the lower portion of the fuel bundle on about 20 inch centers. The increased number of spacers in the upper two phase region of the fuel bundle includes placing them on a pitch of less than 20" so as to allow for the addition of at least one spacer in the upper two phase region of the fuel bundle. The additional spacer is not required for the traditional purpose of preventing either rod bow or flow induced vibration. Indeed the additional spacer causes the pressure loss in the upper two phase region of the fuel bundle to be in part restored to that pressure loss that would be present if the fuel bundle contained an array having full length fuel rods only. However, the additional spacer causes the critical power of the fuel bundle to be improved. There results a fuel bundle with part length rods having all of the advantages inherent in the part length rod construction plus the added benefit of increased critical power. Alternately, and in addition to the disclosed decrease in spacer pitch, spacers incorporating vanes can be used. By way of example, these vanes can be our preferred partial or complete swirl vane arrays. The vanes are incorporated to the spacers in the interstitial volumes between the fuel rods. Such spacers, although increasing pressure drop, cause improvement in critical power. In the case of the incorporation of vanes to the spacer, increased pitch of spacers is not required. Other expedients of spacer modification for realization of pressure drop are disclosed. Spacers on the same pitch having increased vertical height can be utilized. Further, spacer fabricated from thicker metallic construction can be used. In short, an device--preferably a spacer--in the upper two phase region of the fuel bundle which adds back the pressure drop lost by the use of part length rods is sufficient for the practice of this invention. Separation devices can also be used. Two classes of separation devices are disclosed. A first type of device fits to the end of part length rods and is primarily intended for preventing water passing along the surface of the part length rod adjacent the end of the part length rod from entering the volume overlying the part length fuel rod. A second type of device resides in the volume overlying part length rods. This device serves the purpose of ejecting water entrained into the steam vent volume overlying part length rods. These devices can be extended and interconnected. In either case, improved concentration of steam to the vent volume overlying the part length rods with high liquid fraction residing in the surrounding full length rods results. OTHER OBJECTS, FEATURES AND ADVANTAGES A fundamental difficulty in BWR fuel design results from the large variations in moderator density caused by vapor formation. Current design approaches provide some compensation for this by introducing captive-liquid within the fuel bundle. Examples are the various water-rod and water-cross designs. While these approaches provide for effective neutron moderation, their associated blockage of normal coolant flow area causes entirely adverse thermal hydraulic effects. This is particularly true as the blockages become large. In contrast, the steam-vent approach provides synergistic benefits for both neutron moderation and thermal hydraulics. Diverting significant vapor into a low-resistance flow path will allow the average vapor velocity to increase, and thereby reduce the average void fraction. More importantly, local void fractions around the fuel rods will be reduced even more due to the removal of vapor from that region. In contrast, the flow blockages caused by captive-liquid regions force all of the normal liquid and vapor to flow together around the fuel rods, at even higher velocities. This increases local void fractions around the fuel rods. Thus the neutron moderation benefits with steam-vent designs can easily exceed those achieved using large captive liquid regions. The low resistance flow path for vapor will reduce pressure drop in the two-phase region. Removal of normal spacer structure within the steam-vent path will reduce the pressure drop from each spacer, allowing for more spacers to be added (with associated critical power and rod-bow benefits). Channel stability will be improved both by the reduced two-phase pressure drop, and by the damping effect from a separate high velocity flow path within the fuel bundle. An object of this invention is to disclose a first class of separation devices for inhibiting the entry of water into the steam vent volumes overlying the part length rods. According to this aspect of the invention, the part length rod is provided with an attachment at its upper terminal end. This attachment can be either a flared end, deflecting tabs, or a spirally wound piece of metal, hereinafter referred to as a swirl vane. Steam and water passing along the length of the outside of the part length rod adjacent the rod end impact the attachment. Water--with its higher mass--is deflected. Steam--with its lower mass--continues substantially undeflected upwardly into the vent volume overlying the part length rod. There results a reduction of water introduction into the steam vent volume overlying the part length rod. An additional object of this invention is to place steam separation devices in the region overlying one or more part length rods. These devices can be placed at discrete locations, some distance from the part length rods, or they can extend continuously through the void volume overlying the part length rods. Preferable attachment and suspension of such devices is from spacers overlying the ends of the part length rods, or from the upper tieplate. The suspended devices can include twisted metal strips, hereinafter referred to as swirl vanes, cones, or other steam separation devices. Remaining water introduced into and entrained into the steam vent volume is ejected. An advantage of both the attachment to the end of part length rods and the separation device overlying the end of part length rods is flexibility in placement of part length rods while maintaining more effective steam vent channels side-by-side with surrounding higher liquid fraction about the full length rods. There results improved nuclear reaction, improved heat transfer, improved stability and lower pressure drop. An object of this invention is to disclose a balance between the loss of pressure drop due to judicious use of part length rods and the increase in critical power due spacer attached devices restoring the originally decreased pressure drop. There results an improved critical power. A further object of this invention is to set forth preferable spacer attached devices for the increase of critical power through increased pressure drop. By way of example, either increased spacer pitch or the addition of vanes, such as swirl vanes can be used. In either case, the decrease in critical power due to the presence of the part length rods is considerably less than the increase in critical power due to spacers causing the recaptured pressure drop. As a result, overall critical power is improved. By way of example, and using the combination of actual tests and the spacer pitch of FIGS. 2A and 2B with a 9 by 9 array of fuel rods with eight part length rods distributed in a fuel bundle, pressure drop improves 8% or 1.2 psi. in the upper two phase region of the fuel bundle. Critical power loss due to the presence of the part length rods may be in the range of 2 to 4%. At the same time, and as a result of the decreased spacer pitch, pressure drop increases 0.8 psi. in the upper two phase region of the bundle. At the same time critical power gains over the part length rod array have been measured experimentally to be as much as 12%. Thus the net overall gain in critical power could be as much as 10% with pressure drop remaining substantially unchanged relative to the same fuel rod bundle having full length rods. Regarding decreased spacer pitch, the total number of spacers in the upper two phase region of the fuel bundle is increased. Alternately, the spacers may be increased in vertical height. Further, and as a substitute, the thickness in material from which the spacers are fabricated can be increased. In either event, upon the recapture of the originally obtained pressure drop, improved critical power results. Regarding the vane embodiment of this invention, the reader will understand that vanes incorporated to spacers have two effects. First, they are higher pressure loss devices causing pressure drop and hence improved critical power "downstream" (up above) their particular location in a fuel bundle. Thus, where spacers with vanes are utilized, decreased spacer pitch may not be required. The reader should understand that we do not necessarily identify the specific mechanism causing the beneficial increase in critical power. We do identify that where pressure drop is increased, critical power is likewise increased in the upper two phase region of the fuel bundle. The reader will understand that fuel rods are designed to have reduced power output above the last spacer. This being the case, it will be understood that the top most or last spacer is not required to have an appreciable pressure drop effect on the passing fluid flow. Thus in this last location, the use of an Inconel spacer having minimal critical power effect on the passing fluid flow with corresponding reduced pressure drop can be used.
	description	This application claims priority to U.S. Provisional Application Ser. No. 62/345,307, filed Jun. 3, 2016, the contents of which are hereby incorporated by reference in their entirety. Mass spectrometry has risen to prominence in the life sciences because it is indispensable for identifying and quantifying structural and functional modifications to proteins. However, only a small fraction of the information potentially available can be accessed by current instruments. In high-throughput, bottom-up proteomics experiments, only about 16% of peptides are identifiable with the best currently available technology. The speed, resolution and high mass accuracy of modern mass spectrometers have revolutionized many fields, such as proteomics, for example to determine the location of fragile post-translational modifications that control most cellular processes. However, accurate identification and quantitation of phosphorylation sites remain a major challenge in proteomics. The key weakness with mass spectrometry for phospho-proteomics lies in the methods used to induce fragmentation, because phosphoryl bonds are among the most labile chemical bonds in proteins and are lost in complex ways by current collision-based fragmentation approaches. An alternative fragmentation methodology called electron capture dissociation (ECD) is well established to produce exceptional spectra of phosphopeptides, but is currently feasible only in expensive FTICR mass spectrometers. The fundamental limitation to ECD is providing enough low-energy electrons to efficiently fragment peptides. FIG. 1 illustrates one example of a currently known single pass ECD cell, which uses elements disclosed in U.S. Pat. Nos. 8,723,113 and 9,305,760. The single pass ECD cell 100 has an electron emitting filament 102. Magnets 104 and 106 are located on either side of the electron emitting filament 102. End cap lenses 108 and 110 are located on the side of magnets 104 and 106, respectively, opposite electron emitting filament 102. End cap lenses 108 and 110 can be used to control the flow of electrons. In operation, the ion packet 112 passes through cell 100 a single time. One of the limitations of the single pass ECD cell 100 is that, for peptides containing two positive charges, which are commonly analyzed in proteomics, the efficiency is generally in the range of 5%. Only one in twenty peptides is fragmented, which limits sensitivity. The single pass ECD cell 100 is useful in many applications, but the efficiency of fragmentation, partially for small molecular ions with two or fewer positive charges could be improved. Reflectron-electromagnetostatic cells of the present technology may increase the efficiency of fragmentation in mass spectrometers to improve the identification of both small molecules (e.g., drugs, metabolites, environmental chemicals) and large molecules (e.g., proteins, glycoproteins, lipids, DNA, RNA). FIGS. 2-9 illustrate some examples of reflectron-electromagnetostatic cells of the present technology, which cause an ion packet to pass through the cell multiple times. Reflectron-electromagnetostatic cells of the present technology differ from previously known ECD cells in several ways. For example, reflectron-electromagnetostatic cells of the present technology utilize the addition of ion control elements that cause ions to be reflected or slowed through the electromagnetostatic ECD cell. Such alteration of the flow path of ion packets in the cell may increase the efficiency of fragmentation by electron capture dissociation. The ion control elements may include at least one reflectron having at least one electrostatic element, and a controller that applies appropriate DC voltages to the electrostatic element in order to modulate the movement of the ions in the ion packets. A reflectron may include at least one electrostatic lens, or a plurality of electrostatic lenses. In such a reflectron, each electrostatic lens may be a metal disk, and may have an aperture of a desired size to allow the passage of ions in an ion packet to pass through the disk. Although specific numbers of lenses are shown for each reflectron in the illustrated examples, it should be understood that, generally, each reflectron may have at least one lens, and that the number of lenses may vary. A reflectron may also be substituted by an ion trap operated to cool and return ions through the ECD cell. Each reflectron may be maintained at an electrical potential sufficient to slow or reflect molecular ions as they pass through the ECD cell. A controller should be operable to adjust the DC voltage of any electrostatic element of a reflectron in the range of −100 to +100 volts on a minimum time scale of 1 microsecond. As shown in FIG. 2, the reflectron-electromagnetostatic cell 200 has an ECD cell 230 and two reflectrons 226 and 228. The ECD cell 230 includes a thermo electron emitter, such as electron emitting filament 202. The electron emitting filament 202 may also generate infrared radiation that slightly heats molecular ions, which may help dissociate native proteins and large complexes of molecules held together by weak intermolecular interactions. This may improve the sensitivity and quality of mass spectra. Multiple passes through the filament as described here may increase the ability to dissociate native proteins and other molecular complexes. Magnets 204 and 206 are located on either side of the electron emitting filament 202. End cap lenses 208 and 216 are located on the outer sides of magnets 204, and 206, respectively, opposite the electron emitting filament 202. A reflectron is located on one side of each of the ECD cell 230, in each case on the side opposite electron emitting filament 202. As shown, a first reflectron 226 consists of lenses 210-214 located to the left of magnet 204, and a second reflectron 228 consists of lenses 218-222 located to the right of magnet 206. Each of the lenses 210-214 and 218-222 is operatively connected to a controller 224, which controls the voltage of each of the lenses, and can adjust the voltage in each lens. The flow path of the ion packet 232 during operation of the reflectron-electromagnetostatic cell 200 is shown in FIGS. 2 and 3. The controller 224 establishes a voltage gradient and adjusts the voltage gradient over time, using pulsed voltages, to alter the flow path of the ion packet 232. For example, as shown, when the ion packet 232 enters and passes through the electron emitting filament 202 a first time, the controller 224 creates a voltage gradient in first reflectron 226 (lenses 208-214) that traps the ion packet 232 in the cell 200 and reflects the ion packet 232 back through the electron emitting filament 202 a second time. Then, likely within a few microseconds, the controller raises the voltages in the second reflectron 228 (lenses 216-222) to trap the ion packet 232 in the cell 200 and reflect the ion packet 232 back through the electron emitting filament 202 a third time. The ion packet 222 may be reflected by the first and second reflectrons back and forth through the electron emitting filament 202 a number of times. Finally, the controller lowers the voltages in first reflectron 226 (lenses 210-214) to allow the ion packet 232 to exit the cell 200. As shown in FIG. 4, reflectron-electromagnetostatic cell 400 includes an ECD cell 422 and reflectron 420. The ECD cell 422 includes electron emitting filament 402. Magnets 404 and 406, and magnet inserts 408 and 410, are located on either side of the electron emitting filament 402, respectively. End cap lenses 412 and 414 are located on the side of magnet 404 and magnet insert 408 opposite electron emitting filament 402. End cap lenses 414 and 416 are located on the side of magnet 406 and magnet insert 410 opposite electron emitting filament 402. A reflectron 420, consisting of a series of lenses 422-430, is located on the side of end cap 418 opposite the electron emitting filament 402. The reflectron may be operatively connected to a controller that adjusts the voltages of each of the lenses. FIG. 5 illustrates reflectron-electromagnetostatic cell 500, which uses a reflectron 512 consisting of a series of lenses 502-508 with increasing positive voltage to reverse the course of ions back through an ECD cell 528. It is estimated that reflectron-electromagnetostatic cell 500 would at least double the efficiency of fragmentation as compared to single pass ECD cell 100. ECD cell 528 includes an electron emitting filament 514, a first magnet 516 on the right side of the electron emitting filament 514, a second magnet 518 on the left side of the electron emitting filament 514, a first end cap lens 520 on the right side of the first magnet 516 (the side opposite the electron emitting filament 514), a second end cap lens 522 on the left side of second magnet 518 (the side opposite the electron emitting filament 514). The ion packets entering the cell flow from left to right, as shown by arrow 524. The reflectron 512 stops the ion packets, preventing them from leaving the cell on the right side, and redirect the ion packets back through the electron emitting filament 514. Fragments leave the cell 500 in a flow path from right to left, as shown by arrow 526. Each lens of the series of lenses 502-508 in the reflectron 512 is a metal disk. Each of the lenses is 502-508 connected to a DC power supply controller 510. Controller 510 provides each lens with a constant voltage of a desired amount. In this example, the constant voltage of each lens increases for each lens in the series from left to right, creating a progressively increasing series of constant voltages across the lenses 502-508. Thus, lens 504 has a higher voltage than lens 502, lens 506 has a higher voltage than lens 504, and lens 508 has a higher voltage than lens 506. Another embodiment of this configuration includes placing the reflectron lens 512, or a series of lenses forming a reflectron, between the first magnet and the filament. In this way, ions would be reflected before entering the filament. The filament could then be made as a solid disk to allow more electrons to enter the ECD cell than possible from loop filaments used in the other embodiments of the invention In alternative embodiments, the electrostatic reflectron 512 of FIG. 5 could be used in the place of a classical reflectron in a Time of Flight (ToF) mass spectrometer. This may allow for efficient fragmentation by ECD. A pusher pulse could be applied to ions exiting the cell to initiate the separation of fragments. FIG. 6 illustrates reflectron-electromagnetostatic cell 600, which uses an reflectron 612 consisting of a series of lenses 602-608 with increasing positive voltage to reverse the course of ions back through the cell 600. Reflectron-electromagnetostatic cell 600 includes an ECD cell 628. ECD cell 628 includes electron emitting filament 618, a first magnet 620 on the right side of the electron emitting filament 618, a second magnet 622 on the left side of the electron emitting filament 618, a first end cap lens 624 on the right side of the first magnet 620 (the side opposite the electron emitting filament 628), a second end cap lens 626 on the left side of second magnet 622 (the side opposite the electron emitting filament 618), and reflectron 612. Each lens in the series of lenses 602-608 is a metal disk connected to a DC power supply controller 610. The controller 610 provides a constant voltage to each lens, and can provide a progressively increasing series of constant voltages across the lenses 602-608. Thus, lens 604 has a higher voltage than lens 602, lens 606 has a higher voltage than lens 604, and lens 608 has a higher voltage than lens 606. The reflectron-electromagnetostatic cell 600 also includes an ion trap 614, which contains a cooling gas to trap ions before being sent through the reflectron-electromagnetostatic cell 600. Appropriate voltages can be applied to eject ions with low energy out of the ion trap 614, into the reflectron-electromagnetostatic cell 600 and then reflected back. Both the parent ions and the fragments are cooled on their return to the ion trap 614. By adjusting the length of time or by pulsing ions out of the ion trap 614, it is possible to make multiple passes of the ions to achieve the maximal degree of fragmentation desired within milliseconds. The ions can then be passed from the ion trap 614 in a different path for analysis of the fragmentation by a mass analyzer 616, such as an Orbitrap or ToF mass analyzer. FIG. 7 illustrates a reflectron-electromagnetostatic cell 700 of the present technology in a mass spectrometer 702 The direction of the flight path of the ion packets is from the right to the left, from the electro-spray ionization source 704, through the transfer optics 706, and then through the C-trap 708 before entering the reflectron-electromagnetostatic cell 700. The C-trap 708 is a specific type of ion trap used to squeeze ions into a tight ion packet before they are injected into the Orbitrap mass analyzer 710 for measuring molecular weights of the fragment ions. However, the ion packets may be first injected into a higher energy collision-induced dissociation (HCD) ion trap 702. Ions can be transferred into the HCD cell with energy ranging from 1-200 volts to fragment by collisions with gas molecules. Alternatively, ions can be passed through the reflectron-electromagnetostatic cell 700 only and are returned to the C-Trap without entering the HCD collision cell to produce an ECD spectrum. In addition, the ions can be dissociated by two processes simultaneously—by transferring to HCD cell with energy enough to fragment by CID process and by ECD process in reflectron-EMS cell. The ability to rapidly fragment molecular ions by two complementary methods that cause different forms of fragmentation can be extremely valuable for improving the identification of molecules by mass spectrometry. FIG. 8 illustrates a reflectron-electromagnetostatic cell 800 of the present technology, in which ions are passed through an ECD cell from two ion traps 802 and 804. In this example, each ion trap 802 and 804 functions as a reflectron, redirecting the ion packets back through the ECD cell 818. The ECD cell 818 includes an electron emitting filament 806, a first magnet 808 on the right side of the electron emitting filament 806, a second magnet 810 on the left side of the electron emitting filament 806, a first end cap lens 812 on the right side of the first magnet 808 (the side opposite the electron emitting filament 806), a second end cap lens 814 on the left side of second magnet 810 (the side opposite the electron emitting filament 806). Ions from the mass spectrometer source enter ion trap 802 from the left through a holed in the electrostatic plate. Each of the ion traps 802 and 804 has may or may not have a closed electrostatic end plate. Once ions have been trapped in ion trap 802, they may be electrostatically propelled through the ECD cell 800 by raising the overall potential. After passage through the ECD cells, ions may be reflected ions back through trap 804 by subsequently raising the DC electrostatic potentials on its end plates and trap elements. The voltages can be adjusted for the end plates within the ion traps to drive ions with a small amount of kinetic energy (e.g., 1-20 eV) between the ion traps through the cell 800. One application for reflectron-electromagnetostatic cell 800 would be for use instead of reflectron-electromagnetostatic cell 600 in mass spectrometer 700 of FIG. 7. FIG. 9 illustrates a series of ECD cells and ion traps operating together to enable multiple levels of precursor selection and fragmentation to be carried out. Ion traps 902, 904 and 906 are alternately placed with ECD cells 908 and 910. First ECD cell 908 includes an electron emitting filament 912, a first magnet 914 on the right side of the electron emitting filament 912, a second magnet 916 on the left side of the electron emitting filament 912, a first end cap lens 918 on the right side of the first magnet 914 (the side opposite the electron emitting filament 912), a second end cap lens 920 on the left side of second magnet 916 (the side opposite the electron emitting filament 912). Second ECD cell 910 includes an electron emitting filament 922, a first magnet 924 on the right side of the electron emitting filament 922, a second magnet 926 on the left side of the electron emitting filament 922, a first end cap lens 928 on the right side of the first magnet 924 (the side opposite the electron emitting filament 922), a second end cap lens 930 on the left side of second magnet 926 (the side opposite the electron emitting filament 922). As shown, ion packets from a mass spectrometer ion source from left to right in the direction of arrow 932. The ion trap 902 may be operated to selectively eject precursor ions to produce fragments that are trapped in ion trap 904. A fragment that is too large to identify may be further selected for further fragmentation in the ECD cell and collection in the third ion trap 906. The process may be continued to allow the analysis of macromolecular complexes that are too large for direct analysis by current mass analyzers. ECD Fragmentation of Substance P Substance P is an eleven amino acid peptide and naturally occurring hormone that has become widely used as a standard for evaluating ECD fragmentation. Hence, substance P is well known to a tough peptide to fragment by ECD, which is why it is used as a standard for ECD experiments. FIG. 10 shows the ECD spectrum for Substance P as measured with a single pass ECD cell on a modified Sciex Q-ToF. The major peak is at 674 m/z and is the unfragmented doubly charged precursor peptide. Enlargements of the spectrum are provided in FIGS. 11 and 12 to show that the small peaks from ECD are clearly resolved while CID peaks are absent. FIG. 13 shows an ECD spectrum from a modified mass spectrometer operated in a dual ion trap mode, where the substance P peptide is passed through the ECD twice. The C5 and C6 ions are each about 10% of the parent Substance P intensity. There are a number of other CID peaks present at low intensity. Finally, about 13% of the parent Substance P had captured one electron and becomes singly charged [M+2H]+. This is called ECnoD, but provides useful information. These peaks are clearly present in single scans, showing that the fragmentation is efficient and exceptionally fast (estimated to occur in about 10 microseconds) and thus does not slow the duty cycle of the mass spectrometer. FIG. 14 shows an ECD spectrum of Substance P operated in reflectron mode with one ion trap on a mass analyzer. This spectrum is very clean, quite intense, and is the first spectrum with the C2 being identifiable. The B10(2+) CID fragment is very small, which is quite unusual. Finally, the parent substance P ion is only 15% of the signal and C5 is the most intense peak in the spectrum. There is a chance that the low signal intensity for substance P(2+) is an artifact of the way the reflectron is operating (it may have been preferentially scattered or lost). ECD Fragmentation of Phosphopeptides FIG. 15 shows an ECD spectrum of a phosphopeptides from the reflectron mode. This spectrum shows that the fragile phosphoserine modification is retained in our ECD cell. From the foregoing, it will be appreciated that although specific examples have been described herein for purposes of illustration, various modifications may be made without deviating from the spirit or scope of this disclosure. It is therefore intended that the foregoing detailed description be regarded as illustrative rather than limiting, and that it be understood that it is the following claims, including all equivalents, that are intended to particularly point out and distinctly claim the claimed subject matter.
045129495	description	DETAILED DESCRIPTION OF PREFERRED EMBODIMENT Referring now to the drawings in detail, FIG. 1 illustrates diagrammatically a local power monitoring system for the fuel assembly of a nuclear power reactor, the system being generally referred to by reference numeral 10. The row data acquisition for the system is located in the reactor fuel core and consists of a plurality of local power rate sensors generally referred to by reference numeral 12 in FIG. 1. The signal outputs of the sensors are fed along two parallel paths through a direct analog signal processing line 14 and a precision computer line 16 in order to produce an averaged power readout 24 and a precision power readout 18, respectively. Data input to the precision computer is obtained from other sources, including for example, information calculated from sensor sensitivity models, power shock models, and various correction factors such as core condition and time domain corrections. In the processing path of computer 16, the sensor signal lines are individually biased by precalibration to obtain precision heat rate measurements from the sensor signals which are converted into local fuel power outputs corrected in accordance with various plant condition parameters from the data sources denoted by reference numeral 20 in FIG. 1. The precision power readout 18 so obtained may be fed to an analyzer 22 to provide fuel power failure forecasts and power distribution recommendations for failure avoidance purposes. The analyzer may alternatively receive its input from the averages power readout 24 to which the signal processor 14 feeds its output in the form of local fuel power rate measurements. A calibrator 26 is connected to the signal processor 14 through which on-line correction of the processed signal output thereof may be effected by comparison of the readout 24 with the precision readout 18 while it is in operation. Thus the readout 24 may be operated continuously to provide the necessary information to the utility operator while computer 16 is non-functional in order to avoid power plant shut down because of interruptions in the supply of data to computer 16 for various reasons such as data updating. The type of sensor utilized in the power monitoring system of the present invention is very critical. As shown in FIG. 2, neutron flux sensors heretofore utilized for precision power monitoring purposes exhibited a significant change with time in signal level for a constant linear heat generation rate for a unit fuel rod length, as depicted by curve 28, assuming no emitter burn-out. With emitter burn-out compensation, the change in signal level for the neutron flux sensor is denoted by curve 30. In contrast thereto, the signal level change for a gamma sensor of the type disclosed in the aforementioned prior application is depicted by curve 32 in FIG. 2, requiring less drastic time domain correction. FIG. 5 illustrates one of the gamma sensors 34 extending through a guide tube 36 from a reactor installation to the seal flange connector 38 located at an instrument removal zone, of a pressure water reactor, for example. The sensor extends through the seal flange 40 and the thermocouple signal cables 42 thereof project through the seal plug 44 to the power monitoring hardware. Thus, gamma radiation produced by fission products in the reactor fuel assembly cause internal heating of the inner core 46 of the sensor to generate the signals in the thermocouple cables 42. While these signals provide for more accurate determination of linear heat generation rate because of its substantially direct relationship thereto, there is a signal response delay when a change in power occurs, as exhibited by the signal characteristic curve 48 shown in FIG. 3. In accordance with the present invention, the signal is modified to compensate for such slow signal response as indicated by deconvoluted heating rate signal curve 50. Referring now to FIG. 4, the signal cables from each of the sensors 34 are shown connected to a terminal box 52 thorugh which signals of millivolt level are fed to a scanner or multiplexer 54. By way of example, eight sensors 34 are associated each fuel rod assembly of a reactor core and each sensor has two signal cables associated therewith to provide sixteen signal cables from each fuel rod assembly. In a light water reactor, between 350 to 450 of such signals are present to provide the local power rate measurements through the terminal box 52 to the scanner 54. The scanner may be a solid state multiplexer from which a signal sequence is fed to a first analog signal corrector 56 through which the signals are calibrated to provide a plurality of analog signals in signal path 58, representing local heat rates in the sensors. The signal path 58 represents a plurality of signal lines fed in parallel to the direct analog processing line in the precision signal processing line as aforementioned in connection with FIG. 1. In the precision processing line, the input analog signals enter a precision signal converter 60 through which the sensor signals are given an individual bias and corrected in accordance with a signal sensitivity model though calibrator 62 in order to obtain precision heat rate signals that are fed to a plant process computer 64 which input data is also fed from model data storage 66 and plant condition data source 68. The signal output of the computer is then modified through a dynamic filter 70 to compensate for slow signal response as discussed with respect to FIG. 3. The signal output is then applied to the precision readout 18 in the form of a precision power display monitor furnishing local fuel power rate information for each fuel rod. Direct conversion of the signals in path 58 to local power rate information is effected through a second signal converter 72 to produce outputs reflecting the local fuel power rate for fuel rods adjacent to each of the sensors. The signal outputs are then modified by a dynamic filter 74 and passed through an extrapolator 76 to the continuous display monitor 24 as averaged power rate information. Signal correction may be effected through a calibrator 78. A substantially accurate readout is obtained by such direct signal processing only because of the more accurate signal information furnished by sensors 34 and the measures taken to compensate for slow signal response and on-line calibration through calibrator 28 from comparison with data obtained from the precision monitor 18. FIG. 6 illustrates a less complex version of the system insofar as the direct continuous signal processing path is concerned. The outputs of the sensors are fed through analog signal lines directly to calibrated voltmeters 82. The signals in these lines 80 are also fed to the contacts of a scanner 84 from which the signals are fed in sequence to the precision signal processing line 16 as hereinbefore described with respect to FIGS. 1 and 4.
	summary
	summary
	summary
048266493	abstract	A hydraulic control rod drive for a water-cooled nuclear reactor includes a control valve assembly outside the reactor pressure vessel for influencing the fluid quantity on the pressure side of a fluid pump assembly for adjusting control rods in raising and lowering directions and to maintain a control rod position. A control valve assembly includes the following control branches for actuating each of the control rods: a holding branch connected between a pressure line and a pressure side of a piston/cylinder system, a first fluid throttle and a bypass fluid throttle upstream thereof relative to a drop of the first fluid throttle for discharging into a drain, the first fluid throttle and the bypass fluid throttle having throttle cross sections allowing a fluid flow therethrough sufficient to hold a given control rod in a given position with the fluid pump assembly running; a raising branch connected to the holding branch upstream and downstream of the first fluid throttle, and a series circuit having a raising valve assembly and a second fluid throttle; and a lowering branch connected to the holding branch downstream of the first fluid throttle relative to the drop of the first fluid throttle and discharging into a cooling water reservoir, and a series circuit of a lowering valve and a third fluid throttle. A device is also provided for automatically opening the lowering valve in the lowering branch if the raising valve in the raising branch sticks in an open position.
	summary
	abstract	The present invention includes a filtering apparatus for a CT imaging system or equivalently for an x-ray imaging system. The filtering apparatus may be translated along a first axis or a transverse axis to with respect to an attenuation pattern of a subject during an imaging session to reduce radiation exposure to anatomical regions of the subject sensitive to radiation exposure and/or regions from which data is not being acquired.
063305259	description	DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS a. Apparatus Referring to FIG. 1, shown is a rotating machine and motor system designated generally 10. It should be understood that the apparatus for diagnosing a rotating machine and motor system may be used to diagnose rotating equipment including pumps, turbines, fans, blowers, compressors or other types of equipment. A pump and motor system is shown in FIG. 1 for purposes of example only. Pump and motor system 10 includes motor 12 and a rotating machine or rotating equipment, such as pump 14. Motor 12 may be an electric motor, diesel engine or turbine, or other power source. Motor 12 is operatively connected to rotating equipment 14 via coupler 16. Rotating equipment 14 has inlet 18 and outlet 20. Downstream from outlet 20 of rotating equipment 14 is typically provided a final control element, such as control valve 22. The diagnostic apparatus for one embodiment of the invention is designated generally 24 (FIG. 2). The system can be used effectively used for: a) validation of correct installation of pump 14 and ancillary equipment attached to pump 14; PA1 b) diagnosis of change in an operating condition of pump and motor system 10 for purposes of maintenance and for changing the operation and control of pump and motor system 10; PA1 c) verification that maintenance was properly conducted through a validation of the correct dynamic performance of the repaired equipment; and PA1 d) collection of equipment base line or original performance data for use with maintenance information systems to provide an audit trail of maintenance records. PA1 a) a portable, battery powered field hardened PC with I/O for use in field diagnosis of the rotating machine, shown in FIG. 2, or PA1 b) a field mounted continuously monitoring apparatus, shown schematically in FIG. 3, with data I/O, logging, and communication capability for real time acquisition and diagnosis of the rotating machine, and optionally displaying the pump signatures on a remote display or host, shown in system with a remote host in FIG. 3a, or PA1 c) a host with I/O shown in FIG. 4b and a means of executing the method described herein. Hosts capable of using this method include a compressor or turbine control system, a programmable logic controller (PLC), a maintenance information system, a personal computer, supervisory control and data acquisition system (SCADA) or a traditional process control system, or PA1 d) the method may be implemented in a motor controller or a PLC, shown in FIG. 4a, often used in a motor control center for the motor used to drive the pump. PA1 I=Moment of Inertia of pump shaft/impeller assembly PA1 N=Pump Speed, rpm PA1 Tf=Fluid Torque PA1 Tb=Frictional Torque of bearings PA1 Ts=Frictional Torque of Seal/packing PA1 Qv=CvA(.DELTA.P/SG)**0.5 PA1 Cv=Valve Flow Coefficient at position, y (valve data) PA1 .DELTA.P=Pressure Drop Across the Valve PA1 SG=Liquid Specific Gravity PA1 A=Flow Area of the Valve PA1 N is the operating speed, rpm PA1 H is the pump head, ft PA1 Q is the flow rate, gpm. PA1 where .eta. p is the pump efficiency PA1 Pp is the power delivered to machine by the motor (also known as brake horsepower) PA1 Pf is the fluid power delivered by the machine. Diagnostics apparatus 24 can be applied to any rotating equipment. However, the preferred embodiment of this apparatus is the diagnosis of the centrifugal pump. Diagnostic apparatus 24 includes process sensors for measuring process conditions and for generating process variables, which are key to determining a change or degradation of performance of pump and motor system 10. Sensors, including process sensors, may communicate variables and diagnostics parameters via a network connection to a host computer including digital control systems (DCS's) such as the Foxboro I/A.RTM., supervisory control and data acquisition (SCADA) systems such as that provided by the Intellution Fix.RTM., or a maintenance information system such as that provided by the SAP for the purpose of providing predictive and preventative maintenance information. Process sensors may include outlet pressure sensor 26, shown in FIG. 1, which is positioned proximate outlet 20 of pump 14, for determining pump outlet pressure. Process sensors may also include flowmeter 28 for determining a flow rate of product downstream of rotating machine 14, or other sensors for monitoring process conditions. Further examples of process sensors include temperature sensing device 30, which is approximately positioned upstream or downstream of rotating machine 14 for determining temperature of a process fluid; inlet pressure sensor 32, which is positioned proximate rotating equipment inlet 18 of rotating machine 14 for determining rotating machine inlet pressure; and valve position sensor 34. Valve position sensor 34 is preferably mounted on control valve 22 and communicates with input/output device 36 for converting electrical signals to digital signals. Valve position sensor 34 is provided to determine the position of a control valve or shaft. Additionally, valve position sensor 34 provides input for a method to calculating flow through pump or rotating equipment 14. The flow through valve 22 can be calculated from the valve position, the pressure drop across the valve and known fluid properties and geometry from the valve supplier. The flow through valve 22 may then be and stored as original data. This information enables a baseline head vs. flow (H v Q) performance reference curve to be developed in the absence of a flowmeter. Additionally, knowledge of valve position provided by valve position sensor 34 is used to alert possible deadheading of pump or rotating equipment 14. Input/output device 36 of diagnostic apparatus 24 communicates with process sensors for receiving process variables therefrom. Input/output device 36 transmits process variables received from process sensors to computing device 38. The computing apparatus may be: FIG. 2 is a schematic of diagnostic apparatus 24. Box 40 represents pump and motor system 10. Data is shown being transmitted from pump and motor system box 40, as represented by a plurality of arrows generally designated 42. Examples of data being transmitted include process variables generated by process sensors and condition monitoring variables generated by machine sensors, to be discussed below. Data is transmitted to a sensor excitation and conversion device, represented by box 44. Converted data signals are then transmitted from sensor excitation and conversion device 44 to signal multiplexers, represented by box 46. Alternately, the sensor inputs may be inputted directly to the A/D converter shown in box 52. Sensor data may be multiplexed to microprocessor 48 to provide for asynchronous measurement of selected inputs which are not time critical or do not need to be sampled continuously. Converted data transmitted by sensor excitation and conversion device 44 to signal multiplexers 46 is represented by arrows, designated generally 50. From signal multiplexers 46, data is then preferably transmitted to an A/D converter, such as those manufactured by Analog Devices and Crystal Semiconductor, represented by box 52. Examples of microprocessor 48 include Motorola's 16-bit 68 HC16 or 32-bit LC302. D/A converter, represented by box 54, is provided in the preferred embodiment so that microprocessor 48 may communicate with the pump and motor system, represented by box 40. Diagnostic apparatus 24 may also include a real time clock 59 with optional battery backup that can be used to time stamp data acquired synchronously or asynchronously. Real time data may be alternatively acquired via the network 115 from a host computer as is provided with Foundation Fieldbus or Ethernet networking technology. In the preferred embodiment, microprocessor 48 is in communication with memory storage 56, co-processor 58, and a disk drive or other data storage or retrieval means 60. Co-processor 58 is optional. Examples of a suitable co-processor include Texas Instrument's DSP microcontroller, with embedded frequency analysis algorithms such as fast fourier transform (FFT) or wavelets. Co-processor 58 may be provided to process spectral data from sensors such as accelerometers. The co-processor is used to off load microprocessor 48. Additionally, diagnostic apparatus 24 may be provided with the following: an A/C power supply receiving device 62, as is commonly known in the art; charger 64; battery 66; power supply 68, commonly known in the art; communication receiving device 70; keypad 72; keyboard 74; and an output device, such as printer 76 and CRT display 78. In the preferred operation of diagnostic apparatus 24, microcomputing device 48 receives data 42 from input/output device 36 and stores data in memory storage 56. To establish an original condition, original data must be entered into memory storage 56. For purposes of this application, original data includes tables of machine geometry, machine installation parameters, ancillary equipment parameters original performance curves and fluid properties of the pumped product, as well as previous condition data. Previous condition data refers to data gathered in a previous set of measurements that is stored for retrieval and comparison purposes. Therefore, measured data, including process variables and condition monitoring variables, may be compared to original data to determine performance deterioration of rotating machine and motor system 10. Microprocessor device 48 of diagnostic apparatus 24 compares measured data with original data for generating an output via printer 76, CRT display 78 or other output devices based on the comparison. Referring again to FIG. 1, in the preferred embodiment diagnostic apparatus further comprises machine sensors for generating condition monitoring variables. Machine sensors allow data to be gathered from individual components for determining specific problems with pump and motor system 10. Computing device 38 is used to compare condition monitoring variables with stored original data for diagnosing rotating equipment degradation and for generating an output based upon that comparison. A discussion of various types of machine sensors follows. Machine sensors may include rotating equipment vibration sensor 80, which is preferably mounted on rotating equipment 14 for determining vibration of rotating equipment 14. Vibration sensor 80 is in communication with input/output device 36 for providing condition monitoring variables to computing device 38. A further machine sensor is dynamic pressure sensor 82, which is positioned in the product fluid stream downstream from rotating equipment outlet 20 or positioned within rotating equipment casing 84 of rotating equipment 14 and is in contact with the process fluid. Diagnostic apparatus 24 (FIG. 2) may include additional machine sensors, including motor vibration sensor 86, which is preferably mounted proximate a bearing for determining bearing vibration. Motor vibration sensor 86 is preferably in communication with input/output device 36 for providing condition monitoring variables thereto. By receiving data from gearbox vibration sensor 88, which is mounted proximate gearbox 87 of rotating equipment 14, and from motor supply sensor 90, which senses motor current and motor voltage, and from alignment sensor 92, diagnostic apparatus 24 may diagnose whether rotating equipment 14 requires impending maintenance. Diagnostic apparatus 24 may also include rotating machine seal leakage detector or sensor 94. Seal leakage sensor 94 is mounted proximate a shaft seal on rotating machine 14 for detecting seal leakage. Seal leakage sensor 94 provides condition monitoring variables to input/output device 36 for providing computing device 38 with condition monitoring variables. Diagnostic apparatus 24 may include additional machine sensors, such as oil contamination sensor 96. Oil contamination sensor 96 is preferably mounted in gearbox 87 or on an oil sump for detecting oil contamination. Oil contamination sensor 96 provides condition monitoring variables to input/output device 36 for providing computing device 38 with condition monitoring variables. Additional machine sensors, such as viscosity degradation sensor 98, may also be provided. Viscosity degradation sensor 98 is preferably mounted proximate a gearbox for detecting oil viscosity degradation. Oil viscosity degradation sensor 98 is for providing computing device 38 with an oil condition monitoring variable. Additional machine sensors include torque sensor 100, which is preferably mounted proximate to the shaft of rotating machine 14. Torque sensor 100 is in communication with input/output device 36 for providing computing device 38 with torque data. Machine sensors may also include angular velocity sensor 102, preferably mounted proximate to shaft of rotating machine 14. Angular velocity sensor 102 is in communication with input/output device 36 for providing computing device 38 with angular velocity data for computing input power to rotating machine 14 and computing the output fluid power of rotating machine 14 and the efficiency of rotating machine 14. Additional machine sensors include corrosion sensor 104. Preferably, corrosion sensor 104 is mounted on rotating machine casing 84 for measuring degradation of rotating machine casing 84 resulting from undesirable conditions, such as corrosion, pump cavitation or erosion. Corrosion sensor 104 is preferably in communication with input/output device 36 for providing condition monitoring variables thereto. A typical corrosion sensor uses electrical potential generated by corrosion to provide a voltage measurement. Corrosion sensor 104 can be located anywhere in rotating equipment 14 of pump and motor system 10 where high corrosion is expected, e.g., a thin section or areas of high flow. Further machine sensors include ultrasonic thickness sensor 106. Ultra-sonic thickness sensor 106 is preferably mounted on rotating machine casing 84 for measuring degradation of rotating machine casing 84 from undesirable conditions such as corrosion, pump cavitation or erosion. Ultrasonic thickness sensor 106 is preferably in communication with input/output device 36 for providing condition monitoring variables thereto. Additional machine sensors include accelerometer 108, bearing temperature sensor 110, bearing vibration sensor 112, and axial displacement sensor 113. Diagnostic apparatus 24 may be configured in one of two classes. In a first class, embedded systems, such as microcontrollers, contain software that is burned into the chip's logic, i.e., firmware. The embedded system provides a software instruction set which is permanent. Embedded systems are used in a field hardened embodiment of diagnostic apparatus 24, discussed below. Another form of the embedded system embodiment uses downloadable executable code in electrically alterable memory such as EEPROM or FLASH for equipment identification numbers, specific flow data--fluid parameters, pump performance curves, etc. A second class of diagnostic apparatus comprises a real time computing platform. Configurable logic will normally be remotely located in a computing host. Examples include personal computers, workstations, PLC, DCS, and minicomputers. A secondary form of this real time computing platform is a portable real time computing platform. A portable computing device allows testing to be performed near pump and motor system 10, thereby allowing for observation of the equipment. In one embodiment of the invention, diagnostics apparatus 114, FIG. 3, operates via a bus wherein there exists no central controller. Such a system is provided with the enhanced digital HART protocol, proprietary protocols, such as Honeywell's Del., Yokogawa's Brain, proprietary protocols as provided by Bailey and Foxboro for their field instruments, and emerging field buses such as Foundation Fieldbus, Profibus, or World FIP, Ethernet, etc. In a more fully featured embodiment shown in FIG. 3a, the diagnostic apparatus 24 is powered by and communicates over a multi-wire network, such as a three-wire network in which DC power 117 is remotely provided over a separate set of wires or a four-wire network in which DC power is remotely provided over a separate set of wires. Protocols typically used include Modbus (RS232 and RS485), Foundation Fieldbus H2, Profibus H2, and Ethernet, I/P, TCP/IP, UDP/IP, etc. In one embodiment of the invention, shown in FIG. 1, machine sensors are integrated with input/output device 36 and computing device 38 for comparing measured performance signatures of rotating machine 14 at a second time with an original condition signature at a first time for diagnosing degradation of rotating machine performance. In the preferred embodiment, process sensors and machine sensors are electrically isolated from the apparatus. Comment: Electrical isolation is well known. It is accomplished with transformers or optically with OPTO/couplers. In another embodiment of the invention, shown in FIG. 4a, a PLC is used as the diagnostic apparatus platform, and the PLC's microcontroller 188, which is positioned proximate rotating machine 14 for controlling rotating machine 14. For example, microcontroller 188 may control rotating machine 14 by issuing a control set point to control valve 22, I/P 35. Preferably, microcontroller 188 possesses firmware for providing instructions to rotating machine 14. A further embodiment of the invention, shown in FIG. 3a, provides that field hardened computing device 114 of diagnostic apparatus 24 is positioned proximate rotating machine 14 and that computing device 114 provides a control signed to the control valve 22 or variable speed drive. By providing that diagnostic apparatus 114 controls the process as a hardware platform, one benefit is the ability to utilize a combination of known condition monitoring variables, e.g., vibration variables from machine sensors, with process variables from process sensors. Process sensors provide information about the performance of pump and motor system 10. Machine sensors provide knowledge of the health of rotating equipment and motor system 10. Examples of machine sensors that provide vibration variables include motor vibration sensor 86 or bearing vibration sensor 112. When known condition monitoring variables and process variables are combined, decisions can be made through logical deduction about the condition of pump and motor system 10, the process and the ability of pump and motor 10 to provide its intended function. Referring now to FIG. 3, a field hardened remote embodiment of the invention is shown. Field hardened computing device, designated generally 114, of diagnostic apparatus 24 is designed to be positioned proximate rotating machine 14. Field hardened, networked diagnostic apparatus 114 may be used with pumps using standard communication protocols used in the process control and factory automation industries. Preferably, field hardened apparatus 114 is configured to download executable code specific to a particular rotating machine 14 for operating rotating machine 14. Field hardened remote embodiment 114 is preferably encased in field hardened enclosure 116, is remote-powered, and is a networked. In a preferred embodiment, field hardened computing device 114 has digital communications with a network 146 and serves both as a publisher and a subscriber of data over the network. Preferably, field hardened computing device 114 is powered by a remote power supply 115, shown in FIG. 3a. The field hardened embodiment is preferably designed for operation in inclement environments without additional protection. The device may be mounted on or proximate to the pump or other rotating machine 14 and should be designed to withstand high humidity, extreme temperatures, high EMF (electrical noise), rain and snow and other harsh environmental conditions. Additionally, field hardened apparatus 114 should be provided with explosion-proof protection, i.e., be designed not to cause a spark or explosion in hazardous gases. Such an apparatus may be powered by and communicate over a two-wire loop. The process control industry routinely uses field-hardened sensors, actuators, and instruments that are remotely powered with a DC power supply 115 (typically 12-24 V) over a twisted shielded pair of wires. Communication is also provided in a full duplex fashion with process industry protocols to and from the field device from host computers such as a PLC or DCS. Field hardened apparatus 114 is preferably capable of satisfying international safety standards for electronic apparatus such as FM, SAA, JIS, CENELEC, and CSA two-wire intrinsic safety and explosion proof devices. Field hardened enclosure 116 is also preferably moisture proof (NEMA 4) and capable of achieving IEC CE mark requirements for heavy industry electrical field mounted instruments. Intrinsic safety standards limit the available power to the field device to avoid ignition of hazardous or flammable gases that may be in the area near the device. Use of low power consumption electronics and microcontrollers is essential to meet these safety requirements. Field hardened apparatus 114, shown in FIG. 3, is encased in field hardened enclosure 116, and receives data from process and machine sensors, designated generally 118. Data received from process and machine sensors 118 is represented by arrows designated generally 120, and is transmitted to I/O, 121 and then to an excitation and conversion device, represented by box 122. Converted data signals are then preferably transmitted from sensor excitation and conversion device 122 to signal multiplexers, represented by box 124. Converted data is then preferably transmitted to an A/D converter, represented by box 126, which communicates with microcontroller 128. Conditioned sensor data signals may be optionally transmitted directly to an A/D converter 126 without use of the multiplexer 124. Microcontroller 128 is preferably in communication with co-processor 130, which has the ability to time-stamp data received. ROM 127 communicates with A/D converter 126, microcontroller 128 and co-processor 130 for providing instructions. Time-stamping of data is facilitated by an optional real time clock 132. Additionally, microcontroller 128 is in communication with electrically alternatable memory 134 for acquisition of pump system, fluid property, pump signature data. Communications device 136 is in communication with microcontroller 128 for transmitting information to a network. Finally, in the preferred embodiment, field hardened apparatus 114 is provided with display 138 so that an operator can get information from the device in the field. An optional communication port 146 permits data transfer from handheld vibration monitors 142 or pump diagnostic subsystems 150. Referring now to FIG. 4a, an additional embodiment of diagnostic apparatus 24 uses a programmable logic controller (PLC) 240 as a platform. Programmable logic controllers are commonly used for control in factory and process control applications and are frequently used for motor control in motor control centers. PLCs by construction provide I/O, the ability to power sensors and actuators through the I/O, A/D converters and a microcontroller with configurable logic algorithms. PLCs also have communication interfaces 190 with standard process control protocols as well as support for remote PC hosts and printers. PLC logic is often configured using a HMI 194 such as those provided by S-S Technologies as well as PLC manufacturers such as Allen Bradley or Siemens. The PLC has all of the necessary elements for implementing the disclosed diagnostic method. The shortcomings of a PLC implementation include the inability to obtain intrinsic safety (two-wire) approvals due to the high power consumption of a PLC and the need to house a PLC in a Division II, sheltered environment. The PLC does, however, provide an ideal platform for the diagnostics method as it is a cost effective package for the necessary elements and has the ability to provide the logic configuration needed for the pump diagnostics method. Further, the diagnostics method running on the PLC can provide the diagnostics alerts 154 for off-BEP operation of a pump so that operator could provide immediate corrective control action to operate the pump in a BEP regime through a change in the control set point. In this embodiment, shown in FIG. 4a, diagnostic apparatus 240 uses a PLC platform for providing sensor I/O, A/D conversion and signal conditioning. The PLC platform additionally provides microcontroller 188 and method logical elements that are embedded in firmware resident in the PLC's microcontroller 188. This embodiment further includes a PLC output 192 and communication network port 190. Additionally, this embodiment of diagnostic apparatus 240 may further include logic configurator 194 for establishing pump method logic in PLC language and for downloading pump logic into PLC microcontroller 188. Examples of logic include ladder logic, sequence charts, function blocks, etc. The apparatus may further include a function block with sensor inputs, outputs, alerts and the pump method. A further embodiment of diagnostic apparatus 240, shown in FIG. 4b, wherein a host computer 236 is used as the platform. A host computer is most often used for maintenance information or maintenance systems, but may also be the DCS control system. The apparatus will include sensors or data from sensors gathered through from a database (data historian from a digital control system) 210, I/O 228 and A/D converters as appropriate 238, a microprocessor with the pump diagnostics method, a database for storing pump diagnostic results 210, alarm and alert management system, communications 212 for networking with other host computers 256, such as DCS, maintenance engineer's PC via an Ethernet TCP/IP network, the Internet, or the plant information management (IS) system network. The host computer embodiment of diagnostic apparatus 240 acquires sensor input via point-to-point or multidrop wired sensors or transmitters such as 32, 28, 26, and 30, wired to I/O 228, which provide conversion and networks digital sensor data via a bus to the microprocessor based host. Sensor data may be alternatively gathered via a bussed sensor network 230 commonly called fieldbus. Commercial workstations, PCs, and servers like the IBM 400 are the preferred computing platforms for maintenance information systems. I/O interfaces with appropriate A/D converters and signal conditioning which convert the required sensors (physical and condition monitoring) to digital data are readily available from companies like GE Fanuc and National Instruments. The maintenance information system can process sensor inputs using diagnostics methods within the workstation or PC microprocessor. Plug-in communication output boards are readily available from National Instruments for the many process communication protocols, and can be readily networked with the DCS or maintenance engineer's PC with Ethernet TCP/IP based network protocols. Host computers are able to share data over a network connection through the use and support of standard data sharing network services such as those provided by Microsoft's Windows environment through OLE, OPC, JAVA, netDDE, DDE and to databases through standard database services like ODBC, OLEDB, SQLSERVER, etc. In the host computer platform embodiment, shown in FIG. 4b, the diagnostic apparatus 236 may further include sensors wired to a central input/output 228, A/D card 238 with sensor signal conditioning, a card connection to an input/output network, sensor input/output network 240, such as a DCS data highway, computer 236, such as a PC DCS workstation, etc., that includes data input bus 240, computing element, memory, input device, such as a keyboard, network communications, a display 224, data storage 210, real time clock, and a software-based implementation of the pump method. Diagnostic apparatus 236 preferably includes an alert device that responds to a condition of rotating equipment 14. An alert is transmitted to a host computer 256 via the network 212. Apparatus may further include network services, such as OLE, OPC, Net DDE, or ODBC, for publishing pump data and alerts with software applications resident on the computer. In the preferred embodiment, shown in FIG. 3a, diagnostic apparatus 114 possesses communication port 70 for importing condition monitoring variables from portable hand-held data logging device 142. Examples of data logging devices include hand-held vibration monitoring systems, oil analysis devices, corrosion and ultra-sonic thickness gauges, etc. Preferably, portable hand-held data logging device 142 possess a database for storing the input devices. Additionally, portable hand-held data logging devices 142 may use an intelligent network device. Diagnostic apparatus 114 may additionally possess process communication port 70 for communicating with intelligent network devices. Examples include Hart, Foundation Fieldbus, Profibus, Modbus, Ethernet TCP/IP, etc. An example of an intelligent network device for communicating with process variable digital bus 70 includes a control valve position sensor 34, shown in FIG. 3a. Diagnostic apparatus 114 may further include monitoring system digital bus 146 for communicating with intelligent network devices having computing engines for collecting condition monitoring variables. In one embodiment of the invention, diagnostic apparatus 114 includes condition monitoring subsystems 150 for rotating machine 14. The apparatus can serve to collect data from other smart diagnostics subsystems such as a smart motor and provide a database for the entire rotating equipment system over a network for analysis by others with a maintenance information system, expert system, control system or SCADA system. Condition monitoring subsystems 150 are interfaced with computing device 114 via standard communication network interfaces for transmitting subsystem data over a standard communication network. Examples of condition monitoring subsystems include a Bentley Nevada Trendmaster 2000, a smart motor, and gearbox condition monitoring system and Fisher Controls Fieldvue.RTM. valve diagnostics system. A Bentley Nevada system is primarily used with compressors and steam turbines for determining vibration and uses a proximity sensor positioned near a shaft for determining eccentricity or orbit of the shaft in the bearing. In a further embodiment of the invention, diagnostic apparatus 114 comprises external processed data storage device 152 for storing subsystem data. The storage of subsystem data is necessary when diagnostic apparatus 114 is a network client having a memory database for storing data from a network rotating machine subsystem. In this embodiment, subsystem data is stored as a substitute for direct sensor or pump subsystem component condition monitoring inputs. If any other subsystem is analyzed, then data must be stored. Otherwise, diagnostic apparatus 114 must include its own sensors. One reason that subsystem data must be stored is that a subsystem may already have a fast fourier transform (FFT). Therefore, this embodiment of diagnostic apparatus 114 must treat data differently since information has already been preprocessed. In the embodiment of the invention, schematic FIG. 3 shows co-processor 158 of diagnostic apparatus 114 is in communication with microcontroller 128 for providing spectral signal reduction of condition monitoring variables from the frequency domain sensors 118. These include pump vibration sensor 80, motor vibration sensor 110, dynamic pressure sensor 82, and bearing vibration sensor 112, shown in FIG. 1. Further examining the diagnostic apparatus schematic, FIG. 3, diagnostic apparatus 114 is preferably provided with alert device 154 for indicating when undesirable equipment conditions occur. Undesirable equipment conditions are determined by comparing process or equipment conditions with user configured levels for sensor-computed variables or high limits. Examples of undesirable equipment conditions include vibration levels that exceed the manufacturer's recommended amplitude levels. In one embodiment, when an alert indicates an undesirable equipment condition, an optional contact closure 156 is provided to shut down pump and motor system. Contact closure 156 is located in diagnostic apparatus 114 to switch voltage or current to provide an alert or safe equipment operation. For example, in one embodiment, contact closure 156 is always "ON" and disconnects when an alert is generated. Conversely, contact closure 156 may default to the "OFF" position and connect when an alert is generated. Other uses for contact closures include lighting a warning light, disconnecting a motor, reducing power to a motor, etc. If a variable speed drive motor is utilized, contact closure 156 can be located proximate the motor or may be positioned in a control room. The combination of contact closure 156 with diagnostics results in improved control of the pump and motor system 10. FIG. 3a shows field hardened apparatus 114, in a process control system connected to an host computer, 236, typically a DCS system. Diagnostic apparatus 114 may additionally include a final control element, such as control valve 22 whereby the final control element is responsive to the output communication 70 generated by computing device 38 for operating pump 14 and motor system 12 in a recommended operating design regime. A final control element is typically used to control flow through pump 14 to meet piping and process system requirements, and may be used to conduct tests required to generate a performance curve. Closing control valve 22 by providing an output signal to the valve I/P 35 increases resistance and causes rotating equipment or pump 14 to operate at a higher pressure and a lower flow rate. Similarly, opening control valve 22 results in reduced system resistance, increased flow and lowering pressure. Another example of a final control element is a variable speed drive connected to the pump which may be used as a controller. A variable speed drive works to provide a required flow and pressure demand by adjusting the speed of the rotating equipment 14. FIG. 3 shows diagnostic apparatus 114 includes, in the preferred embodiment, optional real time clock 132 in communication with computing device 128, for time stamping process variables and original data for time-based comparisons. Diagnostic apparatus 114 may further comprise a display for displaying a performance signature at a first time and at a second time. In an additional embodiment shown in FIG. 2, diagnostic apparatus 24 is a portable battery-powered field apparatus. In this embodiment, diagnostic apparatus 24 further includes co-processor 58 which contains a software resident spectral analysis engine 158. Spectral analysis engine 158 is for processing signals from frequency domain sensors. Frequency domain sensors include rotating equipment vibration sensor 80 and dynamic pressure sensor 82, as well as motor vibration sensor 110 and bearing vibration sensor 112. Co-processor 58 receives data from microprocessor 48 or directly from frequency domain sensors. Diagnostic apparatus 24 may also include a network communication port 160. Network communication port 160 is for communication with portable vibration monitor 142 for communicating output from computing device 48 to a network 115, and communication device 70 for communicating data from computing device 48 to a networked host. b. Method The method of practicing the invention enables diagnosis of rotating equipment commonly used in the factory and process control industry. The method is intended to be used to assist a maintenance engineer in the diagnosis of turbines, compressors, fans, blowers and pumps. The preferred embodiment is a method for diagnosing pumps, particularly centrifugal pumps. The method of the invention is based on a comparison of measured pump signature curves resulting from the acquisition of process variables from sensors monitoring a current condition of the pump and the original or previous pump performance curve from prior monitoring or knowledge of pump geometry, installation data, ancillary equipment data and properties of pumped process liquid. The diagnostics method can be used in conjunction with diagnostic apparatus 24, shown in FIG. 2, apparatus 114 shown in FIGS. 3 and 3a, PLC apparatus shown in FIG. 4a or PC host 236 shown in FIG. 4b, which provides for the acquisition of process and condition monitoring variables, the computation of the required pump signatures and curves, the display of the computed curves, a logic element for deducing and diagnosing the pump by component, and optionally a communication to a host computer. The method of the invention identifies and interprets changes in the performance curve, or pump performance curve, by monitoring and analyzing key pump conditions. Typical pump performance curves are shown in FIG. 5. Changes in the pump performance curve may be used to diagnose a root cause of pump component failures. The diagnosis is beneficial in failure prognosis, maintenance planning, changing the operating condition of the pump to avoid damage and is often used with a companion host system. The centrifugal pump performance curve in FIG. 6 is provided by a pump manufacturer based on a standard test described by the Hydraulics Institute, the recognized standards authority for the pump industry. The pump performance curve is routinely used by the end user to properly select the appropriate pump and impeller to provide the desired fluid flow or head condition. Changes to the pump performance result from the use, wear, misapplication and operation of the pump outside the design conditions. These changes alter the pump performance curve. These changes can be used as the first step in diagnosing: 1) root cause analysis of failing pump components; 2) incorrect pump application or installation; 3) pump operation at flow/pressure conditions different than original design (BEP). The method of the invention uses the pump performance curve to identify possible problems, which are often due to pump misapplication or failing components. Misapplication problems are diagnosed by comparing the measured operating conditions with the BEP region or recommended operating design regime of the pump performance curve. Misapplication results in operation outside the recommended operating regime, leading to pump stress, wear and failure. Pumps are designed by the manufacturer to operate at the best efficiency point (BEP) or recommended operating design regime. The highest reliability occurs at the best efficiency point of the pump. Pump designs preferably minimize radial and thrust bearing loads, vibration levels, preclude recirculation or cavitation, and provide for the best conversion of mechanical energy to fluid energy at the BEP. Operation at conditions different from the BEP (off-BEP) can result in rapid deterioration of the pump. The diagnosis of off-BEP operation can facilitate pump component failure analysis. If diagnostic information is communicated to a control system, adjustments to pump operation for operating closer to the BEP increases pump life. The method of the invention utilizes the full range, at all operating conditions, of pump performance curves. The pump operating variables of head, pump efficiency, brake horsepower, net positive suction head required, and specific speed are plotted vs. flow rate, as shown in FIG. 9. The current pump operating performance curve is plotted vs. the original or previous (at last maintenance/commissioning) pump performance curve and is adjusted for operating fluid properties. In particular, the method of the invention for diagnosing rotating equipment includes forming a hypothesis of component failure from the a pump operating condition. Referring now to FIG. 10, to generate a hypothesis, diagnostic apparatus 24 first stores original data, represented by box 1010. Original data may further include geometric parameters of a pump system and the components of a pump system, a new or original condition pump performance curve, a previously measured pump performance curve, fluid properties data, maintenance record data and output display drivers. Original data may be used to construct an original performance curve for rotating equipment or pump 14, as shown in FIG. 6, and represented in box 1012 of FIG. 10. The original data possesses a recommended operating design regime 166, referred to as Best Efficiency Point (BEP) 164 when referring to a pump as shown in FIG. 6a. Recognized recommended operating design regime 166 is shown in FIG. 6a on an example pump curve. The acquisition of process variables from process sensors that gather process data from pump or rotating equipment 14 is represented by box 1014. The method of the invention includes inputting process variables from process sensors into computing device 38 (FIG. 1), as represented by box 1016. A process data point is then obtained from the process variables, as represented by box 1018, which represents an operating condition of rotating equipment or pump 14. Computing device 38 then compares the process data point with the original data, as represented in box 1020, to determine whether the operating performance is outside of recognized recommended operating design regime 166 (FIG. 6a). If the data point is determined to be inside the recommended operating design regime 166, the pump is operating efficiently. If the data point is determined to be outside the recommended operating design regime 166, the pump is operating inefficiently, as represented by boxes 1022 and 1024, in FIG. 10. In a preferred embodiment, computing device 38 also determines from a comparison of process data with original data whether the process data point, referred to in box 1018, is below the recommended operating design regime 166, as shown in FIG. 6a, wherein the process data point is designated 168. Operating a pump below the recommended operating design regime 166 will cause a pump to experience possible recirculation. Therefore, diagnostic apparatus 24 (FIG. 2) will then form a hypothesis that the pump is operating in an area of possible recirculation. Additionally, diagnostic apparatus 24 performs an analysis to determine whether the process data point is operating above the operating design regime 166. If a pump is operating above the recommended operating design regime 166, as represented by data point 170 in FIG. 6a, the pump will experience possible cavitation. Thus, diagnostic apparatus 24 will hypothesize that the pump may be operating in an area of cavitation. This process is set forth in FIG. 11. Referring now to FIG. 11, initially, original data having a recommended operating design regime 166 must be stored as represented in box 1110. A head vs. flow curve is then constructed from original data, as is represented in box 1112. Process variables are then acquired from process sensors, as represented by box 1114, and the process variables are input into computing device 38, as represented by box 1116. An operating performance data point is generated from the process variables as represented by box 1117. Diagnostic apparatus 24 then determines whether the pump is operating outside the recommended design regime 166, as represented by boxes 1118, 1120 and 1122. If it is determined in box 1118 that the pump is operating outside of design regime 166, as indicated in box 1122, then computing device 38 determines whether a current operating performance data point indicates a higher head pressure than the recommended design regime 166, as represented in box 1124. If so, a diagnosis of possible pump recirculation is made by diagnostic apparatus 24, as represented in box 1126. Additionally, diagnostic apparatus 24 determines whether the operating performance data point indicates a lower head pressure than the recommended design regime 166, as indicated in box 1128. If the current operating performance data point is lower than the recommended design regime 166, then a diagnosis of possible pump cavitation is made by diagnostic apparatus 24, as indicated in box 1130. A similar analysis will be conducted regardless of whether the rotating equipment is a pump or other type of rotating equipment. However, if the rotating equipment is not a pump, but is a gas rotating machine such as a compressor, fan, turbine or blower, then the diagnosis in the case of a current operating performance data point operating at a higher head pressure than the recommended design regime 166 will be surge as is shown in FIG. 5e for a compressor. An operating performance data point indicating a lower head pressure than the recommended design regime 166 will result in a diagnosis of stall as shown in FIG. 5e. After a hypothesis has been formulated by diagnostic apparatus 24, in the preferred embodiment diagnostic apparatus 24 performs a step of verifying whether the process data point is outside the design regime 166, shown in FIG. 6a, and determines the cause of degraded performance. The step of verifying the hypothesis may be performed by analyzing equipment monitoring variables generated by machine sensors. When pump 14 is operating outside recommended operating design regime 166, or outside BEP 164, pump component failure can be hypothesized and verified through the use of a second tier of condition monitoring variables and curves. Four secondary curves which permit confirmation of expected degraded pump components are included in this diagnosis method. The four secondary curves (condition signatures) include: 1) dynamic pressure sensor spectra 172 shown in FIG. 7a; 2) velocity 173 and acceleration vibration spectra 174 obtained from an FFT analysis of accelerometer sensor data shown in FIG. 7b; 3) bearing forces 180 vs. pump flow rate curve, shown in FIG. 9; and 4) a break horse power 182 vs. pump flow rate curve, shown in FIG. 9. The vibration spectra for both velocity and acceleration provide a basis for diagnosing radial and trust bearings, damage to the pump impeller from recirculation or cavitation causing impeller imbalance, pump shaft imbalance wear of pump seals and wear plates and degradation of ancillary pump system components. Dynamic pressure spectra 172 provides for a means of measuring pump pressure noise which will indicate insufficient net positive suction head leading to flashing or cavitation and for evidence of recirculation. Dynamic pressure pulsations are also known to increase dramatically whenever the NPSH available drops below the NPSH required as shown in FIG. 7c. The NPSH required is computed from the manufacturer's recommended levels adjusted for fluid vapor pressure and operating temperature. Examples of machine sensors, shown in FIG. 2, used to monitor pump and motor system 10 include rotating machine vibration sensor 80, dynamic pressure sensor 82, motor vibration sensor 86, gearbox vibration sensor 88, motor supply sensor 90, which may be a motor current or motor voltage sensor, alignment sensor 92, seal leak detector or sensor 94, oil contamination sensor 96, viscosity degradation sensor 98, torque sensor 100, angular velocity sensor 102, corrosion sensor 104, ultrasonic thickness sensor 106, accelerometer 108, bearing temperature sensor 110, bearing vibration sensor 112, displacement sensor 113, and an motor insulation resistance sensor 90 or other sensors to monitor equipment conditions. Referring now to FIG. 12, it can be seen that in the preferred embodiment of the method, original data is stored as represented by box 1210. Original data is used to construct an original performance curve, as designated by box 1212. An example of an original performance curve is shown in FIG. 6. Process variables are acquired from process sensors, as represented by box 1214. Condition monitoring variables are acquired from machine sensors, as indicated by box 1216. A hypothesis is formed by diagnostic apparatus 24 regarding whether rotating machine and motor system 10 is operating outside of recommended operating design regime 166, shown in FIG. 6a, as represented by box 1218, as shown in FIG. 10. If diagnostic apparatus 24 determines that rotating equipment 12 is operating within recommended operating design regime 166, as indicated in box 1220, or if diagnostic apparatus 24 determines that rotating equipment 12 is operating outside recommended operating design regime 166, as represented by box 1222, diagnostic apparatus 24 then performs a verification step, as indicated by box 1224. The general method described herein is applicable to pumps as well as other types of rotating equipment. Referring now to FIG. 13, a method for verifying that a pump is cavitating includes constructing an original performance curve from original data, constructing a measured performance curve from process variables, and then comparing the measured performance curve with the original pump performance curve for determining if the pump is cavitating. By performing the comparison of the performance curves, it can be determined whether a "droop" condition exists. An example of a "droop" condition is shown in FIG. 7d. If diagnostic apparatus 24 determines that there is an observable droop, as indicated in box 1310, then a diagnosis can be made that cavitation exists, as indicated in box 1312. This determination can be made because a droop condition indicates that insufficient net positive suction head is available, which results in pump cavitation. Referring now to FIG. 14, an additional verification step that can be undertaken that includes acquiring a measured flow rate from process sensors, such as flowmeter 28. Diagnostic apparatus 24 may determine if the measured flow rate is less than the original flow rate, as indicated in box 1410. If measured flow rate is less than the original flow rate, then a diagnosis of possible seal leakage is made, as represented by box 1412. [45] Apparatus 24 then gathers and examines leak sensor data from optional seal leak detector 94, as represented by box 1418. Diagnostic apparatus 24 then makes a diagnosis of verification as represented by box 1416. The step of verifying a hypothesis and diagnosing specific problem areas by diagnostic apparatus 24 may be accomplished in a variety of ways and by examining a variety of machine sensors. The various machine sensors each gives diagnostic apparatus 24 information about different components for verifying or disproving a hypothesis and providing information on various aspects of pump and motor system 10. Each verification step is valuable for its information regarding a particular component and for its ability to verify or disprove a hypothesis generated by diagnostic apparatus 24 and provides a root cause analysis for the failure. Hereinbelow is a description of various verification methods that deal with different components of diagnostic apparatus 24. Referring now to FIG. 15, a verification step includes acquiring original condition dynamic pressure spectra having amplitude, frequency and phase components as well as acquiring equipment condition monitoring variables comprised of measured dynamic pressure sensor spectra having amplitude, frequency and phase components. FIG. 7a shows an example of dynamic pressure spectra wherein an increase in amplitude in frequency region 176 indicates a condition of recirculation and an increase shown in the amplitude of higher frequency region 178 indicates cavitation. Diagnostic apparatus 24 makes a determination whether amplitude and frequency components of measured dynamic pressure sensor spectra 172 is greater than original condition amplitude and frequency components, as represented by box 1510. Diagnostic apparatus 24 then makes a diagnosis of possible pump cavitation, as represented by box 1512, or a diagnosis of possible pump recirculation, as represented by box 1514. Referring to FIG. 16 and to pump cross sectional drawing FIG. 1b, an additional verification step may be conducted wherein original condition bearing velocity vibration spectra 174 and original condition acceleration vibration spectra are acquired, as well as measured velocity vibration spectra and measured acceleration vibration spectra. Each of the measured and original condition acceleration and vibration spectra has components of amplitude, frequency and phase. Diagnostic apparatus 24 compares at least one of these components selected from the group of amplitude, frequency and phase, as indicated in box 1610, to determine whether possible impeller degradation exists, as indicated in box 1612. It is noted that a continuous high level of vibration at impeller resonant frequency indicates impeller 316 degradation. Increased impeller vibration occurs prior to impeller degradation. Therefore, impeller degradation is preventable. If, during a comparison of the measured velocity vibration spectra, as represented in box 1610, it is determined that the measured vibration velocity spectra is higher than original condition velocity spectra, then it is possible that impeller degradation exists. If a diagnosis of possible impeller degradation is made by diagnostic apparatus 24, as represented by box 1612; then in one embodiment of the method, a measured pump performance curve is constructed as represented by box 1614. A determination is then made whether a phase shift has occurred, as represented by box 1616, and if so, a diagnosis of possible fouling or coating of an impeller in the rotating equipment is made, as represented by box 1618. Referring now to FIG. 17, an additional verification step may be conducted wherein original data is comprised of original condition velocity vibration spectra 174 from rotating machine vibration sensor 80 and original condition acceleration vibration spectra from accelerometer 108, (FIG. 1) wherein the original and measured velocity and acceleration spectra have amplitude, frequency and phase components. A comparison is made of at least one of the components selected from the group of amplitude, frequency and phase of the original condition velocity vibration spectra with at least one of the components of the measured velocity vibration spectra, as well a comparison between one of the components of the original condition acceleration vibration spectra with at least one of the components of the measured acceleration vibration spectra, as represented in box 1712. A determination is then made whether radial bearing 310 degradation exists, as represented in box 1714. Bearing frequency, resonant frequency and harmonics are distinct from impeller vibration, frequency and harmonics. Therefore, if the measured vibration velocity amplitude is higher and the impeller frequency than original condition velocity vibration amplitude 173, then possible impeller degradation exists. Referring now to FIG. 18, another verification step includes gathering equipment monitoring variables, including pump input torque data from torque sensor 100 and pump shaft angular velocity data from angular velocity sensor 102. With this condition monitoring data, a frictional torque is calculated for the rotating equipment, as indicated in box 1810. A comparison of the measured condition frictional torque with the original condition frictional torque is made, as represented by box 1812, to determine whether bearings 310, 312 and seal 314 or wear plate wear 320 is occurring. Diagnostic apparatus 24 will diagnose possible seal 314, degradation if measured frictional torque is less than the original condition frictional torque, as represented by box 1814. Alternatively, diagnostic apparatus 24 may diagnose bearings 310, 312 seal wear 314 or wear plate 320 wear if the measured frictional torque is greater than original condition frictional torque, as indicated by box 1816. Frictional torque may be calculated from the equation below: ##EQU1## where Tp=Torque to pump The measured torque delivered by the motor can be compared to the motor manufacturer's recommended "torque to failure" to provide an early warning alert of imminent motor failure if the pump is not repaired and the high torque condition is not corrected. In an additional verification step, original data is comprised of original vibration, acceleration and velocity spectra from rotating machine vibration sensor 80 or bearing vibration sensor 112, and measured velocity spectra from accelerometer 108, wherein both spectra have amplitude, frequency and phase components. After a diagnosis of possible bearing degradation is made, as indicated in box 1816, a comparison is made of at least one of the components selected from the group of amplitude, frequency and phase of the original vibration velocity or acceleration at the radial bearing resonant frequency or harmonics or acceleration spectra, with at least one of the components of measured vibration velocity spectra 174 to determine whether the measured vibration amplitude is greater than the original vibration amplitude, as indicated in box 1818. If so, a diagnosis of radial bearing 310, FIG. 1b, failure is made, as indicated in box 1820. Referring now to FIG. 19, measured radial vibration velocity spectra and measured radial bearing acceleration spectra are obtained from bearing vibration sensor 112. Each of the original and measured radial bearing and acceleration spectra possesses components of amplitude, frequency and phase. A determination is made by comparing at least one of the components selected from the group of amplitude, frequency and phase of the original radial bearing vibration velocity spectra with a component of the measured radial vibration spectra as well as a comparison of the original radial bearing acceleration spectra with at least one component of the measured radial bearing acceleration spectra, as indicated in box 1910. If at least one component of the measured vibration velocity and acceleration spectra is greater than the original component, then a determination is made by diagnostic apparatus 24 of possible bearing degradation, as indicated in box 1912. Referring to FIG. 20, a further verification step requires a comparison of original radial bearing 310 operating temperature with measured radial bearing operating temperature as indicated in box 2010. The original radial bearing operating temperature is obtained from original data and the measured radial bearing operating temperature is obtained from temperature sensor 118. If the measured radial bearing operating temperature is determined by diagnostic apparatus 24 to be greater than original radial bearing temperature, then a diagnosis of possible radial bearing degradation is made, as represented by box 2012. Referring to FIG. 21, a further verification step is that of comparing at least one of the components of amplitude, frequency and phase of original thrust bearing vibration velocity spectra with at least one of the components of measured velocity vibration spectra obtained from bearing vibration sensor 112. Additionally, a comparison is made between at least one of the components of original thrust bearing acceleration spectra with at least one of the components of measured acceleration spectra obtained from accelerometer 108, as represented by box 2110. If it is determined that at least one of the components of the measured vibration velocity and acceleration spectra is greater than an original component of vibration velocity spectra, then a diagnosis of possible thrust bearing 312 degradation is made by diagnostic apparatus 24, as represented by box 2112. Referring now to FIG. 22, a further verification step may be conducted by comparing original thrust bearing 312 operating temperature obtained from original data, and measured thrust bearing operating temperature obtained from bearing temperature sensor 110 to determine whether thrust bearing degradation exists. If measured thrust bearing operating temperature is greater than original thrust bearing operating temperature, as indicated by box 2210, then a diagnosis of possible thrust bearing degradation is made by diagnostic apparatus 24, as represented by box 2212. Original thrust bearing operating temperature is obtained from original data. Referring to FIG. 23, an additional verification step is conducted to determine if sufficient measured available net positive suction head exists to operate pump 14 without cavitation. Measured available net positive suction head is calculated by using a well known equation from data obtained from inlet pressure sensor 32 (FIG. 1). This determination is made by determining if the measured net positive suction head is greater than the net positive suction head required, as represented by box 2310. If so, a diagnosis of possible cavitation is made by diagnostic apparatus 24, as indicated in box 2312. Referring now to FIG. 24, an additional verification step is made to determine if sufficient measured net positive suction head available exists to operate without cavitation. However, in the preferred method, the additional step of correcting the measured net positive suction head for the measured operating temperature and fluid vapor pressure is made, as represented by box 2410. A determination is then made whether the corrected measured net positive suction head available is greater than the required net positive suction head as represented by box 2412. If not, then diagnostic apparatus 24 makes a diagnosis of possible cavitation, as indicated in box 2414. The original required net positive suction head and the fluid vapor pressure, both of which are available from original data, are compared with the measured net positive suction head and the measured net positive suction head and calculated utilizing the measured operating temperature of the process fluid is obtained by temperature sensing device 30 (FIG. 1). Referring to FIG. 25, a further verification step is conducted to determine if thrust bearing degradation exists. Original axial thrust bearing displacement data is obtained from original data and measured axial thrust bearing displacement data is obtained from displacement sensor 113. A comparison of the original axial thrust bearing displacement data with measured axial thrust bearing displacement data is conducted to determine whether measured axial displacement data is greater than original axial displacement data, as represented by box 2510. If diagnostic apparatus 24 determines that measured axial displacement data is greater than original, and the bearing clearance is in excess of the manufacturer's recommended clearance, then a diagnosis of possible thrust bearing 312 degradation is made, as represented by box 2512. It is noted that axial displacement sensor 113 measures the distance from thrust bearing 312 to a reference housing 322. Typically, bearing 312 will move due to backpressure from rotating equipment 14 which forces thrust bearing 312 into its race, thereby compressing bearing 312. A measurement may be made by an electronic proximity sensor such as those provided by Bently Nevada. Original axial thrust bearing displacement data is obtained from a manufacturer to provide an acceptable clearance specification for the thrust bearing. Displacement sensors may also be used to measure radial bearing clearance. Referring now to FIG. 26, an additional verification step may be conducted to determine whether radial bearing 310 degradation exists. A comparison is made between original radial bearing displacement data obtained from original data with measured radial bearing displacement data obtained from proximity sensor 113. If measured radial bearing displacement data is determined to be greater than original radial bearing displacement data, as indicated in box 2610, then diagnostic apparatus 24 determines that radial bearing degradation exists, as represented in box 2612. Referring to FIG. 27, an additional verification step may be conducted to determine whether impending motor failure exists. This diagnosis is made by comparing the manufacturer's original motor breakdown torque, which is obtained from original data, with measured electric motor output torque 100. Diagnostic apparatus 24 determines whether measured motor torque exceeds the manufacturer's recommended torque, as indicated by box 2710. If so, a diagnosis of impending motor 12 failure is made, as presented by box 2712. Referring now to FIG. 28, an additional verification step may be made wherein a display is generated of the performance curve and secondary curve for comparison. Examples of secondary curves in FIG. 9 include NPSH v. H&Q, BHP v. H&Q, efficiency v. H&Q, specific speed v. H&Q, bearing force v. H&Q, and Dynamic Pressure v. H&Q. To perform this verification step, a selected secondary curve is constructed from equipment condition monitoring variables, as represented by box 2812. An original secondary curve is constructed, represented by box 2810, and a display of the original performance curve and the secondary curve is made for comparison, as represented by box 2814. An additional step may be conducted to generate alerts if rotating equipment 14 is operating outside of its recommended design regime 166 or BEP regime 164 (FIG. 6a). One method of acquiring data sufficient to generate an alert includes constructing an original performance curve from original data, as represented by box 2910, and then constructing a measured performance curve from equipment condition monitoring variables, as represented by box 2912. Optionally, diagnostic apparatus 24 time-stamps the measured performance curve, as represented by box 2914. Diagnostic apparatus 24 then compares the original performance curve and the measured performance curve to determine the change in the pump performance variables, as represented in box 2916. If the change exceeds the manufacturer's recommended range, then diagnostic apparatus 24 generates an alert, as represented by box 2918, so that action may be taken to prevent operation of rotating equipment 14 outside of its recommended design regime 166 (FIG. 6a). Additionally, diagnostic apparatus 24 may alert a controller to correct pump operating conditions to within the operating design regime 166, as indicated by box 2920. Additionally, a similar procedure may be undertaken, except that instead of constructing original performance curves and measured performance curves, a process data point may be plotted from process variables and a secondary data point may be plotted from equipment condition monitoring variables to determine if rotating equipment 14 is operating outside of its recommended design regime 166 (FIG. 6a). Referring to FIG. 30, the verification step may also include alerting a controller to correct pump operating conditions to within a design condition. The steps of alert and correction are accomplished by constructing an original performance curve from original data, as represented by box 3210, constructing an original secondary curve from original data, as represented by box 3212, constructing a measured secondary curve from condition monitoring variables as represented by box 3214, constructing a measured secondary curve from equipment monitoring variables, as represented by box 3216, and then comparing the original performance curve with the measured performance curve to determine the change in the pump performance variables, as represented in box 3218. If the change exceeds the manufacturer's recommended range, an alert is generated, as represented by box 3220. From the comparisons, diagnostic apparatus 24 may alert a controller to correct pump operating conditions to within an operating design regime 166 (FIG. 6a), as indicated by box 3222. Referring now to FIG. 31, an additional verification step includes determining whether valve cavitation exists. This determination is made by comparing at least one of the components of amplitude, frequency and phase of measured dynamic pressure sensor spectra obtained from dynamic pressure sensor 82 (FIG. 1) with at least one component of original condition dynamic pressure sensor spectra obtained from original data, as represented by box 3310. If at least one component of measured dynamic pressure sensor spectra is greater than a component of original condition pressure spectra, as indicated by box 3310, then diagnostic apparatus 24 hypothesis possible valve cavitation, as indicated by box 3312. An additional verification step may be made by determining if sufficient corrected measured net positive suction head available exists, such that the pump is not cavitating. This verification involves the step of correcting the original net positive suction head required for operating fluid temperature 30 (FIG. 1) and fluid vapor pressure, as indicated in box 3314. Diagnostic apparatus 24 then makes a determination of whether measured net positive suction head available is greater than net positive suction head required, as indicated in box 3316. If so, diagnostic apparatus 24 makes a determination that the diagnosis of valve cavitation is verified, as represented in box 3318. That is, if NPSH.sub.R >NPSH.sub.A, it is likely that the pump is cavitating. However, if cavitation is detected and pump NPSH.sub.A >NPSH.sub.R, then the source of cavitation is a valve and not the pump 14. An additional verification step includes determining whether measured vibration spectra has increased in an expected pump cavitation frequency range. This determination is made by comparing at least one of the components of amplitude, frequency and phase of measured vibration spectra with at least one of the components of original condition vibration spectra to determine whether at least one component of measured vibration spectra is greater than a component of original condition vibration spectra, as represented by box 3320. If so, then the measured vibration spectra has increased in the expected pump cavitation frequency range, as indicted by box 3322, which verifies the determination of cavitation made above in box 3312. Referring to FIG. 32, a further verification step may be made to verify pump cavitation. This diagnosis is made by comparing at least one of the components of amplitude, frequency and phase of measured vibration spectra with at least one of the components of original condition vibration spectra to determine whether at least one of the components of measured dynamic pressure spectra is greater than at least one of the components of original condition pressure spectra, as represented by box 3610. It is noted, however, that the comparison must be made in the appropriate frequency range. If it is determined that at least one component of the measured dynamic pressure sensor spectra is greater than a component of the original condition pressure spectra, then diagnostic apparatus 24 diagnoses valve cavitation, as represented in box 3612. Referring now to FIG. 33, an additional step of diagnosing a pump deadhead condition and sending a signal to shut down rotating equipment (FIG. 1) 14 or open valve 22 is made by acquiring control valve shaft position data from control valve position sensor 34. From control valve shaft position data, a determination is made whether valve 22 is closed, as represented in box 3710. A determination is then made by comparing measured head with original condition head to determine whether head is at a maximum, as represented by box 3712. If so, a diagnosis of pump deadhead condition is made, as represented in box 3714, and diagnostic apparatus 24 sends a signal to the controller to shut down rotating equipment 14 or open valve 22 to alleviate pump deadhead condition, as represented by box 3716. Referring to FIG. 34, additional steps may be undertaken to determine whether valve packing leakage or valve seal leakage is occurring. This determination is made by obtaining control valve flow data from original data and obtaining the control valve position from valve position sensor 34 (FIG. 1). Diagnostic apparatus 24 then calculates valve flow from the valve data at the control valve position, as represented by box 3810. A comparison is then made between measured pump output flow with calculated valve flow to determine if measured pump output flow is greater than calculated valve flow, as represented by box 3812. If so, diagnostic apparatus 24 makes a diagnosis of valve packing leakage or valve seat leakage as represented by box 3814. The equation used to calculate valve flow is as follows: where: Qv=Valve Volumetric Flow Referring now to FIG. 35, additional steps may be undertaken to diagnose a plugged output pipe of rotating equipment 14. The diagnosis requires that original head and original outlet pump flow be obtained from original data and that measured outlet pipe flow be obtained from flowmeter 28 (FIG. 1) and measured pump head be calculated from process variables as described above. The method further includes operating the pump at a measured head equal to the original head, as indicated in box 3910. Diagnostic apparatus 24 then makes a determination whether the measured pump outlet pipe flow is less than the original outlet pipe flow at the identical head, as represented by box 3912. If the measured flow is less than the original flow, then diagnostic apparatus 24 makes a determination of a plugged outlet pipe 20, as represented by box 3914. This method of comparison is based on the presentation of data as shown in FIG. 6b, where the original flow at original head is represented by a point designated 180 and new measured flow point is designated 182. Referring now to FIG. 36, additional steps may be taken to diagnose a plugged suction line by determining if original net positive suction head available is greater than measured net positive suction head available. In order to make this determination, the original flow rate and original net positive suction head available may be obtained from original data. Measured net positive suction head may be calculated from the inlet pressure. A comparison is then made between the original net positive suction head available with the measured net positive suction head available. If the original net positive suction head available is greater than the measured net positive suction head available, as indicated in box 4110, then a diagnosis of a plugged suction line 18 is made by diagnostic apparatus 24, as indicated in box 4112. Original data for the pump performance curve, FIG. 6, is typically provided at a design speed determined by the manufacturer. However, if a pump or rotating equipment is operated at a different speed than the design speed, then data must be corrected utilizing pump affinity equations. To calculate a speed change (N), the following affinity law relationships for flow (Q), head (H) and break horsepower (BHP) are utilized. Q1/Q2=N1/N2 and H1/H2=(N1/N2).sup.0.5 and BHP1/BHP2=(N1/N2).sup.3 ##EQU2## where: Ns is the specific Speed Referring now to FIG. 37, original data is gathered, as represented by box 4210, and an original performance curve is constructed, as represented by box 4212. Process variables are acquired, as represented by box 4214. The process variables are input into computing device 38 (FIG. 1), as represented in box 4216. A comparison is then made between the original performance curve and the measured operating point to determine if rotating equipment 14 is operating outside of design regime 166, as represented in box 4218. If rotating equipment 14 is operating within design regime 166, then diagnostic apparatus 24 so indicates, as represented in box 4220. If the operating performance is outside of design regime 166, diagnostic apparatus 24 so indicates, as represented by box 4222. If it is determined that rotating equipment 14 is operating outside of design regime 166, as represented by box 4222 (FIG. 6a), then a diagnosis of high bearing stress is made by diagnostic apparatus 24, as represented by box 4224. It is noted that impending bearing failure will occur if a process operating point is either above or below a BEP regime 164 (FIG. 6a) on an original performance curve. If operation is outside of a design regime 166, then bearing stress will be increasingly higher the further away from of design regime 166 that the process data point occurs. This is equally true for a high head-recirculation case or a high flow-cavitation case. This concept is illustrated graphically in FIG. 9a, where it can be seen that bearing forces are lowest at point 184, which corresponds to BEP point 186. If a diagnosis is made that rotating equipment 14 is operating outside of recommended operating design regime 166, as represented by box 4222, an additional determination of whether a measured performance curve has shifted downward as compared with the original performance curve is made by diagnostic apparatus 24, as represented by box 4226. If so, a diagnosis of fouling or coating of an impeller 316 (FIG. 1b) is made, as represented in box 4228. Referring to FIG. 38, in another embodiment of the invention, a determination of whether pump 14 is operating in a recognizable, recommended operating design regime 166 (FIG. 6a) is made by comparing a system head operating point with a measured performance curve. This determination is made by obtaining a calculated system demand curve at a specific flow rate from original data, wherein the calculated system design curve is determined by piping system geometry, fluid properties and pump operating conditions. Additionally, a calculated fluid frictional head loss at a specific flow rate is determined from original data, wherein the calculated fluid frictional head loss is determined by piping system geometry. Finally, a calculated velocity head at a specific flow rate is gathered from original data wherein the calculated velocity head is determined by piping system geometry. The method includes the steps of constructing a measured performance curve from process variables as is known in the art, and which is represented by box 4410. Next, a system head operating point is calculated from the calculated system demand curve at a flow rate, and the calculated fluid frictional head loss and the calculated velocity head, as represented in box 4412. Diagnostic apparatus 24 then determines if rotating equipment 14 is operating in the recommended operating design regime 166, shown in FIG. 6a, by comparing the intersection of system head operating point with the measured performance curve. If the operating point is outside the recommended range 166 then an alert can be generated. It is noted that pumps or rotating equipment produce flow and pressure, i.e., head, required by a fluid system. The fluid flow system is constructed of pipe sections, pipe fittings (elbow, tees, etc.), valves, and vessels. Each of these components exhibit fluid friction, and as the fluid flow passes through each element a pressure drop occurs due to friction with the element. The sum of the pressure drops throughout the system represents the system head and the pump provides exactly the required pressure head. Some of the flow system components are variable frictional elements, such as a control valve. When a valve is closed, the pressure drop across the valve increases and the pump must put out higher pressure to correspond to this reduction in flow. When the pump pressure or head increases, the operating or measured operating point will move to the left on a head (H) v flow (Q) curve. This represents higher head (H) pressure and lower flow (Q). If the system head operating point moves too far to the left, indicating increasing head, the pump may be operating outside of its design regime 166, shown in FIG. 6, and recirculation can occur. For the opposite case of decreasing pressure and increasing flow, cavitation would be a possibility. A pump, valve and piping system must be correctly engineered to provide for operation of a pump within a design regime 166, while delivering the pressure and flow required by the process. Referring now to FIG. 39, a diagnosis of degraded rotating machine efficiency can be obtained by comparing measured rotating machine efficiency with original performance curves. This can be accomplished by acquiring rotating machine input torque data from torque sensor 100 (FIG. 1), as represented by box 4510, and rotating machine shaft angular velocity data from angular velocity sensor 102. The method calculates the measured rotating machine efficiency by calculating the input power to the pump, as represented in box 4516, and by calculating the fluid outlet power calculated from the flow sensor 28 and pump geometry, represented by box 4518. The rotating machine efficiency may then be calculated by the following equation: Pump Efficiency, .eta.p=Pf/Pp Diagnostic apparatus 24 then determines whether measured pump efficiency is less than original condition efficiency, as represented by box 4518. If so, then diagnostic apparatus 24 makes a determination that pump efficiency is degrading, as represented by box 4520. A further embodiment of the method of the invention is disclosed for conducting a field test to permit the actual measurement and construction of pump performance curves and secondary performance curves that can be compared with original performance data. The method includes a mode for controlling the pump throughout its operating range consistent with the Hydraulics Institute test method, known in the art. This method provides for operating a pump through its range of operation by the driving of the valve I/P, 35 (FIG. 1), or variable speed drive motor. This method can be used to construct pump performance curves in an automated fashion or for manually setting head or flow conditions to assist in the manual diagnosis of a rotating machine when a maintenance technician is looking to reproduce desired operating conditions. The method operates the pump through its range of operation by controlling the rate of flow through the pump. The method is applicable to either a variable speed drive providing a full range of speed adjustment to the motor or via the control valve through a full range of valve flow control positions. The method includes storing original data and adjusting a pump final control element to a desired setting, as presented in box 4610. The pump final control element may be either a valve 22, FIG. 1, or a variable speed drive connected to a motor 12. Process variables are acquired from operational rotating equipment 14 at the desired final control element setting, as represented in box 4612. The process variables are then input into computing device 38. Diagnostic apparatus 24, FIG. 2, constructs measured performance curves from the process variables, as represented by box 4614, and repeats the steps of storing, acquiring, inputting and constructing a plurality of times wherein the pump final control element is adjusted to correspond to a defined set of test conditions for constructing the measured performance curves, as represented by box 4616. The measured performance points are stored, as represented in box 4618. An in situ performance curve and secondary curve are finally constructed from process and condition monitoring variables, as represented in box 4620. In one embodiment of the field diagnostic test process, a means is provided for manually establishing flow or head conditions, including manually adjusting the valve 22, manually adjusting the current or flow to motor 12, or other methods of manually adjusting the pump final control element to a desired condition. An additional embodiment of a method for diagnosing rotating equipment includes storing original data having a recognized, recommended operating design regime 166 (FIG. 6a), as represented by box 5010 and acquiring a process variable from operating rotating equipment 14, FIG. 1, wherein a process variable is selected from a group consisting of fluid outlet pressure obtained from outlet pressure sensor 26, and fluid flow obtained from flowmeter 28, as represented by box 5012. The process variable is then input into computing device 38, as represented in box 5014, and a determination whether the process variable is within the recommended operating design regime 166 (FIG. 6a) is made, as represented by box 5016. If not, then diagnostic apparatus 24, FIG. 2, diagnoses that pump and motor system 10 is operating outside the recommended design regime 166, FIG. 6a, as represented by box 5018. Whereas, the present invention has been described in relation to the drawings attached hereto, it should be understood that other and further modifications, apart from those shown or suggested herein, may be made within the spirit and scope of this invention.
	claims	1. A method for processing a sample held by a nanomanipulator tip comprising:bringing the nanomanipulator tip into contact with a stabilizing support; and,stabilizing the sample using feedback control;where stabilizing the sample using feedback control further comprises:continuing to move the nanomanipulator tip against the stabilizing support until substantially no discernible vibration of the sample is observable. 2. The method of claim 1 further comprising orienting the sample to optimize further processing. 3. The method of claim 1 further comprising preparing the stabilized sample for analysis. 4. The method of claim 1 further comprising analyzing the stabilized sample. 5. The method of claim 1, where bringing the nanomanipulator tip into contact with the stabilizing support further comprises translating the nanomanipulator tip to contact the stabilizing support. 6. The method of claim 1, where bringing the nanomanipulator tip into contact with the stabilizing support further comprises translating the stabilizing support to contact the nanomanipulator tip. 7. The method of claim 3 where preparing the sample further comprises ion-beam milling to shape the sample. 8. The method of claim 4 where analyzing the sample further comprises scanning transmission electron microscopy of the sample. 9. The method of claim 4 where analyzing the sample further comprises energy dispersive X-ray analysis of the sample. 10. A method for processing a sample in a charged-particle beam microscope, the method comprising:collecting the sample from a substrate;attaching the sample to a nanomanipulator tip;orienting the sample to optimize further processing;bringing the nanomanipulator tip into contact with a stabilizing support;stabilizing the sample using feedback control;where stabilizing the sample using feedback control further comprises:continuing to move the nanomanipulator tip against the stabilizing support until substantially no discernible vibration of the sample is observable;preparing the sample for analysis; and,analyzing the sample. 11. The method of claim 10 where preparing the sample further comprises ion-beam milling to shape the sample. 12. The method of claim 10 where analyzing the sample further comprises scanning transmission electron microscopy of the sample. 13. The method of claim 10 where analyzing the sample further comprises energy dispersive X-ray analysis of the sample.
063046296	claims	1. A scanner apparatus comprising: a tunnel housing comprised of: a. a first slot in one of its portions near its entrance opening, and b. a second slot in one of its portions near its exit opening; and wherein said isolating device comprises: c. a first bracket having a first curtain extending from it, said first bracket and said first curtain and said first slot of said tunnel housing being adaptable so that said first curtain can be inserted into and through said first slot but said first bracket cannot be inserted through said first slot, said first curtain, alter insertion, being adapted to substantially cover the entrance opening of said tunnel housing, said first bracket, after insertion, being substantially fixed to a portion of said tunnel housing,; and d. a second bracket having a second curtain extending from it, said second bracket and said second curtain and said second slot of said tunnel housing being adaptable so that said second curtain can be inserted into and through said second slot but said second bracket cannot be inserted through said second slot, said second curtain, after insertion, being adapted to substantially cover said exit opening of said tunnel housing, said second bracket, after insertion, being substantially fixed to a portion of said tunnel housing. a. constructing a tunnel housing comprised of a top portion, a bottom portion, first and second side portions, which form a substantially enclosed area, an entrance opening and an exit opening, said top portion and side portions of said tunnel housing each having a thickness ranging from about 0.0625 to 0.5 inch; b. constructing a bed assembly housing located substantially beneath said bottom portion of said tunnel housing, said bed assembly housing being constructed so that said bed assembly has a top portion which is substantially used as said bottom portion of said tunnel housing; c. locating an isolating device at said entrance and exit openings of said tunnel housing; d. locating a conveyor device substantially in said bed assembly housing, said conveyor device being used for moving an object through said entrance opening of said tunnel housing and into said substantially enclosed area, subsequently through said substantially enclosed area, and thereafter out of said substantially enclosed area and out said exit opening of said tunnel housing; and e. providing an analysis device for analyzing objects within said substantially enclosed area of said tunnel housing. a. constructing said bed assembly housing so that said bed assembly housing has first and second side portions; and b. fixing said first and second side portions of said bed assembly housing to said first and second side portions of said tunnel housing, respectively. a. providing a first slot in one of the portions of said tunnel housing near its entrance opening; and b. providing a second slot in one of the portions of the tunnel housing near its exit opening; a. inserting a first bracket having a first curtain extending from it, through said first slot b. substantially fixing said first bracket to a portion of said tunnel housing near said entrance opening of said tunnel housing; c. inserting a second bracket having a second curtain extending from it, through said second slot; and d. substantially fixing said second bracket to a portion of said tunnel housing near said exit opening of said tunnel housing. 2. A scanner apparatus, as recited by claim 1, wherein said bed assembly further comprises first and second side portions and wherein said first and second side portions of said tunnel housing are substantially fixed to said first and second side portions of said bed assembly housing, respectively. 3. A scanner apparatus, as recited by claim 1, wherein said analysis device is comprised of an internally mounted detector array constructed within a metal member which contains a detector slit, to reduce the slitting of said tunnel housing. 4. A scanner apparatus, as recited by claim 1, wherein said tunnel housing further comprises: 5. A method for constructing a scanner for scanning objects, comprising the steps of: 6. A method as recited by claim 5, further comprising the steps of: 7. A method for constructing a scanner for scanning objects, as recited by claim 5, further comprising the step of using said analysis device to connect said tunnel housing with said bed assembly housing. 8. A method for constructing a scanner for scanning objects, as recited by claim 5, further comprising the steps of:
	claims	1. A method of automatically cutting off power in a mobile electronic unit comprising:cutting off the power of the mobile electronic unit when a battery voltage is detected in a first check section as not being in a normal state during a booting period of the mobile electronic unit;(a1) checking the battery voltage before a predetermined time from a starting time of the first check section;(a2) checking the battery voltage after a predetermined time from an ending time of the first check section; and(a3) generating a power cutting off signal when a difference between the battery voltages checked in steps (a1) and (a2) is more than a predetermined reference value. 2. The method of claim 1, further comprising cutting off the power of the mobile electronic unit when the battery voltage detected in the first check section is in the normal state and when a battery voltage is detected in a second check section as not being in a normal state during a period of time after the booting period of the mobile electronic unit is completed. 3. The method of claim 1, further comprising comparing a battery voltage detected during a performance period of an operation mode where a current higher than a standard consumption current is used with a threshold voltage and generating a power cutting off signal when the detected battery voltage is less than the threshold voltage for more than a predetermined number of times. 4. A method of automatically cutting off power in a mobile electronic unit comprising cutting off the power of the mobile electronic unit when a battery voltage is detected in a first check section as not being in a normal state during a booting period of the mobile electronic unit, wherein the first check section includes at least one of a first sub-section, corresponds to an on-time section of primary elements at an initial stage of booting, and a second sub-section includes a driving period of elements where a current higher than a standard consumption current is used, the method further comprising;(a) generating a power cutting off signal when a battery voltage checked in the first sub-section is less than a first reference value; and(b) generating the power cutting off signal when the battery voltage checked in the first sub-section is areater than the first reference value, and when a difference between the battery voltage detected before a predetermined time from a starting time of the second sub-section and the battery voltage detected after a predetermined time from an ending time of the second sub-section is greater than a second reference value. 5. A method of automatically cutting off power in a mobile electronic unit comprising:cutting off the power of the mobile electronic unit when a battery voltage is detected in a first check section as not being in a normal state during a booting period of the mobile electronic unit, andcutting off the power of the mobile electronic unit when the battery voltage detected in the first check section is in the normal state and when a battery voltage is detected in a second check section as not being in a normal state during a period of time after the booting period of the mobile electronic unit is completed, wherein the second check section includes one of a third sub-section which corresponds to a stabilization period after booting of the mobile electronic unit is completed, a fourth sub-section including a driving period of elements at an initial stage of a predetermined operation mode, and a fifth sub-section including a performance period of an operation mode where a current higher than a standard consumption current is used. 6. The method of claim 5 further comprising:(a) checking the battery voltage before a predetermined time from a starting time of the fourth sub-section;(b) checking the battery voltage after a predetermined time from an ending time of the fourth sub-section; and(c) generating a power cutting off signal when a difference between the battery voltages checked in steps (a) and (b) is greater than a predetermined reference value. 7. The method of claim 6 further comprising comparing a battery voltage detected during the third sub-section with a threshold voltage and generating a power cutting off signal when the detected battery voltage is less than the threshold voltage for more than a predetermined number of times. 8. The method of claim 5 further comprising:(a) generating the power cutting off signal when a difference between the battery voltage detected before a predetermined time from a starting time of the fourth sub-section and the battery voltage detected after a predetermined time from an ending time of the fourth sub-section is greater than a first reference value; and(b) generating the power cutting off signal when a difference between the battery voltage detected before a predetermined time from the starting time of the fifth sub-section and the battery voltage detected after a predetermined time from an ending time of the fifth sub-section is greater than a second reference value. 9. The method of claim 8 further comprising comparing a battery voltage detected during the third sub-section with a threshold voltage and generating a power cutting off signal when the detected battery voltage is less than the threshold voltage for more than a predetermined number of times. 10. The method of claim 5 further comprising:(a) comparing a battery voltage detected during the third sub-section with a threshold voltage and generating a power cutting off signal when the detected battery voltage is less than the threshold voltage for more than a predetermined number of times; and(b) generating the power cutting off signal when a difference between the battery voltages in step (a) is greater than the threshold voltage and when a difference between the battery voltage detected before a predetermined time from the starting time of the fourth sub-section and the battery voltage detected after a second predetermined time from the ending time of the fourth sub-section is greater than a first reference value; and(c) generating the power cutting off signal when a difference between the battery voltages in step (b) is less than a first reference value and when a difference between the battery voltage detected before a predetermined time from the starting time of the fifth sub-section and the battery voltage detected after a predetermined time from the ending time of the fifth sub-section is greater than a second reference value. 11. A computer-readable recording medium comprising:a program for cutting off the power of the mobile electronic unit when a battery voltage detected in a first check section is not in a normal state during a booting period of the mobile electronic unit; anda program for cutting off the power of the mobile electronic unit when the battery voltage detected with respect to the first check section is in the normal state and when a battery voltage detected in a second check section is not in the normal state during a period after booting of the mobile electronic unit is completed. 12. The computer-readable recording medium of claim 11, further comprising a program for cutting off the power of the mobile electronic unit when the battery voltage detected in the first check section is in the normal state and when a battery voltage is detected in a second check section as not being in a normal state during a period of time after the booting period of the mobile electronic unit is completed. 13. The computer-readable recording medium of claim 12, wherein the second check section includes at least one of a third sub-section which corresponds to a stabilization period after booting of the mobile electronic unit is completed, a fourth sub-section including a driving period of elements at an initial stage of a predetermined operation mode, and a fifth sub-section including a performance period of an operation mode where a current higher than a standard consumption current is used. 14. The computer-readable recording medium of claim 13 further comprising:(a) a program for checking the battery voltage before a predetermined time from a starting time of the fourth sub-section;(b) a program for checking the battery voltage after a predetermined time from an ending time of the fourth sub-section; and(c) a program for generating a power cutting off signal when a difference between the battery voltages checked by the programs in (a) and (b) is greater than a predetermined reference value. 15. The computer-readable recording medium of claim 14 further comprising a program for comparing a battery voltage detected during the third sub-section with a threshold voltage and generating a power cutting off signal when the detected battery voltage is less than the threshold voltage for more than a predetermined number of times. 16. The computer-readable recording medium of claim 13 further comprising:(a) a program for generating the power cutting off signal when a difference between the battery voltage detected before a predetermined time from a starting time of the fourth sub-section and the battery voltage detected after a predetermined time from an ending time of the fourth sub-section is greater than a first reference value; and(b) a program for generating the power cutting off signal when a difference between the battery voltage detected before a predetermined time from the starting time of the fifth sub-section and the battery voltage detected after a predetermined time from an ending time of the fifth sub-section is greater than a second reference value. 17. The computer-readable recording medium of claim 16 further comprising a program for comparing a battery voltage detected during the third sub-section with a threshold voltage and generating a power cutting off signal when the detected battery voltage is less than the threshold voltage for more than a predetermined number of times. 18. The computer-readable recording medium of claim 13 further comprising:(a) a program for comparing a battery voltage detected during the third sub-section with a threshold voltage and generating a power cutting off signal when the detected battery voltage is less than the threshold voltage for more than a predetermined number of times; and(b) a program generating the power cutting off signal when a difference between the battery voltages determined by the program in (a) is greater than the threshold voltage and when a difference between the battery voltage detected before a predetermined time from the starting time of the fourth sub-section and the battery voltage detected after a second predetermined time from the ending time of the fourth sub-section is greater than a first reference value; and(c) a program for generating the power cutting off signal when a difference between the battery voltages determined by the program in (b) is less than a first reference value and when a difference between the battery voltage detected before a predetermined time from the starting time of the fifth sub-section and the battery voltage detected after a predetermined time from the ending time of the fifth sub-section is greater than a second reference value. 19. The computer-readable recording medium of claim 11, further comprising a program for comparing a battery voltage detected during a performance period of an operation mode where a current higher than a standard consumption current is used with a threshold voltage and generating a power cutting off signal when the detected battery voltage is less than the threshold voltage for more than a predetermined number of times.
	description	This application is a National Phase of PCT/EP2011/070909, filed Nov. 24, 2011, entitled, “PROCESS FOR SEPARATING AMERICIUM FROM OTHER METALLIC ELEMENTS PRESENT IN AN ACIDIC AQUEOUS OR ORGANIC PHASE AND APPLICATIONS THEREOF”, which claims the benefit of French Patent Application No. 10 59749, filed Nov. 25, 2010, the contents of which are incorporated herein by reference in their entirety. The present invention relates to a process which allows separation of americium present in an acid aqueous phase or in an organic phase from other metal elements also found in this phase. It also relates to a process for selective recovery of americium from an acid aqueous phase containing, in addition to americium, other metal elements, which comprises the application of this separation process. The invention may be used in the field of processing and recycling irradiated nuclear fuels where it has a most particular interest for recovering americium from aqueous solutions with high activity such as raffinates from the first purification cycle of a PUREX or COEX™ process, which contain americium, curium, possibly californium, as well as fission products including lanthanides but which, on the other hand, are free of uranium, plutonium and neptunium or which only contain these last three elements in trace amounts. The process, which allow extraction and purification of uranium and plutonium present in the dissolution liquors of irradiated nuclear fuels such as the PUREX process (which is presently used in irradiated nuclear fuel processing plants) and the COEX™ process (which is described in PCT International Application WO 2007/135178, [1]), generate effluents to which the name of raffinates is given. These raffinates are aqueous solutions with high nitric acidity, typically from 2 to 5 M, which contain americium, curium, lanthanides such as lanthanum, cerium, praseodymium, neodymium, samarium and europium, fission products other than lanthanides like molybdenum, zirconium, rubidium, ruthenium, rhodium, palladium and yttrium, as well as corrosion products such as iron. Their handling presently consists of concentrating them to a maximum and then of packaging them in glassy matrices with view to temporary storage before ultimate storage. Americium is the main contributor to residual radioactivity after 300 years of wastes from the packaging of raffinates. As an illustration, the time required for this radioactivity to come back to a level of the same order as that of natural uranium which is used for making nuclear fuels is about 10,000 years. Selective recovery of americium present in the raffinates, before the latter are sent to vitrification, would therefore allow a significant reduction in the thermal load of the vitrified wastes, and thereby their storage coverage. Moreover, curium 244 which represents the majority isotope of curium present in nuclear waste is a powerful neutron emitter source of significant radioactivity. Recovering americium without curium would therefore also simplify the manufacturing, the handling and the transport of assemblies of transmutation fuels containing americium. It is found that most extractants, the use of which has been proposed for liquid-liquid extractions, does not have pronounced selectivity, or even absolutely no selectivity, towards americium relatively to curium, to lanthanides and to yttrium. This is due to the very great similarity existing between the physicochemical properties of these elements. The result of this is that it is presently extremely difficult to separate by liquid-liquid extraction, americium from curium on the one hand, and americium from lanthanide and yttrium on the other hand, and that these separations, when they are possible, require, in order to obtain satisfactory separation performances, the use of a high number of stages, which is a penalty from an industrial point of view. Now, it happened that within the scope of their work, the inventors noticed that: water-soluble derivatives of ethylenediamine, which have been described as ligands of lanthanides and proposed for making luminescent lanthanide complexes for medical use (reference [2]), have unexpectedly, when they are in acid aqueous solution, a capability of complexing americium which is much greater than the one they have towards curium, lanthanides and a certain number of other fission products including yttrium, and that this capability of complexing americium may notably be utilized for selectively recovering americium from an acid aqueous phase in which it is found together with other metal elements. And it is on these observations that the present invention is based. Firstly, the object of the invention is therefore a process for separating americium from other metal elements present in a phase P1, which process: comprises one or more operations each comprising putting the phase P1 into contact with a phase P2 which is not miscible with it, and then separating the phase P1 from the phase P2, one of the phases P1 and P2 being an acid aqueous phase and the other one of these phases being an organic phase which contains at least one extractant in an organic diluent, and is characterized in that the acid aqueous phase contains a derivative of ethylenediamine fitting the general formula (I) hereafter: wherein A1, A2, A3 and A4, which are either identical or different, represent a group of general formula (II) hereafter: wherein: either X represents a nitrogen or sulfur atom, in which case one of R1, R2 and R4 represents a complexing group selected from the groups —COOH, —SO3H, —PO3H2, —CONH2 and —CON(CH3)2, while the other ones of R1, R2 and R4 represent, independently of each other, a hydrogen atom or a group selected from the groups —OH, —NH2, —N(CH3)2, —COOH, —COOCH3, —CONH2, —CON(CH3)2, —SO3H, —SO3CH3, —PO3H2, —PO(OCH3)2, —O(CH2CH2)n—OH and —O(CH2CH2)n—OCH3 wherein n is an integer equal to or greater than 1; or X represents a carbon atom bearing a hydrogen atom or a group R3, in which case one of R1, R2, R3 and R4 represents a complexing group selected from the groups —COOH, —SO3H, —PO3H2, —CONH2 and —CON(CH3)2, while the other ones of R1, R2, R3 and R4 represent, independently of each other, a hydrogen atom or a group selected from the groups —OH, —NH2, —N(CH3)2, —COOH, —COOCH3, —CONH2, —CON(CH3)2, —SO3H, —SO3CH3, —PO3H2, —PO(OCH3)2, —O(CH2CH2)n—OH and —O(CH2CH2)n—OCH3 wherein n is an integer equal to or greater than 1; or a salt thereof. Within the scope of the invention, it is preferred that, in the general formula (I), A1, A2, A3 and A4 all represent a group of general formula (II) wherein X represents a nitrogen atom, or a carbon atom bearing a hydrogen atom or a group R3 as defined earlier. In which case, it is more particularly preferred that X represents a nitrogen atom, or a carbon atom bearing a hydrogen atom or a group capable of promoting solubility in water of the ethylenediamine derivative such as for example, a —OH group or a —(CH2CH2)n—OH group wherein n is an integer equal to or greater than 1. It is also preferred that, in the general formula (II), at least one of R1, R2 and R4 represent a complexing group —COOH. In which case, it is most particularly preferred that the other ones of R1, R2 and R4 represent a hydrogen atom. Moreover, it is preferred that, in the general formula (I), A1, A2, A3 and A4 be identical with each other and this for more greatly facilitating the synthesis of the ethylenediamine derivative. Ethylenediamine derivatives which meet all these preferences are for example: N,N,N′,N′-tetrakis[(6-carboxypyridin-2-yl)methyl]ethylene-diamine, which fits the general formula (Ia) hereafter: N,N,N′,N′-tetrakis[(6-carboxy-4-hydroxypyridin-2-yl)methyl]-ethylenediamine, which fits the general formula (1b) hereafter: N,N,N′,N′-tetrakis[(6-carboxy-4-polyethyleneglycolpyridin-2-yl)-methyl]ethylenediamines, which fit the particular formula (Ic) hereafter: wherein n is comprised between 1 and 12 and preferably is equal to 1, 2, 4, 6, 8, 10 and 12; and N,N,N′,N′-tetrakis[(6-carboxypyrazin-2-yl)methyl]ethylenediamine which fits the particular formula (Id) hereafter: Among these ethylenediamine derivatives, N,N,N′,N′-tetrakis[(6-carboxypyridin-2-yl)methyl]ethylenediamine is most particularly preferred, which will be designated more simply by H4TPAEN in the following. Indeed, this derivative proved to have, in addition to a particularly interesting affinity for americium, a capability of complexing this element even in aqueous phases with moderate acidity, i.e. in practice a pH of the order of 1 (which corresponds to a nitric acid concentration of the order of 0.1 mol/L in the case of a nitric aqueous phase). This last feature is very advantageous since it gives the possibility of notably doing without the use of a buffer system intended for stabilizing the pH of the acid aqueous phase, this is not the case with the biphasic systems proposed in the state of the art for separating americium from other metal elements and operating at a pH above 1.5. Thus, the acid aqueous phase may, if this is desired, only consist of the ethylenediamine derivative of the particular formula (Id), of an acid and water. As mentioned earlier, the ethylenediamine derivative of general formula (I) may be present in the aqueous phase in its acid form or in the form of a salt like a salt of an alkaline metal such as of the sodium or potassium salt type, or a salt of an earth alkaline metal such as of the magnesium or calcium salt type, or an organic salt such as of the hydroxylamine salt type. Within the scope of the invention, the acid aqueous phase is preferably a nitric aqueous phase for which the nitric acid concentration preferentially ranges from 0.001 to 3 mol/L and, even better, from 0.01 to 1 mol/L and more preferably from 0.01 to 0.3 mol/L. Moreover, the ethylenediamine derivative of general formula (I) or its salt is advantageously present in this acid aqueous phase at a concentration ranging from 10−3 to 10−1 mol/L, preferably from 10−4 to 10−2 mol/L and even better from 10−3 to 5×10−2 mol/L. The extractant(s) present in the organic phase may notably be selected from solvating extractants and cation exchange extractants. As examples of solvating extractants which may be suitable, mention may be made of: malonamides such as N,N′-dimethyl-N,N′-dibutyltetradecyl-malonamide (or DMDBTDMA), N,N′-dimethyl-N,N′-dioctylhexylethoxymalonamide (or DMDOHEMA), N,N′-dimethyl-N,N′-dioctyloctylmalonamide (or DMDOOMA), N,N′-dimethyl-N,N′-dioctylhexylmalonamide (or DMDOHxMA), N,N′-dimethyl-N,N′-dioctyl-heptylmalonamide (or DMDOHpMA) or N,N′-dimethyl-N,N′-dibutyldodecylmalonamide (or DMDBDDEMA); tetradentate N,N,N′,N′-tetraalkyl-3,6-dioxaoctanediamide extractants such as N,N,N′,N′-tetraoctyl-3,6-dioxaoctanediamide (or DOODA-C8), N,N,N′,N′-tetradodecyl-3,6-dioxaoctanediamide (or DOODA-C12); lipophilic diglycolamides (i.e. for which the total number of carbon atoms is greater than 24) such as N,N,N′,N′-tetraoctyl-3-oxapentanediamide (or TODGA), N,N,N′,N′-tetradecyl-3-oxapentanediamide (or TDDGA) or N,N,N′,N′-tetra-2-ethylhexyl-3-oxapentanediamide (or TEHDGA); alkylphosphine oxides such as trioctylphosphine oxide (or TOPO), tributylphosphine oxide (or TBPO) or the mixture of trialkylphosphines known under the shortcut TRPO; carbamoylphosphine oxides such as octylphenyl-N,N-diisobutyl-carbamoylmethylphosphine (or CMPO); carbamoylphosphonates such as dihexyl-N,N-diethylcarbamoyl-methylphosphonate (or DHDECMP); dialkyl sulfides such as dihexyl sulfide; substituted pyridines such as bistriazinyl-1,2,4-pyridines (or BTP); 2,2′-dibenzimidazoles; and bisphenylphosphonic acid alkyl esters. As examples of cation exchange extractants which may be suitable, mention may be made of: alkylphoshoric acids such as di(2-ethylhexyl)phosphoric acid (or HDEHP), dihexylphosphoric acid (or HDHP), bis-(1,3-dimethylbutyl)phosphoric acid (or HBDMBP) or diisodecylphosphoric acid (or DIDPA); alkylphosphonates such as p-2-ethylhexyl-o-2-ethylhexylhydrogen-phosphonate (or PC88A), p-propyl-o-heptylhydrogenphosphonate, p-butyl-o-octyl-hydrogenphosphonate or p-pentyl-o-hexylhydrogenphosphonate; alkylphosphinic acids such as bis(2,4,4-trimethylpentyl)phosphinic acid (or Cyanex 272); lipophilic carboxylic acids such as decanoic acid or cyanodecanoic acid; sulfonic acids such as dinonylnaphthalene sulfonic acid (or HDNNS); thiophosphoric acids, thiophosphonic acids, thiophosphinic acids such as bis(2,4,4-trimethylpentyl)dithiophosphinic acid (or Cyanex 301), thiophosphorous acids, lipophilic hydroxyoximes and lipophilic β-diketones such as 3-phenyl-4-benzoyl-5-isoxazolone (or HPBI). As for the organic diluent, it may be selected from all polar or aliphatic organic diluents for which the use was proposed for achieving liquid-liquid extractions in the field of the processing of irradiated nuclear fuels, such as toluene, xylene, t-butyl-benzene, di- or tri-isopropylbenzene, kerosene, dodecanes either linear or branched, such as n-dodecane or hydrogenated tetrapropylene (or TPH), isane, a normal paraffinic hydrocarbon (or NPH), metanitrobenzotrifluoride, 5,5′-oxybis(methyleneoxy)]-bis(1,1,2,2,3,3,4,4-octafluoropentane), alcohols such as 1-octanol, and mixtures thereof. The organic phase may further comprise one or more phase modifying agents capable of increasing the loading capacity of this phase, i.e. the maximum concentration of metal elements which this phase may have without causing formation of a third phase by demixing. In which case, these phase modifying agent(s) may notably be selected from alkyl phosphates such as tri-n-butylphosphate (or TBP) or tri-n-hexylphosphate (or THP), alcohols such as 1-octanol, 1-decanol or isodecanol, monoamides such as N,N-dihexyloctanamide (or DHOA), N,N-dibutyldecanamide (or DBDA), N,N-di(ethylhexyl)acetamide (or D2EHAA), N,N-di(2-ethylhexyl)propionamide (or D2EHPRA), N,N-di(2-ethylhexyl)isobutyramide (or D2EHiBA) or N,N-dihexyldecanamide (or DHDA), and malonamides such as DMDBTDMA, DMDOHEMA, DMDOOMA, DMDOHxMA, DMDOHpMA or DMDBDDEMA. The organic phase may therefore be of the same type as the ones used in the process of the state of the art which aim at recovering actinides(III), by liquid-liquid extraction, from acid aqueous solutions, either selectively or together with lanthanides and in particular, those which use: a diglycolamide extractant (references [3] to [7]); a diamide tetradentate extractant N,N,N′,N′-tetraalkyl-3,6-dioxaoctanediamide (reference [8]); a malonamide extractant (references [9] and [10]); a mixture of a malonamide extractant and of an alkylphosphoric acid extractant (DIAMEX-SANEX process, references [11] and [12]); a mixture of an alkylphosphoric extractant and of a carbamoyl-phosphine oxide extractant (reference [13]); an alkylphosphoric acid extractant (TALSPEAK process and its alternatives, references [14] to [16]; DIDPA process, references [17] and [18]); a bisphenylphosphinic acid alkyl ester extractant (reference [19]); an alkylphosphonate extractant (reference [20]); a β-diketone extractant (references [21] and [22]); a carbamoylphosphine extractant (SEFTICS process, references [23] and [24]; TRUEX process, references [25] and [26]); an alkylphosphine oxide extractant (references [27] to [29]); a substituted pyridine extractant (references [30] and [31]); or a thiophosphonic acid extractant (references [32] to [35]). The result of this is—and this is one of the many advantages of the americium separation process according to the invention—that this process may be applied to process which have been proposed in the state of the art for recovering actinides(III), by liquid-liquid extraction, from acid aqueous solutions, either being integrated into these process as a step or used as a supplementary step, i.e. downstream, from these process. It thus becomes possible to use these process of the state of the art for selectively recovering americium from acid aqueous solutions. Therefore, the object of the invention is also a process for selective recovery of americium present in an acid aqueous phase containing, further to americium, other metal elements, characterized in that it comprises the implementation of a process for separating americium as defined earlier. Within the scope of the invention, this acid aqueous phase preferably contains, as other metal elements, at least curium and fission products including lanthanides, but is free of uranium, plutonium and neptunium or only contains these last three elements in trace amounts. Such an aqueous phase may notably be a raffinate stemming from the first purification cycle of a PUREX or COEX™ process. In a first preferred embodiment of this process for selective recovery of americium, the latter comprises at least the following steps: a) extraction of the americium and of all or part of the other metal elements present in the acid aqueous phase, which extraction comprises at least one operation in which this aqueous phase is put into contact with an organic phase which is non-miscible with it, containing at least one extractant in an organic diluent, and then separated from this organic phase; and b) selective stripping of the americium present in the organic phase from step a), which stripping comprises at least one operation in which this organic phase is put into contact with an acid aqueous phase, containing an ethylenediamine derivative of general formula (I) or a salt thereof, and then separated from this aqueous phase. Thus, in this first embodiment, the process for separating americium according to the invention is used for selectively stripping americium from an organic phase in which this americium has been extracted beforehand together with all or part of the other metal elements. Therefore it is this organic phase which corresponds to the phase P1 while the acid aqueous phase used for achieving the selective stripping of americium corresponds to the phase P2. As known per se, the acid aqueous phase subject to step a) may contain one or more complexing agents, capable of avoiding or at the very least limiting the extraction of certain metal elements, the presence of which in the organic phase stemming from step a) would be able to interfere with the selective stripping of americium in step b). In which case, this (these) complexing agent(s) may notably be selected from: hydrophilic diglycolamides (i.e. for which the total number of carbon atoms does not exceed 24) such as N,N,N′,N′-tetramethyldiglycolamide (or TMDGA), N,N,N′,N′-tetraethyldiglycolamide (or TEDGA), N,N,N′,N′-tetrapropyl-diglycolamide (or TPDGA) or N,N,N′,N′-tetra(2-ethylhexyl)diglycolamide (or TEHDGA); carboxylic acids such as oxalic acid, malonic acid or mesoxalic acid (also known as ketomalonic acid); polyaminocarboxylic acids such as N-(2-hydroxyethyl)ethylene diamine triacetic acid (or HEDTA), nitrilotriacetic acid (or NTA) or diethylene triamine pentaacetic acid (or DTPA); pyridine polycarboxylic acids such as dipicolinic acid (or DPA, also known as 2,6-pyridine dicarboxylic acid); hydroxycarboxylic acids such as glycolic acid, citric acid or tartaric acid; amines, polyazines grafted with alkyl chains comprising from 1 to 8 carbon atoms, hydrophilic hydroxyoximes, sulfonic acids, hydroaxamic acids and hydrophilic β-diketones; and this, depending on the extractant(s) which is (are) present in the organic phase, on the one hand, and on the metal element for which it is intended to avoid or limit the extraction, on the other hand. According to a first preferred arrangement of this first embodiment: step a) further comprises, after the separation of the organic and aqueous phases, at least one operation of washing the organic phase with an acid aqueous phase possibly containing the same complexing agent(s) as the one or those present in the acid aqueous phase subject to step a); and/or step b) further comprises, after the separation of the organic and aqueous phases, at least one operation of washing the aqueous phase with an organic phase having the same composition as the one used in step a). According to another preferred arrangement of this first embodiment, the process for selectively recovering americium further comprises a step c) of stripping metal elements present in the organic phase stemming from step b), which stripping comprises at least one operation in which this organic phase is put into contact with an acid aqueous phase and then separated from this aqueous phase. There again, the acid aqueous phase used for this stripping may contain one or more complexing agent(s) capable of facilitating the migration of certain metal elements into the aqueous phase. In which case, this (these) complexing agent(s) may notably be selected from the complexing agents mentioned earlier. According to yet another preferred arrangement of this first embodiment, the organic phase used in step a) contains a mixture of a malonamide extractant and of an alkylphosphoric acid extractant such as a mixture of DMDOHEMA and HDEHP, or else a diglycolamide extractant such as TODGA. In a second preferred embodiment of the process for selectively recovering americium according to the invention, this process comprises at least one step a) of selective extraction of all the metal elements other than americium present in the acid aqueous phase, which extraction comprises at least one operation in which this aqueous phase is put into contact with an organic phase which is non-miscible with it, containing at least one extractant in an organic diluent, and then separated from this organic phase, and is carried out after or simultaneously with the addition of at least one ethylenediamine derivative of general formula (I) or a salt of the latter to the acid aqueous phase. Thus, in this second embodiment, the process for separating americium according to the invention is used for selectively extracting all the metal elements other than americium from the acid aqueous phase in which the americium and the other metal elements are present initially. It is therefore this acid aqueous phase which corresponds to the phase P1 while the organic phase used for achieving selective extraction of all the metal elements other than americium corresponds to phase P2. According to a first preferred arrangement of this second embodiment, step a) further comprises, after separation of the organic and aqueous phases, at least one operation of washing the organic phase by putting this organic phase into contact with an acid aqueous phase containing the same ethylenediamine derivative of general formula (I) as the one used in the previous operation. According to a preferred arrangement of this second embodiment, the process further comprises a step b) of stripping metal elements present in the organic phase stemming from step a), which stripping comprises at least one operation in which this organic phase is put into contact with an acid aqueous phase, and then separated from this aqueous phase. There again, the acid aqueous phase used for this stripping may contain one or more complexing agents, capable of facilitating the migration of certain metal elements into the aqueous phase, in which case this (these) complexing agent(s) may notably be selected from the complexing agents mentioned earlier. According to yet a further preferred arrangement for this second embodiment, the organic phase contains an alkylphosphoric acid extractant such as, for example, HDEHP mixed with a phase modifier such as TBP or DMDOHEMA, or a diglycolamide extractant such as TODGA. Regardless of how the selective recovery process for americium is implemented, the ethylene-diamine derivative of general formula (I) is preferably H4TPAEN which is used at a concentration preferentially ranging from 10−4 to 10−2 mol/L and, even better, from 10−3 to 5×10−2 mol/L. The process for selective recovery of americium according to the invention has many advantages. In particular: it allows recovery of more than 99% of the americium initially present in an acid aqueous phase with less than 1% of the other metal elements initially present in this phase, as shown in the following examples; it does not set into play any oxidation-reduction reaction of americium or of any other metal element and therefore does not comprise any of the drawbacks related to such a reaction; as an organic phase, it may use any of the organic phases, the use of which has been proposed in process from the state of the art which aim at recovering actinides(III), by liquid-liquid extraction, from acid aqueous solutions, either selectively or together with lanthanides and may therefore be easily used instead of these process or as an addition to the latter; and it may be applied to the treatment of aqueous phases having a high nitric acid concentration, i.e. typically comprised between 0.1 and 3 mol/L of nitric acid, without it being necessary to reduce the acidity of these phases. Other features and advantages of the invention will become apparent from the additional description which follows and which relates to exemplary embodiments of the process for selective recovery of americium according to the invention, as well as to experimental tests having allowed validation of these examples. It is obvious that these examples are only given as illustrations of the object of the invention and should by no means be interpreted as a limitation of this object. In FIGS. 1 and 2, the rectangles referenced as 1 to 6 represent multistage extractors such as those conventionally used in the processing of irradiated nuclear fuels (mixers-decanters, pulsed columns, centrifugal extractors). The organic phases flowing in and out of these extractors are symbolized by double lines, while the aqueous phases flowing in and out of these extractors are symbolized by solid lines. Reference is first made to FIG. 1 which schematically illustrates a first exemplary embodiment of the process for selective recovery of americium according to the invention, corresponding to an application of the process for separating americium according to the invention to the DIAMEX-SANEX process. It is recalled that the DIAMEX-SANEX process was initially proposed for separating actinides(III) from lanthanides present in a raffinate stemming from the first purification cycle of a PUREX process and is based on the use of two extractants operating in disconnected chemical domains, one of which is a malonamide while the other one is an alkylphosphoric acid. It is also recalled that a raffinate stemming from the first purification cycle of a PUREX process is an aqueous solution with strong nitric acidity, typically from 2 to 5 M, which contains americium, curium, lanthanides (La, Ce, Pr, Nd, Sm, Eu, Gd, . . . ), fission products other than lanthanides (Mo, Zr, Ru, Rd, Pa, Y, . . . ) as well as corrosion products such as iron. On the other hand, this solution is free of uranium, plutonium and neptunium or, if any of these elements is present, it is only present as trace amounts, i.e. with a mass content not exceeding 0.3%. As visible in FIG. 1, the process for selective recovery of americium according to the invention comprises a first step designated as “Extraction” in this figure and wherein the raffinate is first of all circulated in a first extractor (referenced as 1 in FIG. 1), as a counter-current against an organic phase which contains a malonamide and an alkylphosphoric acid in solution in an organic diluent. Like in the DIAMEX-SANEX process, the malonamide is preferably DMDOHEMA which is used at a concentration typically from 0.5 to 0.7 mol/L, for example 0.6 mol/L, while the alkylphosphoric acid is preferentially HDEHP which is used at a concentration typically from 0.1 to 0.5 mol/L, for example 0.3 mol/L. The organic diluent, as for it, is TPH. Before or after its introduction into the extractor 1, the nitric acid content of the raffinate is rectified if necessary, for example by adding nitric acid at 5 mol/L, so that it is preferably located between 3 and 5 mol/L, for example 4 mol/L. Moreover, the raffinate is added with at least one complexing agent, for example a polyaminocarboxylic acid such as HEDTA, at a concentration typically from 0.01 to 0.1 mol/L, for example 0.05 mol/L and the function of which is to inhibit the extraction of palladium by the organic phase. In a second step called “Washing” in FIG. 1, the organic phase flowing out of the extractor 1 is circulated in a second extractor (referenced as 2 in FIG. 1), as a counter-current against an aqueous phase which preferentially contains from 0.01 to 0.5 mol/L of nitric acid, for example 0.05 mol/L, as well as the same complexing agent(s)—and in the same ranges of concentrations—as the one or those having been added to the raffinate. Thus, an organic phase is obtained at the end of these first two steps, which contains americium, curium, lanthanides, yttrium, molybdenum, zirconium and iron, and which is directed towards a third extractor (referenced as 3 in FIG. 1) where the third step of the process takes place, i.e. the selective stripping of americium from this organic phase. This stripping which is designated as “Am Stripping” in FIG. 1, is achieved by applying the process for separating americium according to the invention, i.e. by circulating the organic phase flowing out of the extractor 2 (which in this case corresponds to the phase P1) as a counter-current against an aqueous phase (which therefore corresponds to the phase P2) preferentially containing from 10−2 to 0.3 mol/L of nitric acid, for example 0.1 mol/L, and an ethylenediamine derivative of general formula (I) such as H4TPAEN, which is used at a concentration preferably ranging from 10−4 to 10−2 mol/L, for example 10−3 mol/L. As visible in FIG. 1, this stripping is advantageously completed by a fourth step called “Cm/FP Washing” in this figure and which consists in circulating the aqueous phase flowing out of the extractor 3 into a fourth extractor (extractor 4 in FIG. 1), as a counter-current against a “fresh” organic phase, identical in its composition to the one used in the first step, and this so as to recover in the organic phase the possible trace amounts of curium and of fission products which may have followed americium into the aqueous phase during its stripping and thus to enhance the selectivity of this stripping. Thus, at the end of the third and fourth steps, an aqueous phase is obtained which exclusively or quasi-exclusively contains americium and which therefore leaves the cycle, and an organic phase which no longer or almost no longer contains any americium but which still contains curium, lanthanides, yttrium, molybdenum, zirconium and iron having been extracted during the first step. This organic phase is then directed towards a fifth extractor (extractor 5 in FIG. 1) where the fifth step of the process takes place, i.e. the stripping of all the metal elements still present in this phase. This stripping, which is designated as “Other elements Stripping” in FIG. 1, is achieved by circulating the organic phase flowing out of the extractor 3 as a counter-current against an aqueous phase which preferentially contains from 0.5 to 1.5 mol/L of nitric acid, for example 1 mol/L, as well as one or more complexing agents such as water-soluble diglycolamide like TEDGA, which is used at a concentration typically from 0.01 to 0.5 mol/L, for example 0.2 mol/L, together with a carboxylic acid such as oxalic acid, which itself is used at a concentration typically from 0.05 to 0.8 mol/L, for example 0.5 mol/L. Thus, at the end of this fifth step, an organic phase is obtained which no longer contains any of the metal elements having been extracted during the first step but which contains, in addition to the malonamide extractant and the alkylphosphoric extractant, a certain number of impurities and degradation products, notably from radiolyses, which have accumulated during the previous steps. As visible in FIG. 1, this organic phase is therefore directed towards a sixth extractor (extractor 6 in FIG. 1) in order to be purified, for example by one or more washings with an aqueous solution of a strong base, with a pH equal to or greater than 8, like a solution of sodium carbonate or sodium hydroxide of 0.1 to 0.3 M and accessorily by one or more filtrations in the case that it contains a precipitate. The thereby purified organic phase may then be sent back towards the extractors 1 and 4 for applying a new processing cycle. Reference is now made to FIG. 2 which schematically illustrates a second exemplary embodiment of the process for selective recovery of americium according to the invention, corresponding to an application of the process for separating americium according to the invention to the TODGA process. The TODGA process was initially proposed for recovering together actinides(III) with lanthanides present in a raffinate from the first purification cycle of a PUREX process. This process is based on the use of a diglycolamide extractant, in this case TODGA, which is a more powerful extractant, at a strong nitric acidity, than DMDOHEMA. Also, in this exemplary embodiment, the process for selective recovery of americium according to the invention comprises a first step designated as “Extraction” in FIG. 2 and in which the raffinate is circulated in a first extractor (referenced as 1 in FIG. 2) as a counter-current against an organic phase which contains TODGA, at a concentration typically from 0.1 to 0.2 mol/L, in solution in an organic diluent, for example TPH. A dialkylmonoamide at least as lipophilic as the solvating extractant, such as DHOA or else a alkylphosphate such as TBP, may also be present in the organic phase, for example at a concentration of 0.5 mol/L, in order to increase the load capacity of this phase. Like in Example 1, the nitric acid content of the raffinate is, if necessary, rectified, either before or during its introduction into the extractor 1, for example by adding 5 mol/L nitric acid, so that it is preferably located between 3 and 5 mol/L, for example 4 mol/L. This raffinate is moreover added with at least two complexing agents, one of which has the function of inhibiting the extraction of palladium while the other one has the function of inhibiting the extraction of zirconium and iron. The first of these complexing agents is therefore, for example, HEDTA like in Example 1, while the second one is, for example, a carboxylic acid such as oxalic acid, which is used at a concentration typically of 0.5 mol/L. In a second step designated as “Washing” in FIG. 2, the organic phase flowing out of the extractor 1 is circulated in a second extractor (referenced as 2 in FIG. 2), as a counter-current against a first aqueous phase which preferentially contains from 1 to 4 mol/L of nitric acid, for example 3 mol/L, as well as the same complexing agents—and in the same ranges of concentrations—as those having been added to the raffinate, and then as a counter-current against a second aqueous phase more weakly acid than the previous one, for example with 0.5 mol/L of nitric acid. Thus, at the end of both of these first steps, an organic phase is obtained which contains americium, curium, californium, lanthanides and yttrium, and which is directed towards a third extractor (referenced as 3 in FIG. 2) where the third step of the process takes place, i.e. the selective stripping of americium from this organic phase. This stripping, which is designated as “Am Stripping” in FIG. 2, is achieved by applying the process of separating americium according to the invention, i.e. by circulating the organic phase flowing out of the extractor 2 (which corresponds in this case to the phase P1) as a counter-current against an aqueous phase (which therefore corresponds to the phase P2) which preferentially contains from 0.03 to 0.14 mol/L of nitric acid, for example 0.1 mol/L, an ethylenediamine derivative of general formula (I) such as H4TPAEN, which is used at a concentration preferably ranging from 10−4 to 10−2 mol/L, for example 10−3 mol/L, and accessorily a desalting salt such as sodium, lithium or hydroxylamine nitrate, which is used at a concentration typically from 0.1 to 3 mol/L, for example 1 mol/L. As visible in FIG. 2, this stripping is advantageously completed by a fourth step called “Cm Washing” in this figure and which consists in circulating in a fourth extractor (extractor 4 in FIG. 2) the aqueous phase flowing out of the extractor 3 through a “fresh” organic phase, identical in its composition with the one used in the first step, and this so as to recover in the organic phase the possible trace amounts of curium, californium, of fission products and corrosion products which may have followed the americium into the aqueous phase during its stripping and, thus enhancing the selectivity of this stripping. Thus, at the end of the third and fourth steps, an aqueous phase is obtained which exclusively or quasi-exclusively contains americium and which therefore leaves the cycle, and an organic phase which no longer or quasi-no longer contains any americium but which still contains curium, californium, lanthanides and yttrium having been extracted during the first step. This organic phase is directed towards a fifth extractor (extractor 5 in FIG. 2) where the fifth step of the process takes place, i.e. stripping of all the metal elements still present in this phase. This stripping, which is designated as “Other elements Stripping” in FIG. 2, is achieved by circulating the organic phase flowing out of the extractor 3 as a counter-current against an aqueous phase which preferentially contains from 0.005 to 0.05 mol/L of nitric acid, for example 0.01 mol/L, and which is advantageously free of any complexing agent. Like in Example 1, the organic phase flowing out of the extractor 5 is directed towards a sixth extractor (extractor 6 in FIG. 2) so as to be purified before being sent back to the extractors 1 and 4 for applying a new processing cycle. Experimental tests intended to verify the validity of the process described in Examples 1 and 2 are conducted by using H4TPAEN as the ethylenediamine derivative of general formula (I). For the needs of these tests, H4TPAEN was synthesized by using pyridine-2,6-dicarboxylic acid as starting product, by following a procedure substantially different from the one proposed in reference [2]. This synthesis is therefore described hereafter and schematized in FIG. 3. 5.2 g (3.1×10−2 mol) of pyridine-2,6-dicarboxylic acid, noted as 1 in FIG. 3, are suspended in 20 mL of anhydrous methanol. A volume of 900 μL of 97% sulfuric acid is added and the mixture is refluxed for 16 hours. After cooling, the methanol is evaporated in vacuo so as to obtain a white solid. Saturated sodium dicarbonate is added up to a pH=7, i.e. about 200 mL. An equal volume of dichloromethane is then used for carrying out a first extraction. The aqueous phase is re-extracted with 100 mL of dichloromethane. The organic phases are collected and washed with 50 mL of saturated sodium chloride. The final organic phase is dried on anhydrous sodium sulfate. The solvent is evaporated in vacuo. Thus, 5.3 g of dimethyl 2,6-pyridine carboxylate, noted as 2 in FIG. 3, are obtained as a white solid, with a yield of 90%. The proton NMR analysis of this compound is the following: 1H NMR (CDCl3, 300 MHz, 298K), δ (ppm): 8.25 (d, J=7.3 Hz, 2H); 7.97 (t, J=7.3 Hz, 1H); 3.96 (s, 6H, CH3) 2 g (10−2 mol) of dimethyl 2,6-pyridine carboxylate are suspended in 90 mL of methanol. The medium is cooled to 0° C. and then 590 mg (1.56×10−2 mol) of sodium borohydride are added in three times at this temperature. The solution becomes limpid and the medium is stirred at room temperature for 24 hours. The pH is brought to 3 with 37% hydrochloric acid. The solvent is evaporated and the solid is then resuspended with 100 mL of water and saturated sodium bicarbonate in order to obtain a pH of 7. The extraction of the product in the organic phase is achieved with 100 mL of dichloromethane. The aqueous phase is re-extracted with the same amount of solvent. The organic phases are grouped and dried on anhydrous sodium sulfate. 1.41 g of methyl 6-hydroxymethyl-2-pyridine carboxylate is thereby obtained, noted as 3 in FIG. 3, as a white solid, i.e. a yield of 82%. The proton and carbon 13 NMR analysis of this compound are the following: 1H NMR (CDCl3, 300 MHz, 298K), δ (ppm): 8.04 (dt, J=7.7 Hz, J=0.6 Hz, 1H); 7.86 (t, J=7.7 Hz, 1H); 7.57 (dt, J=7.7 Hz, J=0.6 Hz, 1H); 4.88 (s, 2H, CH2OH); 3.99 (s, 6H, CH3) 13C NMR, DEPT 135, (CDCl3, 300 MHz, 298K), δ (ppm): 138.1; 124.5; 124.2; 65.1 (CH2OH); 53.3 (CH3) 2.25 g (1.28×10−2 mol) of methyl 6-hydroxymethyl-2-pyridine carboxylate are reacted at 0° C. with 4.5 mL (6.1×10−2 mol; 4.5 equiv.) of thionyl chloride used both as a reagent and a solvent. The reaction occurs at 0° C. for 1 hour. The excess of thionyl chloride is evaporated in vacuo at room temperature and methanol is added until there is no gas evolvement. After 5 minutes, the solution is evaporated in vacuo. The yellow oil is taken up with 100 mL of toluene and washed twice with 50 mL of cold 10% sodium bicarbonate. The aqueous phases are re-extracted with 100 mL of toluene. The organic phases are grouped, washed and dried with saturated sodium chloride. Thus, 2.32 g of methyl 6-chloromethyl-2-pyridine carboxylate, noted as 4 in FIG. 3, are obtained as a yellow oil which crystallizes, i.e. a yield of 90%. The proton and carbon 13 NMR analysis of this compound are the following: 1H NMR (CDCl3, 300 MHz, 298K), δ (ppm): 8.10 (d, J=7.71 Hz, 1H); 7.92 (t, J=7.71 Hz, 1H); 7.75 (d, J=7.71 Hz, 1H); 4.79 (s, 2H, CH2Cl); 4.03 (s, 6H, CH3) 13C NMR, DEPT 135, (CDCl3, 300 MHz, 298K), δ (ppm): 138.6; 126.6; 124.9; 53.5 (CH3); 40.7 (CH2Cl) 2 g (1.08×10−2 mol) of methyl 6-chloromethyl-2-pyridine carboxylate are introduced into the reactor and the circuit is purged by sweeping with an argon stream. A volume of 36 mL of anhydrous acetonitrile is added and then, after dissolution of the product, 175 μL (2.63×10−3 mol) of ethylenediamine and then 1.49 g (1.08×10−2 mol) of potassium carbonate are added. The mixture is refluxed for 14 hours and the solution becomes orange. The solvent is evaporated for obtaining an oil which crystallizes. The latter is taken up with 100 mL of dichloromethane. The organic phase is washed twice with 40 mL of water and then dried on anhydrous sodium sulfate, which gives the possibility of obtaining 2.48 g of an orange solid which is recrystallized from isopropanol. 700 mg of purified N,N,N′,N′-tetrakis[(6-carboxymethylpyridin-2-yl)-methyl]ethylenediamine, noted as 5 in FIG. 3, are thus recovered as a beige solid, i.e. a yield of 40%. Proton NMR analysis of this compound is the following: 1H NMR (CDCl3, 300 MHz, 298K), δ (ppm): 7.97 (dd, J=6.96 Hz, J=1.68 Hz, 1H); 7.71 (massive, 2H); 3.98 (s, 12H, CH3); 3.89 (s, 8H, PyCH2N); 2.78 (s, 4H, NCH2CH2) 825 mg of N,N,N′,N′-tetrakis[(6-carboxymethylpyridin-2-yl)methyl]-ethylenediamine are suspended in 4.5 mL of 6 M hydrochloric acid. The mixture is refluxed for 14 hours and a brown precipitate appears at room temperature. This solid is filtered, washed twice with 2 mL of water and then dried in vacuo at room temperature for 14 hours. 690 mg of H4TPAEN are thus obtained as a beige powder, i.e. a yield of 80%. The proton NMR analysis of this compound is the following. 1H NMR (DMSOd6, 300 MHz, 298K), δ (ppm): 7.91 (massive, 2H); 7.67 (massive, 1H); 4.51 (s, 8H, PyCH2N); 3.70 (s, 4H, NCH2CH2) Extraction/Washing: Tests in tubes are conducted by using: an aqueous phase simulating a raffinate stemming from the processing of an irradiated nuclear fuel of the UOX3 type by a PUREX process except as regards to americium 241 and curium 244 which are only present as trace amounts; an organic phase containing 0.6 mol/L of DMDOHEMA and 0.3 mol/L of HDEHP in TPH; and for the washing, distilled water, voluntarily free of any complexing agent so as not to inhibit the extraction of palladium and to be able to study its behavior during the subsequent step of selective stripping of americium. The nitric acidity of the aqueous phase simulating the raffinate is 4 mol/L. Its qualitative and quantitative composition in metal elements is given in Table I hereafter. All these elements are dissolved as nitrates. TABLE IConcentrationsElementsmmol/Lmg/L241Am5.9 × 10−41.4 × 10−1244Cm8.2 × 10−6 2 × 10−3Ce5.5760Eu0.3248Fe1.8100Gd0.2336La2.8391Mo121137Nd9.01297Pd4.2448Pr2.6363Sm1.9282Y0.6154Zr131189 The organic phase and the aqueous phase simulating the raffinate are first of all put into contact with each other, volume to volume, and left with stirring for 10 minutes at a constant temperature of 25° C. After decantation and separation of the organic phase from the aqueous phase, the activities of americium 241 and curium 244 are measured by α spectrometry in each of these phases while the concentrations of the other metal elements are measured by inductively coupled plasma atomic emission spectrometry, also known under the shortcut ICP-AES in the aqueous phase alone. The distribution coefficients of americium 241 and of curium 244 are determined by calculating the (activity in the organic phase)/(activity in the aqueous phase) ratio while the distribution coefficients of the other metal elements are determined by calculating the ((initial concentration—final concentration)/initial concentration) ratio. Next, the organic phase is put into contact with distilled water, in an amount of 8 volumes of distilled water for 1 volume of organic phase, and the whole is left with stirring for 10 minutes at a constant temperature of 25° C. After decantation and separation of the organic and aqueous phases, the activities of americium 241 and of curium 244 are measured by α spectrometry in each of these phases while the concentrations of the other metal elements are measured by ICP-AES in the aqueous phase alone. The distribution coefficients of americium 241, curium 244 and of the other metal elements are determined in the same way as previously. Table II hereafter shows the distribution coefficients (DM) and the thereby obtained separation factors (FSAm/M). The distribution coefficients of nitric acid are also indicated in this table. TABLE IIExtractionWashingDMFSAm/MDMFSAm/MElements241Am8.122244Cm5.11.6201.1Ce7.91.0191.1Eu5.91.41320.17Fe820.10>200<0.11Gd4.31.9430.5La6.01.482.7Mo1360.063870.1Nd7.01.2250.9Pd5.41.5211.7Pr8.11.0240.9Sm6.41.3440.5Y3.42.4>20<1.1Zr6520.015970.04HNO30.150.04 This table shows that the extraction step allows extraction of the major portion of metal elements present in the raffinate since the distribution coefficients of these elements are all greater than 3. Also, by using, on an industrial scale, an extractor with 8 stages and an O/A (organic over aqueous) flow rate ratio equal to or greater than 1, it should be possible to extract in an organic phase more than 99.9% of the metal elements initially present in the raffinate. The washing step has the goal of having nitric acid, which was able to be extracted together with the metal elements, return to the aqueous phase. Now, the distribution coefficients for nitric acid given in Table II show that this acid is not very extractible with the DMDOHEMA/HDEHP mixture. At the end of the washing step, the nitric acid concentration of the organic phase is less than 5×10−3 mol/L which is negligible. On the other hand, the distribution coefficients of the metal elements are all greater than 2, which means that these elements in majority remain in the organic phase. Selective Stripping of Americium: Tests in tubes are conducted by using: the organic phase from the test dealing with the washing performed previously and therefore containing 241Am, 244Cm, Ce, Eu, Fe, Gd, La, Mo, Nd, Pd, Pr, Sm, Y and Zr; and an aqueous phase containing 0.1 mol/L of nitric acid and 0.001 mol/L of H4TPAEN. Both of these phases are put into contact with each other, volume to volume, and left with stirring for ten minutes at a constant temperature of 25° C. After decantation and separation of the organic and aqueous phases, the activities of americium 241 and of curium 244 are measured by α spectrometry in each of these phases while the concentrations of the other metal elements are measured by ICP-AES in the aqueous phase alone. The distribution coefficients of americium 241 and of curium 244 are determined by calculating the (activity in the organic phase)/(activity in the aqueous phase) ratio. The distribution coefficients of the other metal elements are determined by calculating the (concentration in the organic phase)/(concentration in the aqueous phase) ratio, the concentration in the organic phase being estimated by stripping these elements in a strongly complexing nitric aqueous phase (HNO3=1 mol/L; TEDGA=0.2 mol/L; oxalic acid=0.5 mol/L; 1 volume of organic phase for 1 volume of aqueous phase; duration of the stirring=10 minutes; temperature=25° C.) and by measuring by ICP-AES the concentration of said elements in the aqueous phase stemming from the stripping. Table III hereafter shows the distribution coefficients (DM) and the thereby obtained separation factors (FSAm/M). TABLE IIIElementsDMFSAm/M241Am1.1244Cm3.02.7Ce8.97.9Eu5145Fe>200>150Gd3027La5.24.6Mo226200Nd1110Pd0.320.3Pr109Sm2320Y>30>25Zr>600>540 This table shows that the separation factors between americium 241 and the other metal elements are all greater than 2.5 except for palladium which is better stripped from the organic phase than americium. It is therefore necessary, if it is intended to prevent stripped americium from being contaminated with palladium, to use during the extraction and washing steps which precede the selective stripping step of americium, a complexing agent giving the possibility of inhibiting extraction of the palladium, for example HEDTA as described in Example 1 hereinbefore. Complexation of palladium by HEDTA has already been validated on a real solution with high activity in reference [14]. Table III also shows that except for palladium, lanthanides and curium 244 are elements which are less well separated from americium. This is why an additional test is conducted by using: a first nitric aqueous phase S1, containing 0.001 mol/L of H4TPAEN, as well as Ce, Eu, Gd, La, Nd, Pr, Sm and Y dissolved in the form of nitrates and for which the pH was adjusted to 1; a second nitric aqueous phase S2, only differing from phase S1 in that its pH has been adjusted to 2; and an organic phase containing 0.6 mol/L of DMDOHEMA and 0.3 mol/L of HDEHP in TPH, having been used for extracting americium 241, curium 244, cerium 139 and europium 152 from an aqueous solution containing 4 mol/L of nitric acid and having been washed at the end of this extraction with distilled water; the cation concentrations of this organic phase, as measured by γ spectrometry at the end of this washing, are the following:[152Eu]=10−3 mg/L[139Ce]=2.7×10−6 mg/L[241Am]=9.5×10−2 mg/L, and[244Cm]=1.3×10−3 mg/L. The initial concentrations of metal elements in the phases S1 and S2 as determined by ICP-AES are shown in Table IV hereafter. TABLE IVConcentrations(mg/L)ElementsS1S2Ce377393Eu2425Gd2324La189195Nd642668Pr154159Sm142148Y6265 The phases S1 and S2 are put into contact in parallel, volume to volume, with a fraction of the organic phase and left with stirring with it for 15 minutes at a constant temperature of 25° C. After decantation and separation of the organic and aqueous phases, the activities of americium 241, curium 244, cerium 139 and europium 152 are measured, by α and γ spectrometry respectively, in each of these phases while the concentrations of the other metal elements (Ce, Eu, Gd, La, Nd, Pr, Sm, Y) are measured by ICP-AES in the aqueous phase alone. The distribution coefficients of americium 241, curium 244, cerium 139 and europium 152 are determined by calculating the (activity in the organic phase)/(activity in the aqueous phase) ratio. The distribution coefficients of the other metal elements are determined by calculating the (concentration in the organic phase)/(concentration in the aqueous phase) ratio, the concentration in the organic phase being estimated by stripping these elements in a strongly complexing nitric aqueous phase (HNO3=1 mol/L; TEDGA=0.2 mol/L; oxalic acid=0.5 mol/L; 1 volume of organic phase for 1 volume of aqueous phase; duration of the stirring=10 minutes; temperature=25° C.) and by measuring with ICP-AES the concentration of said elements in the aqueous phase stemming from this stripping. Table V hereafter shows the distribution coefficients (DM) and the thereby obtained separation factors (FSAm/M) for each of the phases S1 and S2. TABLE VS1S2Final pH = 1final pH = 1.5ElementsDMFSM/AmDMFSM/Am241Am0.300.19244Cm0.702.30.573.0139Ce2.48.06.635Ce2.47.96.535152Eu1032129685Eu1238>20>100Gd1654>20>100La1.13.76.937Nd3.4119.249Pr3.0107.339Sm6.62235188Y>30>100>30>150 This table shows that the distribution coefficients of cerium 139 and of europium 152 initially present in the organic phase are equivalent to those of cerium and of europium initially present in the aqueous phase. This means that there is reversibility between the extraction and the stripping of the lanthanides in the presence of H4TPAEN. These results may therefore be compared with those shown in Table III hereinbefore and which have been obtained for elements which were initially in the organic phase. This additional test confirms that it is possible to separate americium from curium, from lanthanides and from yttrium by means of a nitric aqueous phase containing 0.001 mol/L of H4TPAEN. It also shows that under the operating conditions used in this test, the distribution coefficient of americium is less than 0.4. The application on an industrial scale of the step of selective stripping of americium by using a nitric aqueous solution with a pH from 1 to 1.5 containing 0.001 mol/L of H4TPAEN, and an O/A flow rate ratio from 1 to 2 on 32 stages should therefore allow recovery of more than 99% of the extracted americium with less than 1% of curium and extracted lanthanides. Stripping of the Other Metal Elements: Tests in tubes are conducted by using: the organic phase from the test dealing with the stripping of americium, conducted earlier and therefore containing 244Cm, Ce, Eu, Fe, Gd, La, Mo, Nd, Pr, Sm, Y and Zr; and an aqueous phase containing 1 mol/L of nitric acid, 0.2 mol/L of TEDGA and 0.8 mol/L of oxalic acid. Both of these phases are put into contact with each other, volume to volume, and the whole is left with stirring for 10 minutes at a constant temperature of 25° C. After decantation and separation of the organic and aqueous phases, the activity of curium 244 is measured by α spectrometry in each of these phases while the concentrations of the other metal elements are measured by ICP-AES in the aqueous phase alone. The distribution coefficient of curium 244 is determined by calculating the (activity in the organic phase)/(activity in the aqueous phase) ratio while the distribution coefficients of the other metal elements are determined by calculating the (concentration in the organic phase)/(concentration in the aqueous phase) ratio, the concentration in the organic phase being estimated by stripping these metal elements into a strongly complexing nitric aqueous phase (HNO3=1 mol/L; TEDGA=0.2 mol/L; oxalic acid=0.5 mol/L; 1 volume of organic phase for 1 volume of aqueous phase; duration of the stirring=10 minutes; temperature=25° C.) and by measuring with ICP-AES their concentration in the aqueous phase stemming from this stripping. Table VI hereafter shows the thereby obtained distribution coefficients (DM). TABLE VIElementsDM244Cm0.008Ce0.001Eu0.009Fe0.04Gd0.02La0.005Mo0.03Nd0.001Pr0.002Sm0.006Y0.015Zr0.005 This table shows that the distribution coefficients are much less than 0.1 for all the metal elements. This means that it should be possible to obtain on an industrial scale, quantitative stripping of all these elements by using an aqueous solution with 1 mol/L of nitric acid, 0.2 mol/L of TEDGA and 0.8 mol/L of oxalic acid, and an O/A flow rate ratio of the order of 10 on only 4 stages. The first, second and fifth steps of the process described in Example 2 having already been validated by implementation in centrifugal extractors (reference [9]), the tests reported here are only intended to validate the possibility of achieving selective stripping of americium in this process by complexation with H4TPAEN. Two tests are conducted, one for testing the behavior of americium, curium, lanthanum and europium and the other one for measuring the efficiency of the americium/californium separation. Selectivity of the Stripping of Americium Towards Curium, Lanthanum and Europium: This test is conducted by using an organic phase containing 0.1 mol/L of TODGA in TPH. This organic phase is first of all put into contact, volume to volume, with an aqueous phase of the following composition:[Eu]=6.5×10−5 mol/L;[La]=5.8×10−5 mol/L;Trace amounts of 241Am, 244Cm and 152Eu;[NaNO3]=3 mol/L. The europium and lanthanum are dissolved in this phase in the form of nitrates and their concentration is measured by ICP-AES. The pH is adjusted to 2 by adding NaOH. The organic and aqueous phases are left with stirring for 15 minutes at a constant temperature of 25° C. After decantation and separation of the organic phase from the aqueous phase, the activities of americium 241, curium 244, and europium 152 are measured by α and γ spectrometry, respectively, in each of these phases. In parallel, the concentrations of the other metal elements are measured by ICP-AES in the aqueous phase alone. The obtained results show that the major portion of these metal elements is extracted into the organic phase. An organic phase containing 0.1 mol/L of TODGA in TPH, trace amounts of 241Am, 244Cm and of 152Eu, 5×10−5 mol/L or europium (inactive) and 5.8×10−5 mol/L of lanthanum is put into contact, volume to volume, with aqueous phases containing 6.5×10−4 mol/L of H4TPAEN, 3 mol/L of NaNO3 in nitric acid with a molarity ranging from 0.03 to 0.045. The organic and aqueous phases are left with stirring for 15 minutes at a constant temperature of 25° C. After decantation and separation of the organic and aqueous phase, the activities of americium 241, curium 244, and europium 152 are measured, by α and γ spectrometry, respectively, in each of these phases while the concentrations of lanthanum and europium (inactive) are measured with ICP-AES in the aqueous phases alone. The distribution coefficients of curium 244 and europium 152 are determined by calculating the (activity in the organic phase)/(activity in the aqueous phase) ratio while the distribution coefficients of lanthanum and of europium (inactive) are determined by calculating the (initial concentration−final concentration)/(initial concentration) ratio. Table VII hereafter shows the distribution coefficients (DM) and the thereby obtained separation factors (FSM/Am) according to the nitric acid concentration exhibited by the aqueous phases at the end of the stripping of americium. TABLE VII[HNO3]final =[HNO3]final =[HNO3]final =Metal0.023 mol/L0.035 mol/L0.044 mol/LelementsDMFSM/AmDMFSM/AmDMFSM/Am241Am0.0900.581.1244Cm0.333.72.13.63.93.6152Eu63700159290202177La1.3153.86.67.46.7Eu3842497168125114 This table confirms that, within the scope of a TODG process, curium 244 is the most difficult element to separate from americium 241. However, as the separation factor between curium and americium is greater than 3.5 and this regardless of the acidity of the aqueous phase, it should be possible to recover more than 99% of the americium selectively from the other elements with an extractor with at least 30 stages. Selectivity of the Stripping of Americium with Respect to Californium: This test is conducted by using an organic phase containing 0.2 mol/L of TODGA and 0.5 mol/L of TBP in TPH. The TBP is used as a phase modifying agent. In a first phase, this organic phase is put into contact, volume to volume, with an aqueous phase of the following composition:249Cf=8,500 kBq/L=2.4×10−2 mg/L;241Am=10,000 kBq/L=7.9×10−2 mg/L;152Eu=11,300 kBq/L=1.8×10−3 mg/L;[HNO3]=3 mol/L; and the whole is left with stirring for 30 minutes at a constant temperature of 25° C. This operation has the purpose of extracting the radiotracers in the organic phase. Next, after decantation and separation of the organic and aqueous phases, the organic phase is put into contact, volume to volume, with an aqueous phase containing 0.01 mol/L of nitric acid and the whole is left with stirring for 30 minutes at a constant temperature of 25° C. This operation has the purpose of stripping the nitric acid which may have been extracted during the previous operation. After decantation and separation of the organic and aqueous phases, the activities of americium 241, californium 249 and of europium 152 are measured, by α and γ spectrometry, respectively, in each of these phases. The obtained results show that the major portion of these radiotracers has been extracted in the organic phase. The thereby obtained organic phase which therefore contains trace amounts of 241Am, 249Cf and 152Eu is then put into contact, volume to volume, with an aqueous phase containing 0.1 mol/L of nitric acid and 0.001 mol/L of H4TPAEN and the whole is left with stirring for 30 minutes at a constant temperature of 25° C. After decantation and separation of the organic and aqueous phases, the activities of americium 241, californium 249 and of europium 152 are measured by α and γ spectrometry, respectively, in each of these phases and their distribution coefficients are determined by calculating the (activity in the organic phase)/(activity in the aqueous phase) ratio. Table VIII hereafter shows the distribution coefficients (DM) and the thereby obtained separation factors (FSM/Am). TABLE VIII[HNO3]final =0.14 mol/LElementsDMFSM/Am241Am0.075249Cf2.634152Eu3.243 This table shows that it is possible to separate americium from californium by means of an aqueous phase containing 0.001 mol/L of H4TPAEN, even with nitric acidity of 0.14 mol/L. The advantage of being able to use such an acidity is dual, i.e.: that of suppressing the requirement of using a buffer system for stabilizing the pH of the aqueous phase used for the stripping, and that, in the case of selective stripping of americium, of suppressing the requirement of using a desalting salt such as sodium nitrate, capable of increasing the distribution coefficients of the elements which do not have to be stripped. The aqueous phase may therefore only consist of H4TPAEN, nitric acid and water. The distribution coefficient of americium is less than 0.1 while the separation factor between californium and americium is greater than 40. The application on an industrial scale of the step of selective stripping of americium by using a nitric aqueous solution with a pH from 1 to 1.5, containing 0.001 mol/L of H4TPAEN, and an O/A flow rate ratio close to 3 on 12 stages should therefore give the possibility of recovering 99.9% of the extracted americium with less than 0.1% of extracted californium. [1] International PCT application WO 2007/135178 [2] French patent application 2 890 657 [3] R. B. Gujar, S. A. Ansari, M. S. Murali, P. K. Mohapatra, V. K. Manchanda, J. Radioanal. Nucl. Chem. 284, 377-385 (2010) [4] R. B. Gujar, S. A. Ansari, P. K. Mohapatra, V. K. Manchanda, Solv. Ext. Ion Exch., 28, 350-366 (2010) [5] S. A. Ansari, P. N. Pathak, V. K. Manchanda, M. Husain, A. K. Prasad, V. S. Parmar, Solv. Ext. Ion Exch., 23, 463-479 (2005) [6] S. Tachimori, S. Susuki, Y. Sasaki, A. Apichaibukol, Solv. Ext. Ion Exch., 21(5), 707-715 (2003) [7] G. Modolo, H. Asp, H. Vijgen, R. Malmbeck, D. Magnusson, C. Sorel, Solv. Ext. Ion Exch., 26, 62-76 (2008) [8] Y. Sasaki, Y. Morita, Y. Kitatsuji, T. Kimura, Solv. Ext. Ion Exch., 28, 335-349 (2010) [9] M. C. Charbonnel, C. Nicol, L. Berthon, P. Baron, Proceedings of the International Conference GLOBAL '97, Yokohama, Japan (1997). [10] L. Spjuth, J. O. Liljenzin, M. Skålberg, M. J. Hudson, G. Y. S. Chan, M. G. B. Drew, M. Feaviour, P. B. Iveson, C. Madic, Radiochimica Acta, 78, 39-46 (1997) [11] French patent application 2 845 616 [12] P. Baron, X. Hérès, M. Lecomte, M. Masson, <<Separation of the Minor Actinides: the DIAMEX-SANEX Concept>>, Proceedings of the International Conference GLOBAL '01, Paris, France (2001) [13] P. S. Dhami, R. R. Chitnis, V. Gopalakrishnan, P. K. Wattal, A. Ramnujam, A. K. Bauri, Sep. Sci. Technol., 36(2), 325-335 (2001) [14] B. Weaver, F. A. Kappelmann, <<TALSPEAK: A New Process of Separating Americium and Curium from the Lanthanides by Extraction from an Aqueous Solution of Aminopolyacetic Acid Complex with a Monoacidic Organophosphate or Phosphonate>>, Rapport ORNL-3559 (1964) [15] M. Kubota, Y. Morita, R. Tatsugae, T. Fujiwara, Y. Kondo, <<Development of Partitioning Process at JAERI>>, Third International Information Exchange Meeting on Actinide and Fission Product Partitioning and Transmutation, Cadarache, France (1994). [16] S. Tachimori, A. Sato, H. Nakamura, J. Nucl. Sci. Technol., 16(6), 434 (1979) [17] M. Kubota, Y. Morita, <<Preliminary assessment on four group partitioning process developed in JAERI>>, Proceedings of the International Conference GLOBAL '97, Yokohama, Japan (1997) [18] Y. Morita, J. P. Glatz, M. Kubota, L. Koch, G. Pagliosa, K. Roemer, A. Nicholl, Solv. Ext. Ion Exch., 14(3), 385-400 (1996) [19] J. Yamagawa, M. Goto, F. Nakashio, Solv. Ext. and Res. Dev., 4, 12-22 (1997) [20] S. D. Chaudhary, P. S. Dhami, V. Gopalakrishnan, A. Ramanujam, J. N. Mathur, <<Solvent extraction of trivalent actinides and lanthanides from various aqueous media using KSM-17>>, NUCAR 97: Nuclear and Radiochemistry Symposium. Department of Atomic Energy, Bombay, India (1997) [21] P. N. Pathak, R. Veeraraghavan, P. K. Mohapatra, V. K. Manchanda, <<Use of 3-phenyl-4-benzoyl-5-isoxazolone for the recovery of americium(III) from simulated nuclear waste solution>>, NUCAR 97: Nuclear and Radiochemistry Symposium, Department of Atomic Energy, Bombay, India (1997) [22] M. L. P. Reddy, R. L. Varma, T. R. Ramamohan, T. P. Rao, C. S. P. Iyer, A. D. Damodaran, J. N. Mathur, M. S. Murali, R. H. Iyer, Radiochimica Acta, 69, 55-60 (1995) [23] French patent application 2 738 663 [24] Y. Koma, M. Watanabe, S. Nemoto, Y. Tanaka, J. Nucl. Sci. Technol., 35(2), 130-136 (1998) [25] J. D. Law, T. G. Garn, D. H. Meikrantz, J. Warburton, Sep. Sci. Technol., 45, 1769-1775 (2010) [26] K. Arai, M. Yamashita, M. Hatta, Nucl. Sci. Techn., 34(5), 521-526 (1997) [27] Y. Zhu, C. Song, Nucl. Technol., 108, 361 (1994) [28] E. M. Bond, U. Engelhardt, T. P Deere, B. M. Rapko, R. T. Paine, J. R. FitzPatrick, Solv. Ext. Ion Exch., 16(4), 967-983 (1998) [29] L. Rao, Y. Xia, B. M. Rapko, P. F. Martin, Solv. Ext. Ion Exch., 16(4), 913-929 (1998) [30] German patent application 198 10 895 [31] D. Magnusson, B. Christiansen, R. S. Foreman, A. Geist, J. P. Glatz, R. Malmbeck, G. Modolo, D. Serrano-Purroy, C. Sorel, Solv. Ext. Ion Exch., 27(2), 97-106 (2009) [32] B. Christiansen, C. Apostolidis, R. Carlos, O. Courson, J. P. Glatz, R. Malmbeck, G. Pagliosa, K. Römer, D. Serrano-Purroy, Radiochim. Acta, 92, 475-480 (2004) [33] G. Modolo, S, Nabet, Solv. Ext. Ion Exch., 23(3), 359-373 (2005) [34] J. Chen, R. Jiao, Y. Zhu, Radiochimica Acta, 76, 129-130 (1997) [35] D. R. Peterman, M. R. Greenhalgh, R. D. Tillotson, J. R. Klaehn, M. K. Harrup, T. A. Luther, J. D. Law, Sep. Sci. Technol., 45(12), 1711-1717 (2010)
055219500	summary	BACKGROUND OF THE INVENTION The present invention relates generally to tooling and a process for inserting, rearranging and/or removing the control rods in a boiling water reactor pressure vessel. The control rods in a boiling water reactor contain an absorbent material that when positioned in the reactor core can be used to slow the fission rate of the nuclear fuel. However, the absorbent material is subject to degradation after extended use. Therefore, it is periodically necessary to replace the control rods. Since different regions of the reactor core have different levels of irradiation fluence, in order to reduce expenses, it is common to periodically reposition the control rods within the core to maximize, their useful life. In order to pull a control rod out of its associated core location, it is also necessary to pull out the associated fuel support since the control rod's velocity limiter cannot slide past an installed fuel support. Therefore, the tools commonly used to reposition and/or replace the control rods include a first grapple for lifting the fuel support. A second grapple is then used for uncoupling the control rod from its associated control rod drive and lifting the uncoupled control rod. Operators that use just these two tools have been known to occasionally drop the control rod. Therefore, a third grapple tool is often used to grab the top bail handle of the control rod when the control rod is being lifted. When the control rods are being rearranged, it is customary to set the fuel support on the reactor pool floor in a sheltered area. The control rod is then taken out of the pressure vessel and placed in a fuel pool located adjacent the pressure vessel. When the control rod is to be reinserted, it must be transferred back from the fuel pool to the pressure vessel. When the fuel support is to be reinserted, it must be picked up from the floor. These transferring motions take a relatively long time and in the case of the control rods result in the undesirable exposure of a radioactive component. SUMMARY OF THE INVENTION Accordingly, it is an objective of the present invention to provide an improved tool set and an improved method for rearranging and/or replacing control rods in a boiling water reactor. To achieve the foregoing and other objects and in accordance with the purpose of the present invention, a tool set and a method of using those tools is disclosed that is especially well adapted to the function of rearranging and/or replacing the control rods and fuel supports in a boiling water reactor. In a first aspect of the invention a grapple is disclosed that is capable of simultaneously picking up both a control rod and its associated fuel support. The grapple includes a frame, a slidable control rod holding mechanism that is adapted to grab the bail handle of a control rod, and a fuel support holding mechanism adapted to grasp a fuel support. In a second aspect of the invention, an unlatching tool is disclosed for pulling the control rod's release handle in order to decouple the control rod from a control rod drive. The unlatching tool includes a housing having a positioning projection adapted to engage the fuel support associated with the control rod being detached in order to help position the unlatching tool during use. An unlatching finger is pivotally mounted to the housing near its distal end and an actuating mechanism is provided to actuate the unlatching finger. The actuating mechanism is adapted to move the finger between a withdrawn position wherein the finger is substantially parallel with the housing and an extended position wherein the finger extends substantially perpendicular to the housing such that it can readily engage the control rod's release handle. In a third aspect of the invention a storage rack suitable for mounting within the reactor pressure vessel is provided for storing a fuel support and a pair of control rods when the control rods are being shifted about the reactor core area. The storage rack is designed such that it can be temporarily installed in the reactor pressure vessel and includes a frame, a pair of control rod holders and a fuel support storage seat for holding a fuel support. The control rod holders each include a control rod seat that is shaped to receive the socket of a control rod velocity limiter. In a method aspect of the invention, a method of removing and/or rearranging the position of control rods and fuel supports is disclosed. The method includes the step of pulling the control rod release handle using an unlatching tool. Thereafter, the control rod and its associated fuel support are lifted together using a single grapple tool that is separate from the unlatching tool. When removing the control rod, the control rod can be simply lifted out of the pressure vessel. However, when rearranging the control rods, the first control rod and its associated fuel support are placed a storage rack that is temporarily positioned within the reactor pressure vessel. Then the unlatching and lifting out steps are repeated for a second control rod/fuel support assembly. The second control rod is placed in the storage rack without releasing the second fuel support. Thereafter, the first control rod is removed from the storage rack and placed together with the second fuel support in the position formerly occupied by the second control rod.
052934160	description	DESCRIPTION OF THE PREFERRED EMBODIMENTS A radiography apparatus for producing x-ray shadowgraphs, constructed in accordance with the principles of the present invention, is shown in FIG. 1. The apparatus includes an x-ray radiator 1 having a focus 2. The focus 2 is displaceable by a focus displacement unit la along a dot-dash line 3 in the direction of the arrow. In the embodiment of FIG. 1, the focus displacement unit la is shown as a unit for physically displacing the x-ray radiator 1. The x-ray beam emanating from the focus 2 and emerging from the x-ray radiator 1 is gated by a stationary screen diaphragm 4, so that a fan-shaped x-ray beam is generated which is incident on a detector array 5 for each measuring position. The detector array 5 is formed by a row of detector elements extending perpendicularly relative to the plane of the drawing. Accordingly, one detector element 5a of the detector array 5 is visible in FIG. 1. Four of the plurality of different measuring positions of the x-ray radiator 1 are shown in FIG. 1, being referenced 1, 11, Ill and IV. As can be seen in FIG. 1, the diaphragm shafts of the screen diaphragm 4 are aligned onto the detector array 5. As a result of mechanical movement of the x-ray radiator 1 in the direction of the arrow, a measuring field 6 is scanned, and a subject in the measuring field 6 is transirradiated by a fan-shaped x-ray beam from different directions. The fan plane of this x-ray beam proceeds perpendicular to the plane of the drawing. The detector elements 5a (and others) of the detector array 5 are all electrically connected to a computer 7, which calculates an x-ray shadowgraph of the subject in the measuring field 6 from the electrical output signals of the detector elements, corresponding to the intensity of the attenuated radiation thereon and effects the reproduction of the shadowgraph on a display monitor 8. The screen diaphragm 4 blanks out radiation which is not effective for generating the shadowgraphed image before that radiation reaches the subject. The screen diaphragm 4 can alternatively be movable, i.e., it can be adjustable in direction of the arrow together with the x-ray radiator 1, in which case a single diaphragm shaft is sufficient. The radiography apparatus constructed in accordance with the principles of the present invention can be incorporated in a computer tomography apparatus. The components of a computer tomography apparatus for explaining the interaction with the radiography apparatus of the invention are shown in FIG. 2. These components include the focus 2 of an x-ray radiator (not separately shown) and a CT detector array 9, which is curved on a arc centered on the focus 2. The CT detector 9 is composed of a row of individual detector elements. For preparing computer tomograms, the measuring unit consisting of the x-ray radiator with the focus 2 and the CT detector array 9 is rotated around a system axis 13 in the direction of the arrow 12. A computer 10 calculates a computer tomogram of an examined slice of a subject from the output signals of the detector elements of the CT detector array 9. A visual reproduction of this computer tomogram is displayed on a monitor 11. The detector array 5 for the production of x-ray shadowgraphs in accordance with the principles of the present invention is arranged perpendicularly to the CT detector array 9. The detector array 5 can be brought from a standby position to a position for preparing x-ray shadowgraphs, so that it does not represent a disturbing factor in the production of computer tomograms. The x-ray beam emanating from the focus 2 is gated using a diaphragm 14 for preparing x-ray shadowgraphs so that the detector array 5 is irradiated by a fan-shaped x-ray beam 15. For preparing computer tomograms, the diaphragm 14 gates the x-ray beam to produce a fan-shaped x-ray beam 16. The fan-shaped beam 16 is in a plane which is substantially perpendicular to the plane of the beam 15 used for preparing x-ray shadowgraphs. For preparing an x-ray shadowgraph, only the x-ray radiator having the focus 2 is mechanically moved, so that a measuring field is penetrated by the fan-shaped x-ray beam 15 from different directions, as explained in connection with FIG. 1. The detector elements of the detector array 5 thus generate output signals which, as shown in FIG. 1, are processed by a computer 7 to form an x-ray shadowgraph which can be reproduced on a display 8. In the embodiment of FIG. 3, a diaphragm 17 is provided which, in addition to gating the fan-shaped x-ray beam 16 for the production of computer tomograms, can also gate a fan-shaped x-ray beam 18 for generating x-ray shadowgraphs. The fan-shaped x-ray beam 18, like the x-ray beam 15 in the embodiment of FIG. 2, is disposed perpendicularly relative to the plane of the x-ray beam 16, however, in contrast to the beam 15 of FIG. 2, the beam 18 is disposed laterally next to the plane of the x-ray beam 16. Consequently, the detector array 5 for preparing x-ray shadowgraphs also lies laterally next to the CT detector array 9. This results in the avoidance of the need to mechanically move the detector array 5 into position before the production of x-ray shadowgraphs. The diaphragms 14 and 17 permit the gating of a fan-shaped x-ray beam 16 for the production of computer tomograms, and also permit gating, respectively, of the fan-shaped x-ray beams 14 and 18 proceeding in a plane perpendicularly to the plane in which the x-ray beam 16 is disposed. The diaphragm 14 or 17 can also be moved along a circular arc, around a rotational axis lying in the detector array 5. In this case, only one stationary diaphragm for gating a fan-shaped x-ray beam having a single diaphragm aperture is sufficient. Although modifications and changes may be suggested by those skilled in the art, it is the intention of the inventors to embody within the patent warranted hereon all changes and modifications as reasonably and properly come within the scope of their contribution to the art.
	description	1. Field of the Invention The present invention relates to a medical diagnostic imaging technique. 2. Description of the Related Art Recently, virtual reality technologies have been introduced in the medical field. For the surgical field, operation simulation has been developed, in which surgeons conduct a virtual operation on a trial basis, assuming various techniques and approaches based on the condition of a patient in a preoperative plan. In, for example, conducting endoscopic surgery or using an angiographic imaging apparatus which senses an X-ray fluoroscopic images of the blood flow in blood vessels in which a contrast medium has been injected and allows a doctor to observe and diagnose the image, as in Japanese Patent Laid-Open No. 2004-81569, an operator wearing a head mounted display conducts an operation or makes a diagnosis while observing both a catheter insertion portion and a fluoroscopic image. The above-described system using a virtual reality technology or a head mounted display is sufficiently effective for operation simulation that also serves as a practice or for training of new-fledged doctors. In a real operation, test, or diagnosis, the operator must be able to instantaneously observe the state or operative field of a patient when his/her condition has taken a sudden turn for the worse, or any trouble has occurred. That is, primary importance to the system is safety in an actual scene more than operability and convenience. However, if the patient's condition has taken a sharp turn for the worse, or trouble has occurred during diagnosis, the fluoroscopic image displayed on the head mounted display is obstructive. The present invention has been made in consideration of the above-described problem, and has as its object to provide a diagnostic imaging technique which ensures safety by setting the ratio of a fluoroscopic image and a field image that is a background image in accordance with a display condition and displaying a composite image of the field image and the fluoroscopic image while changing the display priority order in accordance with the display condition. According to one aspect of the present invention, there is provided a display control apparatus for controlling display of a radiograph to be displayed on a head mounted display, comprising: a generation unit adapted to generate an X-ray moving image by detecting X-rays that irradiate a subject; a setting unit adapted to, when displaying the X-ray moving image superimposed on a main image to be displayed on a display unit of the head mounted display, set a display ratio of the main image and the X-ray moving image in accordance with a display condition; an image composition unit adapted to generate a composite image by superimposing the X-ray moving image on the main image on the basis of the ratio set by the setting unit; a display processing unit adapted to display the composite image on the display unit of the head mounted display; and a viewpoint detection unit adapted to detect information about a viewpoint of a user who is wearing the head mounted display, wherein when the viewpoint detection unit detects that the viewpoint of the user exists in a display area of the X-ray moving image, the setting unit switches the ratio to display the X-ray moving image with a priority over the main image, and the image composition unit generates the composite image by superimposing the X-ray moving image on the main image on the basis of the ratio switched by the setting unit. According to the present invention, it is possible to provide a diagnostic imaging technique which ensures safety by setting the ratio of a fluoroscopic image and a field image. Further features of the present invention will become apparent from the following description of exemplary embodiments (with reference to the attached drawings). A preferred embodiment of the present invention will now be described in detail with reference to the accompanying drawings. The constituent elements described in the embodiment are merely examples. The technical scope of the present invention is defined by the scope of claims and is not limited by the following embodiment. (Arrangement of X-Ray Diagnostic Imaging System) FIG. 1 is a view for explaining the arrangement of an X-ray diagnostic imaging system (to be referred to as a diagnostic imaging system hereinafter). The diagnostic imaging system has a C arm 103 that hangs from a ceiling hanging unit 102. The ceiling hanging unit 102 hangs from the ceiling via a moving mechanism 101. The moving mechanism 101 can move in a plane (X- and Y directions) and position the ceiling hanging unit 102. The X-ray diagnostic imaging system functions as a radiograph display control system. The C arm 103 has, at its lower end, an X-ray tube 104 for irradiating a subject with X-rays. The C arm 103 has, as its upper end, an X-ray receiving unit 105 which receives a radiograph based on the X-rays emitted from the X-ray tube 104. The C arm 103 can rotate about a rotation axis 160 of the ceiling hanging unit 102. A subject 150 can be placed on a top 106. An examination table 107 can move the top 106 in the X direction. A head mounted display (to be referred to as an HMD hereinafter) 110 is a medical display control device the operator wears on the head. It is a see-through type HMD capable of observing both a radiographed moving image (fluoroscopic image) and the actual state of a patient. The see-through HMD 110 is usable in the technical field of virtual reality. The HMD 110 looks like a helmet or swimming goggles and is put on the head of an operator or the like. The HMD 110 includes an image input unit which inputs an image, an image display unit which displays an image, a viewpoint detection unit which detects the operator's viewpoint position, and a direction detection unit which detects the tilt of the operator's head. A display device 109 can display a sensed radiograph. A control unit 108 can control the overall diagnostic imaging system. (Internal Arrangement of HMD 110) There are an HMD of optical see-through type and an HMD of video see-through type. In the optical see-through type, external light directly reaches the eyes of the HMD wearer. Since a processed image is also displayed simultaneously, the HMD wearer sees the images as if they were superimposed on each other. In the video see-through type, external light does not directly reach the eyes of the wearer. For example, as shown in FIG. 3, a double-sided mirror 301 changes the direction of external light so that the light strikes an image sensor 302. An image to be presented to the HMD wearer is displayed on a display element 303 and visually recognized by him/her via the double-sided mirror 301. When an external image incident on the image sensor 302 is output to the display element 303, the HMD 110 functions as simple eyeglasses. The HMD 110 can display a processed diagnostic image superimposed on an external image on the display element 303. The HMD 110 according to this embodiment is preferably of a video see-through type which can receive an image actually seen by the wearer (operator) of the HMD 110 from the image sensor 302. The image received from the image sensor 302 is composited with a fluoroscopic image obtained by X-ray imaging using a method called alpha blending. Then, the composite image can be displayed the display element 303. (Functional Arrangement of Diagnostic Imaging System) The functional arrangement of the diagnostic imaging system will be described next with reference to FIG. 11. The same reference numerals as in the diagnostic imaging system shown in FIG. 1 denote the same constituent elements in FIG. 11. The X-ray tube 104 irradiates the subject 150 lying on the top 106 with X-rays. The X-ray receiving unit 105 receives the X-rays transmitted through the subject 150. An amplifier circuit (not shown) converts the X-rays (transmitted X-rays) transmitted through the subject 150 into an optical image. A TV camera converts the optical image into an analog signal. An A/D conversion unit 1104 converts the analog signal into a digital signal and transmits it to an image processing unit 1105. The image processing unit 1105 executes image processing such as contract and gamma characteristic conversion for the digital image signal received from the A/D conversion unit 1104 and stores the image processing result in a recording unit 1106 formed from, for example, a hard disk. The X-ray tube 104, X-ray receiving unit 105, A/D conversion unit 1104, and image processing unit 1105 can function as a generation unit which generates a fluoroscopic image of X-rays that have irradiated the subject 150. The image processing unit 1105 transmits the processed fluoroscopic image to an image composition unit 1107. The HMD 110 includes an image input unit 1201 which inputs a field image, an image display unit 1108 which displays a composite image generated by the image composition unit 1107, a viewpoint detection unit 1109 which detects the operator's viewpoint position, and a tilt detection unit 1200 which detects the tilt of the operator's head. The viewpoint detection unit 1109 can detect a point on a displayed image, which the operator (wearer) wearing the HMD 110 is looking at. The viewpoint detection unit 1109 can function as a determination unit which detects information concerning the viewpoint position and viewpoint movement of the head mounted display and determines, based on the detection result, whether to change the display condition. The tilt detection unit 1200 can detect the tilt of the head of the operator (wearer) who is wearing the HMD 110 by using, for example, a gyro sensor. The tilt detection unit 1200 can function as a determination unit which detects the tilt of the head mounted display and determines, based on the detection result, whether to change the display condition. The determination result based on the operator's viewpoint position detected by the viewpoint detection unit 1109 and the determination result based on the tilt of the operator's head detected by the tilt detection unit 1200 are input to a blending ratio setting unit 1202 to be described later. The image input unit 1201 receives an external field image that the wearer is actually seeing via the HMD 110 and transmits the received field image to the image composition unit 1107 to display a fluoroscopic image superimposed on the field image. An auxiliary device data read unit 1203 can read medical measurement data (to be referred to as measurement data hereinafter) 1204 of an auxiliary device used for diagnosis and operation. The auxiliary device data read unit 1203 has a function of receiving measurement data of, for example, a sphygmomanometer, electrocardiograph, or contrast medium injector. The auxiliary device data read unit 1203 can function as a determination unit which analyzes whether the measurement data 1204 falls within a normal range with respect to a reference value and determines, based on the analysis result, whether to change the display condition. The determination result based on the measurement data 1204 read by the auxiliary device data read unit 1203 is sent to the blending ratio setting unit 1202. A voice input unit 1205 can input (voice-input) the voice of the operator who is wearing the HMD 110 as voice information. The voice input unit 1205 can function as a determination unit which determines, based on comparison between voice input and reference voice information, whether to change the display condition. The determination result by the voice input unit 1205 is sent to the blending ratio setting unit 1202. A word to be used as a key and a voice level reference value are registered in the voice input unit 1205 in advance. The voice input unit 1205 determines whether a voice-input word matches the registered word, or whether the voice level of the input voice exceeds the reference value. The voice input unit 1205 can determine based on this determination whether to change the display condition. The voice input unit 1205 is separated from the HMD 110 in the functional arrangement shown in FIG. 1. However, the HMD 110 may include the voice input unit 1205. When displaying a fluoroscopic image superimposed on a field image of the head mounted display, the blending ratio setting unit 1202 sets the display ratio of the field image and the fluoroscopic image in accordance with the display condition. This ratio is called a blending ratio. The blending ratio setting unit 1202 sets the blending ratio on the basis of the determination results from the viewpoint detection unit 1109, tilt detection unit 1200, auxiliary device data read unit 1203, and voice input unit 1205 to display the field image and the fluoroscopic image in a different display priority order. In this embodiment, a fluoroscopic image is superimposed on a field image that is the main image. However, a measurement screen of an auxiliary device may be displayed as the main image. A blending ratio storage unit 1206 can store a plurality of blending ratio settings corresponding to display conditions. The blending ratio storage unit 1206 stores various kinds of information corresponding to display conditions, including a fluoroscopic image blending ratio in an initial display or normal mode, and a display ratio in an emergency mode. The blending ratio setting unit 1202 can refer to the information in the blending ratio storage unit 1206, read out a blending ratio corresponding to a display condition, and set it in the image composition unit 1107. The image composition unit 1107 can generate a composite image by superimposing an X-ray fluoroscopic image on a field image received by the image input unit 1201 based on the blending ratio set by the blending ratio setting unit 1202. The image composition unit 1107 inputs the generated composite image to the image display unit 1108 of the HMD 110. Upon receiving the composite image from the image composition unit 1107, the HMD 110 displays it on the image display unit 1108. (Process of Diagnostic Imaging System Based on Viewpoint Detection) The sequence of the process of the diagnostic imaging system based on viewpoint detection will be described next with reference to the flowchart in FIG. 2. The blending ratio setting unit 1202 can set a blending ratio based on the operator's viewpoint position, movement (tilt) of the operator's head, voice input information, and the measurement data 1204 read by the auxiliary device data read unit 1203. In the process shown in FIG. 2, the blending ratio setting unit 1202 sets a blending ratio in the image composition unit 1107 based on the information of operator's viewpoint position detected by the viewpoint detection unit 1109. The image composition unit 1107, viewpoint detection unit 1109, and blending ratio setting unit 1202 execute the process in FIG. 2 under the overall control of the control unit 108 of the diagnostic imaging system. First, to prepare for X-ray irradiation, the control unit 108 adjusts the positions of the C arm 103 and the top 106 and aligns the subject 150 as a diagnosis target. In step S201, X-ray irradiation and imaging start. The X-ray tube 104 starts emitting X-rays. The X-ray receiving unit 105 receives the X-rays transmitted through the subject 150. When the X-ray receiving unit 105 receives the X-rays (transmitted X-rays) transmitted through the subject 150, the amplifier circuit (not shown) described with reference to FIG. 11 converts the transmitted X-rays into an optical image. The TV camera converts the optical image into an analog signal. The A/D conversion unit 1104 converts the analog signal into a digital signal. The image processing unit 1105 executes image processing for the digital signal. A processed fluoroscopic image is input to the image composition unit 1107. In step S202, the blending ratio setting unit 1202 reads out blending ratios stored in the blending ratio storage unit 1206 in advance. For example, the blending ratio setting unit 1202 sets a fluoroscopic image blending ratio α1 in the initial display or normal mode and a display ratio α2 in the emergency mode to α1=A1, and α2=A2 (0≦A1≦1, 0≦A2≦1) The blending ratio setting unit 1202 inputs the set blending ratios to the image composition unit 1107. The blending ratio setting unit 1202 can set the blending ratios in the image composition unit 1107 based on information transmitted from the viewpoint detection unit 1109, tilt detection unit 1200, voice input unit 1205, and auxiliary device data read unit 1203. In step S203, the image input unit 1201 receives an external image (field image) actually seen by the operator and inputs the field image to the image composition unit 1107 as a background image. The image composition unit 1107 can display a moving image of, for example, an operative field or catheter insertion portion as the background image (field image). The image composition unit 1107 generates a composite image by compositing (superimposing) the fluoroscopic image obtained by X-ray imaging with the background image (field image) at the blending ratio (=α1) in the normal mode, which is read out in step S202. The image display unit 1108 displays the composite image in a superimposed manner. To display the superimposed images, a method called alpha blending is usable. The pixel output format of the image composition unit 1107 contains an opacity A (alpha value) (0≦A≦1) in addition to three primary colors RGBA. The image composition unit 1107 can control generation of the composite image of the background image (field image) and the X-ray fluoroscopic image in accordance with the value of the opacity A. Assume that the RGB values of a pixel of the background image (field image) are (R1,G1,B1), the RGB values of a pixel of the fluoroscopic image are (R2,G2,B2), and the opacity value is A. In this case, the RGB values of the composite image are given by(R1×(1−A)+R2×A, G1×(1−A)+G2×A, B1×(1−A)+B2×A) (1) Hence, when the images are composited using the blending ratio (A=α1) in the normal mode, Expression (1) is rewritten to(R1×(1−α1)+R2×α1, G1×(1−α1)+G2×α1, B1×(1−α1)+B2×α1) (2) When the blending ratio α1=1, the RGB values of the composite image equal the RGB values (R2,G2,B2) of the fluoroscopic image. The operator cannot see the background image (field image) through the fluoroscopic image at all. FIG. 7 is a view showing an example of display of a fluoroscopic image and a background image (field image). When a background image 701 and a fluoroscopic image 702 are composited using the blending ratio α1=1, the fluoroscopic image 702 is displayed on the near side, and the background image 701 is invisible. The image display unit 1108 of the HMD 110 displays the image composited by the image composition unit 1107. In step S204, the viewpoint detection unit 1109 detects the operator's viewpoint position. In step S205, the viewpoint detection unit 1109 determines, based on the detection result of the operator's viewpoint position, whether the operator's viewpoint has gone out of the area of the X-ray fluoroscopic image. If the operator's viewpoint exists in the area of the X-ray fluoroscopic image (e.g., within the range of the fluoroscopic image 702 in FIG. 7) without going out of the area (NO in step S205), the process returns to step S204 to cause the viewpoint detection unit 1109 to repeatedly detect the operator's viewpoint position. If it is determined in step S205 that the operator's viewpoint has gone out of the area of the fluoroscopic image, and the time required for the viewpoint movement is shorter than a predetermined reference time (YES in step S205), the process advances to step S206. The viewpoint detection unit 1109 can measure the coordinates of the operator's viewpoint position and the viewpoint measurement time. The viewpoint detection unit 1109 can use a timer (not shown) to measure the measurement time. FIG. 8 is a view for explaining movement of the operator's viewpoint. The viewpoint detection unit 1109 can periodically detect the position of the viewpoint of the operator who is wearing the HMD 110. In FIG. 8, viewpoints 801, 802, . . . , and 807 indicate viewpoint positions detected by the viewpoint detection unit 1109. The position coordinates of the respective viewpoints are represented by the viewpoint 801 (X1,Y1), viewpoint 802 (X2,Y2), . . . , and viewpoint 807 (X7,Y7). The viewpoint detection times are represented by t1, t2, . . . , and t7. The viewpoint detection unit 1109 determines the times t1, t2, t3, . . . , and t7 by referring to the timer upon detecting the position coordinates. The time elapses in the order of t1→t2→t3→ . . . →t7. Referring to FIG. 8, the viewpoint 804 (X4,Y4) is detected outside the area of the fluoroscopic image 702. The viewpoint 807 (X7,Y7) is measured when the viewpoint has returned inside the area of the fluoroscopic image 702. Examine the viewpoints 803 and 804. The viewpoint detection unit 1109 calculates the moving time (t4−t3) from the viewpoint 803 in the area of the fluoroscopic image 702 to the viewpoint 804 outside the area of the fluoroscopic image 702 and compares the time with the reference time. If the viewpoint detection unit 1109 determines in step S205 that the moving time (t4−t3) is shorter than the reference time (YES in step S205), the process advances to step S206. On the other hand, if the viewpoint detection unit 1109 determines that the moving time (t4−t3) is longer than the reference time (NO in step S205), the process returns to step S204 to cause the viewpoint detection unit 1109 to repeatedly detect the viewpoint position. The viewpoint detection unit 1109 determines whether each detected viewpoint exists within the fluoroscopic image area. When the viewpoint has gone out of the fluoroscopic image area, the viewpoint detection unit 1109 compares the moving time with the reference time. When the moving time is shorter than the reference time, the viewpoint detection unit 1109 determines emergency and inputs identification information representing the emergency to the blending ratio setting unit 1202. The blending ratio setting unit 1202 can switch the blending ratio setting based on the identification information received from the viewpoint detection unit 1109. The blending ratio setting unit 1202 switches the blending ratio α1 set for the fluoroscopic image in the initial display or normal mode to the blending ratio α2 in the emergency mode and sets it in the image composition unit 1107. In step S206, the image composition unit 1107 receives the setting of the blending ratio α2 in the emergency mode and composites the fluoroscopic image with the background image (field image) based on the set blending ratio α2 in the emergency mode. The images are composited using the above-described alpha blending method. When the RGB values of a pixel of the background image (field image) are represented by (R1,G1,B1), the RGB values of a pixel of the fluoroscopic image are represented by (R2,G2,B2), and the blending ratio in the emergency mode is represented by α2, the RGB values of the composite image are given by(R1×(1−α2)+R2×α2, G1×(1−α2)+G2×α2, B1×(1−α2)+B2×α2) (3) In step S207, the image display unit 1108 of the HMD 110 displays the composite image generated by the image composition unit 1107 in step S206. Upon detecting an operator's steady gaze on the fluoroscopic image or the background image (field image) for a predetermined time, the viewpoint detection unit 1109 can determine that the state has returned from the emergency mode to the normal mode. The viewpoint detection unit 1109 inputs, to the blending ratio setting unit 1202, identification information representing that the state has returned to the normal mode. The blending ratio setting unit 1202 switches the blending ratio α2 in the emergency mode to the blending ratio α1 in the normal mode and sets it in the image composition unit 1107 to change the image display in the emergency mode to that in the normal mode. FIG. 9 is a view showing an example of an image displayed on the HMD 110 in case of emergency. The operator can see a background image 901 including the state of the patient and the monitors of apparatuses through a fluoroscopic image 902. This allows the operator to more accurately confirm the situation without taking off the HMD 110. (Process of Diagnostic Imaging System Based on Head Tilt Detection Amount) The sequence of the process of the diagnostic imaging system based on detection of the movement (tilt) of the head of the operator who is wearing the HMD 110 will be described next with reference to the flowchart in FIG. 4. The image composition unit 1107, tilt detection unit 1200, and blending ratio setting unit 1202 execute the process in FIG. 4 under the overall control of the control unit 108 of the diagnostic imaging system. In steps S401 to S403 of FIG. 4, the same process as in steps S201 to S203 of the flowchart in FIG. 2 is executed. In step S404, the tilt detection unit 1200 detects the movement (tilt) of the head of the operator who is wearing the HMD 110. Using, for example, a gyro sensor as a tilt detection mechanism, the tilt detection unit 1200 can detect the movement (tilt) of the head of the operator who is wearing the HMD 110 as an amount of tilt in an action of, for example, moving the head from side to side or up and down. In step S405, the tilt detection unit 1200 compares the detection result (tilt amount) of the movement (tilt) of the head of the operator who is wearing the HMD 110 with a predetermined tilt reference value. If the detection result (tilt amount) is equal to or more than the tilt reference value, the tilt detection unit 1200 determines an emergency and inputs identification information representing the emergency to the blending ratio setting unit 1202. The blending ratio setting unit 1202 can switch the blending ratio setting based on the identification information received from the tilt detection unit 1200. The blending ratio setting unit 1202 switches the blending ratio α1 set for the fluoroscopic image in the initial display or normal mode to the blending ratio α2 in the emergency mode and sets it in the image composition unit 1107. In step S406, the image composition unit 1107 receives the setting of the blending ratio α2 in the emergency mode and composites the fluoroscopic image with the background image (field image) based on the set blending ratio α2 in the emergency mode. The images can be composited using the above-described alpha blending method. When the RGB values of a pixel of the background image (field image) are represented by (R1,G1,B1), the RGB values of a pixel of the fluoroscopic image are represented by (R2,G2,B2), and the blending ratio in the emergency mode is represented by α2, the RGB values of the composite image are given by Expression (3), as described above. In step S407, the image display unit 1108 of the HMD 110 displays the composite image generated by the image composition unit 1107 in step S406. Upon detecting another head tilt (e.g., moving the head back and forth or from side to side) as a trigger, the tilt detection unit 1200 can determine that the state has returned from the emergency mode to the normal mode. The tilt detection unit 1200 inputs, to the blending ratio setting unit 1202, identification information representing that the state has returned to the normal mode. The blending ratio setting unit 1202 switches the blending ratio α2 in the emergency mode to the blending ratio al in the normal mode and sets it in the image composition unit 1107 to change the image display in the emergency mode to that in the normal mode. (Process of Diagnostic Imaging System Based on Voice Input) The sequence of the process of the diagnostic imaging system based on voice input will be described next with reference to the flowchart in FIG. 5. The image composition unit 1107, voice input unit 1205, and blending ratio setting unit 1202 execute the process in FIG. 5 under the overall control of the control unit 108 of the diagnostic imaging system. In steps S501 to S503 of FIG. 5, the same process as in steps S201 to S203 of the flowchart in FIG. 2 is executed. In step S504, the voice input unit 1205 starts a voice input process. In step S505, the voice input unit 1205 determines whether the voice-input word matches a word that is registered in advance as a key. If the voice input unit 1205 determines that the voice-input word does not match the word registered in advance (NO in step S505), the process returns to step S504. If the voice input unit 1205 determines in step S505 that the voice-input word matches the word registered in advance (YES in step S505), the process advances to step S506. In step S506, the voice input unit 1205 compares the voice level of the input word with a predetermined voice level reference value. If the voice level of the input word is equal to or more than the voice level reference value, the voice input unit 1205 determines emergency (YES in step S506). The voice input unit 1205 inputs identification information representing the emergency to the blending ratio setting unit 1202. If it is determined in step S506 that the voice level of the input word is less than the voice level reference value (NO in step S506), the process returns to step S504 to repeat the voice input process. The blending ratio setting unit 1202 can switch the blending ratio setting based on the identification information received from the voice input unit 1205. The blending ratio setting unit 1202 switches the blending ratio α1 set for the fluoroscopic image in the initial display or normal mode to the blending ratio α2 in the emergency mode and sets it in the image composition unit 1107. In step S507, the image composition unit 1107 receives the setting of the blending ratio α2 in the emergency mode and composites the fluoroscopic image with the background image (field image) based on the set blending ratio α2 in the emergency mode. The images can be composited using the above-described alpha blending method. When the RGB values of a pixel of the background image (field image) are represented by (R1,G1,B1), the RGB values of a pixel of the fluoroscopic image are represented by (R2,G2,B2), and the blending ratio in the emergency mode is represented by α2, the RGB values of the composite image are given by Expression (3), as described above. In step S508, the image display unit 1108 of the HMD 110 displays the composite image generated by the image composition unit 1107 in step S507. Upon detecting another voice input that satisfies the references (S505 and S506), the voice input unit 1205 can determine that the state has returned from the emergency mode to the normal mode. The voice input unit 1205 inputs, to the blending ratio setting unit 1202, identification information representing that the state has returned to the normal mode. The blending ratio setting unit 1202 switches the blending ratio α2 in the emergency mode to the blending ratio α1 in the normal mode and sets it in the image composition unit 1107 to change the image display in the emergency mode to that in the normal mode. (Process of Diagnostic Imaging System Based on Measurement Data 1204) The sequence of the process of the diagnostic imaging system based on the measurement data 1204 read by the auxiliary device data read unit 1203 will be described next with reference to the flowchart in FIG. 6. The image composition unit 1107, auxiliary device data read unit 1203, and blending ratio setting unit 1202 execute the process in FIG. 6 under the overall control of the control unit 108 of the diagnostic imaging system. In steps S601 to S603 of FIG. 6, the same process as in steps S201 to S203 of the flowchart in FIG. 2 is executed. In step S604, the auxiliary device data read unit 1203 starts reading the medical measurement data 1204 associated with the subject 150 from a medical auxiliary device. A medical auxiliary device indicates a medical device necessary for a test, diagnosis, or operation, including an electrocardiograph and a sphygmomanometer. FIG. 10 is a view showing an electrocardiographic wave as an example of the measurement data 1204. The P wave in FIG. 10 indicates the atrial activity. The QRS wave indicates the venticular systole. The T wave indicates the process of returning the contracted heart to the initial state. It is possible to estimate an abnormality of the heart by comparing the waveform and rhythm based on the measurement data 1204 with a normal waveform. For example, an irregularity in the RR interval indicates fluctuations in the rhythm of heart beat. The rise and fall of the waveform in the ST interval are key factors mainly in determining an ischemic heart disease. In step S605, under the control of the control unit 108, the auxiliary device data read unit 1203 compares the measurement data 1204 read from the auxiliary device with a medical data reference value that is set in advance as normal medical data in each auxiliary device. The control unit 108 and the auxiliary device data read unit 1203 can function as an analysis unit which analyzes whether the measurement data 1204 falls within a normal range with respect to the medical data reference value. Under the control of the control unit 108, if the difference between the read measurement data 1204 and the medical data reference value is equal to or larger than a predetermined value, the auxiliary device data read unit 1203 determines that the measurement data 1204 is abnormal (emergency). The auxiliary device data read unit 1203 inputs identification information representing the emergency to the blending ratio setting unit 1202. The blending ratio setting unit 1202 can switch the blending ratio setting based on the identification information received from the auxiliary device data read unit 1203. The blending ratio setting unit 1202 switches the blending ratio α1 set for the fluoroscopic image in the initial display or normal mode to the blending ratio α2 in the emergency mode and sets it in the image composition unit 1107. In step S606, the image composition unit 1107 receives the setting of the blending ratio α2 in the emergency mode and composites the fluoroscopic image with the background image (field image) based on the set blending ratio α2 in the emergency mode. The images can be composited using the above-described alpha blending method. When the RGB values of a pixel of the background image (field image) are represented by (R1,G1,B1), the RGB values of a pixel of the fluoroscopic image are represented by (R2,G2,B2), and the blending ratio in the emergency mode is represented by α2, the RGB values of the composite image are given by Expression (3), as described above. In step S607, the image display unit 1108 of the HMD 110 displays the composite image generated by the image composition unit 1107 in step S606. Upon detecting that the difference between the measurement data 1204 and the medical data reference value is smaller than the predetermined value, the auxiliary device data read unit 1203 can determine that the state has returned from the emergency mode to the normal mode. The auxiliary device data read unit 1203 inputs, to the blending ratio setting unit 1202, identification information representing that the state has returned to the normal mode. The blending ratio setting unit 1202 switches the blending ratio α2 in the emergency mode to the blending ratio α1 in the normal mode and sets it in the image composition unit 1107 to change the image display in the emergency mode to that in the normal mode. In the above description, the blending ratio setting unit 1202 can flexibly set the blending ratio of the diagnostic image and the background image (field image) in the initial display mode in accordance with the application purpose. The blending ratio setting unit 1202 can arbitrarily set the diagnostic image blending ratio within the range of 0.0 to 1.0. For example, when injecting a contrast medium in a blood vessel using a catheter, and observing and diagnosing the blood flow on the basis of an X-ray fluoroscopic image, the blending ratio setting unit 1202 sets the blending ratio in the initial (normal) mode to α1=1, and the blending ratio in the emergency mode to α2=0.3. When the blending ratio α1=1, the RGB values of the composite image equal the RGB values (R2,G2,B2) of the fluoroscopic image, as described with reference to Expression (2). The operator cannot see the background image (field image) through the fluoroscopic image at all. When the blending ratio α1=1 is set, the image composition unit 1107 can control the display of the composite image by giving a higher priority to the X-ray fluoroscopic image. When the blending ratio α2=0.3, the image composition unit 1107 generates a composite image by compositing the background image (field image) with the X-ray fluoroscopic image by a ratio of 7:3. The image composition unit 1107 can also control the display of the composite image by giving a higher priority to the background image (field image) so that the operator can observe the patient state or the field around the hands of his/her own in case of emergency. On the other hand, for, for example, a heart surgery, the blending ratio setting unit 1202 sets α1=0.3 contrary to a test or the like. It is therefore possible to display the X-ray fluoroscopic image with a priority over the background image (field image) in the initial (normal) mode. In the initial (normal) mode, the background image (field image) of, for example, an operative field is easy to see. If an abnormality is detected, the blending ratio setting unit 1202 switches the blending ratio setting. In case of emergency, the blending ratio setting unit 1202 sets α2=1 so that an electrocardiographic indicator 1250 of the measurement data 1204 can be displayed as a diagnostic image, as shown in FIG. 12, to quickly confirm the cause of the abnormality. It is possible to provide a diagnostic imaging technique which ensures safety by setting the ratio of a fluoroscopic image and a field image that is a background image in accordance with a display condition and displaying a composite image of the field image and the fluoroscopic image while changing the display priority order in accordance with the display condition. That is, according to the embodiment, it is possible to provide a diagnostic imaging technique which ensures safety by controlling the composition ratio of a field image and a fluoroscopic image to be displayed on a head mounted display. While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions. This application claims the benefit of Japanese Patent Application No. 2007-123892, filed May 8, 2007, which is hereby incorporated by reference herein in its entirety.
	summary
	description	The present invention relates to imagers that use one or more laser beams to expose material, e.g., for computer-to-plate (CTP) imaging to expose a printing plate. Back-reflection is a known problem with laser-based computer-to-plate imagers exposing a film or photopolymer plate. Note that imagers for imaging plates are also commonly called imagesetters. Many state of the art imagers are designed to process a wide variety of different plate types, not only from different vendors but also used for very different technical purposes. For example, Cyrel™ digital imagers made by Esko-Graphics NV of Gent Belgium, may be used for imaging film, imaging conventional polymer flexographic plates, and also imaging metal-backed polymer plates. Any one of these materials is referred to as a plate herein. Different types of plates typically might use different mechanisms to hold a plate onto the drum. Metal-backed plates for example, are preferably held onto the drum by permanent magnets embedded into the drum surface. Film plate and conventional computer-to-plate (CTP) polymer plates are preferably held onto the drum surface by vacuum, e.g., by vacuum applied from the inside of the drum to vacuum grooves and/or holes on the drum surface. In many ablative plate and film imagers, problems arise from laser light not being absorbed by the layer of laser-light-sensitive ablatable material, called the “ablatable-layer” herein. This unabsorbed light can be reflected by the drum surface back to the rear side of the plate or film. This can cause several problems. A first problem is that back-reflected light can start undesired ablation or uncontrolled vaporization of the remaining ablatable-layer on the front side of the plate or film. A second problem is that the grooves and/or magnets on the surface of the drum, that is, variations in the surface property of the drum will affect the amount of back-reflected light either because of the variations in the drum surface absorption or because of variations relative amounts of reflected light and scattered light. As an example of the second problem, suppose, for example, that image data is used that in a properly exposed plate would generate an image having a constant screen ruling. Suppose further that the grooves and/or magnets on the surface of the drum are regular structures. These structures cause changes of the back-reflected light, and as a result, instead of the image having a constant screen ruling, there may be, in addition, images that are similar to the regular variations on the drum surface caused by the grooves and/or magnets. One common workaround is to use a laser whose laser radiation has high divergence. One example of such a laser is a multi mode laser diode. In such a case, the light from the laser will diverge so strongly that the back-reflected beam is not likely to have sufficient energy density to cause any ablation or other effect on the ablatable layer of the plate. This approach however has the disadvantage that the depth of focus for such a laser beam is very small. Consequently, the distance between any focusing optics used to focus the beam, and the plate surface has to be accurately maintained at a constant level, either by use of high mechanical accuracy or by an automatic focusing systems. In either case, the solution is relatively expensive. Another solution is to use a use a drum whose surface is made from a material that absorbs radiation well. Unfortunately, most good absorbing materials such as black paint or anodized aluminium, might be, and likely will be ablated or discolored if exposed to a laser beam, so in time, the radiation absorbing property will be significantly reduced. It is a general object of the present invention to overcome or ameliorate at least one disadvantage of the prior art, or to provide a useful alternative. One particular embodiment includes a method comprising exposing a plate on a support surface of an imager using one or more laser beams, the exposing while there is a metallic screen structure located on the support surface between the plate and the support surface such that the amount of back-reflected radiation is reduced compared to the plate being placed directly on the support structure with no screen between the plate and support surface. One embodiment includes an apparatus comprising: a base structure including a support surface of an imager that uses one or more laser beams to expose a plate, the support surface configured to support a plate thereon; and a metallic screen structure located on the support surface between the plate and the support surface such that the amount of back-reflected radiation is reduced during imaging of the plate using the imager compared to the plate being placed directly on the support structure with no screen between the plate and support surface. In one embodiment, the screen structure is made of a metallic material that is relatively resistant to laser radiation in the range energy densities that would occur at the rear side of a plate during the imaging if no metallic screen structure was located on the support surface. In one embodiment, the imager is a drum imager including a drum, and wherein the support surface is the surface of the drum. In one embodiment, the imager is a flatbed imager and the support surface is the relatively flat surface of the flatbed imager. In one embodiment, the plate is metal-backed plate, and the support surface has one or more magnetic structured configured to help keep the metal-back plate on the surface, and wherein the metallic screen structure includes a magnetizable material such that the plate is maintainable on the combination of the support surface and the metallic screen structure thereon. In one embodiment, the support surface has one or more vacuum grooves and/or holes to which a vacuum is applicable, and the screen structure has sufficient relative permeability to air, such that when a vacuum is applied to the vacuum grooves and/or holes, the plate is maintainable on the combination of the support surface and the metallic screen structure thereon. Described herein is a method and an apparatus that is operative to ensure a relatively low level of back-reflected laser radiation during exposure of a plate in a computer-to-plate imager that uses one or more laser beams for the exposure. Embodiments of the invention are applicable to both drum imagers and flatbed imagers. The description, however, is mostly of an embodiment for use in an external drum imager. How to modify for a flatbed imager would be clear and straightforward to one of ordinary skill in the art. FIG. 1A shows in simplified form a perspective view of one embodiment of an external drum imager 100, e.g., a computer-to-plate exposing imager that can include an embodiment of the present invention. The imager 100 includes a substantially cylindrically shaped drum 105 that is rotatable about an axis 113. The drum has a support surface on which a plate is placeable. The drum 105 and its support surface 103 is shown with a plate 107 wrapped around the drum's support surface 103. The imager 100 includes a laser and optical system, shown in simplified form as 109, generating a laser beam 111 that is modulated by image data provided by a computer (not shown). Many of the elements of the imager are not included in order to simplify illustrating the imager 100. As the drum 105 is rapidly rotated with the plate 107 on the surface 103 of the drum sleeve 105, the laser beam moves in a transverse (fast scan) direction 115 relative to the drum surface and this generates one or more exposed circumferential lines in the transverse direction perpendicular to the direction of the axis 113 of rotation. At the same time in one embodiment, the laser beam moves in the longitudinal (slow-scan) direction 116 parallel to the axis of rotation 113. Such exposing is commonly known for external drum scanners. In one embodiment, the drum 105 includes a set of vacuum grooves 119, with in one version, each groove forming a circular track around the circumference of outer surface of the drum 105. Other versions have the vacuum grooves arranged differently, and in all versions, the vacuum grooves, if present, are arranged to help maintain a plate on the outer surface by applying suction to the grooves. In another embodiment, vacuum holes rather than grooves are used. In yet another embodiment, a combination of grooves and holes is used. In one embodiment, the drum includes permanent magnets 117 embedded into the drum surface in order to help maintain a metal-backed plate on the outer surface. FIG. 1B shows in simplified form a perspective view of an alternate embodiment of an imager, this imager 150, e.g., a computer-to-plate exposing imager being a flatbed imager 150 that can include an embodiment of the present invention. The imager 150 includes a support structure 155 having a substantially flat support surface 153 on which a plate is placeable, such a structure 155 shown with a plate 157 on the surface 153. The imager 150 includes a laser and optical system in combination with a modulation system generating a laser beam 161 that is modulated by image data provided by a computer (not shown). As in FIG. 1A, many of the elements of the imager are not included in order to simplify illustrating the imager 150. A mechanism, either in the form of a rotating polygon, or a holographic system is used to case the laser beam to generate exposed lines in the transverse direction 165 substantially perpendicular to a longitudinal direction 166. The plate and beam are slowly moved relative to each other in the longitudinal direction 166. Such exposing is commonly known for flatbed scanners. The support surface 153 may also include a set of vacuum grooves and/or vacuum holes (not shown) arranged to help maintain a plate on the surface by applying suction to the grooves, and may further have a set of permanent magnets (not shown). The remainder of the description will be mostly for the drum scanner, e.g., as shown in FIG. 1A, and those in the art will understand how to modify the description for the flatbed configuration of FIG. 1B. Internal drum imagers also are known, and an embodiment of the invention also may be applicable to such an imager. FIG. 2 shows in simplified and enlarged form a cross-section near the support surface of an imaging drum or flatbed scanner. Suppose this is the surface 103 of the drum 105 of the drum scanner of FIG. 1A near the edge of the plate. Note that for simplicity, no curvature is shown. The plate 107 is assumed to be a polymer plate with a layer 203 of ablatable material. The plate is shown on the support surface 103 of the drum. The laser beam 111 is shown moving on the transverse (fast) direction 115 as a result of rotation of the drum. After traversing the cross-section of the plate, some of the beam 111 is back-reflected to back-reflected beams 205 from the surface 103, and as shown, some of this may expose the back of the ablatable material 203. It is desired to reduce or eliminate the back-reflected light 205 that can hit the back of the ablatable material 203. One embodiment of the invention is shown in the flowchart of FIG. 5 and includes in 503 attaching or placing a metallic screen structure on the support surface of the imager; and in 505 exposing a plate on the support surface of the imager using one or more laser beams while there is the metallic screen structure located on the support surface between the plate and the support surface, such that the amount of back-reflected radiation is reduced compared to the plate being placed directly on the support structure with no screen between the plate and support surface. The screen structure is made of a metallic material that is relatively resistant to laser radiation in the range energy densities that would occur at the rear side of a plate during the imaging if no metallic screen structure was located on the support surface Another embodiment of the invention includes the support surface of the imager and a metal screen in sheet form that is modified to be on the support surface 103 of the imager, e.g., surface 103 of drum 105. FIG. 3A shows a substantially cylindrically shaped sleeve 301 made of a metal screen material and configured to fit over the imaging drum, e.g., drum 105 on the support surface 103. FIG. 3B shows the support surface 103 of drum 105 with the embodiment of the sleeve 301 of screen material on the surface 103. The screen material is also configured to be relatively permeable to air so that covering vacuum groves or holes such as grooves 119 does not substantially reduce the attractive forces of the vacuum to the plate. Experiments were performed using a sleeve 301 made from off-the shelf metal screen originally designed for another purpose—for rotary screen textile printing. Manufacturers of such screen material include Stork Prints B.V. of Boxmeer, the Netherlands, Saxon Screens Rotationsschablonen GmbH of Frankenberg, Germany; Saueressig GmbH+Co. of Vreden, Germany, and Rothtec Engraving Corporation, New Bedford, Mass., USA. Such screens are typically made of nickel or a nickel alloy that the inventors have found is sufficiently resistant to laser radiation in moderate energy densities as would typically occur at the rear side of a polymer plate or film during exposure as a result of back-reflected radiation. Such screens have been found by the inventors to easily be attracted by the magnetic forces of a drum equipped with magnets such as magnets 117. Furthermore, the inventors found that such screen material is very permeable to air. For example, in some embodiments, the screen material has rhombic structures, and in other embodiments, honeycomb-like grid structures. The relative permeability to air makes it possible to cover vacuum groves or holes such as grooves 119 without substantially reducing the attractive forces of the vacuum to the plate. One embodiment the screen structure includes a woven metallic fabric. In another embodiment, the screen structure is made using a galvanic process. While off-the shelf screens manufactured for other purposes are usable, the inventors found that there are some properties that are even more desirable to reduce unwanted ablation by back-reflected laser radiation. One property is that the holes are not too wide so that the screen sufficiently reduces the back-reflected laser light during exposure. The inventors carried out initial tests with 60 holes per inch and 125 holes per inch and these worked well. Mesh of up to 200 holes per inch work sufficiently well. Typically, a screen with between 110 and 140 holes per inch is used. Another property is relative permeability to air. The inventors have found that screens with a relative open area of approximately 25 to approximately 50% of the overall area are suitable, at a mesh range of between 60 and 200 holes per inch work sufficiently well. Another property is relative roughness in order to reduce backscatter from the screen itself. The undesired effects of backscatter are based mainly on reflection. FIG. 4A shows a perspective view including a cross-section through the grid of one rotary screen 403 on the support surface 103. The top surface 405 of the screen has a relatively large area parallel to the plate surface. FIG. 4A shows four example incident beams 411, 413, 415, and 417, and each incident beam's respective resulting reflected beam 412, 414, 416, and 418, respectively. As can be seen, because of the top surface 405 having a significant area parallel to the plate, the reflected beams 412, 416, and 418 are reflected straight back (shown almost parallel to the respective incident beam but at a slight angle in FIG. 4A for illustrative purpose) either from the top surface 405 or the drum surface 103. Such a screen allows a significant amount of light to be reflected back to the plate surface. FIG. 4B shows a cross section of an improved screen 421. The shape of the screen 421 is slightly modified from that of the screen 403 of FIG. 4A in a way that the main part of oncoming light is more or less scattered in various directions. In particular, the sides of walls of holes are relatively curved, e.g., more than the case of FIG. 4A in order to direct more of the incoming radiation into different directions. The flat part on top of the grid is also curved for the same reason and small compared to the structure of FIG. 4A. That is, the screen structure has a structure closest to the back of the plate and parallel to the support surface that is relatively small. These properties result in a reduction of the direct back-reflection of the laser radiation propagating towards the surface of the drum. More of the radiation is reflected in a diffuse manner instead of being reflected in the direction of origin as is the case with the screen of FIG. 4A. Furthermore, the opening between the bars has become smaller reducing the area of the drum surface which can directly reflect the incoming light, even though the % of the screen is the same. Consider again the four example incident beams 411, 413, 415, and 417, and each incident beam's respective resulting reflected beam 422, 424, 426, and 418, respectively. Reflected beams 422 and 426 are now less likely to cause a problem than the corresponding reflected beams 412 and 416 of FIG. 4A. Reflected beam 418 could be problematic in both cases, being through the opening and from the support surface 103, and reflected beams 414 and 424 are not likely to cause back-reflection problems in both cases. As can be seen, because of the top surface 405 having a significant area parallel to the plate, the reflected beams 412, 416, and 418 are reflected straight back (shown almost parallel to the respective incident beam but at a slight angle in FIG. 4A for illustrative purpose). Such a structure as shown in FIG. 4B can be easily obtained from a structure such as shown in FIG. 4A by using a galvanic manufacturing process as is commonly used for nickel screen sleeves for textile printing. One embodiment uses a 125 holed per inch screen made by a galvanic process to have relatively curved sides and relatively little flat area on the top surface. Those in the art will be familiar with many galvanic processes. One such process includes: 1. A copper cylinder being covered with an opaque material, e.g., a black ink-like material. 2. In a laser engraving machine, an image of a honeycomb-like structure in the size of the desired mesh being ablated from the cylinder. 3. In a galvanic solvent, nickel is accumulated to the areas on the copper cylinder revealed by the engraving process. 4. After the nickel screen which now has been built around the copper cylinder has reached a required thickness, the nickel screen is expanded by hot water and thus removed from the copper cylinder to result in a nickel sleeve. In one embodiment, the surface of the screen has a relatively rough surface rather than a relatively smooth surface. One embodiment includes etching the screen to result in a screen with a fine etched surface. While one embodiment uses a screen made from nickel, alternate embodiments may be made from any kind of metal and metal alloy that can be arranged in a screen or fabric structure. Different embodiments use one or more of nickel, iron, steel, brass, aluminum, copper, silver, gold, and/or platinum. While one embodiment includes exposing a plate on a rotating drum imager which has a screen structure thereon, another embodiment includes exposing a plate on a flatbed imager. While the discussion above mentions screens that are likely to have a regular structure, alternate embodiments use screens that do not have a regular structure. Similarly, the relative transparency of the screen need not be uniform, and so forth. Many variations are possible. Reference throughout this specification to “one embodiment” or “an embodiment” means that a particular feature, structure or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, appearances of the phrases “in one embodiment” or “in an embodiment” in various places throughout this specification are not necessarily all referring to the same embodiment, but may. Furthermore, the particular features, structures or characteristics may be combined in any suitable manner, as would be apparent to one of ordinary skill in the art from this disclosure, in one or more embodiments. Similarly it should be appreciated that in the above description of exemplary embodiments of the invention, various features of the invention are sometimes grouped together in a single embodiment, figure, or description thereof for the purpose of streamlining the disclosure and aiding in the understanding of one or more of the various inventive aspects. This method of disclosure, however, is not to be interpreted as reflecting an intention that the claimed invention requires more features than are expressly recited in each claim. Rather, as the following claims reflect, inventive aspects lie in less than all features of a single foregoing disclosed embodiment. Thus, the claims following the Detailed Description are hereby expressly incorporated into this Description of Example Embodiments, with each claim standing on its own as a separate embodiment of this invention. Furthermore, while some embodiments described herein include some but not other features included in other embodiments, combinations of features of different embodiments are meant to be within the scope of the invention, and form different embodiments, as would be understood by those in the art. For example, in the following claims, any of the claimed embodiments can be used in any combination. Furthermore, some of the embodiments are described herein as a method or combination of elements of a method that can be implemented by a processor of a computer system or by other means of carrying out the function. Thus, a processor with the necessary instructions for carrying out such a method or element of a method forms a means for carrying out the method or element of a method. Furthermore, an element described herein of an apparatus embodiment is an example of a means for carrying out the function performed by the element for the purpose of carrying out the invention. In the description provided herein, numerous specific details are set forth. However, it is understood that embodiments of the invention may be practiced without these specific details. In other instances, well-known methods, structures and techniques have not been shown in detail in order not to obscure an understanding of this description. As used herein, unless otherwise specified the use of the ordinal adjectives “first”, “second”, “third”, etc., to describe a common object, merely indicate that different instances of like objects are being referred to, and are not intended to imply that the objects so described must be in a given sequence, either temporally, spatially, in ranking, or in any other manner. All publications, patents, and patent applications cited herein are hereby incorporated by reference. Any discussion of prior art in this specification should in no way be considered an admission that such prior art is widely known, is publicly known, or forms part of the general knowledge in the field. In the claims below and the description herein, any one of the terms comprising, comprised of or which comprises is an open term that means including at least the elements/features that follow, but not excluding others. Thus, the term comprising, when used in the claims, should not be interpreted as being limitative to the means or elements or steps listed thereafter. For example, the scope of the expression a device comprising A and B should not be limited to devices consisting only of elements A and B. Any one of the terms including or which includes or that includes as used herein is also an open term that also means including at least the elements/features that follow the term, but not excluding others. Thus, including is synonymous with and means comprising. Similarly, it is to be noticed that the term coupled, when used in the claims, should not be interpreted as being limitative to direct connections only. The terms “coupled” and “connected,” along with their derivatives, may be used. It should be understood that these terms are not intended as synonyms for each other. Thus, the scope of the expression a device A coupled to a device B should not be limited to devices or systems wherein an output of device A is directly connected to an input of device B. It means that there exists a path between an output of A and an input of B which may be a path including other devices or means. “Coupled” may mean that two or more elements are either in direct physical or electrical contact, or that two or more elements are not in direct contact with each other but yet still co-operate or interact with each other. Thus, while there has been described what are believed to be the preferred embodiments of the invention, those skilled in the art will recognize that other and further modifications may be made thereto without departing from the spirit of the invention, and it is intended to claim all such changes and modifications as fall within the scope of the invention. For example, any formulas given above are merely representative of procedures that may be used. Functionality may be added or deleted from the block diagrams and operations may be interchanged among functional blocks. Steps may be added or deleted to methods described within the scope of the present invention.
	description	The present disclosure relates to a passive containment cooling system for a boiling water reactor. After a nuclear reactor shuts down, byproducts of the nuclear reaction continue to undergo radioactive decay and generate heat. Decay heat from the byproducts of the nuclear reaction is removed in order to limit and/or prevent damage to the nuclear fuel. If the nuclear reactor has a containment system, the decay heat may be removed from the containment system to limit and/or avoid over-pressurization and damage to the containment system. Nuclear plants with passive-safety features may remove this decay heat by natural convection, conduction and/or radiant heat transfer unassisted by forced flow or electric power. Some reactor designs include a Passive Containment Cooling System (PCCS) to remove the reactor's decay heat from the containment system. The PCCS system may include PCCS condensers, which can condense the steam generated if the reactor core cooling fails or there is a leak. PCCS condensers may include channels (e.g., tubes and/or parallel plates) and may transfer heat to a pool outside of containment and release it to the atmosphere as water vapor, or directly transfer it to the air. In an accident scenario, the nuclear reactor may be depressurized to the containment system. For a nuclear plant with a PCCS, depressurizing the nuclear reactor to the containment system may force steam, nitrogen and other non-condensable gases into the Primary Containment Vessel. After reactor depressurization, the steam condenses on the exterior of the PCCS condenser and may be mostly steam and may include trace amounts of non-condensable gases (e.g., hydrogen, oxygen and nitrogen). Some example embodiments relate to a boiling water reactor comprising a reactor building, a reactor cavity pool, a primary containment vessel, and a passive containment cooling system (PCCS). The reactor building includes a top wall defining a penetration therein, a bottom wall, and at least one side wall. The top wall, the bottom wall, and the at least one side wall define a chamber. The reactor cavity pool is adjacent the reactor building. At least a portion of the primary containment vessel is in the chamber of the reactor building. The passive containment cooling system is configured to receive water and expel hot water. The passive containment cooling system includes a thermal exchange pipe. The thermal exchange pipe includes an outer pipe having a first outer pipe end and a second outer pipe end. The first outer pipe end is closed and the second outer pipe end is open. The first outer pipe end is within the primary containment vessel. The second outer pipe end extends through the penetration in the top wall of the reactor building and into the reactor cavity pool such that the outer pipe is in fluid communication with the primary containment vessel and the reactor cavity pool. The thermal exchange pipe also includes an inner pipe at least partially within the outer pipe. The inner pipe has a first inner pipe end and a second inner pipe end. The first inner pipe end and the second inner pipe end are open. The second inner pipe end extends out of the outer pipe and into the reactor cavity pool such that the second inner pipe end is in fluid communication with the reactor cavity pool. In at least one example embodiment, the outer pipe comprises a pipe wall defining an opening. The inner pipe comprises a portion between the first inner pipe end and the second inner pipe end. The portion extends through the opening in the side of the pipe wall. In at least one example embodiment, the outer pipe has a diameter of 200 mm to 520 mm. The inner pipe has a diameter of 50 mm to 200 mm. The inner pipe and the outer pipe comprise stainless steel or appropriate materials for pressure retaining and corrosion. In at least one example embodiment, the boiling water reactor further comprises at least one seal around the outer pipe and adjacent the penetration in the top wall of the reactor building. In at least one example embodiment, the passive containment cooling system includes a plurality of thermal exchange pipes. The passive containment cooling system includes two to twenty thermal exchange pipes. In at least one example embodiment, the boiling water reactor further includes at least one support within the primary containment vessel. The at least one support is configured to support the first end of the outer pipe of the thermal exchange pipe. The at least one support comprises a spring support, which is configured to allow vertical movement of the thermal exchange pipe caused by expansion due to absorption of heat. In at least one example embodiment, the passive containment cooling system is valve-free, pump-free, or both valve-free, and pump-free. At least one example embodiment relates to a passive containment cooling system. In at least one example embodiment, a passive containment cooling system comprises a thermal exchange pipe. The thermal exchange pipe includes an outer pipe and an inner pipe. The outer pipe has a first outer pipe end and a second outer pipe end. The first outer pipe end is closed and the second outer pipe end is open. The first outer pipe end is within a primary containment vessel of a boiling water reactor. The second outer pipe end extends into a reactor cavity pool, such that the outer pipe is in fluid communication with the primary containment vessel and the reactor cavity pool. The inner pipe is at least partially within the outer pipe. The inner pipe has a first inner pipe end and a second inner pipe end. The first inner pipe end and the second inner pipe end are open. The second inner pipe end extends out of the outer pipe and into the reactor cavity pool, such that the second inner pipe end is in fluid communication with the reactor cavity pool. In at least one example embodiment, the outer pipe comprises a pipe wall defining an opening. The inner pipe comprises a curved portion between the first inner pipe end and the second inner pipe end. The curved portion extends through the opening in the pipe wall. The outer pipe has a diameter of 200 mm to 520 mm. The inner pipe has a diameter of 50 mm to 200 mm. The inner pipe and the outer pipe comprise stainless steel. At least one example embodiment relates to a method of installing a passive containment cooling system. The method of installing a passive containment cooling system comprises placing a thermal exchange pipe at least partially in a primary containment vessel, such that a portion of the thermal exchange pipe extends into a reactor cavity pool. Example embodiments will now be described more fully with reference to the accompanying drawings, in which some example embodiments are shown. Example embodiments, may, however, be embodied in many different forms and should not be construed as being limited to the embodiments set forth herein; rather, these example embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of example embodiments to those of ordinary skill in the art. In the drawings, like reference numerals in the drawings denote like elements, and thus their description may be omitted. It should be understood that when an element or layer is referred to as being “on,” “connected to,” “coupled to,” or “covering” another element or layer, it may be directly on, connected to, coupled to, or covering the other element or layer or intervening elements or layers may be present. In contrast, when an element is referred to as being “directly on,” “directly connected to,” or “directly coupled to” another element or layer, there are no intervening elements or layers present. Like numbers refer to like elements throughout the specification. As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items. It should be understood that, although the terms first, second, third, etc. may be used herein to describe various elements, components, regions, layers and/or sections, these elements, components, regions, layers, and/or sections should not be limited by these terms. These terms are only used to distinguish one element, component, region, layer, or section from another region, layer, or section. Thus, a first element, component, region, layer, or section discussed below could be termed a second element, component, region, layer, or section without departing from the teachings of example embodiments. Spatially relative terms (e.g., “beneath,” “below,” “lower,” “above,” “upper,” and the like) may be used herein for ease of description to describe one element or feature's relationship to another element(s) or feature(s) as illustrated in the figures. It should be understood that the spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. For example, if the device in the figures is turned over, elements described as “below” or “beneath” other elements or features would then be oriented “above” the other elements or features. Thus, the term “below” may encompass both an orientation of above and below. The device may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein interpreted accordingly. The terminology used herein is for the purpose of describing various embodiments only and is not intended to be limiting of example embodiments. As used herein, the singular forms “a,” “an,” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “includes,” “including,” “comprises,” and/or “comprising,” when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. Example embodiments are described herein with reference to cross-sectional illustrations that are schematic illustrations of idealized embodiments (and intermediate structures) of example embodiments. As such, variations from the shapes of the illustrations as a result, for example, of manufacturing techniques and/or tolerances, are to be expected. Thus, example embodiments should not be construed as limited to the shapes of regions illustrated herein but are to include deviations in shapes that result, for example, from manufacturing. Thus, the regions illustrated in the figures are schematic in nature and their shapes are not intended to illustrate the actual shape of a region of a device and are not intended to limit the scope of example embodiments. Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which example embodiments belong. It will be further understood that terms, including those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein. It should also be noted that in some alternative implementations, the functions/acts noted may occur out of the order noted in the figures or described in the specification. For example, two figures or steps shown in succession may in fact be executed substantially and concurrently or may sometimes be executed in the reverse order or repetitively, depending upon the functionality/acts involved. FIG. 1 is a schematic illustration of a boiling water reactor including a passive containment cooling system according to at least one example embodiment. In at least one example embodiment, as shown in FIG. 1 a boiling water reactor 100 may be a BWRX-300 reactor and may have components and characteristics of the BWRX-300 reactor. It is understood that components described therein are usable with other plant configurations. Referring to FIG. 1, the reactor 100 may include a reactor building 110, a primary containment vessel 120, a reactor cavity pool 130, and a passive containment cooling system (PCCS) 140. In at least one example embodiment, the primary containment vessel 120 is housed in a chamber of the reactor building 110. The reactor cavity pool 130 is a water-filled tank used to cool the hot water from the passive containment cooling system in the event of an accident and/or during use. The reactor cavity pool 130 may sit above the reactor building 110 and the primary containment vessel 120 that is at least partially within the reactor building 110. In at least one example embodiment, the boiling water reactor 100 further includes a core including fuel, channels, control rods, and instrumentation, core support structures including a shroud, shroud support, top guide, core plate, control rod guide tube, and orificed fuel support, chimney, steam dryer assembly, feed water spargers, and in-core guide tubes (not shown). In at least one example embodiment, the PCCS 140 includes at least one thermal exchange pipe 150. The thermal exchange pipe 150 extends from a chamber in the primary containment vessel, through a wall of the primary containment vessel, through a wall of the reactor building 110, and into the reactor cavity pool 130. In at least one example embodiment, the PCCS 140 is configured to allow water from the reactor cavity pool 130 to enter the primary containment vessel 120 via the thermal exchange pipe 150. As the thermal exchange pipe 150 absorbs heat, the water is heated to form hot water, which is released via a pathway in the thermal exchange pipe 150 due to differential density. The hot water exits the thermal exchange pipe 150 and enters the reactor cavity pool 130, where the hot water mixes with the reactor cavity pool water and cools by evaporation. The PCCS 140 does not include any valves and pumps, and relies on gravity to feed the water from the reactor cavity pool 130 to the primary containment vessel 120. The cooling process of the PCCS 140 is a continuous process and the water naturally circulates without any forced action. FIG. 2 is a perspective, cross-sectional view of the boiling water reactor of FIG. 1 according to at least one example embodiment. In at least one example embodiment, as shown in FIG. 2, the boiling water reactor 100 is the same as in FIG. 1, but is shown in greater detail. As shown in FIG. 2, the reactor building 110 includes a top wall 200, a bottom wall 210, and at least one side wall 220. The reactor building 110 is formed of concrete. The top wall 200, the bottom wall 210, and the at least one side wall 220 define a chamber 230 that houses the primary containment vessel 120. The top wall 220 of the reactor building 110 may define a penetration 240 therein. The thermal exchange pipe 150 extends through the penetration 240. As shown, the boiling water reactor 100 includes multiple thermal exchange pipes 150 and multiple penetrations 240. Each thermal exchange pipe 150 extends through a corresponding one or the multiple penetrations 240 and into the reactor cavity pool 130. In at least one example embodiment, the primary containment vessel 130 defines at least one passage 250 in a wall thereof. Each of the thermal exchange pipes 150 extends through a respective one of the at least one passages 250 and into the primary containment vessel 120. FIG. 3 is a side cross-sectional view of a thermal exchange pipe of the passive containment cooling system of FIGS. 1 and 2 according to at least one example embodiment. In at least one example embodiment, as shown in FIG. 3, each of the thermal exchange pipes 150 of the PCCS 140 includes an outer pipe 300 having a first outer pipe end 310 and a second outer pipe end 320. The first outer pipe end 310 is a closed end that is positioned within the primary containment vessel 120. The second outer pipe end 320 is an open end having an outlet 325 that is positioned in the reactor cavity pool 130. The outlet 325 is configured to release hot water into the reactor cavity pool 130. In at least one example embodiment, the second outer pipe end 320 may be angled. In some example embodiments, the second outer pipe end 320 has an angle “A” of about 10° to about 80° (e.g., about 20° to about 70°, about 30° to about 60°, or about 40° to about 50°). For example, the angle “A” may be 45°. The outer pipe 300 may have a diameter of about 200 mm to about 520 mm (e.g., about 250 mm to about 350 mm). The outer pipe 300 may have a length of about 5,000 mm to about 25,000 mm (e.g., about 10,000 mm to about 20,000 mm). In at least one example embodiment, the thermal exchange pipe 150 includes an inner pipe 330 having a first inner pipe end 340 and an second inner pipe end 360. The first inner pipe end 340 includes an outlet 365 and the second inner pipe end 360 includes an inlet 370, such that there is fluid communication between the inner pipe 330, the reactor cavity pool 130, and an internal portion of the outer pipe 300. Water from the reactor cavity pool 130 enters the inner pipe 330 via the inlet 370 and exits into the outer pipe 300 via the outlet 365. In at least one example embodiment, the inner pipe 330 is at least partially contained within the outer pipe 300. In at least one example embodiment, the inner pipe 330 has a diameter of about 50 mm to about 200 mm (e.g., about 100 mm to about 175 mm or about 120 mm to about 160 mm). The inner pipe 330 may have a length that is slightly less than the length of the outer pipe 300, such that the first inner pipe outlet 365 is about 100 mm to about 300 mm (e.g., about 150 mm to about 250 mm or about 175 mm to about 225 mm) from the closed first outer pipe end 310 of the outer pipe 300. In at least one example embodiment, the inner pipe 330 may have a curved portion 350, such that a portion of the inner pipe 330 extends through a hole 392 defined in a wall of the outer pipe 300. The curved portion 350 may be angled at about a 90° angle in relation to the remainder of the inner pipe 330. In other example embodiments, the curved portion 350 may be angled at about 10° to about 80° with respect to the remainder of the inner pipe 330. In other example embodiments, the portion 350 may be an angled portion or a straight portion. In at least one example embodiment, as shown in FIG. 3, the thermal exchange pipe 150 extends through the passage 250 in the primary containment vessel 120 and through the penetration 240 in the top wall 200 of the reactor building 110. In at least one example embodiment, the PCCS 140 can include a seal 375 surrounding each thermal exchange pipe 150 at a point where the thermal exchange pipe 150 exits the penetration 240 in the top wall 200. The seal 375 may be any suitable heat tolerant seal. As shown in FIG. 3, the curved portion 350 starts at a point above the seal 375 and the top wall 200 of the reactor building 110. In at least one example embodiment, each of the thermal exchange pipes 150 is supported by a support 380. The support 380 may include a spring 385 (or flexible support) and a base 390. The spring 385 or flexible support has a first end that acts against the closed end of the outer pipe and a second end that acts against the base 390. Use of a spring 385 or flexible support in the support 380 allows for the thermal exchange pipe 150 to still be supported as the thermal exchange pipe 150 expands due to heat absorption. In at least one example embodiment, the spring 385 may be about 300 mm to about 500 mm in length. For example, the spring may be about 400 mm in length. The spring 385 may be formed of any suitable material, such as stainless steel. FIG. 4 is top view of a portion of the boiling water reactor of FIG. 1 according to at least one example embodiment. In at least one example embodiment, as shown in FIG. 4, the PCCS 140 includes a plurality of thermal exchange pipes 150 extending into the reactor cavity pool 130, which is filled with water. The PCCS 140 can includes two to twenty thermal exchange pipes 150 (e.g., three to nineteen, four to eighteen, five to seventeen, six to sixteen, seven to fifteen, eight to fourteen, nine to thirteen, or ten to twelve). For example, as shown in FIG. 4, the PCCS 140 includes ten thermal exchange pipes 150. The thermal exchange pipes 150 may be substantially uniformly spaced about a perimeter of the primary containment vessel 120. In other example embodiments, the thermal exchange pipes 150 may be arranged non-uniformly about the primary containment vessel 120 or may be arranged in clusters. In use, the thermal exchange pipes 150 of the PCCS 140 allow for natural circulation of water from the reactor cavity pool 130 into the primary containment vessel 120 via the inlet 370 of the inner pipe 330 of the thermal exchange pipes 150. As the thermal exchange pipes 150 absorb heat, the water is heated and transformed into hot water, which is then released via the outlet 325 in the outer pipe 320 of the thermal exchange pipes 150. At least one example embodiment relates to a method of installing a passive containment cooling system. The method of installing a passive containment cooling system comprises placing a thermal exchange pipe at least partially in a primary containment vessel, such that a portion of the thermal exchange pipe extends into a reactor cavity pool. When the passive containment cooling system is retrofitted into an existing boiling water reactor, the method may include drilling penetrations and/or passages through a top wall of the reactor building and through a portion of the primary containment vessel. The method may also include installing supports for each thermal exchange pipe and installing thermal exchange pipes. While a number of example embodiments have been disclosed herein, it should be understood that other variations may be possible. Such variations are not to be regarded as a departure from the spirit and scope of the present disclosure, and all such modifications as would be obvious to one skilled in the art are intended to be included within the scope of the following claims.
	description	This application is a continuation application of U.S. patent application Ser. No. 13/386,629, entitled “Nuclear Battery Based on Hydride/Thorium Fuel”, filed on Jan. 23, 2012, which is a 371 national stage entry application of PCT application No. PCT/US2010/042730, entitled ‘Nuclear Battery Based on Hydride/Thorium Fuel”, filed on Jul. 21, 2010, which claims priority to U.S. patent application No. 61/228,104, entitled ‘Nuclear Battery Based on Hydride/Thorium Fuel”, filed on Jul. 23, 2009, the contents of which are incorporated herein by reference in their entirety. This technology relates generally to portable nuclear fuel reactors. Presently, there are approximately 150 metric tons of known weapons grade plutonium and approximately 850 metric tons of known reactor-grade plutonium in the world, with 50 metric tons of reactor-grade plutonium being produced every year. There is likely to be more such plutonium in the world that is unaccounted for. Since these types of plutonium can be used to make weapons of mass destruction, such as thermonuclear bombs and dirty bombs, it is desirable to process any such plutonium so as to render the plutonium difficult to use in making a weapon of mass destruction or to transform any such plutonium into a form that is difficult to use in making any kind of weapon of mass destruction. Currently, there are two approaches to processing weapons-grade and reactor-grade plutonium such that the end product is either difficult or substantially impossible to use in constructing a weapon of mass destruction. The first approach is to immobilize the plutonium. Typically, this approach involves immobilizing plutonium powder in a glass matrix and then placing the plutonium/glass matrix in a secure storage location. The second approach is to incorporate the plutonium in a nuclear fuel that is burned at a nuclear power plant. The burning of such a fuel results in much of the plutonium being transformed into an isotope that is unsuitable for use in a weapon of mass destruction. Presently, a plutonium-based nuclear fuel that is being used to reduce the supply of plutonium that might be used to produce a weapon is a blend of plutonium-239 and natural or depleted uranium, which is commonly referred to as a mixed oxide fuel (MOX). There are plutonium-based nuclear fuels suitable for use in a light water reactor (LWR) generating electricity and in which ordinary water is used as a coolant and a moderator to slow down neutrons to the point where their energy ranges fall into the range of higher fission probability. There are two types of LWR, namely, a pressurized water reactor (PWR) and a boiling water reactor (BWR). The plutonium-based nuclear fuel is comprised of plutonium, zirconium hydride, and thorium, which may act as a moderator inside the fuel. In one embodiment, the zirconium hydride comprises 20-50% by weight of the fuel. Alternatively, the plutonium is less than 10% by weight of the fuel; the zirconium hydride is 20-50% by weight of the fuel; and the thorium is 20-50% by weight of the fuel. Further alternatives of the fuel, have about 40-94% of the plutonium in the fuel as plutonium-239. Other alternative fuel a comprises a zirconium hydride in which the hydrogen to zirconium ratio is in the range of about 1.6-1.8. These fuels may also be used in an LWR reactor, e.g., a TRIGA reactor (Training Research Isotopes General Atomics). There are benefits to using zirconium hydride alloy fuel in nuclear reactors, at least in part because of its safety characteristics. In fuel the moderator and fuel are intimately mixed. Among the research reactors that commonly use this type is the TRIGA reactor. The NERI program in applying this fuel to the LWR (Z. Shayer and E. Greenspan “Physics Characteristic of U-ZrH1.6 Fueled PWR Cores”, PHYSOR 2004, Chicago, Illinios, Apr. 25-29, 2004) The introduction of hydrogen within the fuel permits attainment of neutron moderation to aid plutonium incineration by thermalizing more neutrons, enhancing the neutron absorption probability in the 0.3 eV resonance peak of Pu-239. Use of this fuel may have several advantages over the existing MOX (Mixed Oxide fuel, blends of Uranium and Plutonium oxide) fuel: (a) increased core-life; (b) increased energy generation per fuel loading; (c) reduced waste volume and toxicity due to higher discharge number and to partial utilization of thorium; (d) utilization of thorium resources; (e) improved safety due to the large negative temperature coefficient; (f) improved proliferation resistance by burning up more plutonium and use of thorium; (g) additional significant benefits of the proposed zirconium hydride matrix are better thermal conductivity and fuel storage heat capacity; and (h) the reported experiments with TRIGA fuels indicated low fission gas release. The neutronic parametric study previously reported is limited directed mainly to infinite pin cell calculations that were performed by WIMSD-5B (WIMSD-5B (98/11), “Deterministic Code System for Reactor-Lattice Calculations”, RSICC CCC-656, user manual (1998), (WIMSD-5B stands for Winfrith Improved Multigroup Scheme Version D-5B, computer code) a deterministic code for reactor core lattice calculations. This code was benchmarked for hydride fuel applications against the well-established codes such as MCNP4B2 and SCALE4.4 codes to provide additional justification of the applicability of the code for the hydride fuel parametric study. Generally there was very good agreement between the codes for various ranges of neutronic parameters and spectrum (Z. Shayer, Neutronic Parametric Analysis: U-ZrH1.6 Unit Cell in PWR NERI Project—Rev. 4, NERI02-189-TM 2 (2003). The initial analysis shows significant advantages of the proposed fuel over the MOX for incineration of plutonium. Several calculations were performed by the WIMSD-5B to determine the benefit of Pu/ZrHx/Th matrix fuel. FIG. 1 is a sample of the results obtained from this study, which shows the variation of K∞ (Kinf Infinite—Multiplication factor for neutrons)) versus burnup (in GWd/Te ihm; GW days per ton equivalent initial heavy metal [U or Th]) for several fuel types (MOX and oxide fuel). The presence of some Th-232 provides additional fissile material through conversion of Th-232 to U-233, which increases the discharge burnup values to around 80,000 MWd/Te as compared to MOX fuel with LEU (Low Enriched Uranium) that reached only to 65,000 MWd/Te (At K∞=1.03 for a single batch). For a comparison, the discharge burnup value of HEU oxide fuel is only about 45,000 MWd/Te. From FIG. 2 we can see that the destruction rate of Pu-239 is significantly better fast compared to the destruction rate of than the MOX fuel, at 50,000 MWd/Te for MOX fuel, only about 50% of initial Pu-239 is consumed as compared to about 70% for the proposed fuel. This value is increase to 92% for the Pu/ZrHx/Th matrix fuel as compare to only 63% for MOX at 80,000 MWd/Te. The preliminary results show that this fuel is may be suitable ideal for the non-proliferation program to dispose of weapon and power grades plutonium. In this example the calculations were performed for typical PWR rods. The fuel, clad and water temperatures were assumed to be 978 K, 607 K and 579 K, respectively. Initial results indicated that this Pu/ZrHx/Th matrix fuel would may be very attractive to the disposition of weapon and power grades plutonium. The fuel destruction rates measured in the non-limiting examples described above, were is almost an order of magnitude higher than conventional MOX fuel of containing plutonium. Due to the higher discharge burnup in a smaller core volume, with beneficial safety characteristics and a high prompt reactivity coefficient, a Pu/ZrHx/Th matrix fuel with Zr or SS cladding offers excellent advantages over the conventional MOX fuel for plutonium disposition. The present disclosure is directed to transportable nuclear batteries comprising, sealed reactor shell; a reactor core; and a generator. The transportable nuclear battery may further comprises a nuclear fuel comprising in the reactor core wherein the fuel comprises plutonium, carbon, hydrogen, zirconium and, thorium. The fuel may further comprise hydrogen containing glass microspheres, wherein the glass microspheres, may be coated with a burnable poison, and other coating materials that may aid in keeping the hydrogen within the microsphere glass at relatively high temperature. The use of nuclear battery to serve remote sites without ready access to fuel is not new. In the 1960s, the U.S. Army Portable Nuclear Power Program deployed several small nuclear plants at locations such as Greenland and Antarctica. Since then several advanced concept studies, sponsored by government and industry, have addressed the problem with similar conclusions, i.e., it is extremely difficult for small nuclear plants to be cost-competitive with diesel generators and gas turbines, even with high fuel and maintenance costs. The main reason is that previous small nuclear plant concepts were burdened with the same safety requirements and sophisticated technical infrastructure as large nuclear plants. Additional concerns for security and nonproliferation generally have made small, remotely-sited nuclear reactors unattractive. Nevertheless, it may be time to re-examine the “small reactor dream.” There are two reasons: there is greater incentive for reducing the economic disparity between remote and central communities, and the available technology for solving problems unique to small remote reactors has evolved substantially in the last decade. The Nuclear Thorium/Hydride Fuel Battery (NTHFB) is a novel reactor concept based in part on the fuel element depicted in FIG. 3. In this reactor, fission-generated heat may be transferred to gas turbine to generate electricity. This may allow the reactor module to have a simplified design, and to provide electricity, heat or hydrogen to the remote areas, or to serves as backup system to the renewable energy systems such as, without limitation, wind or solar. The NTHFB module may be fabricated and fueled in the factory and transported to the site sealed, for example, without limitation, by welding. The NTHFB may operate for 10-20 years without refueling and with limited reactivity swing. After its operational life, it may be replaced by another module, and the old module may be transported to a nuclear waste repository site or a fuel recycling system. The electricity range of the proposed battery may be 0.1-50 MWe (MegaWatt electricity). The proposed small reactor may be also useful for space exploration program. The proposed Nuclear Battery may provide for various benefits such as, without limitation, a sealed module that may never need to be opened on site, it may provide enough power for 10-30 years, it may be capable of being removed & refueled, or buried underground out of sight without risk to environment, the proposed battery may also be transportable by train, ship, truck, and may in some cases lack mechanical parts in the core to malfunction thus leading to an inherent safety. The proposed battery may also not produce greenhouse gases which may lead to global warming emissions. The proposed Nuclear Battery may further aid in providing inherently safe, secure power to remote communities, hospital, and military bases. The proposed battery may be able to provide steady-state power in the range of 10 to 100 MWe. This power range may be sufficient for communities of 10,000 to 50,000 people. In addition, the battery could provide heat for district heating or for desalination of seawater, or hydrogen production. The battery and associated equipment may be transportable by truck over rural roads. The battery may also be monitored from a central point through a variety of communications methods for example, satellite uplink, cellular phone, or radio. The fuel may be made from ultra-high quality coated particle fuel and may aid in preventing radioactive contamination of power equipment and may also aid in preventing radioactivity releases even in the event of accidents. The proposed nuclear battery may serve as an energy source for a variety of methods and for various purposes including without limitation, electricity through Bryton cycle (with efficiency of 50%), thermoelectric, heat, water desalination, or hydrogen production. In solid hydride fuel, the moderator (hydrogen) may be placed inside the fuel. The hydride fuel may be based on, for example, Uranium, Plutonium and Thorium. Very Light fuel may be beneficial for applications in space, which may include without limitation, power production for propulsion, electronic systems, optics systems as well as electric batteries for stationary settlements, manned and unmanned, on planets or satellites of solar system. Space exploration may benefit from power systems able to provide electricity in the range of hundreds to thousands of KWe (KiloWatt electricity). The light weight fission based system may provide a viable compact technology system that may provide electricity in these ranges of power, and may do so in a safe reliable and economical manner. The present disclosure is directed toward a light nuclear power reactor that may feed an electric engine, for example without limitation, on board a space craft for nuclear electric propulsion or for use at manned or unmanned stationary settlements. The present disclosure may also provide reliable reactor for long-time operability (for example in some embodiments for 15 years or longer) with little or no intervention (with minimum control requirements). The presently disclosed system may be based on, for example without limitation, reactor technology developed for modular high temperature gas cooled reactors (HTGR). In some embodiments the present disclosure may provide for one or more of the following: minimization of overall mass and volume; using medium U-235 enrichment or plutonium for nuclear spent fuel (the use of plutonium may also alleviate nuclear waste problems); electrical power in the range of 100-5000 KWe; operating life time may be up to, or greater than 15 years; low core power density; and minimal use of fluids in the system, or no fluid at all. In various embodiments, the reactor design may be based on the modular version of high temperature gas cooled reactor with, for example, the Brayton cycle. Fuel composition may be based on hydride fuel type, for example without limitation, those used in TRIGA research reactor. In some embodiments, the moderator may be present in both the fuel and the coolant. Use of moderator in the fuel and coolant may impact the neutronic and safety characteristic of this core. The uranium-zirconium hydride fuel, in which the hydrogen moderator may be homogeneously distributed within a fuel, may lead to the large prompt negative fuel temperature coefficient of reactivity and may help to mitigate accidental reactivity insertion events and prevent fuel from melting. In some embodiments, the density of this fuel may be around 8.2 g/cm3 as compare to 10.2 g/cm3 of UO2, which is commonly used today in commercial nuclear power plants. The presently disclosed fuel may save about 20% in weight of the reactor compared to other fuel types. In addition TRIGA-type fuels, on which the presently disclosed fuel may be based, are considered to be inherently safe fuel types which may possess highly thermalized neutrons inside the fuel due to the presence of moderator within the fuel. The presently disclosed fuel formulation may be based on TRIGA fuel compositions, for example without limitation a Pu/ZrHx/Th matrix fuel. This formulation may further reduce the mass of the core by additional 10-15%, due to the lower density of thorium (11.72 g/cc as compare to 19.2 g/cc of uranium). The neutronic behavior of one embodiment of the currently disclosed fuel formulation may be described in Table 1. Table 1 fissile isotopes are presented at thermal neutron energy of 0.0253 eV. Where, a is the ratio of capture-to-fission cross-section, and η is the number of fission produced per neutron absorption, and υ is the number of neutrons produced per fission. The number of neutrons produced per neutron absorption, may provide a factor in determining the system's operational life-time and may indicate the ability to produced fissile isotopes for each fissile atom destroyed. Furthermore, in some embodiments, some neutrons may be absorbed in non-fuel material or may leak out from the reactor core, therefore Table 1 also lists the quantity of η−2 which the prospective fissile materials to breed fissile atoms. TABLE 1Basic nuclear data related to fissionable isotopes U-233, U-235, Pu-239and Pu-241Nuclear DataU-233U-235Pu-239Pu-241σγ (barns)45.598.3269.3358.2σf (barns)529.1582.6748.11001.1α0.0860.1690.3600.354η2.2962.0752.1151.169η − 20.2960.0750.1150.169υ2.492.422.882.94Energy per191194200202Fission The currently disclosed fuel formulation may be used in at least two types of hydride based pellets fuel: First type of fuel is Pu/ZrHx/Th fuel matrix as described above, and Conventional microsphere fuel types, for example without limitation, those similar to types used in Pebble Bed reactor or GA prismatic fuel (TRISO, tri-structural isotropic, particles) with highly enriched uranium or weapon grade/power grade plutonium in the form oxide or carbon (for example without limitation; UO2, UC, UCO, PuO2, PuC, PuCO). The fuel microsphere dimensions may be in the same range as conventional TRISO particles, for example without limitation, 300-350 μm. This microsphere fuel may be protected by as many as four carbon based layers. The carbon layers may comprise a low density carbon buffer, a high density pyrolitic carbon layer, a silicon carbide layer, and a high density pyrolitic carbon. The overall microsphere dimensions of the entire fuel particles may be in the range of 750-800 μm. In addition to the TRISO particles described above, microsphere glass, filled with hydrogen, may be used as a moderator (replacing the hydride fuel in form of ZrHx) and to control the reactivity of the reactor core. The hydrogen-containing microspheres may be coated with burnable poison film, such as boron carbide or boron, erbium, etc. A schematic view of one possible embodiment of the microsphere glass is depicted in the FIG. 4. The, at least, two types of microsphere particles may be mixed together randomly or may be layered with graphite powder and then compacted to the cylindrical fuel pellets. In one embodiment, compact cylindrical pellets may be formed in the range of about two centimeters in length and about 1 cm in diameter. These pellet embodiments may be inserted into holes which may, for example, without limitation be drilled in a hexagonal graphite moderator block. This embodiment is illustrated in the FIG. 5. In one embodiment of the hexagonal graphite moderator block, the center hydride fuel rod may be surrounded by six fertile material pellets. In this embodiment, the pellets may be made of thorium, such as for example without limitation, various forms of oxide, carbonate or hydrides (ThO2, ThC, Th2 . . . ). The fuel pellets may be made from this fuel formulation in various ways, such as for example, directly or in the form of TRISO particles and/or microsphere glass filled with hydrogen configuration as describe above. In a further embodiment, where only fuel kernel replaced by fertile materials (thorium or U-238). Then the mixing these fertile fuels with microsphere glasses filled with hydrogen and thin film of burnable poison will be also examined in this study. The productions of the fertile pellets are similar to that of fuel pellets. FIG. 5B is a hexagonal basic graphite block reactor core configuration. In some embodiments, a reactor core that may be capable of producing power in the ranges of couple of hundred KWth up to few MWth may be assembled with fuels described above. In some embodiments, the reactor may be comprised of several hundred hexagonal graphite blocks. In further embodiments, holes may be drilled for helium cooling system (FIG. 5 shows six holes, but the number may be greater or smaller in other embodiments). In some embodiments, the active core may be surrounded by reflector. The reflector thickness may vary from about two cm in some embodiments to more than two or less than two in other embodiments. In further embodiments, microsphere glass may be embedded in the reflector to aid reactivity control. TRISO particles may reach 100 MWd/kg burnup without fission gas release or damage. The temperature and pressure will be determined by more detail analysis, including the coupling between the heat source (reactor core) and entire plant balance. In some embodiments, values of 800° C. may be achieved, however further embodiments may achieve temperatures above 900° C. in various embodiments, a reduction in power density may provide for continuous operation time above 20 years, further embodiments may have a duration time of 30 years. In various embodiments, an electrical generator may be used, for example without limitation a thermoelectric generator or a Brayton cycle. Embodiments that include microsphere glass benefit from the control the reactivity, changes in the neutron spectra, or shifting the neutron energy profile during the reactor operation. In some embodiments, the neutron spectrum may be harder (more high energetic neutrons exist in the system). The hardness of the neutron spectrum may be due to presence of a thermal neutron absorber in the system (for example, without limitation burnable poison film). The thermal neutron absorber may tend to increase the absorption rate in the fertile thorium materials (high capture rate of neutrons in the resonance energy range). In some embodiments, depletion of a burnable poison during reactor operation may shift the neutron energy spectrum toward more softer spectrum (more low neutron energy). This shifting may be due to exposing more neutron to slowing down process with hydrogen collisions, for example, without limitation inside the microsphere glasses, this may improve the fuel utilization of the fissile material U-233, generated from neutrons absorption rate in Th-232. Microsphere Glass Technology The filling process of hydrogen may be aided by heating the spheres which may result in the permeability to hydrogen increasing. This heating, may provides the ability to fill the spheres by placing the warmed spheres in a high-pressure hydrogen environment. The hoop stresses achievable for glass microspheres can range from 345 Mpa (50,000 psi) to 1,034 Mpa (150,000 psi). Once cooled the spheres may lock the hydrogen inside. The fill rates of microspheres may be related to the properties of the glass used to construct the spheres, and may also vary with the temperature at which the gas is absorbed (for example without limitation, between 150° C. and 40° C., or greater than 150° C.) and may also vary with the pressure of the gas during absorption process. Fill rates may be directly proportional to the permeability of the glass spheres to hydrogen which increases with increasing temperature. For example, fill rate at 225° C. may be approximately 1 hour and at 300° C. it may be approximately 15 minutes. This increase in hydrogen permeability with temperature may allow the microspheres to maintain low hydrogen losses at storage conditions while providing sufficient hydrogen flow when needed. Engineered microspheres may provide for high density storage of hydrogen. For example, without limitation, a bed of 50 μm diameter engineered microspheres may be able to store hydrogen at 62 Mpa (9000 psi) with a safety factor of 1.5 and a hydrogen mass fraction of 10%. This may produce a hydrogen density of 20 kg/m3. FIG. 6 shows how the hydrogen mass fraction and volumetric density may change under various storage pressures. This figure was taken from NASA report NASA/CR-2002-211867 “Hydrogen Storage for Aircraft Application Overview. TABLE 2Some Non-Limiting Examples of Fuel Elements Zones and DimensionsRadiusDensityZone(cm)Material(g/cm3)Fuel0.622515% reactor/weapon grade Pu, 55%7.65ZrH1.6 30% Th by massGap0.6308HeliumCladding0.6808Zircaloy4 = 0.98 Zr, 0.015 Sn, 0.0026.56Fe, 0.001 CrGraphite0.750Carbon1.75Coolant0.807Helium<0.003Blanket1.707Thorium carbide = ThC10.67 TABLE 3Density and Mass Fraction of Elements in SomeNon-Limiting Pu/ZrH1.6/Th Matrix FuelsPuZrH1.6ThDensityPu-238Pu239Pu-240Pu-241Pu-242Wt %Wt %Wt %gram/cm3Wt %Wt %Wt %Wt %Wt %TotalPower Grade Plutonium555407.4527630.053.11.10.60.1557.55537.57.50150.0754.651.650.90.2257.51055357.5508790.16.22.21.20.31012.55532.57.6009120.1257.752.751.50.37512.51555307.6516120.159.33.31.80.4515Weapon Grade Plutonium555407.45290404.680.30.02057.55537.57.50171507.020.450.0307.51055357.55116909.360.60.0401012.55532.57.601279011.70.750.05012.51555307.652059014.040.90.06015 Possible reactivity swing during the burnup for some non-limiting examples is provided in FIG. 7-10. As can be seen from these figures reactivity may vary between 0.1 to 5%. In some cases, reactivity may be controlled, for example, without limitation, by the use of a burnable poison or automated movement of graphite. Reactor Control In one embodiment of the reactor control design, reactivity may be controlled by dividing the graphite region into, for example without limitation, slices or leaves. In these design embodiments, the slices or leaves may move in and out of the active core region and may accommodate changes in the reactivity. The Effect of Plutonium Content within the Pu/ZrH1.6/Th Matrix on the Reactivity As a part of the parametric study we examine the effect of plutonium content inside the matrix fuel. These calculations are presented in the FIG. 11. The graph in FIG. 11 shows that the for weapon grade plutonium a relatively small amount of plutonium quantity is required to achieved a strong neutron source, while for power grade plutonium (plutonium that came out of nuclear spent fuel) at less 15% of plutonium is required to have a strong neutron source for the entire fuel irradiation. The presence of thorium within the fuel indicates that this strong neutron source will be kept even during burnup due to partially compensation of depleted plutonium by building up of U-233, which has better neutronic characteristic than Pu-239 and U-235, in addition to other advantage as it was discussed in my proposal. Safety Aspects of Pu/ZrH1.6/Th Matrix Fuel The reactivity coefficient of fuel temperature (Doppler Effect) is given in the equation below. The results also depicted in the FIG. 12 below for various plutonium grades and quantities of plutonium (within the Pu/ZrH1.6/Th matrix fuel). Table 4 shows also the comparison of the proposed fuel with the common fuels used in LWR and Gas cooled reactor. As can be seen this fuel is safer from reactivity stand point view more than uranium oxide fuel. Since the moderator is within the fuel, the impact of the graphite temperature is insignificant. The proposed fuel can be also considered as inherently safe fuel. δρ δ ⁢ ⁢ T = K ∞ ⁢ ⁢ T 2 - K ∞ ⁢ ⁢ T 1 ( T 2 - T 1 ) * ( K ∞ ⁢ ⁢ T 2 * K ∞ ⁢ ⁢ T 1 ) TABLE 4Comparison with Other Thermal ReactorsBWRPWRHTGR(Pu/ZrH1.6/Th)Doppler (×10−6) −4 to −1 −4 to −1−7−55 to −25Moderator (×10−6)−50 to −8−50 to −8+1−0.08 to −0.01
046438688	description	DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIG. 1, a portion of the reactor core is shown which includes a pressure vessel head 10, a control drive mechanism (CDM) 12, a shroud 14, and a fuel assembly 16. A grid plate is indicated in dashed lines at 18. These components are, of course, conventional and the purpose of FIG. 1 is to illustrate the location of the module support arrangement of the invention, which is generally denoted 20, in relation to these components. As illustrated, the support arrangement 20 penetrates vessel head 10 and extends between CDM 12 and shroud 14. Referring to FIG. 2, which is a detail of the support arrangement 20 with the installation tool assembly in place, the support arrangement 20 basically comprises a cell support nut 22, which is generally cylindrical in shape and only one half of which is shown in FIG. 2, including an upper flange portion 24 having a downwardly facing bearing surface 24a that engages a corresponding upwardly facing bearing surface 10a of pressure vessel head 10 and a screw threaded portion 26 which engages a corresponding threaded portion 14a of shroud housing 14. A spring loaded spline lock, indicated at 28, prevents nut 22 from loosening during service. Spline lock 28 includes a spring member 28a having a spline 28b located at the free end thereof as illustrated. The head 27a of a bolt 27 located in an aperture 29 in shroud housing 12 is, as explained below, adapted to engage spring member 28a at a point intermediate the ends thereof during installation. The bore of nut 22 is splined at 30 to engage an outwardly projecting portion 32 of a torquing tool 34 described below. The inner surface of shroud housing 14 is shaped to engage a cell lifting and preloading tool 36 which is also described below and to this end, this surface includes an inwardly projecting gripping flange 38 which defines the inner bore of shroud housing 12. In a specific example, this bore is two inches in diameter. The module lifting and preloading tool 36 includes an expanding collet assembly including an elongate, cylindrical lifting member 40 which extends parallel to the longitudinal axis of the shroud housing 14. Lifting member 40 includes an intermediate enlarged portion 42 and an enlarged gripping portion 44 at the shroud (lower) end thereof. The lifting member 40 is bifurcated or otherwise split at the shroud end so as to form the expandable gripping arms of the collet assembly. Gripping portion 44 includes a bearing surface 44a which, when the gripping arms of the lifting member 40 are expanded and member 44 is suitably positioned, engages a corresponding bearing surface 38a of flange 38 of shroud housing 12. A central rod 46 is located in a longitudinal bore or opening formed centrally of lifting member 40 and extends along the length of member 40 as shown in FIG. 2 and FIG. 3. A tapered head 48 at the end of rod 46 cooperates with the expandable gripping arms of member 40 to actuate the expanding collet assembly and in particular, to control expansion and contraction of the gripping arms of lifting member 40 depending on the longitudinal position of head 48. The expanded position is shown in FIG. 2 wherein the gripping portions 44 of member 40 are forced outwardly by rod head 48 and engage flange 38 of shroud housing 12. The normal position is shown in FIG. 3. As illustrated in FIG. 3, the upper end of rod 46, i.e., the end opposite head 48, is threaded as indicated at 50 and a nut 52 controls the longitudinal movement of rod 46. As is also shown in FIG. 3, lifting member 40 further includes, near the upper end thereof, a piston 54 which cooperates with a hydraulic cylinder 56 to provide preloading. Cylinder 56 is suitably supported by struts indicated at 58 and includes a downwardly depending skirt portion 60 which is threaded at 60a and engages threading 62a of a spacer nut 62. Spacer nut 62 controls movement of torquing tool 34 as is described in more detail below. Turning now to a consideration of torquing tool 34, this tool comprises an elongate expandable sleeve member 64 which is somewhat similar in construction to lifting member 40 and which carries splines 32 referred to above at the lower, expandable end thereof. A handle 66 for rotating sleeve 64 is located at the upper end thereof. Spacer nut 62, which was referred to above, includes a lower, enlarged nut portion 67 and an upper tubular sleeve portion 68 which, as mentioned above, includes threading 60a. The lower end of spacer nut 60 abuts the upper end of sleeve member 64 and when nut 60a is screwed downwardly, sleeve member 64 of torquing tool 34 is forced downwardly so that the lower end thereof engages the intermediate enlarged portion 42 of lifting member 40 and is expanded thereby as illustrated in FIG. 2, whereby spline portions 32 are brought into engagement with cell support nut 22. Briefly considering the operation of the module support apparatus described above, assembly of the module support begins with insertion of the installation tool assembly, comprising torquing tool 34 and lifting and preloading tool 36, through the CDM 12. The CDM 12 has a restricted bore (assumed to be 2 inches in diameter in the specific example under consideration) and the installation tool assembly fits through this bore. Next, the cell lifting and preloading tool 36 is expanded into engagement with shroud housing 14, gripping portions 44 of lifting member 40 being expanded into engagement with flange 38 by action of head 48 in response to the upward longitudinal movement of rod 46 as described above. It should be noted that with gripping portions 44 so expanded, bolt 27 will be displaced thereby radially and the head 27a of bolt 27 will contact spring member 28a of spring lock 28 and force spring member 28a out of engagement with cell support nut 22 as shown in FIG. 2. Thus spring lock 28 is disengaged at this point in the operation and support nut 22 can be rotated relative to shroud housing 14. At this time, the cell is lifted into position and preloaded by actuation of the hydraulic piston 54 whose movement controls the longitudinal position of lifting member 40. At this point the lower end 32 of torquing tool 34 is expanded into engagement with the cell support nut 22, this expansion taking place by virtue of the downward movement of sleeve member 64 and the coaction therewith with the enlarged portion 42 of lifting member 40. The engagement of cell support nut 22 with shroud housing 14, and head 10, is tightened through the use of handle 66. This completes the cell installation. After the cell installation has been completed the installation tool assembly is removed by retracting the expanded portions and withdrawing the assembly through the bore in CDM 12. With the removal of the installation tool assembly, shroud housing 14 will be supported by cell support nut 22 and the spline lock 28 will be engaged so as to prevent loosening of the threaded connection between nut 22 and housing 14. The module support nut 22 is constructed so as to be capable of being disengaged through the use of a spanner wrench in the event that jamming occurs and, because of this jamming, the nut 22 cannot be disengaged by normal methods. This use of a spanner wrench requires removal of CDM 12. It will be appreciated that module support arrangement of the invention possesses a number of advantages compared with a conventional PWR module mounting arrangement. In particular, less structural metal is required in the fuel assembly, thereby resulting in improved neutron economy and higher core power and/or endurance. Further, there is less fuel assembly distortion, which results in freer control rod motion and simpler, more reliable refueling. Further, the module support arrangement of the invention also possesses important advantages over other head-supported core arrangements including the features that the CDMs do not have to be removed to gain access to the module suspension hardware and the head thickness can be greatly reduced because only small head penetrations are required. Although the invention has been described relative to an exemplary embodiment thereof, it will be understood by those skilled in the art that variations and modifications can be effected in this exemplary embodiment without departing from the scope and spirit of the invention.
	description	The present invention relates to a corrosion-resistant structure and a corrosion-preventing method for a high-temperature water system, and particularly relates to the corrosion-resistant structure and the corrosion-preventing method for the high-temperature water system, which can effectively prevent the corrosion of a structural material that constitutes a secondary cooling system of a pressurized-water type nuclear power plant (atomic power generation facility) and can effectively reduce the elution of a ferrous component and the like from the structural material. The pressurized-water type nuclear power station (atomic power generation facility) is a reactor facility which heats pressurized water (light water with high pressure) that is a primary coolant to 300° C. or higher with thermal energy generated by a nuclear fission reaction, boils a light water of a secondary coolant with a steam generator to eventually convert the light water into steam of high temperature and high pressure, and rotates a turbine generator by using the steam to generate an electric power. This pressurized-water type reactor is used for large-sized plants such as a nuclear power station, and small plants such as a nuclear vessel (atomic-powered ship). In various plants that include the above described pressurized-water type atomic power generation facility and have a boiler, a steam generator, a heat exchanger and/or the like, in which high-temperature water circulates, it becomes a big problem that ions elute from the metal of the structural material or the structural material itself corrodes. The elution of the metal ions is a representative phenomenon occurring in the high-temperature water, and the elution causes the corrosion of structural members of pipes and equipments, including the structural material, and eventually gives various influences such as an operational problem and the increase of maintenance frequency, on the plant. In addition, the eluted metal ions from the structural material and the like adhere to and deposit on a surface of the pipes in the system, or a high-temperature site of the steam generator and the like, as an oxide, and there is a possibility that impurities form a highly concentrated state, in a narrow portion such as a crevice portion between a heat transfer tubing and a tube-support-plate in a heat exchanger. The impurities also may form an ion-enriched water having strong acidity or strong alkalinity according to the ion balance, and further cause remarkable corrosion. A phenomenon of corrosion cracking in the structural material is also confirmed which is caused by such a phenomenon and a rise of an electrochemical potential due to the oxide which adheres to the surface. Heat transfer also decreases due to the adhering oxide, and accordingly it is needed to remove the oxide on the structural material by chemical cleaning or the like periodically with a high frequency. On the other hand, there has been a high possibility in recent years that the thickness of a carbon steel pipe decreases due to a wall-thinning phenomenon of the pipe and such an accident that the pipe is ruptured also occurs. Thus, the elution, the corrosion phenomenon and the like of the metal are accumulated with time during a plant operation in a long period of time, and potentially show a possibility of suddenly erupting into a disaster at some point when the accumulated amount has reached to a durable limit. Furthermore, the above described corrosion rate is accelerated depending on a shape of a structural site, and a phenomenon which is difficult to be predicted may occur. For instance, in a piping system in which many equipments such as an orifice and a valve are used, erosion or corrosion is caused by the flow of a fluid of high temperature such as a cooling water which passes through the inner space at a high speed. In order to avoid such a problem, various corrosion mitigation methods including a water chemistry control have been conventionally implemented in various plant systems. For instance, in the secondary cooling system of a thermal power station and a pressurized-water type nuclear power station, such measures are taken as to control a pH in a cooling water by injecting ammonia or hydrazine, thereby decrease the elution of iron from the inside of the system and prevent the inflow of the iron component to the steam generator (Patent Literature 1). Furthermore, in order to eliminate the enrichment of alkaline components in the crevice portion, various water chemistry controls have been implemented in an actual plant, such as the control of an Na/Cl ratio, the control of chloride ion concentration for decreasing an influence of a chlorine ion on corrosion, and the control of dissolved oxygen concentration (Patent Literature 2). In recent years, a water chemistry control method is also adopted which uses improved chemicals such as ethanolamine and morpholine. As described above, various technologies for controlling the water chemistry have been proposed as an improved proposal, in addition to the measures which have been already implemented in the actual plant, such as reductions of the corrosion of pipes, the adhesion and deposition of an oxide and the like, and the enrichment of eluted components in the crevice portion. As for the improvement of the chemicals to be injected, for instance, there is a method of using an organic acid such as tannic acid and ascorbic acid as an oxygen scavenger (Patent Literature 3). In addition, as for the water chemistry control method, there are proposed an operation method of controlling a molar ratio of all cations/SO4 (Patent Literature 2), a method of introducing at least one of a calcium compound and a magnesium compound into feed water to a steam generator for a reactor so that the ion concentration becomes 0.4 to 0.8 ppb (Patent Literature 2), and the like. Thus, the measures of suppressing corrosion and elution by water chemistry control with the use of the chemicals are widely implemented under present circumstances as a measure of preventing the corrosion and elution of a plant structural material. However, such a technology is desired which can operate the plant without controlling a water chemistry of the cooling water by injecting the chemicals, from the viewpoints of the complexity of operation management, an operation cost and the safety. Patent Literature 1: Japanese Patent No. 2848672 Patent Literature 2: Japanese Patent No. 3492144 Patent Literature 3: Japanese Patent Laid-Open No. 2004-12162 A present secondary cooling system of a pressurized-water type atomic power generation facility is operated in a state of having a chemical agent such as hydrazine and ammonium injected therein so as to suppress its corrosion. A new technology is necessary in order to enable the plant to be operated without the injection of the chemicals. Then, an object of the present invention is to provide a corrosion-resistant structure and a corrosion-preventing method for a high-temperature water system, which can easily operate the plant while obtaining an effective corrosion-preventing effect, not by controlling the water chemistry of a cooling water by injecting the chemicals into the structure, but by providing a technology of modifying a surface of a structural material. In order to achieve the above described object, a corrosion-resistant structure for a high-temperature water system according to one embodiment of the present invention has a corrosion-resistant film formed from a substance containing at least one of La and Y deposited on a surface in a side that comes in contact with a cooling water, of a structural material which constitutes the high-temperature water system that passes a cooling water of high temperature therein. The corrosion-resistant film which is formed from the substance containing at least one of La and Y and has deposited on the surface can effectively prevent the corrosion of the structural material, and can greatly reduce the elution of a metal component such as iron from a cooling water contact surface of the structural material. In the corrosion-resistant structure for the high-temperature water system, the temperature of the cooling water of high temperature is preferably 20° C. or higher and 350° C. or lower. The above described corrosion-preventing effect of the corrosion-resistant film which has deposited on the surface of the structural material shows an anticorrosive effect in a wide temperature range from the above described ordinary temperature to an operation temperature of the secondary cooling system of the pressurized-water type atomic power generation facility. Furthermore, in the above corrosion-resistant structure of the high-temperature water system, the substance containing La is preferably at least one La compound selected from La2O3, La(OH)3, La2(CO3)3, La(CH3COO)3 and La2(C2O4)3. Any one of these La compounds shows an excellent anticorrosive effect when being contained in the corrosion-resistant film. In the corrosion-resistant structure for the high-temperature water system, the substance containing Y is preferably at least one Y compound selected from Y(OH)3, Y2(CO3)3, Y(CH3COO)3 and Y2(C2O4)3. Any one of these Y compounds shows an excellent anticorrosive effect when being contained in the corrosion-resistant film, though the effects are different to some extent according to the type. In the corrosion-resistant structure for the high-temperature water system, the structural material (structural member) is preferably at least one structural material selected from a carbon steel, a copper alloy and an Ni-based alloy. Any one of the carbon steel, the copper alloy and the Ni-based alloy can effectively prevent the elution of its metal component even though the above described structural material is any one of them. In the corrosion-resistant structure for the high-temperature water system, the deposition amount of La is preferably 1 μg/cm2 or more and 200 μg/cm2 or less. When the deposition amount of La is in the above described range, a high corrosion-preventing effect can be obtained. On the other hand, even when the deposition amount of La exceeds the upper limit of the above described range, the corrosion-preventing effect results in being saturated. Furthermore, in the above corrosion-resistant structure for the high-temperature water system, the deposition amount of Y is preferably 1 μg/cm2 or more and 200 μg/cm2 or less. When the deposition amount of Y is in the above described range, a high corrosion-preventing effect is obtained. On the other hand, even when the deposition amount of Y exceeds the upper limit of the above described range, the corrosion-preventing effect results in being saturated, similarly to the La compound. In addition, a corrosion-preventing method for a high-temperature water system according to the present invention for preventing a corrosion of a structural material constituting the high-temperature water system through which a cooling water of high temperature passes includes steps of: preparing a corrosion inhibitor containing at least one of La and Y; and depositing a prepared corrosion inhibitor on a surface in a side of the structural material, which comes in contact with the cooling water, and forming a corrosion-resistant film thereon. In the above description, it is preferable to previously subject a surface in a side on which the structural material comes in contact with the cooling water, to any one treatment among machining treatment, immersion treatment in high-temperature water and chemical cleaning treatment, before depositing the corrosion-resistant film. In other words, when a cooling water contact surface of the structural material is previously subjected to the machining treatment such as grinding by a liner or the like, thereby an oxide film and a foreign substance of the surface portion are removed and a newly-formed surface is made to appear, the newly-formed surface can enhance an adhesion strength of the corrosion-resistant film. In addition, it is preferable that the structural material is subjected to the treatment of immersion into a high-temperature water of 200° C. to 350° C., thereby an oxide film of the structural material is formed on the surface of the structural material (substrate, base member) and the corrosion resistant film is formed on the surface of this oxide film. This oxide film further enhances a function of the corrosion-resistant film containing La and Y, and can further enhance the corrosion-preventing effect. Furthermore, when the structural material is previously subjected to a chemical cleaning treatment of cleaning the cooling water contact surface of the structural material with an acid or the like, thereby to remove the oxide and the foreign substance and to make a newly-formed surface appear, the newly-formed surface can enhance an adhesion strength of the corrosion-resistant film, similarly to the above described case of the structural material which has been subjected to the machining treatment. In addition, in the above described corrosion-preventing method for the high-temperature water system, the above described method of depositing the corrosion inhibitor on the surface of the structural material is preferably any one of a spray method, a CVD method, a thermal spray method and an immersion method in which the structural material is immersed into a high-temperature water containing the corrosion inhibitor. The above described spray method is a method of spraying the corrosion inhibitor onto the surface of the structural material with a high pressure gas such as nitrogen gas; the CVD method is a method of chemically vaporizing the corrosion inhibitor, and vapor-depositing the corrosion inhibitor on the surface of the structural material; the thermal spray method is a method of spraying a melted corrosion inhibitor onto the surface of the structural material so as to cover the surface with the melted corrosion inhibitor; and the immersion method is a method of immersing the structural material into the high-temperature water containing the corrosion inhibitor and depositing the corrosion inhibitor on the surface of the structural material. Any method can be more promptly and easily applied to the structural material, in comparison with a conventional operation of controlling a water chemistry of a cooling material. According to the corrosion-resistant structure and the corrosion-preventing method for the high-temperature water system of the present invention, a corrosion-resistant film formed from a substance containing at least one of La and Y is deposited on a surface of a structural material, accordingly the structural material can be effectively prevented from causing corrosion, and an elution of a metal component such as iron from the cooling water contact face of the structural material can be greatly reduced. In addition, the above described corrosion-resistant film shows an excellent corrosion-preventing effect even when the deposition amount is small, and on the other hand, maintains the corrosion-preventing effect for a long period of time because of having high adhesion strength between the corrosion-resistant film and the structural material. Examples of the corrosion-resistant structure and the corrosion-preventing method for the high-temperature water system according to the present invention will be more specifically described hereinbelow with reference to the attached drawings. Firstly, an example of the present invention in which a corrosion-resistant film containing a La compound as a corrosion inhibitor is formed on a structural material will be concretely described below with reference to the attached FIG. 1 and FIG. 2. A corrosion-resistant structure for a high-temperature water system according to the present example 1 includes two types of structures, as are illustrated in FIG. 1 and FIG. 2. Specifically, FIG. 1A is a view of an example in which a corrosion-resistant film 3 formed from La2O3 has been formed on the surface of a carbon steel that is used as a structural material (substrate, base member) 1 and has a uniform oxide film 2 formed thereon; and FIG. 1B is a view illustrating an example (test piece) in which the corrosion-resistant film 3 formed from La2O3 has been directly formed on a surface of the structural material 1 from which an ununiform oxide film has been previously removed. For information, the oxide film 2 in FIG. 1A was formed by oxidizing a surface portion of the carbon steel which was used as the structural material 1, in the atmosphere of 150° C. In addition, a carbon steel 1 that was used as the structural material in FIG. 1B had a newly-formed surface exposed thereon which had a smooth and uniform surface roughness, by acid-pickling the surface. Next, a test piece was prepared as a Comparative Example (reference) which was formed only from a carbon steel and did not have an oxide film and a corrosion-resistant film formed thereon, in addition to the two types of the examples in which the corrosion-resistant film was prepared by depositing La2O3 on the carbon steel as was described above. The surface portions of these three types of the test pieces were subjected to a corrosion test under conditions of being immersed in the hot water which contained less than 5 ppb of dissolved oxygen and had a pH of 9.8 at a temperature of 185° C. under a pressure of 4 MPa, for 500 hours. Corrosion amounts (corrosion rates) were calculated from weight changes before and after the corrosion test of each test piece. The measurement calculation results are shown in FIG. 2. As is clear from the result illustrated in FIG. 2, it was proved that the corrosion rates were remarkably suppressed in the two types of the test pieces in the example in which the corrosion-resistant film 3 formed from La2O3 was deposited, in comparison with the test piece formed only from the carbon steel. In addition, it was also confirmed that the corrosion-suppressing effect became more remarkable when the oxide film 2 existed. Thus, it was proved that the corrosion-suppressing function for the carbon steel could be effectively shown by La2O3 which was deposited on the surface of the structural material. It is expected according to the above described experimental results that an effect of suppressing general corrosion due to a cooling water and an effect of suppressing a wall thinning phenomenon due to flow-accelerated corrosion can be exhibited by an La-containing compound which has been deposited on a surface of a carbon steel material constituting a secondary cooling system of a pressurized-water type atomic power generation facility. For information, it is confirmed by an experiment that the above described corrosion-preventing effect is not limited to the case in which La2O3 was used as the corrosion inhibitor but the similar effect can be shown also in the case in which La(OH)3, La2(CO3)3, La(CH3COO)3 or La2(C2O4)3 was used as the corrosion inhibitor to be deposited on the surface. Next, an example of the present invention, in which a corrosion-resistant film containing a Y compound as a corrosion inhibitor has been formed on a structural material, will be described below with reference to the attached FIG. 3. A corrosion resistant structure for a high-temperature water system according to the present example has a structure as is illustrated in a schematic view FIG. 1B. Specifically, a surface of a test piece of the present example is a newly-formed surface which is exposed by removing the oxide film with chemicals. Y(OH)3 was used as a corrosion inhibitor. Then, a corrosion-resistant film 3 was formed with the use of a spray coating method of spraying a chemical agent containing Y(OH)3 onto the cooling water contact surface of a carbon steel together with nitrogen gas and depositing the chemical agent. As a result of having examined a state of the formed corrosion-resistant film 3 through SEM observation, it was confirmed that a spot-shaped lump of Y(OH)3 of a micrometric order was formed on a surface portion of the carbon steel. It was proved from this observation result that the deposition uniformity of the corrosion-resistant film 3 was low and the deposition amount of Y(OH)3 was 90 μg/cm2, but that the film thickness considerably dispersed or scattered depending on the site of the carbon steel. Next, a test piece was prepared as a Comparative Example (reference) which was formed only from a carbon steel and did not have an oxide film and a corrosion-resistant film formed thereon, in addition to the example in which the corrosion-resistant film was prepared by depositing Y(OH)3 on the carbon steel as was described above. The surface portions of these two types of the test pieces were subjected to a corrosion test under conditions of being immersed in the hot water which contained less than 5 ppb of dissolved oxygen and had a pH of 9.8 at a temperature of 185° C. under a pressure of 4 MPa, for 500 hours, in a similar way to that in Example 1. Corrosion amounts (corrosion rates) were calculated from weight changes before and after the corrosion test of each test piece. The measurement calculation results are shown in FIG. 3. As is clear from the result illustrated in FIG. 3, it was proved that the corrosion rate was suppressed to approximately one-tenth in the test piece in Example 2 in which the corrosion-resistant film formed from Y(OH)3 was deposited, and that an excellent corrosion-preventing effect could be shown, in comparison with the test piece formed only from the carbon steel. Thus, it was proved that the corrosion-suppressing function for the carbon steel could be effectively shown by Y(OH)3 which was deposited on the surface of the structural material. It is expected on the basis of the above described experimental result that an effect of suppressing general corrosion of the structural material and an effect of suppressing a wall thinning phenomenon due to flow-accelerated corrosion are shown when Y(OH)3 has been deposited on a surface of a structural material constituting a secondary cooling system of a pressurized-water type atomic power generation facility. In addition, it is confirmed by an experiment that the above described corrosion-preventing effect is not limited to the case in which Y(OH)3 was used as a corrosion inhibitor, but that the similar effect can be shown also in the case in which Y2(CO3)3, Y(CH3COO)3 or Y2(C2O4)3 was used as the corrosion inhibitor to be deposited on the surface of the structural material. Next, an influence which a difference of an operation temperature (temperature of cooling water) gives on a corrosion-resistant structure will be described below with reference to the following Example 3 and FIG. 4. A corrosion-resistant structure for a high-temperature water system according to the present Example 3 has a structure as is illustrated in a schematic view FIG. 1B. Specifically, a test piece used for the test piece of the present example was in such a state that the surface of a carbon steel before a corrosion-resistant film was deposited thereon had been polished and degreased by a sandpaper with #600, and that an oxide film and a foreign substance had been removed therefrom. Then, the test piece according to Example 3 was prepared by depositing Y(OH)3 onto the surface (newly-formed surface) of this carbon steel with a spray method. A deposition amount of Y(OH)3 in this test piece was set at 50 μg/cm2 by adjustment of a spraying period of time. As a result of having examined a state of the formed corrosion-resistant film 3 through SEM observation, the uniformity was low similarly to that in Example 2. Next, a test piece was prepared as a Comparative Example which was formed only from a carbon steel and did not have an oxide film and a corrosion-resistant film formed thereon, in addition to the example in which the corrosion-resistant film was prepared by depositing Y(OH)3 on the carbon steel as was described above. Then, the surface portions of these two types of the test pieces were subjected to a corrosion test under conditions of being immersed in the hot water which contained 5 ppb or less of dissolved oxygen and had a pH of 9.8 at a temperature in two levels of 150° C. and 280° C. under a pressure of 4 MPa and 8 MPa, for 500 hours, in a similar way to that in Example 1. Corrosion amounts (corrosion rates) were calculated from weight changes before and after the corrosion test of each test piece. The measurement calculation result is shown in FIG. 4. As is clear from the result illustrated in FIG. 4, the corrosion amount of the test piece formed only from the carbon steel also decreases under the condition that the temperature is as high as 280° C. This is considered to be because the formed oxide film has high stability because the temperature is high. On the other hand, it is understood that the corrosion rate becomes large when the temperature is 150° C. because the solubility of the oxide film to be formed under the condition of the present test is high, and that the corrosion-suppressing function works due to the deposition of Y(OH)3. Therefore, the corrosion-resistant structure can be applied in such an environment that a cooling water is 20° C. or higher and 350° C. or lower which is an operation temperature of a secondary cooling system of a pressurized-water type atomic power generation facility, in view of the fact that Y(OH)3 is resistant to high temperature. In addition, as is clear from FIG. 4, the corrosion-resistant structure according to the present example is particularly effective in a range of an operation temperature of 150° C. or higher after a deaerator, in a secondary cooling system of a pressurized-water type atomic power generation facility, and it is expected that an effect of suppressing an general corrosion of a structural material and a function of suppressing a wall thinning phenomenon due to flow-accelerated corrosion are effectively shown when a chemical agent containing Y is injected into the system and is deposited on a surface of a structural material. Next, an influence which a difference of a deposition amount of a corrosion inhibitor to be deposited on a surface of a structural material gives on a corrosion amount will be described below with reference to the following Example 4 and FIG. 5. A corrosion-resistant structure for a high-temperature water system according to the present Example 4 has a structure as is illustrated in a schematic view FIG. 1B. Specifically, a test piece used for the test piece of the present Example 4 was in such a state that the surface of a carbon steel before a corrosion-resistant film was deposited thereon had been polished and degreased by a sandpaper with #600, and an oxide film and a foreign substance had been removed therefrom. Then, a large number of two types of test pieces according to Example 4 were prepared by depositing La2O3 or Y(OH)3 onto the surface (newly-formed surface) of this carbon steel with a spray method. For information, a deposition amount of La2O3 or Y(OH)3 was varied and adjusted in a range of 0 to 300 μg/cm2 by adjustment of a spraying period of time. Next, a test piece was prepared as a Comparative Example which was formed only from a carbon steel and did not have an oxide film and a corrosion-resistant film formed thereon, in addition to the example in which the corrosion-resistant film was prepared by depositing La2O3 or Y(OH)3 on the surface of the carbon steel as was described above. Then, the surface portions of these test pieces were subjected to a corrosion test under conditions of being immersed in the hot water which contained 5 ppb or less of dissolved oxygen and had a pH of 9.8 at a temperature of 185° C. under a pressure of 4 MPa, for 500 hours, in a similar way to that in Example 1. Corrosion amounts (corrosion rates) were calculated from weight changes before and after the corrosion test of each test piece. The measurement calculation result is shown in FIG. 5. As is clear from the result illustrated in FIG. 5, it was confirmed that the corrosion amount tended to decrease and the corrosion-suppressing effect tended to increase, as the deposition amount of the corrosion-resistant film increased. It was also confirmed that the corrosion-suppressing effect was saturated and the corrosion rates reached approximately a same level, in a range of a deposition amount of 20 μg/cm2 or more. Accordingly, the deposition amount of the corrosion-resistant film is necessary and sufficient to be in the range of 20 to 120 μg/cm2. Here, a deposition amount of the corrosion inhibitor remaining on a surface of the test piece of which the deposition amount had been set to approximately 50 μg/cm2 before the corrosion test was examined after the corrosion test, and as a result, it was confirmed that the deposition amount was 1 μg/cm2 or less. As a result, it was confirmed that the corrosion-preventing effect continued as long as a fixed deposition amount of an La-containing or Y-containing chemical agent was attained in an initial stage of the application, even though the deposition amount was not always kept constant or the deposition amount decreased due to an exfoliation of the deposited chemical agent during an operation period. It is technically difficult to uniformly deposit the present corrosion inhibitor on the surface of the structural material of the secondary cooling system of the pressurized-water type atomic power generation facility so that the deposition amount becomes uniform, and it is anticipated that the deposition amount of the corrosion inhibitor greatly varies according to an influence of a flow of a cooling water, and depending on a temperature of the cooling water and a structure of the high-temperature water system. However, such a technological knowledge is an important premise for the technology that an initial corrosion-preventing effect develops even when the deposition amount of the corrosion inhibitor has greatly varied depending on the site of the structural body as has been described above, and is extremely useful when the technology is applied to an actual apparatus. Next, an influence which a difference between methods of depositing a corrosion inhibitor on a surface of a structural material gives will be described below with reference to the following Example 5 and FIG. 6. A corrosion-resistant structure for a high-temperature water system according to the present Example 5 has a structure as is illustrated in a schematic view FIG. 1B. Specifically, a test piece used for the test piece of the present Example 5 was in such a state that the surface of a carbon steel before a corrosion-resistant film was deposited thereon had been polished and degreased by a sandpaper with #600, and an oxide film and a foreign substance had been removed therefrom. Then, two types of test pieces according to Example 5 were prepared by depositing La2O3 onto the surface (newly-formed surface) of this carbon steel with a spray method or a chemical deposition method of injecting a chemical substance into a high-temperature water and depositing the chemical substance. In the above description, the deposition amount of La2O3 was adjusted to 50 μg/cm2 by adjustment of a spraying period of time or an amount of the chemical agent to be injected into the high-temperature water. Here, the above described chemical deposition method is a method of making a substance to be deposited exist in a fluid, and depositing the substance onto a surface of a structural material by a flow of the fluid. Next, the surface portions of the two types of the test pieces which were prepared by depositing La2O3 on the surface of the carbon steel with different methods as was described above were subjected to a corrosion test under conditions of being immersed in the hot water that contained 5 ppb or less of dissolved oxygen and had a pH of 9.8 at a temperature of 185° C. under a pressure of 4 MPa, for 500 hours, in a similar way to that in Example 1. Then, corrosion amounts (corrosion rates) were calculated from weight changes before and after the corrosion test of each test piece. The measurement calculation result is shown in FIG. 6. As is clear from the result illustrated in FIG. 6, the corrosion-resistant film which had been deposited and formed with the chemical deposition method was different from and could be more uniformly deposited than the corrosion-resistant film which had been formed with the spray method, and it was confirmed that the corrosion-resistant film which had been formed with the chemical deposition method had a greater corrosion-rate-suppressing function. It is expected that the deposition of the corrosion-resistant film having high uniformity can be achieved by injecting an La-containing substance into a high-temperature cooling water during an operation of the secondary cooling system of the pressurized-water type atomic power generation facility and by depositing the substance onto the surface of the structural material, and that thereby an effect of suppressing general corrosion and an effect of suppressing a wall-thinning phenomenon due to flow-accelerated corrosion are shown. A similar effect can be shown also when a Y-containing substance has been injected into the high-temperature cooling water. Next, an effect appearing when La(OH)3 or Y2(CO3)3 as other corrosion inhibitors has been deposited on a surface of a structural material will be described below with reference to the following Example 6 and FIG. 7. A corrosion-resistant structure for a high-temperature water system according to the present Example 6 has a structure as is illustrated in a schematic view FIG. 1B. Specifically, a test piece used for the test piece of the present Example 6 was in such a state that the surface of a carbon steel before a corrosion-resistant film was deposited thereon had been polished and degreased by a sandpaper with #600, and an oxide film and a foreign substance had been removed therefrom. Then, two types of test pieces according to Example 6 were prepared by depositing La(OH)3 or Y2(CO3)3 onto the surface (newly-formed surface) of this carbon steel with the use of a spray method. For information, a deposition amount of La(OH)3 or Y2(CO3)3 was adjusted to 50 μg/cm2 by adjustment of a spraying period of time. Next, the surface portions of the two types of the test pieces which were prepared by depositing La(OH)3 or Y2(CO3)3 on the surface of the carbon steel as was described above were subjected to a corrosion test under conditions of being immersed in the hot water that contained 5 ppb or less of dissolved oxygen and had a pH of 9.8 at a temperature of 185° C. under a pressure of 4 MPa, for 500 hours, in a similar way to that in Example 1. Then, corrosion amounts (corrosion rates) were calculated from weight changes before and after the corrosion test of each test piece. The measurement calculation result is shown in FIG. 7. As is clear from the results illustrated in FIG. 7, when the corrosion amounts of the two types of the test pieces which were prepared by depositing La(OH)3 or Y2(CO3)3 on the surface of the carbon steel were compared to each other, the corrosion amounts were not greatly different from each other, but it was confirmed that when the two types of the test pieces were compared to the test piece formed only from the carbon steel illustrated in Examples 1 and 2, the corrosion rates were remarkably suppressed. It was experimentally proved that a great corrosion-preventing effect was obtained by depositing and forming a hydroxide of La or a carbonate of Y on the surface of the structural material as in the above described Example 6. Accordingly, it is expected that an effect of suppressing general corrosion of the structural material and an effect of suppressing a wall thinning phenomenon due to flow-accelerated corrosion are shown also when the hydroxide and the carbonate are deposited on the surface of the structural material in the secondary cooling system of the pressurized-water type atomic power generation facility. According to the corrosion-resistant structure and the corrosion-preventing method for the high-temperature water system of the embodiments of the present invention, a corrosion-resistant film formed from a substance containing at least one of La and Y is deposited on the surface of the structural material, accordingly the structural material can be effectively prevented from causing corrosion, and an elution of a metal component such as iron from the cooling water contact surface of the structural material can be greatly reduced. In addition, the above described corrosion-resistant film shows an excellent corrosion-preventing effect even when the deposition amount is small, and on the other hand, can maintain the corrosion-preventing effect for a long period of time because of having high adhesion strength between the corrosion-resistant film and the structural material. 1 Structural material (carbon steel) 2 Oxide film (Oxide layer) 3 Corrosion-preventing film (La2O3 film, Y(OH)3 film, La(OH)3 film or Y2(CO3)3 film) 4 Cooling water (Coolant)
	abstract	A core spray T-box attachment assembly for a core spray nozzle includes a primary cruciform wedge and a secondary cruciform wedge in contact with the primary cruciform wedge to form a cruciform wedge subassembly adapted for insertion within a bore of the core spray nozzle to sealingly engage an interior converging portion of a safe end of the core spray nozzle. The assembly includes a spider in contact with the cruciform wedge subassembly, and a draw bolt engaging an axial bore of a center portion of the cruciform wedge subassembly and the spider to the T-box.
044118570	description	DESCRIPTION OF THE PREFERRED EMBODIMENT In FIG. 1 reference number 10 generally designates an actuator housing that extends through an aperture 12 in the cover 14 of the containment vessel of a nuclear reactor, this housing projecting upwardly from the cover and having mounted herein a pair of vertically disposed lead screws 16, 18 that are respectively threadedly engaged in apertures in a carriage 20. Lead screws 16, 18 are connected to an electric motor 22 by gearing 24. Reference number 26 generally designates a piston-cylinder type ram the housing 28 of which is mounted on carriage 20 and the piston 30 of which is connected to a vertically disposed control rod 32 slidably fitted in an aperture in the carriage. A coil-type spring 34 is located between piston 30 and the top cover of housing 28, and a conduit 36 connects a source of pressurized fluid with the space in the housing below piston 30 through an inlet 37 in the housing wall. Concentrically disposed around control rod 32 is a tubular drive shaft 38 the upper end of which is fixedly secured to carriage 20. Drive shaft 38 is slidably positioned in a central aperture in a seal plug 40 fitted in housing 10, and in the illustrated configuration of the described apparatus the lower end of the drive shaft is disposed adjacent a latch generally designated by reference number 42. This latch 42 comprises the following parts: (1) a disk-shaped latch base 44 formed with a central aperture in which the lower end of rod 32 is fixed; (2) a plurality of elongate, downwardly projecting elements 46 (referred to hereinafter as fingers) which are integrally attached to base 44 at points evenly spaced about the periphery thereof; (3) lugs 48 (referred to hereinafter as detent elements) which are respectively integrally formed on the lower ends of fingers 46 and which project radially from the fingers toward the common longitudinal axis of control rod 32 and drive shaft 38; and (4) first cam elements 50 which are also respectively integrally formed on the lower ends of fingers 46 and project downwardly from detent elements 48, each cam element having a cam surface disposed oblique to the longitudinal axis of drive shaft 38. In the illustrated configuration of the described apparatus, detent elements 48 are positioned in a recess 52 formed in the outer side surface of a vertically disposed shaft 54 at the upper end thereof, the detents abutting the horizontally extending shoulder at the upper end of said recess. At the lower end of drive 38 is a second annular cam element 56 which projects inwardly from the wall of the drive shaft and which comprises a cam surface disposed oblique to the longitudinal axis of the drive shaft. An assembly 58 containing material that captures neutrons is attached to the lower end of shaft 54, which assembly will be referred to hereinafter as the absorber. A shaft 60 depends from this absorber and supports a disk-shaped piston 62 at its lower end. In the illustrated configuration of the described components, absorber 58 is positioned above a nuclear reactor core 64 having an aperture 66 therein. A second embodiment of the invention that is illustrated in FIG. 2 includes a vertically disposed drive shaft 38a connected at its upper end to a carriage of the type designated by reference number 20 in FIG. 1, the carriage being mounted on lead screws 16, 18 connected to a motor 22 as shown in the last-mentioned drawing. The two latch mechanisms that are included in the second embodiment of the invention differ however, from the latch mechanism used in the FIG. 1 embodiment. In the configuration of components illustrated in FIG. 2, the upper end of a vertically disposed, tubular shaft 68 is inserted into the lower end of drive shaft 38a, the upper end of shaft 68 having a reduced diameter so that it releasably fits inside the drive shaft. A flange 70 projects outwardly from the lower end of drive shaft 38a, and a sleeve 72 extends downwardly from the periphery of this flange. Reference number 74 generally designates a first latch comprising a ring 76 the outer side surface of which slidably confronts the inner surface of sleeve 72 and the top surface of which abuts the lower end of drive shaft 38a in the illustrated arrangement of the components. Holes 78 are evenly spaced around the upper surface of ring 76, these holes extending only partially through the ring and being respectively aligned with apertures 80 that extend through flange 70 on drive shaft 38a. A solenoid 82 is mounted around drive shaft 38a adjacent flange 70, and coil-type springs 84 are respectively positioned in holes 78 in ring 76 and apertures 80 in flange 70 with their lower ends engaged with the bottom surfaces of holes 78 and their upper ends engaged with the lower surface of the solenoid. Attached to ring 76 of latch 74 are fingers 46a, detent elements 48a, and first cam elements 50a that are identical to components 46, 48, and 50 of latch 42 illustrated in FIG. 1 and described hereinbefore. Shaft 68 is provided with a recess 52a corresponding to recess 52 depicted in FIG. 1, and in FIG. 2 detent elements 48a of latch 74 are positioned in this recess. Integrally formed on the lower end of sleeve 72 is a second annular cam element 56a identical to cam element 56 in the FIG. 1 embodiment. At the upper end of shaft 68 is a ram 26a having the same type of construction as ram 26 of FIG. 1. A partition 86 in the upper interior portion of shaft 68 forms a chamber 88 in which a piston 30a is slidably situated and a control rod 32a is connected to the piston and slidably engaged in an aperture in the partition. Piston 30a and control rod 32a are biased downwardly by a coil-type spring 34a held between the piston and an end wall 90 on shaft 68. Duplication of the components of ram 26 of the FIG. 1 embodiment of the invention is completed by a conduit 36a that connects a source of pressurized fluid with the space in chamber 88 below piston 30a through an inlet 37a. The lower end of control rod 32a is attached to a second latch generally designated by reference number 90. Like latch 42 of the FIG. 1 embodiment of the invention, latch 90 includes a disk-shaped latch base 92 and a plurality of elongate downwardly projecting elements 94 (referred to hereinafter as fingers) which are integrally attached to the base at points evenly spaced about the periphery thereof. The lower end of each finger 94 has a bulbous gripping element 96 integrally formed thereon. In the illustrated configuration of the latch components, the inner surfaces of gripping elements 96 abut the enlarged end 98 of a short shaft 100 that supports a neutron absorber 58a, and the outer surfaces of the gripping elements abut the inner surface of a cam lip 102 diverging outwardly from shaft 68 at the lower end thereof. Fingers 94 are arranged so that they will spread away from the longitudinal axis of shaft 68 when latch 90 is moved downwardly by control rod 32a and gripping elements 96 are allowed to slide downwardly along the outwardly diverging inner surface of cam lip 102. A permanent magnet 104 mounted on shaft 68 tracks the safety rod by actuating reed switches 106 mounted on a tube 108 located outside the shaft. This position detection is possible only during scrams when the entire safety rod translates. OPERATION OF PREFERRED EMBODIMENT As will be understood from the previous description, when drive shaft 38 and control rod 32 of the first-described embodiment of the invention are positioned as illustrated in FIG. 1, the neutron absorber 58 on the end of shaft 54 is held above the nuclear reactor core 64. If a condition developes that requires shutdown of the reactor, pressuring fluid in housing 28 below piston 30 is released through conduit 36. Spring 34 then forces piston 30 and control rod 32 connected thereto downwardly, which moves first cam elements 50 on the fingers 46 of latch 42 into engagement with the second cam element 56 on the end of drive shaft 38. Since the oblique camming surface on cam element 56 is spaced farther from the longitudinal axis of drive shaft 38 than the oblique camming surface on each of the cam elements 50, the lower ends of fingers 46 are flexed away from shaft 54 and the detent elements 48 on the fingers are moved out of the recess 52 on the last-mentioned shaft. Shaft 54 is thus allowed to move downwardly to a level wherein absorber 58 carried by the shaft is positioned within core 64. As will be recognized by persons familiar with the design of nuclear reactors, pressure can be applied to piston 62 to assist the force of gravity in moving absorber 58 downwardly when the reactor must be scrammed. Retrieval of shaft 54 and absorber 58 from their lowered position is effected by operating motor 22 to rotate lead screws 16, 18 in the direction which lowers carriage 20 and drive shaft 38 mounted thereon to a position where the lower end of the drive shaft is disposed around the upper end of shaft 54 and cam elements 56 are positioned relative to recess 52 in shaft 54 as illustrated in FIG. 1. Fluid is then forced into housing 28 below piston 30 to drive the piston upwardly in the housing. This movement of piston 30 lists cam elements 50 upwardly from cam element 56 and fingers 46 spring back to the position wherein detent elements 48 are disposed in recess 52 in shaft 54. Lead screws 16, 18 are then rotated by motor 22 in the direction which raises drive shaft 38 and shaft 54 to the position thereof that is illustrated in FIG. 1. The apparatus illustrated in FIG. 2 provides for insertion of absorber 58a into a reactor core under different conditions. During normal operation of the reactor with which the apparatus is associated electric current flows through solenoid 82 and the magnetic field of the solenoid holds ring 76 of latch 74 against the flange 70 at the lower end of drive shaft 38a so that shaft 68 and absorber 58a are held in raised position. If a non-seismic event occurs that requires insertion of absorber 58a into the reactor core, flow of electric current through solenoid 82 is terminated. Latch 74 is then pulled downwardly by shaft 68 and absorber 58a, and when cam elements 50a are cammed away from the shaft by cam element 56a, the shaft and absorber are released from the latch. Conduit 36a is in the form of an extensible coil and thus it does not interfere with movement of shaft 68. However, if a seismic event occurs, it is advantageous, for the reasons presented hereinbefore, to release absorber 58a from shaft 68. This can be accomplished by releasing pressurizing fluid from chamber 88 below piston 30a in the upper portion of shaft 68, whereupon spring 34a forces the piston and control rod 32a downwardly and gripping elements 96 move away from, and release, the bulbous upper end of shaft 100. To recover shaft 68 and absorber 58a when shaft 68 has been released, the carriage 20 connected to the upper end of drive shaft 38a is moved downwardly by lead screws 16, 18 until sleeve 72 is positioned around the upper end of shaft 68 as illustrated in FIG. 2. Springs 76 maintain cam elements 50a against cam element 56a while drive shaft 38a is being lowered. Ring 76 of latch 74 is then lifted against flange 70 on the lower end of drive shaft 38a by passing electric current through solenoid 82, which enables detent elements 48a to spring into recess 52a on shaft 68. Lead screws 16, 18 are then rotated to raise carriage 20 and the absorber support assembly. When absorber 58a has been released from shaft 68 to shut down the reactor during a seismic disturbance, carriage 20 is lowered to bring cam lip 102 at the lower end of shaft 68 around the enlargement on shaft 100. Then pressurizing fluid is forced into chamber 88 below piston 30a to lift latch 90, which engages cam elements 96 with the end of shaft 100, absorber assembly attached thereto.
	claims	1. A method, comprising:identifying a drillhole that extends from a terranean surface and into one or more subterranean formations, the drillhole comprising a vertical portion, a curved portion, and a horizontal portion that comprises a hazardous waste repository formed within the horizontal portion of the drillhole;dropping a test canister into the drillhole in a free fall event;determining, based on a travel distance of the dropped test canister into the horizontal portion of the drillhole, a length of a safety runway of the horizontal portion of the drillhole that is approximately equal to the travel distance from into the horizontal portion of the drillhole from a transition between the vertical portion and the horizontal portion;moving at least one hazardous waste canister through an entry of the drillhole, the at least one hazardous waste canister comprising an inner cavity that encloses hazardous waste material;moving the at least one hazardous waste canister through the vertical portion of the drillhole and through the curved portion of the drillhole;moving the at least one hazardous waste canister from the curved portion through the safety runway of the horizontal portion of the drillhole;moving the at least one hazardous waste canister from the safety runway of the horizontal portion of the drillhole into the hazardous waste repository of the horizontal portion of the drillhole, the at least one hazardous waste canister sized to fit from the entry through the vertical portion, the curved portion, the safety runway of the horizontal portion of the drillhole, and into the hazardous waste repository of the horizontal portion of the drillhole; andpositioning the at least one hazardous waste canister exclusively in the hazardous waste repository and externally to the safety runway. 2. The method of claim 1, wherein the hazardous waste material comprises nuclear waste. 3. The method of claim 2, wherein the nuclear waste comprises at least one of spent nuclear fuel or high level radioactive waste. 4. The method of claim 1, wherein the length of the safety runway is determined based at least in part on a terminal velocity of the test canister during the free fall event and a coefficient of friction between the hazardous waste canister or the test canister and the drillhole. 5. The method of claim 1, wherein the drillhole further comprises an inclined portion coupled between the curved portion and the horizontal portion. 6. The method of claim 5, further comprising moving each hazardous waste canister of the at least one hazardous waste canister sequentially from the curved portion into the inclined portion of the drillhole and from the inclined portion into the horizontal portion. 7. The method of claim 5, wherein the length of the safety runway is determined based at least in part on a terminal velocity of the test canister during the free fall event, a coefficient of friction between the hazardous waste canister or the test canister and the drillhole, and an angle of inclination of the inclined portion. 8. The method of claim 5, wherein the inclined portion is angled toward the terranean surface from the curved portion. 9. The method of claim 1, further comprising positioning a seal in the drillhole that isolates the hazardous waste repository from the entry of the drillhole. 10. The method of claim 1, wherein moving the at least one hazardous waste canister through the entry of the drillhole comprises moving each of a plurality of hazardous waste canisters sequentially through the entry. 11. The method of claim 1, wherein moving the at least one hazardous waste canister through the vertical portion of the drillhole and through the curved portion of the drillhole comprises moving each of a plurality of hazardous waste canisters sequentially through the vertical portion of the drillhole and through the curved portion of the drillhole. 12. The method of claim 1, wherein moving the at least one hazardous waste canister from the curved portion through the safety runway of the horizontal portion of the drillhole comprises moving each of a plurality of hazardous waste canisters sequentially from the curved portion through the safety runway of the horizontal portion of the drillhole. 13. The method of claim 1, wherein moving the at least one hazardous waste canister from the safety runway of the horizontal portion of the drillhole into the hazardous waste repository of the horizontal portion of the drillhole comprises moving each of a plurality of hazardous waste canisters sequentially from the safety runway of the horizontal portion of the drillhole into the hazardous waste repository of the horizontal portion of the drillhole. 14. The method of claim 1, wherein the drillhole comprises a single vertical portion, a single curved portion contiguously coupled to the single vertical portion, and a single horizontal portion contiguously coupled to the single curved portion. 15. The method of claim 14, wherein the drillhole further comprises an inclined portion coupled between the single curved portion and the single horizontal portion. 16. The method of claim 15, wherein the length of the safety runway is determined based at least in part on a terminal velocity of the test canister during the free fall event, a coefficient of friction between the hazardous waste canister or the test canister and the drillhole, and an angle of inclination of the inclined portion. 17. The method of claim 15, wherein the inclined portion is angled toward the terranean surface from the single curved portion. 18. The method of claim 1, wherein the test canister is approximately the same size as the at least one hazardous waste canister. 19. The method of claim 1, wherein the test canister is approximately the same weight as the at least one hazardous waste canister. 20. The method of claim 1, further comprising filling the drillhole with a fluid. 21. The method of claim 1, further comprising positioning a casing around the drillhole. 22. The method of claim 1, further comprising roughening a surface of the casing or a surface of the at least one hazardous waste canister. 23. The method of claim 1, further comprising removing the test canister from the drillhole before moving the at least one hazardous waste canister through the entry of the drillhole. 24. The method of claim 1, wherein the test canister is sized to fit from the entry through the vertical portion, the curved portion, the safety runway of the horizontal portion of the drillhole, and into the hazardous waste repository of the horizontal portion of the drillhole. 25. The method of claim 1, wherein dropping the test canister into the drillhole comprises dropping a set of test canisters into the drillhole, the set of test canisters including the test canister. 26. A method, comprising:identifying a drillhole that extends from a terranean surface and into one or more subterranean formations, the drillhole comprising a vertical portion, a curved portion, and a horizontal portion that comprises a hazardous waste repository formed within the horizontal portion of the drillhole;dropping a test canister into the drillhole in a free fall event;determining, based on a travel distance of the dropped test canister into the horizontal portion of the drillhole, a length of a safety runway of the horizontal portion of the drillhole that is approximately equal to the travel distance into the horizontal portion of the drillhole from a transition between the vertical portion and the horizontal portion; andsubsequent to the determination, moving at least one hazardous waste canister through an entry of the drillhole, the at least one hazardous waste canister comprising an inner cavity that encloses hazardous waste material. 27. The method of claim 26, wherein the hazardous waste material comprises nuclear waste. 28. The method of claim 27, wherein the nuclear waste comprises at least one of spent nuclear fuel or high level radioactive waste. 29. The method of claim 26, wherein the length of the safety runway is determined based at least in part on a terminal velocity of the test canister during the free fall event and a coefficient of friction between the at least one hazardous waste canister or the test canister and the drillhole. 30. The method of claim 26, wherein the drillhole further comprises an inclined portion coupled between the curved portion and the horizontal portion. 31. The method of claim 30, further comprising moving the at least one hazardous waste canister from the curved portion into the inclined portion of the drillhole and from the inclined portion into the horizontal portion. 32. The method of claim 30, wherein the length of the safety runway is determined based at least in part on a terminal velocity of the test canister during the free fall event, a coefficient of friction between the at least one hazardous waste canister or the test canister and the drillhole, and an angle of inclination of the inclined portion. 33. The method of claim 30, wherein the inclined portion is angled toward the terranean surface from the curved portion. 34. The method of claim 26, further comprising positioning a seal in the drillhole that isolates the hazardous waste repository from the entry of the drillhole. 35. The method of claim 26, wherein the test canister is approximately the same size as the at least one hazardous waste canister. 36. The method of claim 26, wherein the test canister is approximately the same weight as the at least one hazardous waste canister.
	abstract	Disclosed herein is an apparatus for recovering residual salt from the reduced uranium metal. The apparatus comprising: an evaporating chamber accommodating mixed molten salt or a reduced uranium metal; a heating furnace surrounding the evaporating chamber to heat the mixed molten salt in the evaporating chamber; an insulator disposed over the evaporating chamber to block heat generated from the evaporating chamber, and including an evaporating pipe in a center thereof to move vapor generated from the evaporating chamber; a receiver disposed over the insulator to collect powder formed by condensing and solidifying vapor passing through the evaporating pipe; and a condenser disposed over the receiver to prevent the vapor passing through the evaporating pipe from leaking out of the apparatus.
	summary
	abstract	A control rod drive system (CRDS) for use in a nuclear reactor. In one embodiment, the system generally includes a drive rod mechanically coupled to a control rod drive mechanism (CRDM) operable to linearly raise and lower the drive rod along a vertical axis, a rod cluster control assembly (RCCA) comprising a plurality of control rods insertable into a nuclear fuel core, and a drive rod extension (DRE) releasably coupled at opposing ends to the drive rod and RCCA. The CRDM includes an electromagnet which operates to couple the CRDM to DRE. In the event of a power loss or SCRAM, the CRDM may be configured to remotely uncouple the RCCA from the DRE without releasing or dropping the drive rod which remains engaged with the CRDM and in position.
	abstract	The sealing of a crack in a pool of a nuclear facility, using a robot. The sealing, concerns in particular, that of a crack in a wall of a pool of a nuclear facility. In particular, it implements a mobile robot carrying an adhesive tape dispenser. At least the following are provided: controlling a plurality of suction systems, the dispenser being mechanically integral with a first suction system, and controlling the movement of the first system relative to the other systems of said plurality of systems.
	abstract	There is provided an illumination system. The illumination system includes a light source for emitting light having a wavelength ≦193 nm, an optical system, and a radiation protection wall situated between the light source and the optical system.
	summary
	description	This application is a continuation of U.S. application Ser. No. 11/611,627 entitled “System And Method For Implementing A Suspended Personal Radiation Protection System” filed on Dec. 15, 2006, now U.S. Pat. No. 7,608,847 which claims the benefit of U.S. Provisional Application No. 60/751,371 filed on Dec. 16, 2005, the disclosures of which are incorporated herein by reference. This invention relates in general to medicine and, more particularly, to a suspended personal radiation protection garment. Radiation is used to perform many medical diagnostic and therapeutic tests and procedures. Medical, veterinary, or research personnel may be involved in the performance of such procedures in great numbers and over many years, and are being exposed to scattered radiation as they perform their work. These long-term effects are poorly understood at the present time, but are considered serious enough to warrant mandatory protection to operators in the form of garments or barriers containing materials that absorb a significant proportion of the radiation. In order to properly treat patients, operators require a freedom of motion. Providing a personal radiation protection garment that properly protects operators, while allowing operators to move freely and comfortably presents a significant challenge for medical operators in radiation environments. In accordance with the present invention, a method, a system, and an apparatus for implementing a suspended personal radiation protection garment are provided, which substantially eliminate or reduce the disadvantages and problems associated with previous systems, methods, and apparatuses. In accordance with one embodiment of the present invention, a method for a suspended personal radiation protection device includes providing a garment that substantially contours to an operator's body. The garment is operable to protect the operator from radiation. The garment is suspended from a suspension component. In accordance with another embodiment of the present invention, a method for a suspended personal radiation protection device includes providing a garment that substantially contours to an operator's body while suspended from suspension component. The suspension component is operable for operator wearing protective radiation garment to move freely in the X, Y, and Z spatial planes simultaneously, such that the protective radiation garment is substantially weightless to the operator. The suspension component is further operable to support the partial weight of the operator, such that the operator can move around in substantially zero gravity or such that the operator bears only a portion of his total weight. The suspension component can be mounted to a ceiling. The suspended personal radiation protection device further includes a face shield, such that the face shield is transparent to visible light allowing operator unhindered vision, and the face shield protects operator from radiation. The suspended personal radiation protection device further includes a flap, such that the flap is operable to protect the operator from radiation between the garment and face shield. Important technical advantages of certain embodiments of the present invention include supporting the weight of radiation protection garment, face shield, and flap worn by operators. This allows radiation protection garments to be heavier. As a result, radiation protection garments can protect larger areas of operator's body. Radiation protection garments can be thicker to increase X-ray attenuation. More radiation protection reduces operator's risk of cancers, cataracts, and skin damage. Other important technical advantages of certain embodiments of the present invention include reducing the risk and incidence of musculoskeletal injuries from wearing heavy radiation protection garments. Operators using the present invention have normal freedom of motion as if operator is not wearing heavy material. Furthermore, the present invention allows operator to move about in substantially zero gravity, such that suspension device supports majority of operator's weight, such that operators can work long periods without fatigue. Other technical advantages of the present invention will be readily apparent to one skilled in the art from the following figures, descriptions, and claims. Moreover, while specific advantages have been enumerated above, various embodiments may include all, some, or none of the enumerated advantages. For purposes of teaching and discussion, it is useful to provide some overview as to the way in which the following invention operates. The following foundational information may be viewed as a basis from which the present invention may be properly explained. Such information is offered earnestly for purposes of explanation only and, accordingly, should not be construed in any way to limit the broad scope of the present invention and its potential applications. Radiation is used to perform many medical diagnostic and therapeutic tests and procedures. The human patient or animal is subjected to radiation using doses as low as possible to enable completion of the medical task, and their exposures are monitored to prevent or reduce risks of significant damage as a result of their exposures. Medical, veterinary, or research personnel may be involved in the performance of such procedures in great numbers and over many years, and are being exposed to scattered radiation as they perform their work. Although their daily exposure is generally less than that for the patient, there are adverse effects of the cumulative, long term exposures to the operators. These long-term effects are poorly understood at the present time, but are considered serious enough to warrant mandatory protection to workers in the form of garments, other garments, or barriers containing materials, generally metallic, that absorb a significant proportion of the radiation. There are a wide variety of such barriers commercially available, and all of them have significant limitations for the operators who must come in close contact with the subject. These operators may be physicians and their assistants, or technically skilled medical personnel, who perform simple or complex medical procedures using their bodies and hands in proximity of the patient, in such positions that scatter radiation from the subject or physical elements in the direct radiation beam will pose significant health risks and unacceptably high exposure readings for the operator if he/she were unprotected. Risks of radiation exposure at the levels of medical personnel include cancers, cataracts, and skin damage. A review of current protective systems outlines their limitations. Radiation-absorbing walls are useful to contain the radiation to a room, but do not prevent exposures within their confines. Barriers within the room, such as floor or ceiling supported shields, are effective at blocking radiation for personnel who are not in close contact with the radiation field, such as some nurses and technologists, but must be positioned or repositioned frequently when personnel move around the room, and provide cumbersome interference for operators performing the actual medical procedure. They may also be difficult to keep sterile when attempting to use them within the sterile field. The most commonly used protection for operators involves the use of garments containing radiation-absorbing materials, generally lead or other metals, which are worn in the fashion of an garment, or skirt and vest, and do not contaminate the sterile field because they are worn underneath the sterile covering gown. These garments are heavy and uncomfortable, and their long-term usage is known to be associated with diseases of the spine in the neck and back, knee disorders, and other musculoskeletal problems, which can result in disability, medical expenses, and decreased quality of life for the operator. The trade-off between protection and garment weight results in the frequent use of garments that do not cover the legs optimally, and may provide sub optimal radiation protection due to the thickness of the metallic material being limited by the tolerability of the operator. To protect other radiation sensitive tissues such as the corneas of the eye and the thyroid, special heavy glasses containing metallic compounds and a collar around the neck are often worn. Even when the operator is encumbered with these items, the base of the skull, which may contain sensitive bone marrow, and the face are unprotected. Personal face and neck shields address this problem, and are commercially available, but are rarely worn due to their cumbersome nature and heavy weight. Such problems have been present for many years and there are patents attempting to address them. Modifications to floor-supported mobile shields appear to attempt to provide improved dexterity for the operator relative to the standard bulky mobile barrier, and a floor support system with a modified garment design also attempts the same. However, they still appear to be obstacles to free movement of the operator. A system of barriers around the patient is proposed, but appears expensive, complex, and possibly limiting of operator-patient/subject contact, and frustrating to sterile field operation. Ceiling mounted barriers around the patient also appear to limit contact between patient and operator, and may make control of sterile field difficult. One configuration includes a ceiling mounted device, which supports the weight of a lead garment, involving a dolly movable in one linear axis, with or without an extension arm that rotates around a central point on the dolly. Such mechanical configurations are in place for other types of suspended barriers, and their motion mechanics may not be well suited for use with something attached to the operator's body, since the operator must frequently move rapidly and freely in all three spatial axes, and will walk in unpredictable and rapid patterns over an operating area of several feet by several feet. One configuration includes the garment being suspended by a simple expansion spring, which will provide uneven forces depending on its degree of expansion occurring with operator motion, due to the nature of its simple spring mechanics. It may also result in harmonic motions that affect operator dexterity. In addition, failure of the spring due to cycle stresses could lead to the operator injury in the design as depicted in the patent. Also, location of the spring in a vertical direction above the operator could result in limitations due to ceiling height. Integration of the system with the heavy image intensifier monitor screen as suggested could further encumber the operator from normal motion. A discussion of the types of motion performed by operators during their work is relevant. Operators are generally standing next to an operating table where the patient is positioned. They often reach over the patient to various parts of the body, and they may lean forward while reaching. This puts great stress on the spine when heavy garments are worn. They may bend or stoop to small degrees, but rarely excessively because the workspace containing the patient and all the tools are located at a height requiring minimal vertical motion. In addition, most procedures involve a sterile field where the operator's hands, arms, and torso from neck to waist must remain confined, so excessive vertical motion is not allowed. The operator may move considerably in the X and Y plane, which is horizontal and parallel to the floor, by walking or turning their body. The operator requires freedom of motion in these directions. Overhead cranes have been available for many years and are commonly employed in the materials handling industry. The following is a description of a bridge crane. A bridge crane includes at least one bridge, a trolley moving on the bridge, end trucks arranged at the ends of the main bridge to support the main bridge, wheels arranged to the end carriages intended to move along substantially parallel rails substantially parallel to the end trucks and on the other hand substantially transverse in relation to the main bridge and thus to support the entire crane on the rails, while slides have been arranged between one end truck and the corresponding end of the main bridge allowing a longitudinal movement of the end truck in relation to the main bridge and a rotation of the end truck and main bridge in relation to each other. Smaller cranes such as might be used to support a load up to 250 pounds, are often operated by workers without the aid of motorized assistance, since the crane's movable parts are light enough to be manipulated by hand. Different systems are employed to suspend the load from the cranes, including hoists, balancers, and intelligent assist devices. Tool balancers are also currently available and help to suspend tools in the workspace in a manner that provides ergonomic benefit for workers using them. The tool balancer is generally attached overhead the workspace, and reels out cable from which the tool is suspended. Adjustments may be made to provide a “zero gravity” balancing of the tool at the desired height, such that the worker may move the tool up or down within a working range without having to bear a significant portion of the tool's weight. Different adjustment may cause the tool balancer to exert a stronger upward force such that the operator must apply a downward force on the tool to pull it down to the workspace, and the balancer will cause the tool to rise when the operator releases it. Tool balancers may be of the spring or pneumatic variety, referring to the mechanism, which provides the force for its operation. A spring tool balancer, such as in the preferred embodiment of this invention, generally contains a coiled flat spring, similar to a clock spring, which is attached to a reel with a conical shape and serves as the platform for the winding of the cable. The conical shape provides a variable mechanical advantage, which offsets the variance of the force provided by the spring as it winds or unwinds. The result is a relatively constant force on the cable within a definable working range. Safety concerns mainly involve falling objects, strength of the suspension device, strength of the cable, and operator falls. The balancer is attached to the trolley by its own hook and a safety chain. The suspension device is commercially available at specified maximum loads, which include a wide safety margin. The mounting of the suspension device will be done according to architectural standards. Detachment of the garment from the suspension system will require certain care. A cable stop will prevent the hanger from going higher than the set level. The worker could stand on a step stool and remove the garment without concern for sudden upward, uncontrolled motion of the balancer cable and hanger. In another method of detachment, the hanger could be gripped firmly as another person detaches the garment suspension cables from the hanger, and the hanger could then be slowly raised until the cable stop engages the spring balancer. Alternatively, a weight, which is approximately equivalent to the weight of the garment, could be attached to the hanger prior to disengaging the garment. This will drop the garment and require it to be supported by the worker, who may then disengage it from the hanger. The weight will prevent any upward motion of the hanger in an uncontrolled manner. The next time the garment is attached, the weight could be removed after secure attachment of the garment is confirmed. For most operation, the garment need not be detached from the cable. It could be left suspended and moved out of the way of other activities. Another alternative method would involve setting the force on the balancer to be slightly greater than the weight of the garment. Once removed from the body, the garment would then slowly and safely rise up until stopped by the cable stop. Upon next use, it could easily be pulled back down into position. Annual inspections of the system may be performed for cable frays, hook lock malfunctions, and rail component flaws. In the event of an operator fall, it is unlikely that the system will contribute to operator harm since the balancer cable is long enough to allow the operator to reach the floor. Any harm to the operator should be the same as if not attached to the cable, except perhaps for some beneficial effect of the upward force of the suspension system. In the event that rapid detachment of the operator from the system is necessary due to emergency, this can be achieved by simple removal of the garment from the body without detachment from the system. The garment can be left hanging, and the suspended garment can be moved to the end of the runway, clear of the moving patient or stretcher. FIG. 1 is a simplified block diagram of a suspended personal radiation protection system 10. System 10 includes an operator 12, a patient 14, a radiation source 16, radiation 18, a suspension device 60, a hanger 75, a personal radiation protection garment 20, a face shield 22, and a flap 24. Suspension device 60 includes rails 62, a bridge 64, end trucks 66, a trolley 68, a balancer 70, a cable 72, and a cable stop 74. Other architectures and components of system 10 may be used without departing from the scope of this disclosure. In general, garment 20, shield 22, and flap 24 suspend from hanger 75, which suspends from suspension device 60. Operator 12 positions himself into suspended garment 20, shield 22, and flap 24, such that operator 12 is not supporting the weight of garment 20, shield 22, and flap 24. While using radiation 18 to treat patient 14, operator can move freely in the X, Y, and Z spatial planes, such that garment 20, shield 22, and flap 24 are substantially weightless. In accordance with the teachings of the present invention, suspended personal radiation protection system 10 achieves an effective way for operators 12 to protect themselves properly and comfortably from harmful radiation. garment 20, shield 22, and flap 24 are operable to protect operator from harmful radiation. Suspension device 60 and hanger 75 are operable to suspend garment 20, shield 22, and flap 24, such that operator 12 is not hindered or burdened by the weight from garment 20, shield 22, and flap 24. Operator 12 is able to freely move around in all three axes while garment 20, shield 22, and flap 24 are substantially contoured to operator's body. System 10 offers advantages to operators 12 who work with radiation. This is due, at least in part, to the suspended personal radiation garment 20, shield 22, and flap 24, which protects operator 12 from harmful radiation 18 during fluoroscopically guided operations. For example, operator 12 has complete freedom of motion in the X, Y, and Z planes while the personal radiation protection garment 20, shield 22, and flap 24 are substantially contoured to operator's body. The suspended personal radiation protection system 10 allows operator to have complete freedom of motion commonly used during medical and research procedures. Furthermore, operator can remain sterile while using the suspended personal radiation protection garment 20, shield 22, and flap 24. Details relating to these operations are explained below in FIG. 1 and FIG. 2. Operator 12 may include any individual desiring to wear a personal radiation protection garment 20 in a medical environment, veterinary environment, or research environment. Operator may include an individual who perform simple or complex medical procedures involving radiation 18, such that operator's body and hands are in proximity of patient 14, such that scatter radiation 18 from patient 14 or physical elements in the direct radiation beam will pose significant health risks. Health risks to operator 12 may include cancers, cataracts, and skin damage. For example, operator 12 may include physicians, assistants, or technically skilled medical personnel during fluoroscopically guided operations. The personal suspended radiation protection garment 20, shield 22, and flap 24 allow operator 12 to move freely during fluoroscopically guided operations while providing protection from harmful scatter radiation 18. Patients 14 may include a human or animal involved in a simple or complex medical procedure involving radiation 18. Patient 14 is subjected to radiation 18 doses as low as possible to complete the medical task, and the patient's exposures are monitored to reduce risks of significant damage from the radiation. In another embodiment, patient 14 may include an inanimate object involved in a simple or complex procedure involving radiation 18. Radiation source 16 may include any device emitting radiation 18. For example, in medical procedures, radiation sources may include x-ray machines, nuclear medicine, and devices used for radiation therapy. Radiation source 16 can be any device emitting radiation 18. Radiation 18 may include ionized radiation or non-ionized radiation. Radiation 18 may be man-made radiation or radiation from another source. Some of the major isotopes may include I-131, Tc-99m, Co-60, Ir-192, and Cs-137. In medical procedures, radiation 18 may be emitted from x-ray machines, nuclear medicine, and radiation therapy devices. For example, some parts of the original x-ray beam intercepted by patient, or by another individual or object, may become scattered and change direction, such that operator 12 will absorb some harmful scattered radiation beams 18. Suspended personal radiation protection garment 20 may contain radiation-absorbing materials, such as lead or other metals. Suspended personal radiation protection garment 20 can be thicker and heavier than traditional radiation protection garments, because operator does not support the weight of the suspended personal radiation protection garment 20. Additionally, suspended personal radiation protection garment 20 can cover more of operator's body, such as operator's arms and legs. Suspended personal radiation protection garment 20 suspends from hanger 75, which suspends from suspension device. Suspended personal radiation protection garment 20 can substantially contour to operator's body while garment suspends from hanger, such that hanger supports the weight of garment. Suspended personal radiation protection garment 20 allows operator to move freely in the X, Y, and Z planes simultaneously, such that operator 12 can move normally as if operator 12 is not wearing a heavy radiation protection garment 20. Suspended personal radiation protection garment 20 allows operator 12 to wear sterile gloves and gown in the usual manner. Details relating to the suspension device 60 are explained below in FIG. 1. Details relating to the garment 20 are explained below in FIG. 2. Materials and/or components may be included in suspended personal radiation protection garment 20 in order to achieve the teachings of the protective, free moving, and weightlessness features of the present invention. However, due to its flexibility, suspended personal radiation protection garment 20 may alternatively be equipped with (or include) any suitable component or material, or any other suitable element or object that is operable to facilitate the operations thereof. Considerable flexibility is provided by the structure of suspended personal radiation protection garment 20 in the context of suspended personal radiation protection system 10 and, accordingly, it should be construed as such. Suspended personal radiation protection face shield 22 may contain radiation-absorbing materials, such that face shield attenuates X-rays, but is transparent to visible light allowing operator unhindered vision. Suspended personal radiation protection face shield 22 can be heavier and curve or bend around to cover more of operator's face than traditional radiation protection face shields, because operator 12 does not support the weight of the suspended personal radiation protection face shield 22. The suspended personal radiation protection face shield 22 protects operator 12 from radiation approaching from the sides of operator's face. The operator can wear normal corrective optical lenses behind face shield 22. Suspended personal radiation protection face shield 22 suspends from hanger 75, such that hanger 75 supports the weight of face shield 22. Suspended personal radiation protection face shield 22 allows operator to move freely in the X, Y, and Z planes simultaneously, such that operator 12 can move normally as if operator 12 is not wearing a heavy radiation protection face shield 22. Suspended personal radiation protection face shield 22 may be attached to hanger 75 with a plurality of ropes or wires or rigid rod systems. Details relating to the suspension device 60 are explained below in FIG. 1. Details relating to the face shield 22 are explained below in FIG. 2. Suspended personal radiation protection flap 24 may contain radiation-absorbing materials, such as acrylic lead or other metals. Suspended personal radiation protection flap 24 can be a softer fabric material, such that flap 24 covers the neck area not protected from garment 20 and shield 22. Suspended personal radiation protection flap 24 can be thicker and heavier than traditional radiation protection flaps 24, because operator 12 does not support the weight of the suspended personal radiation protection flap 24. Additionally, suspended personal radiation protection flap 24 can protect more of operator's neck and thyroid area. Suspended personal radiation protection flap 24 suspends from shield 22, which suspends from hanger 75. Suspended personal radiation protection flap 24 allows operator 12 to move freely in the X, Y, and Z planes simultaneously, such that operator 12 can move normally as if operator 12 is not wearing a heavy radiation protection flap 24. Details relating to the suspension device 60 are explained below in FIG. 1. Details relating to the flap 24 are explained below in FIG. 2. In another embodiment, suspended personal radiation protection shield 22 and flap 24 can be integrated, such that one piece is formed. In another embodiment, suspended personal radiation protection garment 20, shield 22, and flap 24 can be integrated, such that one piece is formed. In another embodiment, suspended personal radiation protection garment 20, shield 22, and flap 24 can be integrated with hanger 75, such that one piece is formed. Rails 62 can be permanently affixed to ceiling support structures over the area of operator's workplace. Rails 62 may run parallel with one another, such that rails 62 represent the length of the X-axis that operator 12 can move freely within while wearing the suspended personal radiation protection garment 20, shield 22, and flap 24. The interior of rails 12 can include a runway, such that rollers attached to end trucks 66 can slide along the rail runways. Details relating to rollers and runways are below in FIG. 6. Bridge 64 can be positioned perpendicular between rails 62 over the area of operator's workplace. Bridge 64 represents the length of the Y-axis that operator 12 can move freely within while wearing the suspended personal radiation protection garment 20, shield 22, and flap 24. Bridge 64 is affixed to rails 12 and movable along rails 12 by an end truck 66 on each rail 12. Bridge 64 can include a runway, such that roller attached to trolley 68 can slide along bridge runway. End trucks 66 allow bridge 64 to move along rails 62. End trucks 66 can be attached to bridge 64, such that only a small motion is permitted along bridge 64. This small motion allows slight imperfections in suspension device 60, such that bridge 64 movement along rail runways is smoother. End trucks 66 can include rollers to slide within rail runways, such that bridge 64 moves along rail runways via end truck rollers. The bridge 64 is freely movable along the X-axis of rails 62. The length of the X-axis spatial movement of bridge 64 can be limited to the ends of rail runways, such that end stops prevent further movement. Trolley 68 can include roller, such that trolley roller is positioned in bridge runway. The trolley is 68 freely movable along the Y-axis of bridge 64. The length of the Y-axis spatial movement of trolley 68 can be limited to the ends of bridge runway, such that end trucks prevent further movement. Trolley 68 can attach to balancer 70, which suspends personal radiation protection garment 20, shield 22, and flap 24, such that operator 12 can move freely in the X and Y spatial planes defined above by the length of the rails 62 and the length of the bridge 64. The plane defined by the X and Y spatial axes is designed to correspond to operator's desired work area on the floor. Operator 12 wearing suspended personal radiation protection garment 20, shield 22, and flap 24 has very smooth and facile motion within this plane. In another embodiment of this invention, a telescoping component on bridge 64 can allow extension of trolley 68 farther than the length of the bridge 64, such that the Y spatial axis is greater for operator 12 to freely move within the X, Y plane. In another embodiment, suspension device 60 can include linear motion devices or any other suitable means for allowing bridge 64 and trolley 68 to move freely. For example, linear motion devices are operable for roller bearings to roll inside guides, such that facile motion is allowed. Trolley 68 can include roller bearings operable to roll inside a guide included in bridge 64, such that facile motion in Y-axis is allowed. End trucks 66 can include roller bearings operable to roll inside a guide included in rails 62, such that facile motion in X-axis is allowed. Suspension device 60 is operable by any suitable means to allow free motion in the x and y axes for operator 12 wearing suspended personal radiation protection garment 20, shield 22, and flap 24. Balancer 70 may be a spring balancer 70 attached to trolley 68 by a hook, and a safety chain or cable for the event of hook failure. Spring balancer 70 applies constant and controllable uplifting force on garment 20, shield 22, and flap 24. Spring balancer 70 can include a coiled flat spring, similar to a clock spring, attached to a reel with a conical shape. The conical shape provides a variable mechanical advantage, which offsets the variance of the force provided by the spring as it winds or unwinds, such that there is a relatively constant force on cable within a definable working range. Spring balancer 70 allows operator 12 wearing suspended personal radiation protection garment 20, shield 22, and flap 24 freedom of motion in the vertical Z-axis spatial plane. Operator 12 wearing the heavy and bulky garment 20, shield 22, and flap 24 can freely perform vertical motion activities, such as stooping, leaning, squatting, standing on an elevated surface. The tension can be designed to provide optimum relief of garment's weight for operator, and this force can be constant in all positions by operator 12. Spring balancer 70 applies a constant force to oppose the weight regardless of how much cable 72 is extended. In another embodiment, balancer 70 can be counterweights 70 attached to trolley 68 by a hook, and a safety chain or cable for the event of hook failure. Counterweights 70 apply constant and controllable uplifting force on garment 20, shield 22, and flap 24. Counterweights 70 allow operator wearing suspended personal radiation protection garment 20, shield 22, and flap 24 freedom of motion in the vertical Z-axis spatial plane. Operator 12 wearing the heavy and bulky garment 20, shield 22, and flap 24 can freely perform vertical motion activities, such as stooping, leaning, squatting, standing on an elevated surface. The tension can be designed to provide optimum relief of garment's weight for operator 12, and this force can be constant in all positions by operator 12. Counterweights 70 apply a constant force to oppose the weight regardless of how much cable 72 is extended. In another embodiment, balancer 70 can be a constant force spring 70 attached to trolley 68 by a hook, and a safety chain or cable for the event of hook failure. Constant force spring 70 applies constant and controllable uplifting force on garment 20, shield 22, and flap 24. Constant force spring 70 allows operator 12 wearing suspended personal radiation protection garment 20, shield 22, and flap 24 freedom of motion in the vertical Z-axis spatial plane. Operator 12 wearing the heavy and bulky garment 20, shield 22, and flap 24 can freely perform vertical motion activities, such as stooping, leaning, squatting, standing on an elevated surface. The tension can be designed to provide optimum relief of garment's weight for operator 12, and this force can be constant in all positions by operator. Constant force spring 70 applies a constant force to oppose the weight regardless of how much cable 72 is extended. In other embodiments, balancer 70 can include a pneumatic balancer 70, an air balancer 70, a spring motor arrangement 70, an intelligent assist device 70, or any other system, which provides a counterbalancing function or suspension system for the suspended personal radiation protection garment 20, shield 22, and flap 24. In another embodiment of this invention, servomechanisms can be used to provide near effortless control and rapid response of the suspension device to bodily motions. The servo mechanics may be incorporated into all axes, or simply into the vertical motion axis alone. The servo apparatus will have motion sensors that detect operator movement, and can stimulate power assisted motion and cessation of motion, minimizing the effort of the operator to move the system, and also minimizing any tendency of the system to move operator 12 after the operator stops moving. The power motion is achieved by means of motors in conjunction with belts, chains, or cables along the desired axes along rails 62. In another embodiment, balancer 70 is mounted horizontally along bridge 64 rather than hanging vertically. The balancer 70 mounted horizontally provides more headroom for operator 12 in a low ceiling or low suspension environment. A pulley can be included over operator's head that can enable suspension device to create a constant force, such that operator does not feel the weight of the suspended personal radiation protection garment 20, shield 22, and flap 24. In another embodiment, the suspension force of balancer 70 can be adjusted to be greater than the weight of protective garment 20, shield 22, and flap 24, such that balancer can support a portion or all of operator's body weight. This provides added relief of the burden on the operator's spine, hips, knees, and other support structures during long procedures. A specialized harness system is incorporated into garment 20 utilizing straps and pads around the chest, torso, or thighs. This harness is integrated into the garment 20 in such a way that the support system will result in reduction in weight of the not only the garment 20 upon the operator 12, but the harness also can support a portion or all of the operator's weight. The suspended garment 20 becomes part of the suspension system and reduces the weight of operator 12 to some degree. The harness system can include a rigid seat-like apparatus. Details relating to the harness are explained below in FIG. 3. Cable 72 is suspended from balancer 70 and attaches to hanger 75. In other embodiments, cable 72 may also include a rope or a belt. Cable 72 is several feet long and allows operator 12 to move extensively in the vertical Z-axis. Cable 72 also allows operator 12 to freely move slightly outside the perimeter of the plane formed by the X and Y axes. Cable 72 can include a swivel mount that permits free rotation of the cable suspension mechanism allowing operator 12 to twist as needed. This may include a swivel hook or snap that connects the cable 72 to hanger 75. Cable 72 is operable to safely hold the amount of weight and force caused by the suspended personal radiation protection garment 20, shield 22, and flap 24. Cable stop 74 is a device attached to cable 72 operable to prevent hanger from going higher than the set level. Cable stop 74 will engage the balancer 70, such that cable stop 74 and hanger 75 are prevented from moving too high. For example, operator 12 can remove suspended personal radiation protection garment 20 as another individual firmly grips hanger 75, and hanger 75 could be slowly raised until the cable stop 74 engages balancer 70. Hanger 75 is operable to suspend personal radiation protection garment 20, shield 22, and flap 24. Hanger 75 is attached to cable 72. Hanger 75 is positioned above operator's head to avoid collision with operator's head during manipulations. Personal radiation protection garment 20, shield 22, and flap 24 can be removed from hanger 75, attached to hanger 75, and remain suspended from hanger 75 indefinitely. For example, garment 20 can rest on the hanger 75 similar to a clothes hanger, such that garment 20 is not resting on operator's body. Shield 22 and flap 24 can be suspended from hanger 75 by ropes, wires, cables or any other suitable means. Hanger 75 can take on several embodiments. FIGS. 2A, 2B, and 2C are simplified block diagrams of personal radiation protection garment 20, shield 22, and flap 26 suspending from hanger 75. Suspended personal radiation protection device includes garment 20, shield 22, flap 24, and hanger 75. Garment 20 includes fastening means 26, belt 28, Velcro for adjustable layer 30, and sleeve 32. Hanger includes widget 76, cross bar 78, drop rod 80, nut 82, shoulder plate 84, plate sleeve 86, and shield support cables 88. Suspended personal radiation protection garment 20 may contain radiation-absorbing materials, such as lead or other metals. Suspended personal radiation protection garment 20 can be thicker and heavier than traditional radiation protection garments, because operator 12 does not support the weight of the suspended personal radiation protection garment 20. Additionally, suspended personal radiation protection garment 20 can cover more of operator's body, such as operator's arms and legs. Suspended personal radiation protection garment 20 suspends from hanger 75, which suspends from suspension device 60. Suspended personal radiation protection garment 20 can substantially contour to operator's body while garment 20 suspends from hanger 75, such that hanger 75 supports the weight of garment 20. Suspended personal radiation protection garment allows operator 12 to move freely in the X, Y, and Z planes simultaneously, such that operator 12 can move normally as if operator 12 is not wearing a heavy radiation protection garment 20. Suspended personal radiation protection garment 20 allows operator 12 to wear sterile gloves and gown in the usual manner. Fastening means 26 of garment can be positioned in front, side, or rear of garment 20. Garment 20 can be opened and closed by Velcro, buckles, or any suitable fastening means 26 for attaching two pieces of a heavy material together. For example, if suspended garment 20 has fastening means 26 on the rear of garment 20, then operator 12 can walk up to suspended garment 20 and garment 20 will be suspended over operator 12 for usage. An assistant can fasten the Velcro or buckles, such that operator 12 can quickly and effortlessly receive protection of the suspended personal radiation protection garment 20 that is substantially contoured to operator's body. Operator 12 can wear a sterile gown and sterile gloves in the normal manner. Belt 28 on garment 20 includes Velcro, buckle, or fastening means, such that belt helps garment stay closed. Belt 28 can be fastened on the front, side, or rear of garment 20. Belt 28 also helps suspended personal radiation protection garment 20 substantially contour to operator's body, such that operator's body is properly protected. Velcro, buckle, or fastening means for adjustable garment layer 30 allows operator to adjust the length of suspended personal radiation protection garment 20. For example, a short person can fold up the excess garment material and fasten the garment 30, such that the bottom part of the garment is double-layered. Similarly, a tall person can unfasten the double layered area of the garment 20 to receive more radiation protection on legs, such that the suspended personal radiation garment 20 hangs to the operator's feet. Sleeve 32 can be on left or right arm, and sleeve 32 may contain radiation-absorbing materials, such as lead or other metals. Sleeve 32 allows more protection coverage of operator's body, because operator does not support the weight of the suspended sleeve 32. Hanger 75 is operable to suspend the personal radiation protection garment 20, shield 22, and flap 24. Hanger 75 is attached to cable 72. Hanger 75 is positioned above operator's head to avoid collision with operator's head during manipulations. Personal radiation protection garment 20, shield 22, and flap 24 can be detached to hanger 75, attached to hanger 75, and remain attached to hanger 75 indefinitely. For example, garment 20 can rest on the hanger similar to a clothes hanger, such that garment 20 is not resting on operator's body. Shield 22 and flap 24 can be suspended from hanger 75 by ropes, wires, cables or any other suitable means. Widget 76 connects hanger to cable. Widget 76 can be a hook, a pulley, or any suitable means to attach hanger 75 to cable 72. Widget 76 is made of material that can support a minimum weight of the suspended personal radiation protection garment 20, shield 22, and flap 24. Pulley widget 76 allows operator 12 to bend sideways, such that pulley widget 76 moves along hanger 75 to properly distribute weight. Details relating to pulley widget 76 are explained below in FIG. 5. Cross bar 78 attaches to cable 72 via widget 76. Cross bar 78 is made of material that can support at least a minimum weight of the suspended personal radiation protection garment 20, shield 22, and flap 24. Cross bar 78 is positioned above operator's head to avoid collision with operator's head during manipulations. Cross bar 78 can include grooves where widget 76 attaches, such that weight is properly distributed when operator 12 leans forward or backward. Drop rod 80 attaches to cross bar 78 and is held in place with a nut 82. Drop rod 80 is made of material that can support at least a minimum weight of the suspended personal radiation protection garment 20, shield 22, and flap 24. Drop rod 80 can attach to shoulder plate 84 in various embodiments. In one embodiment, drop rod 80 can be angled inward, such that drop rod 80 is inserted into shoulder plate sleeve 84 closer to operator's neck. This particular embodiment is effective at distributing weight and supporting the suspended garment 20, shield 22, and flap 24. Shoulder plate 84 is suspended by hanger 75. Shoulder plate 84 is made of material that can support at least a minimum weight of the suspended personal radiation protection garment 20, shield 22, and flap 24. Shoulder plate 84 can be one piece that extends over both shoulders or shoulder plate 84 can be two pieces, such that each shoulder plate 84 is positioned over operator's shoulders. Suspended personal radiation protection garment 20 can be placed on shoulder plate 84, such that shoulder plate 84 supports the weight of garment 20. Shoulder plates 84 can be positioned slightly above operator's shoulders, such that shoulder plates 84 act as a substitute for operator's shoulders while the garment 20 is still substantially contoured to operator's body. Plate sleeve 86 can be welded or affixed to shoulder plate 84. Plate sleeve 86 is operable for hanger to be inserted, such that plate sleeve 86 securely attaches shoulder plate 84 to hanger 75. Plate sleeve 86 is made of material that can support at least a minimum weight of the suspended personal radiation protection garment 20, shield 22, and flap 24. Plate sleeve 86 is operable for rotational motion of shoulder plate 84 relative to hanger 75. This allows operator 12 to freely move in the forward bending or rearward bending bodily motions. Bending forward will tilt shoulder plates 84 along with the tilt of the operator's shoulders, and the swivel motion of the sleeve on hanger 75 will allow hanger 75 to maintain a desirable vertical orientation rather than being forced into a tilted angulation, which would apply additional undesirable forces on hanger 75 and suspension device 60, as well as place additional downward force on cable 72. In one embodiment, hanger 75 includes widget 76, cross bar 78, drop rod 80, and nut 82. Widget 76 can be a hook attached to cable 72, such that cable hook attaches to cross bar 78. Drop rod 80 can be positioned inside plate sleeve 86, such that plate sleeve 86 is welded on shoulder plate 84. Garment 20 can be placed over shoulder plates, such that garment 20 is suspended by hanger 75. Details relating to this hanger 75 embodiment are explained below in FIG. 4A and FIG. 4B. In another embodiment, hanger 75 includes widget 76 and drop rod 80. Widget 76 can be a pulley attached to cable 72, such that pulley 76 attaches to hanger 75. Hanger 75 can be positioned inside plate sleeve 86, such that plate sleeve 86 is welded on shoulder plate 84. Garment 20 can be placed over shoulder plates 84, such that garment 20 is suspended by hanger 75. Details relating to this hanger 75 embodiment are explained below in FIG. 5. In another embodiment, hanger 75 can be a unified, rigid piece, such that shoulder plate 84, plate sleeves 86, hanger 75, garment 20, shield 22, and flap 24 are integrated. Suspended personal radiation protection face shield 22 may contain radiation-absorbing materials, such that face shield 22 attenuates X-rays, but is transparent to visible light allowing operator unhindered vision. Suspended personal radiation protection face shield 22 can be heavier and curve or bend around to cover more of operator's face than traditional radiation protection face shields 22, because operator 12 does not support the weight of the suspended personal radiation protection face shield 22. The suspended personal radiation protection face shield 22 protects operator 12 from radiation 18 approaching from the sides of operator's face. The operator 12 can wear normal corrective optical lenses behind face shield. Suspended personal radiation protection face shield 22 suspends from hanger 75. Suspended personal radiation protection face shield 22 allows operator 12 to move freely in the X, Y, and Z planes simultaneously, such that operator 12 can move normally as if operator 12 is not wearing a heavy radiation protection face shield 22. Face shield support cables 88 are operable to suspend face shield 22 from hanger 75, such that operator 12 does not bear the weight of face shield 22. Face shield support cables 88 can also be ropes, wires, straps, rigid rods, or any suitable material to suspend the weight of face shield 22 and flap 24. Face shield support cables 88 can be affixed to hanger 75 in one or more places to achieve proper suspension. Face shield support cables 88 can be adjusted, such that face shield 22 and flap 24 are fitted properly to operator 12. Suspended personal radiation protection flap 24 may contain radiation-absorbing materials, such as acrylic lead or other metals. Suspended personal radiation protection flap 24 can be thicker and heavier than traditional radiation protection flaps, because operator 12 does not support the weight of the suspended personal radiation protection flap 24. Additionally, suspended personal radiation protection flap 24 can cover more of operator's neck and thyroid area. Suspended personal radiation protection flap 24 suspends from shield 22, which suspends from hanger 75. Flap 24 can be suspended from hanger 75 as well as face shield 22. Suspended personal radiation protection flap 24 allows operator 12 to move freely in the X, Y, and Z planes simultaneously, such that operator 12 can move normally as if operator 12 is not wearing a heavy radiation protection flap 24. In another embodiment, suspended personal radiation protection shield 22 and flap 24 can be integrated, such that one piece is formed. In another embodiment, suspended personal radiation protection garment 20, shield 22, and flap 24 can be integrated, such that one piece is formed. In another embodiment, suspended personal radiation protection garment 20, shield 22, and flap 24 can be integrated with hanger 75, such that one piece is formed. FIG. 3 is a simplified block diagram that illustrates a harness integrated with personal radiation protective garment 20 in accordance with an embodiment of the present invention. Garment 20 includes an integrated harness, shoulder reinforcement 102, arm holes 104, and belt 28. Harness includes reinforced stitching 107, chest strap 106, waist strap 108, thigh strap 110, length adjusting strap 112, and length adjusting buckle 114. The suspension force of suspension device 60 can be adjusted to be greater than the weight of the protective garment 20, shield 22, and flap 24, such that suspension device 60 can support a portion or all of operator's body weight. This provides added relief of the burden on the operator's spine, hips, knees, and other support structures during long procedures. A specialized harness system is incorporated into garment 20 utilizing straps and pads around the chest, torso, or thighs. The harness is integrated into the garment 20 in such a way that the support system will result in reduction in weight of the not only the garment 20 upon the operator 12, but the harness also can support a portion or all of the operator's weight. The suspended garment 20 becomes part of the suspension system and reduces the weight of operator 12 to some degree. The operator 12 can freely move, such that a majority of operator's body weight is supported by suspension device 60. The harness system can include a rigid seat-like apparatus. Suspended personal radiation protection garment 20 may contain radiation-absorbing materials, such as lead or other metals. Suspended personal radiation protection garment 20 can be thicker and heavier than traditional radiation protection garments, because operator 12 does not support the weight of the suspended personal radiation protection garment 20. Additionally, suspended personal radiation protection garment 20 can cover more of operator's body, such as operator's arms and legs. Suspended personal radiation protection garment 20 suspends from hanger 75, which suspends from suspension device 60. Suspended personal radiation protection garment 20 can substantially contour to operator's body while garment 20 suspends from hanger 75, such that hanger 75 supports the weight of garment 20. Suspended personal radiation protection garment 20 allows operator 12 to move freely in the X, Y, and Z planes simultaneously, such that operator 12 can move normally as if operator 12 is not wearing a heavy radiation protection garment 20. Suspended personal radiation protection garment 20 allows operator 12 to wear sterile gloves and gown in the usual manner. Shoulder reinforcement 102 on garment 20 provides an even distribution of force along the width of garment 20, such that garment 20 is not distorted while suspended on shoulder plate 84. Shoulder reinforcement 102 can include extra material, reinforcement stitching, or any means suitable to even distribution of force along the width of garment 20. Arm holes 104 are provided for operator 12 to freely move around arms and hands. Arm holes 104 can include sleeves 32 to provide more protection to operator's arms. Belt 28 on garment 20 can include Velcro, buckle, or fastening means, such that belt 20 helps garment stay closed. Belt 28 can be fastened on front, side, or rear of garment. Belt 28 also helps suspended personal radiation protection garment 20 substantially contour to operator's body, such that operator's body is properly protected. Harness chest strap 106 wraps around operator's chest to help secure operator's body. The suspension device 60 can suspend garment 20 and harness, such that suspension device 60 supports a portion or all of operator's weight. The effect of suspending operator 12 allows operator 12 to freely move with reduced weight, such that a majority of operator's body weight is supported by suspension device 60. This provides added relief of the burden on the operator's spine, hips, knees, and other support structures during long procedures. Chest strap 106 can include Velcro, buckle, or fastening means, such that chest strap 106 is secure around operator's chest. Harness waist strap 108 wraps around operator's waist to help secure operator's body. The suspension device 60 can suspend garment 20 and harness, such that suspension device 60 supports a portion or all of operator's weight. The effect of suspending operator 12 allows operator 12 to move about freely move with reduced weight, such that a majority of operator's body weight is supported by suspension device 60. This provides added relief of the burden on the operator's spine, hips, knees, and other support structures during long procedures. Waist strap 108 can include Velcro, buckle, or fastening means, such that waist strap 108 is secure around operator's waist. Harness thigh strap 110 wraps around operator's thighs to help secure operator's body. The suspension device 60 can suspend garment 20 and harness, such that suspension device supports a portion or all of operator's weight. The effect of suspending operator 12 allows operator 12 to move about freely with reduced weight, such that a majority of operator's body weight is supported by suspension device 60. This provides added relief of the burden on the operator's spine, hips, knees, and other support structures during long procedures. Thigh straps 110 can include Velcro, buckle, or fastening means, such that thigh straps 110 are secure around operator's thigh. Length adjusting straps 112 allow operator to customize harness to operator's height. Length adjusting straps 112 can be secured and adjusted by length adjusting buckle 114. Reinforced stitching 107 allows harness to be integrated with garment 20. Reinforced stitching is used on garment 20, chest strap 106, waist strap 108, and thigh straps 110. Reinforced stitching material 107 can support operator's weight. In another embodiment of this invention, the harness system will not be associated with radiation protection garment 20, and harness can be used to support a portion or all of the operator's body weight for the performance of medical or surgical procedures that do not require radiation. This prevents fatigue of operator due to standing in proper position for prolonged periods. FIGS. 4A and 4B are a simplified block diagram that illustrate a hanger 75 attached to shoulder plate 84 via plate sleeve 86 in accordance with an embodiment of the present invention. Hanger 75 includes cross bar 78, drop rod 80, and nut 82. Cross bar 78 attaches to cable via widget. Cross bar is made of material that can support at least a minimum weight of the suspended personal radiation protection garment 20, shield 22, and flap 24. Cross bar 78 is positioned above operator's head to avoid collision with operator's head during manipulations. Cross bar 78 can include grooves where widget attaches, such that weight is properly distributed when operator 12 leans forward or backward. Drop rod 80 attaches to cross bar 78 and is held in place with a nut 82. Drop rod 80 is made of material that can support at least a minimum weight of the suspended personal radiation protection garment 20, shield 22, and flap 24. Drop rod 80 can attach to shoulder plate 84 in various embodiments. In one embodiment, drop rod 80 can be angled inward, such that drop rod 80 is inserted into shoulder plate sleeve 86 closer to operator's neck. This particular embodiment is effective at distributing weight and supporting the suspended garment 20, shield 22, and flap 24. Shoulder plate 84 is suspended by hanger 75. Shoulder plate 84 is made of material that can support at least a minimum weight of the suspended personal radiation protection garment 20, shield 22, and flap 24. Shoulder plate 84 can be one piece that extends over both shoulders or shoulder plate 84 can be two pieces, such that each shoulder plate 84 is positioned over operator's shoulders. Suspended personal radiation protection garment 20 can be placed on shoulder plate 84, such that shoulder plate 84 supports the weight of garment 20. Shoulder plates 84 can be positioned slightly above operator's shoulders, such that shoulder plates 84 are a substitute for operator's shoulders, while garment 20 is still substantially contoured to operator's body. Plate sleeve 86 can be welded on shoulder plate 84. Plate sleeve 86 is operable for hanger 75 to be inserted, such that plate sleeve 86 securely attaches shoulder plate 84 to hanger 75. Plate sleeve 86 is operable for rotational motion of shoulder plate 84 relative to hanger 75. This allows operator 12 to freely move in the forward bending or rearward bending bodily motions. Bending forward will tilt shoulder plates 84 along with the tilt of the operator's shoulders, and the swivel motion of the sleeve on hanger 75 will allow hanger 75 to maintain a desirable vertical orientation rather than being forced into a tilted angulation, which would apply additional undesirable forces on hanger 75 and suspension device 60, as well as place additional downward force on cable 72. In another embodiment, plate sleeve can be fixed. Plate sleeve 86 is made of material that can support at least a minimum weight of the suspended personal radiation protection garment 20, shield 22, and flap 24. FIG. 5 is a simplified block diagram that illustrates a hanger 75 with a sideways bending modification in accordance with an embodiment of the present invention. Hanger 75 suspends from pulley 76, which suspends from cable 72. Shoulder plate 84 with integrated plate sleeve 86 suspend from hanger 75. Cable 72 is suspended from balancer 70 and attaches to pulley 76. In other embodiments, cable 72 may also include a rope or a belt. Cable 72 is several feet long and allows operator 12 to move extensively in the vertical Z-axis. Cable 72 also allows operator to freely move slightly outside the perimeter of the plane formed by the X and Y axes. Cable 72 can include a swivel mount that permits free rotation of the cable suspension mechanism allowing operator 12 to twist as needed. This may include a swivel hook or snap that connects the cable 72 to hanger 75. Cable 72 is operable to safely hold the amount of weight and force caused by the suspended personal radiation protection garment 20, shield 22, and flap 24. Pulley 76 is operable to roll along hanger 75, such that pulley 76 rolls along hanger 75 when operator 12 bends sideways. Pulley 76 attaches to cable 72 and hanger 75. Pulley 76 is made of material to support weight of suspended personal radiation protection garment 20, shield 22, and flap 24. For example, when operator 12 bends sideways, pulley 76 will roll along hanger 75, such that hanger 75 becomes tilted. This effect allows operator 12 to freely bend sideways, such that suspended personal radiation protection garment 20, shield 22, and flap 24 are all properly suspended. Hanger 75 is operable to suspend the personal radiation protection garment 20, shield 22, and flap 24. Hanger 75 can be attached to pulley 76, such that pulley 76 allows hanger 75 to tilt when operator 12 bend sideways. Hanger 75 can be positioned above operator's head to avoid collision with operator's head during manipulations. Personal radiation protection garment 20, shield 22, and flap 24 can be detached to hanger 75, attached to hanger 75, and remain attached to hanger 75 indefinitely. For example, garment 20 can rest on hanger 75 similar to a clothes hanger, such that garment 20 is not resting on operator's body. FIG. 5 illustrates two different embodiments for the design of hanger 75. Hanger 75 can also include a component operable to prevent pulley 76 from moving beyond the hanger's edge. Shoulder plate 84 is suspended by hanger 75. Shoulder plate 84 is made of material that can support at least a minimum weight of the suspended personal radiation protection garment 20, shield 22, and flap 24. Shoulder plate 84 can be one piece that extends over both shoulders or shoulder plate can be two pieces, such that each shoulder plate 84 is positioned over operator's shoulders. Suspended personal radiation protection garment 20 can be placed on shoulder plate 84, such that shoulder plate 84 supports the weight of the garment 20. Shoulder plates 84 can be positioned slightly above operator's shoulders, such that shoulder plates 84 are a substitute for operator's shoulders while garment 20 is still substantially contoured to operator's body. Plate sleeve 86 can be welded on shoulder plate 84. Plate sleeve 86 is operable for hanger 75 to be inserted, such that plate sleeve 86 securely attaches shoulder plate 84 to hanger 75. Plate sleeve 86 is made of material that can support at least a minimum weight of the suspended personal radiation protection garment 20, shield 22, and flap 24. FIG. 6 is a simplified block diagram that illustrates a trolley 68 and a balancer 70 in accordance with an embodiment of the present invention. Suspension device 60 includes bridge 64, roller 65, trolley 68, safety cable 69, balancer 70, hook 71, and cable 72. Bridge 64 can be positioned perpendicular between rails 62 over the area of operator's workplace. Bridge 64 represents the length of the Y-axis that operator can move freely within while wearing the suspended personal radiation protection garment 20, shield 22, and flap 24. Bridge 64 is affixed to rails 62 and movable along rails by an end truck 66 on each rail 62. Bridge 64 can include a runway. Details of bridge 64 interacting with other components are explained above in FIG. 1. Roller 65 attaches to trolley 64 and is positioned in bridge runway, such that roller 65 can slide along bridge runway. Roller 65 is operable to easily slide along bridge runway, such that operator 12 can move freely. Trolley 68 is positioned in bridge runway. Trolley 68 is freely movable along the Y-axis of bridge 64. The length of the Y-axis spatial movement of trolley 68 can be limited to the ends of bridge runway, such that end trucks 66 prevent further movement. Trolley 68 can include a latch for balancer 70 attachment and a safety cable 69. For extra safety, safety cable 69 or chain may be attached to a separate trolley, which is allowed to move adjacent to weight bearing trolley 68. Trolley 68 can support the weight for suspended personal radiation protection garment 20, shield 22, and flap 24, such that operator 12 can move freely in the X and Y spatial planes defined above by the length of the rails 66 and the length of the bridge 64. The plane defined by the X and Y spatial axes is designed to correspond to operator's desired work area on the floor. Operator 12 wearing suspended personal radiation protection garment 20, shield 22, and flap 24 has very smooth and facile motion within this plane. In another embodiment of this invention, a telescoping component on bridge 64 can allow extension of trolley 68 farther than the length of the bridge 64, such that the Y spatial axis is greater for operator to freely move within the X, Y plane. Safety cable 69 can be permanently affixed to trolley 68 and balancer 70. Safety cable 69 is operable to suspend the weight of balancer 70, hanger 75, garment 20, shield 22, and flap 24, such that operator 12 is protected if balancer 70 becomes detached from trolley 68. For extra safety, safety cable 69 or chain may be attached to a separate trolley, which is allowed to move adjacent to weight bearing trolley 68. Balancer 70 can be a spring balancer 70 attached to trolley 68 by a hook 71, and a safety chain 69 or cable for the event of hook failure. Spring balancer 70 applies constant and controllable uplifting force on garment 20, shield 22, and flap 24. Spring balancer 70 can include a coiled flat spring, similar to a clock spring, attached to a reel with a conical shape. The conical shape provides a variable mechanical advantage, which offsets the variance of the force provided by the spring as it winds or unwinds, such that there is a relatively constant force on cable within a definable working range. Spring balancer 70 allows operator 12 wearing suspended personal radiation protection garment 20, shield 22, and flap 24 freedom of motion in the vertical Z-axis spatial plane. Operator 12 wearing the heavy and bulky garment 20, shield 22, and flap 24 can freely perform vertical motion activities, such as stooping, leaning, squatting, standing on an elevated surface. The tension can be designed to provide optimum relief of garment's 20 weight for operator 12, and this force can be constant in all positions by operator 12. Spring balancer 70 applies a constant force to oppose the weight regardless of how much cable is extended. Balancer 70 can also take on the different embodiments explained above in FIG. 1. Hook 71 is affixed to balancer 70 and is a means to suspend balancer 70 from trolley 68. Hook 71 is made of material that can support a minimum weight of balancer 70, hanger 75, operator 12, garment 20, shield 22, and flap 24. If hook 71 fails, then safety cable 69 can prevent damage to operator 12. Cable 72 is suspended from balancer 70 and attaches to hanger 75. In other embodiments, cable 72 may also include a rope or a belt. Cable 72 is several feet long and allows operator 12 to move extensively in the vertical Z-axis. Cable 72 also allows operator to freely move slightly outside the perimeter of the plane formed by the X and Y axes. Cable 72 can include a swivel mount that permits free rotation of the cable suspension mechanism allowing operator 12 to twist as needed. This may include a swivel hook or snap that connects the cable 72 to hanger 75. Cable 72 is operable to safely hold the amount of weight and force caused by the suspended personal radiation protection garment 20, shield 22, and flap 24. FIG. 7 is a simplified block diagram that illustrates a monorail 61 track in accordance with an embodiment of the present invention. A monorail 61 track can be used in place of parallel rail system described above in FIG. 1. Monorail 61 track includes monorail 61, switch 63, roller 65, trolley 68, balancer 70, and ceiling mounts 73. Monorail 61 can be ceiling mounted in the orientation that best fits the particular room and type of operation. Trolley 68 can run freely along the monorail 61 with balancer 70 and garment 20 suspended from trolley 68. Monorail 61 can include curves, and extra tracks connected and controlled by switches 63. Monorail 61 has the advantage of being less expensive, easier to install, and potentially installable in operating rooms that may not accommodate the parallel rail track due to its dimensions. Operator 12 can move freely along the path of monorail 61, but operator 12 would be more limited in the motion away from the monorail 61 in a perpendicular direction. Some motion in this direction would be allowed by the spring balancer 70, which could reel out several feet of cable 72 accordingly. However, balancer 70 would exert some pull forces on the operator 12, which hinder motion somewhat to operator's body. Monorail 61 can include a runway, such that trolley 68 can move along monorail 61. Switches 63 are integrated with monorail 61. Switches 63 are operable to connect different tracks of monorail 61, such that operator 12 can move to other areas of the room. Operator 12 can operate switches by an electronic device or any suitable means. Roller 65 attaches to trolley 68 and is positioned in monorail runway, such that roller 65 can slide along monorail runway. Roller 65 is operable to easily slide along monorail runway, such that operator 12 can move freely. Trolley 68 is positioned in monorail runway. Trolley 68 is freely movable along monorail 61. Trolley 68 can support the weight for suspended personal radiation protection garment 20, shield 22, and flap 24. Operator 12 wearing suspended personal radiation protection garment 20, shield 22, and flap 24 has very smooth and facile motion along monorail 61 path. In another embodiment of this invention, a telescoping component on monorail 61 can allow extension of trolley 68 farther out than monorail 61 path. Balancer 70 can be a spring balancer 70 attached to trolley by a hook, and a safety chain or cable for the event of hook failure. Spring balancer 70 applies constant and controllable uplifting force on garment 20, shield 22, and flap 24. Spring balancer 70 can include a coiled flat spring, similar to a clock spring, attached to a reel with a conical shape. The conical shape provides a variable mechanical advantage, which offsets the variance of the force provided by the spring as it winds or unwinds, such that there is a relatively constant force on cable within a definable working range. Spring balancer 70 allows operator 12 wearing suspended personal radiation protection garment 20, shield 22, and flap 24 freedom of motion in the vertical Z-axis spatial plane. Operator 12 wearing the heavy and bulky garment 20, shield 22, and flap 24 can freely perform vertical motion activities, such as stooping, leaning, squatting, standing on an elevated surface. The tension can be designed to provide optimum relief of garment's weight for operator 12, and this force can be constant in all positions by operator 12. Spring balancer 70 applies a constant force to oppose the weight regardless of how much cable 72 is extended. Balancer can also take on the different embodiments explained above in FIG. 1. Ceiling mounts 73 are affixed to ceiling and attached to monorail 61. Ceiling mounts 73 are operable to securely fasten monorail 61, such that ceiling mounts 73 can support a minimum weight of monorail track 61, trolley 68, balancer 70, hanger 75, operator 12, garment 20, shield 22, and flap 24. FIG. 8 is a simplified flowchart that illustrates an example method of the suspended personal radiation protection system in accordance with an embodiment of the present invention. The flowchart begins at step 800, where operator 12 steps into suspended personal radiation protection garment 20, shield 22, and flap 24. Operator 12 can adjust suspension device's 60 height, such that shoulder plates 20 are suspended slightly above operator's shoulders. Operator 12 can adjust the length of garment 20 by fastening means, such that garment 20 covers substantially all of operator's legs. Suspended garment 20, shield 22, and flap 24 are weightless to operator 12. At step 802, operator 12 or another individual can strap garment 20 closed by fastening means 26, such that garment 20, shield 22, and flap 24 are substantially contoured to operator's body. Operator 12 can fasten belt 28 around garment 20, such that garment 20 is secured even further. Operator 12 can also wear sterile gown and gloves. This process is very fast and effortless. At step 804, operator 12 can move freely in all three spatial planes while wearing suspended personal radiation protection garment 20, shield 22, and flap 24. Operator 12 can walk diagonally, crouch, or bend sideways in a free motion while receiving protection of suspended personal radiation protection garment 20, shield 22, and flap 24. At step 806, operator 12 has complete freedom of motion to use radiation device to properly treat patient 14. Suspended personal radiation protection garment 20, shield 22, and flap 24 are substantially weightless to operator 12, such that operator 12 is comfortable and unhindered. Operator's arms are able to freely move in order to properly treat patient 14. Operator 12 can bend over patient 14 without causing pain to operator's spine. At step 808, suspended garment 20, shield 22, and flap 24 properly protect operator 12 from harmful radiation 18. Since garment 20 is suspended, garment 20, shield 22, and flap 24 can be heavier to provide more protection to operator 12. Suspended garment 20, shield 22, and flap 24 are substantially contoured to operator's body, such that a substantial area of operator's body is protected. Suspended garment 20 can also be made of thicker material to provide extra protection to operator 12. Sleeve 32 on garment 20 can provide further protection to arms and armpit area. At step 810, operator 12 can move freely to return to spot where operator 12 initially stepped into suspended personal radiation protection garment 20, shield 22, and flap 24. Operator 12 can move freely in all three spatial planes while wearing suspended personal radiation protection garment 20, shield 22, and flap 24. Operator 12 can walk diagonally, crouch, or bend sideways in a free motion while receiving protection of suspended personal radiation protection garment 20, shield 22, and flap 24. At step 812, operator 12 or another individual can quickly and effortlessly unfasten garment 20 and belt 28. Operator 12 can easily step out from the suspended garment 20, shield 22, and flap 24. garment 20, shield 22, and flap 24 can remain suspended. It is important to note that the stages and steps described above illustrate only some of the possible scenarios that may be executed by, or within, the present system. Some of these stages and/or steps may be deleted or removed where appropriate, or these stages and/or steps may be modified, enhanced, or changed considerably without departing from the scope of the present invention. In addition, a number of these operations have been described as being executed concurrently with, or in parallel to, one or more additional operations. However, the timing of these operations may be altered. The preceding example flows have been offered for purposes of teaching and discussion. Substantial flexibility is provided by the tendered system in that any suitable arrangements, chronologies, configurations, and timing mechanisms may be provided without departing from the broad scope of the present invention. Accordingly, any appropriate structure, component, or device may be included within suspended personal radiation protection system 10 to effectuate the tasks and operations of the elements and activities associated with executing compatibility functions. FIG. 9 is a simplified block diagram that illustrates a face shield and flap suspending from hanger in accordance with an embodiment of the present invention. Hanger includes widget 76, cross bar 78, drop rod 80, nut 82, shoulder plate 84, plate sleeve 86, and shield support cables 88. Hanger 75 is operable to suspend the personal radiation protection garment 20, shield 22, and flap 24. Hanger 75 is attached to cable 72. Hanger 75 is positioned above operator's head to avoid collision with operator's head during manipulations. Personal radiation protection garment 20, shield 22, and flap 24 can be detached to hanger 75, attached to hanger 75, and remain attached to hanger 75 indefinitely. For example, garment 20 can rest on the hanger similar to a clothes hanger, such that garment 20 is not resting on operator's body. Shield 22 and flap 24 can be suspended from hanger 75 by ropes, wires, cables or any other suitable means. Widget 76 connects hanger to cable. Widget 76 can be a hook, a pulley, or any suitable means to attach hanger 75 to cable 72. Widget 76 is made of material that can support a minimum weight of the suspended personal radiation protection garment 20, shield 22, and flap 24. Pulley widget 76 allows operator 12 to bend sideways, such that pulley widget 76 moves along hanger 75 to properly distribute weight. Details relating to pulley widget 76 are explained below in FIG. 5. Cross bar 78 attaches to cable 72 via widget 76. Cross bar 78 is made of material that can support at least a minimum weight of the suspended personal radiation protection garment 20, shield 22, and flap 24. Cross bar 78 is positioned above operator's head to avoid collision with operator's head during manipulations. Cross bar 78 can include grooves where widget 76 attaches, such that weight is properly distributed when operator 12 leans forward or backward. Drop rod 80 attaches to cross bar 78 and is held in place with a nut 82. Drop rod 80 is made of material that can support at least a minimum weight of the suspended personal radiation protection garment 20, shield 22, and flap 24. Drop rod 80 can attach to shoulder plate 84 in various embodiments. In one embodiment, drop rod 80 can be angled inward, such that drop rod 80 is inserted into shoulder plate sleeve 84 closer to operator's neck. This particular embodiment is effective at distributing weight and supporting the suspended garment 20, shield 22, and flap 24. Shoulder plate 84 is suspended by hanger 75. Shoulder plate 84 is made of material that can support at least a minimum weight of the suspended personal radiation protection garment 20, shield 22, and flap 24. Shoulder plate 84 can be one piece that extends over both shoulders or shoulder plate 84 can be two pieces, such that each shoulder plate 84 is positioned over operator's shoulders. Suspended personal radiation protection garment 20 can be placed on shoulder plate 84, such that shoulder plate 84 supports the weight of garment 20. Shoulder plates 84 can be positioned slightly above operator's shoulders, such that shoulder plates 84 act as a substitute for operator's shoulders while the garment 20 is still substantially contoured to operator's body. Plate sleeve 86 can be welded or affixed to shoulder plate 84. Plate sleeve 86 is operable for hanger to be inserted, such that plate sleeve 86 securely attaches shoulder plate 84 to hanger 75. Plate sleeve 86 is made of material that can support at least a minimum weight of the suspended personal radiation protection garment 20, shield 22, and flap 24. Plate sleeve 86 is operable for rotational motion of shoulder plate 84 relative to hanger 75. This allows operator 12 to freely move in the forward bending or rearward bending bodily motions. Bending forward will tilt shoulder plates 84 along with the tilt of the operator's shoulders, and the swivel motion of the sleeve on hanger 75 will allow hanger 75 to maintain a desirable vertical orientation rather than being forced into a tilted angulation, which would apply additional undesirable forces on hanger 75 and suspension device 60, as well as place additional downward force on cable 72. Suspended personal radiation protection face shield 22 may contain radiation-absorbing materials, such that face shield 22 attenuates X-rays, but is transparent to visible light allowing operator unhindered vision. Suspended personal radiation protection face shield 22 can be heavier and curve or bend around to cover more of operator's face than traditional radiation protection face shields 22, because operator 12 does not support the weight of the suspended personal radiation protection face shield 22. The suspended personal radiation protection face shield 22 protects operator 12 from radiation 18 approaching from the sides of operator's face. The operator 12 can wear normal corrective optical lenses behind face shield. Suspended personal radiation protection face shield 22 suspends from hanger 75. Suspended personal radiation protection face shield 22 allows operator 12 to move freely in the X, Y, and Z planes simultaneously, such that operator 12 can move normally as if operator 12 is not wearing a heavy radiation protection face shield 22. Face shield support cables 88 are operable to suspend face shield 22 from hanger 75, such that operator 12 does not bear the weight of face shield 22. Face shield support cables 88 can also be ropes, wires, straps, rigid rods, or any suitable material to suspend the weight of face shield 22 and flap 24. Face shield support cables 88 can be affixed to hanger 75 in one or more places to achieve proper suspension. Face shield support cables 88 can be adjusted, such that face shield 22 and flap 24 are fitted properly to operator 12. Floor plate 23 can be integrated with shield 24, such that floor plate 23 may contain radiation-absorbing materials, such as acrylic lead or other metals. Floor plate 23 can be a thicker material than flap, such that floor plate 23 protects operator from harmful radiation. Suspended personal radiation protection flap 24 may contain radiation-absorbing materials, such as acrylic lead or other metals. Flap can be a softer fabric containing radiation-absorbing materials. Suspended personal radiation protection flap 24 can be thicker and heavier than traditional radiation protection flaps, because operator 12 does not support the weight of the suspended personal radiation protection flap 24. Additionally, suspended personal radiation protection flap 24 can cover more of operator's neck and thyroid area. Suspended personal radiation protection flap 24 suspends from shield 22, which suspends from hanger 75. Flap 24 can be suspended from hanger 75 as well as face shield 22. Suspended personal radiation protection flap 24 allows operator 12 to move freely in the X, Y, and Z planes simultaneously, such that operator 12 can move normally as if operator 12 is not wearing a heavy radiation protection flap 24. In another embodiment, suspended personal radiation protection shield 22 and flap 24 can be integrated, such that one piece is formed. In another embodiment, suspended personal radiation protection garment 20, shield 22, and flap 24 can be integrated, such that one piece is formed. In another embodiment, suspended personal radiation protection garment 20, shield 22, and flap 24 can be integrated with hanger 75, such that one piece is formed. Although the present invention has been described in detail with reference to particular embodiments, it should be understood that various other changes, substitutions, and alterations may be made hereto without departing from the spirit and scope of the present invention. The illustrated suspension device 60 in FIG. 1 has only been offered for purposes of example and teaching. Suitable alternatives and substitutions are envisioned and contemplated by the present invention: such alternatives and substitutions being clearly within the broad scope of suspension device 60. Using analogous reasoning, the hanger 75 illustrated by FIG. 1 may be supplanted by a single piece hanger, wires, or any other suitable devices that are conducive to properly supporting the weight of the operator 12, garment 20, face shield 22, and flap 24. In addition, while the foregoing discussion has focused on medical procedures, any other suitable environment requiring radiation protection may benefit from the compatibility teachings provided herein. Although the present invention has been described with several embodiments, a myriad of changes, variations, alterations, transformations, and modifications may be suggested to one skilled in the art, and it is intended that the present invention encompass such changes, variations, alterations, transformations, and modifications as fall within the scope of the appended claims.
043024190	abstract	In a catalytic recombiner system a stoichiometric mixture of oxygen and hydrogen are carried by a nitrogen stream through a catalytic converter. The stoichiometric mix is maintained by introducing oxygen into the stream under control of logic circuitry. The logic circuitry responds to the hydrogen level in an inlet stream and to oxygen levels before and after the catalytic converter.
	description	This application claims the benefit of Korean Patent Application No. 10-2014-0158062, filed on Nov. 13, 2014, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein in its entirety by reference. 1. Field of the Invention One or more exemplary embodiments relate to a magnetic jack type control element drive mechanism for precision position control of a control element assembly, and more particularly, to a control element drive mechanism which is applied to a 4-coil magnetic jack type control element drive mechanism to increase resolution of position control of a motor assembly. The present invention is derived from research conducted as part of the Nuclear Power Core Technology Development Program by the Ministry of Trade, Industry & Energy [Project Serial Number: 20131510101680, Title of Research Project: Development of Top-Mounted ICI System and In-Vessel Control Element Drive Mechanism for Severe Accident Mitigation Design. 2. Description of the Related Art A control element drive mechanism is provided to control the power of a nuclear reactor and is classified as, for example, a magnetic-jack type control element drive mechanism, a ball-screw type control element drive mechanism, and a hydraulic type control element drive mechanism. The present invention relates to a magnetic jack type control element drive mechanism. FIG. 1 is a conceptual diagram of a control element drive mechanism used for installation thereof, and FIG. 2 is a schematic cross-sectional view of a conventional control element drive mechanism. FIG. 3 is a magnified cross-sectional view illustrating the main portion of FIG. 2, and FIG. 4 shows a sequence of a control element being withdrawn by a conventional control element drive mechanism. As shown in FIG. 1, a nuclear fuel assembly 2 and a control element 3 are placed in a nuclear reactor 1. The control element 3 controls the fission of the nuclear fuel by adjusting the number of neutrons absorbed by a nuclear fuel. The control element 3 is connected to a control element drive shaft 6. The control element 3 is vertically driven up and down by a control element drive mechanism 5. For the installation of the control element drive mechanism 5, a nozzle 4 is placed on an upper portion of the nuclear reactor 1. As shown in FIG. 2, the control element drive mechanism 5, which may be a 4-coil type control element drive mechanism, includes an upper motor assembly 10, a lower motor assembly 20, and a control element drive coil. The upper motor assembly 10 includes an upper latch 13, an upper stationary magnet 14, an upper lift magnet 15, and an upper latch magnet 16. Meanwhile, the lower motor assembly 20 includes a lower latch 23, a lower stationary magnet 24, a lower lift magnet 25, and a lower latch magnet 26. The control element drive coil includes an upper lifting (UL) coil 11, an upper gripper (UG) coil 12, a lower lifting (LL) coil 21, and a lower gripper (LG) coil 22. The control element drive mechanism 5 controls the vertical movement of the control element 3 by controlling the magnetic force generated by the four coils. In detail, a 4-coil magnetic jack type control element drive mechanism operates a motor assembly in a double-step manner. A first step occurs at the upper motor assembly 10, and a second step occurs at the lower motor assembly 20. The first step and the second step constitute a pitch. Operation of the motor assembly in the double-step manner will be explained in detail by referring to FIG. 4, as follows. For the convenience of explanation, a sequence of withdrawing a control element is provided herein. A process of inserting the control element will be carried out in the reverse order of the withdrawing sequence. The first step is completed by the operation of the upper motor assembly 10. In detail, when current is provided to the UG coil 12, an upper latch 13 engages with teeth 7 of the control element drive shaft 6, whereafter current is provided to the UL coil 11 and the upper lift magnet 14 ascends to drive up the control element drive shaft 6. When current is applied to the LG coil 22, the lower latch 23 engages with the teeth 7 of the control element drive shaft 6, whereafter the current supply to the UL coil 11 and the UG coil 12 is blocked to make the control element drive shaft 6 remain elevated. Meanwhile, the second step is completed by the operation of the lower motor assembly 20. In detail, following a last phase of the first step, current is provided to the LL coil 21 and a lower lift magnet 25 is driven up, and current is provided to the UG coil 12 and the upper latch 13 engages with the teeth 7 of the control element drive shaft 6, whereafter the current supply to the LL coil 21 and LG coil 22 is blocked. As a result, the upper latch 13 is engaged with the teeth 7 of the control element drive shaft 6 to make the control element drive shaft 6 remain elevated. As explained before, the conventional control element drive mechanism completes one pitch of ascending or descending the control element drive shaft 6 only when the first and second steps are all completed. As shown in FIG. 3, a lift gap (d1) of the upper motor assembly 10 and a lift gap (d2) of the lower motor assembly 20 are 7/16 of an inch and ⅜ of an inch, respectively. When the upper motor assembly 10 and the lower motor assembly 20 operate a lifting operation, a space margin between the upper latch 13 and the teeth 7 of the control element drive shaft 6 or a space margin between the lower latch 23 and the teeth 7 of the control element drive shaft 6 is given as 1/32 inch. Therefore, when the upper motor assembly 10 operates, the control element drive shaft 6 ascends or descends by ( 7/16- 1/32) of an inch; when the lower motor assembly 20 operates, the control element drive shaft 6 ascends or descends by (⅜- 1/32) inch. As a result, the distance moved in the first step is different from the distance moved in the second step, and one pitch of moving the control element drive shaft 6 is completed with each sequential operation of the upper motor assembly 10 and the lower motor assembly 20. A final one pitch completed by the operation of the upper motor assembly 10 and the lower motor assembly 20 is calculated using the following formula:Final one pitch= 7/16 of an inch− 1/32 inch+⅜ of an inch− 1/32 inch= 24/32 inch=¾ inch. As explained herein above, the operation type of a conventional control element drive mechanism has a position control resolution of ¾ inch. However, such a conventional method is not precise enough to be used in a small reactor; therefore, there has been a demand for a control element drive mechanism with precise position control capacity. One or more exemplary embodiments include a magnetic jack type control element drive mechanism for precision position control of the control element assembly, which is applied to a 4-coil type control element drive mechanism to improve a position control resolution of a motor assembly. Additional aspects will be set forth in part in the description which follows and, in part, will be apparent from the description, or may be learned by practice of the presented embodiments. According to an aspect of exemplary embodiments, provided is a magnetic jack type control element drive mechanism for precision position control of the control element assembly, wherein the magnetic jack type control element drive mechanism is applied as a 4-coil type control element drive mechanism, includes an upper motor assembly and a lower motor assembly, which drive up and down a control element drive shaft, and satisfies the following formulas:D1=D2=P+D5 (1)D3=P×2; and (2)D4=D3×(N−½), (N is an arbitrary natural number), (3)wherein D1 represents a lift gap of the upper motor assembly, D2 represents a lift gap of the lower motor assembly, D3 represents a space width between adjacent tips of teeth of the control element drive shaft, D4 represents a gap between a upper latch located at the upper motor assembly and a lower latch located at the lower motor assembly, P represents a pitch that is a distance of ascent or descent of the control element drive shaft by operating the upper motor assembly or the lower motor assembly, and D5 represents a margin which is the separation space between the teeth and the upper latch or between the teeth and the lower latch when the upper latch or the lower latch is inserted into the teeth of the control element drive shaft. In some embodiments, P is 10 mm or smaller. In some embodiments, D5 is equal to or greater than 0.1 mm and equal to or smaller than 1.0 mm. In some embodiments, N is 10 or more. Reference will now be made in detail to embodiments, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to the like elements throughout. In this regard, the present embodiments may have different forms and should not be construed as being limited to the descriptions set forth herein. Accordingly, the embodiments are merely described below, by referring to the figures, to explain aspects of the present description. One or more embodiments of the present invention relates to a magnetic jack type control element drive mechanism which is operated as a 4-coil type. A control element drive mechanism according to an embodiment of the present invention may be applied to a reactor which needs precise position control of a control element, particularly to a small reactor which requires a precise position control capacity in terms of its characteristics. Hereinafter, exemplary embodiments of the present invention will be explained in detail by referring to the attached drawings. FIG. 5 is a schematic cross-sectional view of a control element drive mechanism according to an embodiment of the present invention, FIG. 6 is a magnified cross-sectional view illustrating the main portion of FIG. 5, FIG. 7 is a view of a space width between adjacent tips of teeth of a control element drive shaft, FIG. 8 is a view of a space margin when a latch approaches toward the teeth of the control element drive shaft, FIG. 9 is a view of a sequential progression of withdrawing the control element, according to an embodiment of the present invention, FIG. 10 is a schematic view of how a control element drive shaft ascends according to the sequence explained in connection with FIG. 9, FIG. 11 is a schematic view of how the control element drive shaft descends, according to an embodiment of the present invention, and FIG. 12 is a view of the state of a control element drive mechanism installed inside a reactor, according to an embodiment of the present invention. As shown in FIG. 4, in a control element drive mechanism according to an embodiment of the present invention, when an upper motor assembly 100 and a lower motor assembly 200 operates, a pitch for which the control element drive shaft 300 ascends or descends in a first step where the upper motor assembly 100 operates is configured to be equal to a pitch for which the control element drive shaft 300 ascends or descends in the second step where the lower motor assembly 200 operates; therefore, in a 4-coil type control element drive mechanism where the upper motor assembly 100 and the lower motor assembly 200 operate in sequence, the resolution of position control is improved. In this regard, the space width between adjacent tips of the teeth of the control element drive shaft 200 is designed to become twice as wide as the pitch; therefore the constraints of the pitch caused due to too tight space width between adjacent tips of the teeth may less occur. Above all, as shown in FIG. 5, a 4-coil type control element drive mechanism includes the upper motor assembly 100, the lower motor assembly 200, and the control element drive coil. The upper motor assembly 100 includes an upper latch 130, an upper stationary magnet 140, an upper lifting magnet 150, and an upper latch magnet 160. The lower motor assembly 200 includes a lower latch 230, a lower stationary magnet 240, a lower lifting magnet 250 and a lower latch magnet 260. The control element drive coil includes an upper lifting (UL) coil, an upper gripper (UG) coil 120, a lower lifting (LL) coil 210, and a lower gripper (LG) coil 220. With a sequential operation of the four coils—UL coil 110, UG coil 120, LL coil 210, and LG coil—the control element drive shaft 300 ascends or descends; and as a result the control element which is connected to the control element drive shaft 300 ascends or descends. As shown in FIGS. 6 to 8, a control element drive mechanism according to an embodiment of the present invention satisfies the following formulae:D1=D2=P+D5 (1)D3=P×2; and (2)D4=D3×(N−½), (N is an arbitrary natural number), (3)wherein D1 represents a lift gap of the upper motor assembly, D2 represents a lift gap of the lower motor assembly, D3 represents a space width between adjacent tips of teeth of the control element drive shaft, D4 represents a gap between a upper latch located at the upper motor assembly and a lower latch located at the lower motor assembly, P represents a pitch that is a distance of ascent or descent of the control element drive shaft by operating the upper motor assembly or the lower motor assembly, and D5 represents a space margin between the teeth and the upper latch or between the teeth and the lower latch when the upper latch or the lower latch is inserted into the teeth of the control element drive shaft. In detail, D1 means the gap of the ascent of the upper lift magnet 150 when current is provided to the UL coil 110. D2 means the gap of the ascent of the lower lift magnet 250 when current is provided to the LL coil 210 D3 means the width between adjacent tips of the teeth 310, as shown in FIG. 7. The 4-coil magnetic jack type control element drive mechanism includes the upper latch 130 and the lower latch 230 as a pair; D4 means the distance between the upper latch 130 which constitutes the upper motor assembly 100 and the lower latch 230 which constitutes the upper motor assembly 200. P means the unit increment distance of the ascent (the withdrawing process of the control element) or the descent (the insertion process of the control element) of the control element drive shaft 300, when the upper motor assembly 100 or the lower motor assembly 200 operates. In some embodiments, as shown in FIG. 8, the upper latch 130 and the lower latch 230 is designed such that when the upper latch 130 or the lower latch 230 is engaged with the teeth 310 of the control element drive shaft 300, the upper latch 130 or the lower latch 230 approaches the teeth 310 with a little space in between. D5 represents the space margin. Here again, the conditions of the aforementioned formulas are explained in detail as follows. I. Explanation of the Formula (1) According to an embodiment of the present invention, D1 equals D2 while D1 and D2 are set to have the distance of P plus D5. In some embodiments, according to an embodiment of the present invention, P is 10 mm or smaller while D5 is equal to or greater than 0.1 mm and equal to or smaller than 1.0 mm. While the conventional control element drive mechanism has a resolution of ¾ inch (approximately 19.05 mm), embodiments of the present invention provide a more precise resolution. II. Explanation of the Formula (2) According to an embodiment of the present invention, the value of D3 is twice the value of P. In other words, the sum of the distance (P) of the ascent or descent of the control element drive shaft 300 driven by the operation of the upper motor assembly 100 and the distance (P) of the ascent or descent of the control element drive shaft 300 driven by the operation of the lower motor assembly 200 is equal to the space width between adjacent tips of the teeth 310 of the control element drive shaft 300. The space width between adjacent tips of the teeth 310 is one of integral factors that affect control precision of the magnetic jack type control element drive mechanism. According to embodiments of the present invention, the teeth are placed at intervals of double the pitch, which is very advantageous compared to a conventional method. III. Explanation of the Formula (3) D4, which is the separation space between the upper latch 130 and the lower latch 230, is given as the value of multiplying the space width between adjacent tips of the teeth 310 of the control element drive shaft 300 by (natural number −0.5). In some embodiments, D4 is also equal to the value determined by subtracting P from the distance calculated by multiplying a natural number by the space width between adjacent tips of the teeth 310 of the control element drive shaft 300, as follows.D4=D3×(N−½)=(P×2×N)−(P×2×½)=(P×2×N)−P According to an embodiment of the present invention, N is given as 10 or greater. According to an embodiment of the formula, the design of the following may be considered. In the embodiment of the present invention, when the resolution of position control by the control element drive mechanism is designed to set at 10 mm and the margin D5 is designed to set at 0.5 mm, The lift gap D1 of the upper motor assembly 100 and the lift gap D2 of the lower motor assembly 200 are given as 10 mm+0.5 mm=10.5 mm. The space width D3 between adjacent tips of the teeth 310 is given as 10 mm×2=20 mm. The separation space D4 between the upper latch 130 and the lower latch 230 may be given as 20 mm×(23½)=450 mm (here, N is set at 23). However, the above-mentioned numbers are only examples; there may be various designs as long as the formulas (1) to (3) are satisfied. For example, when the natural number applied to the space width between adjacent tips of the teeth 310 of the control element drive mechanism is set at 10, the space width between the upper latch 130 and the lower latch 230 is given as 20 mm×(10½)=190 mm. Such a result may be achieved when the sizes of the upper stationary magnet 140, the upper lift magnet 150, the upper latch magnet 160, the lower stationary magnet 240, the lower lifting magnet 250, and the lower latch magnet 260, which constitute the upper motor assembly 100 () and the lower motor assembly 200, are reduced to less than half of what their respective sizes are at N=23. Hereinafter, by referring to FIGS. 9 to 11, how a control element drive mechanism according to an embodiment of the present invention having the configurations described above operates will be explained in detail. The upper motor assembly 100 and the lower motor assembly 200 operate in sequence, which is the same as in a conventional control element drive mechanism. However, according to an embodiment of the present invention, when the upper motor assembly 100 operates, a pitch of the movement of the control element drive shaft 300 is completed, and when the lower motor assembly 200 operates, another pitch of the movement of the control element drive shaft 300 is completed. In other words, when the upper motor assembly 100 and the lower motor assembly 200 operate once for each in sequence, the control element drive shaft 300 moves by a distance equal to twice the pitch. FIGS. 9, 10, and 11 show an example in which D1=D2=10.5 mm, P=10 mm, D3=20 mm, and D5=0.5 mm are given. In FIGS. 10 and 11, ±10.5 mm means the ascent or descent by 10.5 mm and ±0.5 mm means the ascent or descent by 0.5 mm. First, by referring to FIGS. 9 and 10, how the control element drive shaft 300 ascends according to the sequence of withdrawing of a control element will be explained in detail. As shown in FIG. 10(a), when current is provided to the UG coil 120 of the upper motor assembly 100, the upper latch 130 is engaged with the teeth 310 of the control element drive shaft 300. This is the initial stage for the ascent of the control element drive shaft 300. At this stage, the lower latch 230 remains disengaged from the teeth 310 of the control element drive shaft 300. In a table in FIG. 10, the state of current being provided to the 4 coils is marked as O and the state of current not being provided is marked as X. As shown in FIG. 10(b), when current is provided to the UL coil 110, the upper lift magnet 150 ascends and simultaneously the control element drive shaft 300 ascends. As shown in FIG. 10(c), when current is provided to the LG coil 220, the lower latch 230 enters between the teeth 310 of the control element drive shaft 300. At this stage, the lower latch 230 remains apart from the teeth 310 of the control element drive shaft 300 as much as the margin. As shown in FIG. 10(d), when the current supply to the UL coil 110 is blocked, the control element drive shaft 300 descends as much as the margin and, is latched onto the lower latch 230 which has come between the teeth 310 of the control element drive shaft 300 at stage (c). As shown in FIG. 10, during stages from (a) to (d), the current remains provided to the UG coil 120. Then, as shown in FIG. 10(e), the current supply to the UG coil 120 is blocked. At this stage, the current remains provided to the LG coil 220. As a result, the state in which the upper latch 130 is engaged with the teeth 310 of the control element drive shaft 300 by the UG coil 220 at stage (a) turns into a state in which the lower latch 230 is engaged with the teeth 310 of the control element drive shaft 300 by the LG coil 220 at stage (e). In stage (a) through stage (e), the control element drive shaft 300 ascends as much as half of the space width D3 between adjacent tips of the teeth, i.e., P as required. Next, as shown in FIG. 10(f), when current is provided to the LL coil 210, the lower lifting magnet 250 ascends and simultaneously the control element drive shaft 300 ascends. As shown in FIG. 10(g), when current is provided to the UG coil 120, the upper latch 130 enters onto the teeth 310 of the control element drive shaft 300. At this stage, the upper latch 130 remains apart from the teeth 310 of the control element drive shaft 300 as much as the margin. As shown in FIG. 10(h), when the current supply to the LL coil 210 is blocked, the control element drive shaft 300 descends as much as the margin and get engaged with the upper latch 130 which has come into the teeth 310 of the control element drive shaft 300 at stage (g). Then, as shown in FIG. 10(i), the current supply to the LG coil 220 is blocked. At this stage, the current remains provided to the UG coil 120. As a result, the state in which the lower latch 230 gets latched onto the teeth 310 of the control element drive shaft 300 by the LG coil 220 at stage (e) turns into the state in which the upper latch 130 gets latched onto the teeth 310 of the control element drive shaft 300 by the UG coil 120 at stage (i), i.e., back to stage (a). From stage (f) to stage (i), the control element drive shaft 300 ascends as much as half of the space width between adjacent tips of the teeth D3, i.e., P as required. As a result, a pitch of the ascent of the control element drive shaft 300 when transitioning from stage (a) to stage (e) is the same as a pitch of the ascent of the control element drive shaft 300 when transitioning from stage (f) to stage (i); and, according to an embodiment of the present invention, 2 pitches are completed while a cycle of 8 sequences occurs with a sequence including the sequential operation of the upper motor assembly 100 and the lower motor assembly 200. FIG. 11 shows how the control element drive shaft 300 descends. As shown in FIG. 11(a), when current is provided to UG coil 120 of the upper motor assembly 100, the upper latch 130 gets latched onto the teeth 310 of the control element drive shaft 300. This is the initial stage for the descent of the control element drive shaft 300. At this stage, the lower latch 230 remains disengaged from the teeth 310 of the control element drive shaft 300. In a table in FIG. 11, the state of current being admitted to the 4 coils is marked as O and the state of current not being admitted is marked as X. As shown in FIG. 11(b), when current is provided to the LG coil 220, the lower latch 230 enters between the teeth 310 of the control element drive shaft 300. According to an embodiment of the present invention, the upper latch 130 is engaged with the teeth 310 of the control element drive shaft 300 while the lower latch 230 is located below the upper latch 130 with a space of (N+0.5)×D3 in between. In other words, the lower latch 230 is located in the middle of the space width between adjacent tips of the teeth of the control element drive shaft 300. As shown in FIG. 11(c), when current is provided to the LL coil 210, the lower latch 230 ascends and gets engaged with the teeth 310 of the control element drive shaft 300. At this stage, the lower latch 230 is raised by the height of a pitch plus the margin, and the upper latch 130 is located downward as low as D5 from the teeth 310 of the control element drive shaft 300. As shown in FIG. 11(d), the current supply to the UG coil 120 is blocked, and the upper latch 130 is detached from the teeth 310 of the control element drive shaft 300. As shown in FIG. 11(e), when the current supply to the LL coil 210 is blocked, the control element drive shaft 300 descends while the lower latch 230 remains engaged with the control element drive shaft 300. As a result, like the way the upper latch 130 gets engaged with the teeth 310 of the control element drive shaft 300 by the UG coil 120 at stage (a) shown in FIG. 11, the lower latch 230 get engaged with the teeth 310 of the control element drive shaft 300 by the LG coil 220 at stage (e). At this stage, the control element drive shaft 300 descends as low as one pitch. Then, as shown in FIG. 11(f), when current is provided to the UG coil 120, the upper latch 130 enters between the teeth 310 of the control element drive shaft 300. According to an embodiment of the present invention, the lower latch 230 remains latched onto the teeth 310 of the control element drive shaft 300 while the upper latch 130 is located above the lower latch 230 with a space of (N+0.5)×D3 in between. In other words, the upper latch 130 is located in the middle of the space width between adjacent tips of the teeth of the control element drive shaft 300. As shown in FIG. 11(g), when current is provided to the UL coil 110, the upper latch 130 ascends and gets engaged with the teeth 310 of the control element drive shaft 300. At this stage, the upper latch 130 is raised by the height of a pitch plus the margin, and the lower latch 230 is located downward as low as D5, from the teeth 310 of the control element drive shaft 300. As shown in FIG. 11(h), when the current supply to the LG coil 220 is blocked, the lower latch 230 is disengaged from the teeth 310 of the control element drive shaft 300. Finally, as shown in FIG. 11(i), when the current supply to the UL coil 110 is blocked, the control element drive shaft 300 descends while the upper latch 130 remains latched with the control element drive shaft 300. At this stage, the upper latch 130 descends as low as D1; therefore, the control element drive shaft 300 descends as low as D1. As a result, like the way the lower latch 230 gets latched onto the teeth 310 of the control element drive shaft 300 by the LG coil 220 at stage (e) shown in FIG. 11, the upper latch 130 gets latched onto the teeth 310 of the control element drive shaft 300 by the UG coil 120 at stage (i). At this stage, the control element drive shaft 300 descends as low as one pitch. As aforementioned, the control element drive shaft 300 descends as much as one pitch while going through from stage (a) to stage (e), another pitch from stage (f) to stage (i). As a result, the pitch of the descent of the control element drive shaft 300 while going through from stage (a) to stage (e) is the same as the pitch of the descent of the control element drive shaft 300 while going through from stage (f) to stage (i); and, according to an embodiment of the present invention, 2 pitches are completed while a cycle of 8 sequences occurs with a sequence including the sequential operation of the upper motor assembly 100 and the lower motor assembly 200. As explained before, a magnetic jack type control element drive mechanism for precision position control of a control element assembly according to an embodiment of the present invention controls the distance of the ascent and descent of the control element drive shaft 300 more precisely than a conventional control element drive mechanism. In other words, a conventional control element drive mechanism is configured to complete a pitch when the upper motor assembly 100 and the lower motor assembly 200 operate once for each in a sequential manner; also, the resolution of position control of the control element drive shaft 300 provided for the conventional control element drive mechanism is ¾ inch, which is relatively large. However, according to an embodiment of the present invention, 2 pitches are completed when the upper motor assembly 100 and the lower motor assembly 200 operate once for each in a sequential manner; particularly, one pitch is completed when the upper motor assembly 100 operates and another pitch when the lower motor assembly 200 operates, tremendously increasing the resolution of position control of the control element drive shaft 300. In some embodiments, as shown in FIG. 12, the control element drive mechanism according to an embodiment of the present invention may be installed inside a reactor 400. Inside the reactor 400, a nuclear fuel assembly 450 is placed, and a control element 400 is connected to a control element drive shaft 410; a separate support structure 430 is placed to install the control element drive mechanism 420. In some embodiments, a cable 460 for providing the power supply to the control element drive mechanism 420 is connected to a control system 470 configured outside of the reactor 400 while penetrating the reactor head. In other words, a control element drive mechanism according to an embodiment of the present invention may be installed and operated as an in-vessel type inside the reactor for a small and medium-sized reactor. Of course, it is also possible to be installed outside a reactor. A magnetic jack type control element drive mechanism for precision position control of the control element assembly according to an embodiment of the present invention increases the position control resolution of a motor assembly. Also, it provides even greater capacity for precise control of the reactor control element by increasing the position control resolution of the motor assembly. It should be understood that exemplary embodiments described herein should be considered in a descriptive sense only and not for purposes of limitation. Descriptions of features or aspects within each exemplary embodiment should typically be considered as available for other similar features or aspects in other exemplary embodiments. While one or more exemplary embodiments have been described with reference to the figures, it will be understood by those of ordinary skill in the art that various changes in form and details may be made therein without departing from the spirit and scope of the inventive concept as defined by the following claims.
051805430	abstract	A passive safety injection system relies on differences in water density to induce natural circulatory flow patterns which help maintain prescribed concentrations of boric acid in borated water, and prevents boron from accumulating in the reactor vessel and possibly preventing heat transfer.
	abstract	Methods and apparatus are provided for planning and delivering radiation treatments by modalities which involve moving a radiation source along a trajectory relative to a subject while delivering radiation to the subject. In some embodiments the radiation source is moved continuously along the trajectory while in some embodiments the radiation source is moved intermittently. Some embodiments involve the optimization of the radiation delivery plan to meet various optimization goals while meeting a number of constraints. For each of a number of control points along a trajectory, a radiation delivery plan may comprise: a set of motion axes parameters, a set of beam shape parameters and a beam intensity.
	description	This is a divisional of application Ser. No. 10/208,842 filed Aug. 1, 2002, now U.S. Pat. No. 6,927,901, which is hereby incorporated into the present application by reference and which claims benefit of Provisional Application No. 60/308,861 filed Aug. 1, 2001. 1. Field of the Invention The invention relates to a projection lens for imaging a pattern arranged in an object plane onto an image plane employing electromagnetic radiation from the extreme-ultraviolet (EUV) spectral region. 2. Description of the Related Art Projection lenses of that type are employed on projection exposure systems used for fabricating semiconductor devices and other types of microdevices and serve to project patterns on photomasks or reticles, which shall hereinafter be referred to using the generic terms “masks” or “reticles,” onto an object having a photosensitive coating at ultrahigh resolution. In order to allow creating even finer structures, various approaches to improving the resolving power of projection lenses are being pursued. It is well known that resolving power may be improved by increasing the image-side numerical aperture (NA) of the projection lens. Another approach is employing shorter-wavelength electromagnetic radiation. However, improving resolution by increasing numerical aperture has several disadvantages. The major disadvantage is that the attainable depth of focus (DOF) decreases with increasing numerical aperture, which is disadvantageous because, for example, a depth of focus of the order of at least one micrometer is desirable in view of the maximum-attainable planarity of the substrate to be structured and mechanical tolerances. Systems that operate at moderate numerical apertures and improve resolving power largely by employing short-wavelength electromagnetic radiation from the extreme-ultraviolet (EUV) spectral region have thus been developed. In the case of EUV-photolithography employing operating wavelengths of 13.4 nm, resolutions of the order of 0.1 μm at typical depths of focus of the order of 1 μm may theoretically be obtained for numerical apertures of NA=0.1. It is well known that radiation from the extreme-ultraviolet spectral region cannot be focused using refractive optical elements, since radiation at the short wavelengths involved is absorbed by the known optical materials that are transparent at longer wavelengths. Mirror system that have several imaging, i.e., concave or convex, mirrors that have reflective coatings arranged between their object plane and image plane and define an optical axis of the projection lens are thus employed in EUV-photolithography. The reflective coatings employed are typically multilayer coatings having, for example, alternating layers of molybdenum and silicon. A reflective lens for use in EUV-photolithography that has four mirrors, each of which has reflective coatings with uniformly thick layers, is disclosed in U.S. Pat. No. 5,973,826. Another EUV-photolithographic system is shown in U.S. Pat. No. 5,153,898. That system has a maximum of five mirrors, at least one of which has an aspherical reflecting surface. Numerous combinations of materials for multilayer reflective coatings suitable for use in the EUV are stated. Their layers all have uniform thicknesses. Although reflective coatings with uniform thicknesses are relatively simple to deposit, in the case of imaging systems where the angle of entry, or angle of incidence, of the radiation employed on those areas of the mirrors utilized varies, they usually generate high reflection losses, since the thicknesses of their layers are optimized for a specially selected angle of incidence, or a narrow range of angles of incidence, only. Another of their disadvantages is a nonuniform pupil irradiance that causes a telecentricity error, structurally dependent or field-dependent resolution limits (so-called “H-V-differences or “CD-variations”), and generally lead to a narrowing down of the processing window. Reflective EUV-imaging systems that have mirrors that have graded reflective coatings that are characterized by the fact that they have a film-thickness gradient that is rotationally symmetric with respect to the optical axis of the entire system are also known (cf. U.S. Pat. No. 5,911,858). Employing graded reflective coatings allows achieving a more uniform distribution of the reflected intensity over a certain range of angles of incidence. Photolithographic equipment, or steppers, employ two different methods for projecting a mask onto a substrate, namely, the “step-and-repeat” method and the “step-and-scan” method. In the case of the “step-and-repeat” method, large areas of the substrate are exposed in turn, using the entire pattern present on the reticle. The associated projection optics thus have an image field that is large enough to allow imaging the entire mask onto the substrate. The substrate is translated after each exposure and the exposure procedure repeated. In the case of the step-and-scan method that is preferred here, the pattern on the mask is scanned onto the substrate through a movable slit, where the mask and slit are synchronously translated in opposite directions at rates whose ratio equals the projection lens' magnification. It is one object of the invention to provide an EUV-projection lens operable at high numerical aperture that will allow largely correcting distortion errors along all image directions and providing sufficiently symmetric, high-intensity, illumination of the image field, while maintaining adequate-quality imaging. It is another object to provide a projection lens that, from the optical standpoint, represents a reasonable compromise among wavefront errors, distortion, total transmittance, field uniformity, and uniform pupil irradiance. As a solution to these and other object the invention, according to one formulation, provides a projection lens for imaging a pattern arranged in an object plane onto an image plane employing electromagnetic radiation from the extreme-ultraviolet (EUV) spectral region, wherein several imaging mirrors that have reflective coatings and define an optical axis of the projection lens are arranged between the object plane and the image plane, wherein at least one of those mirrors has an acentric, graded, reflective coating that has a film-thickness gradient that is rotationally symmetric with respect to a coating axis, wherein that coating axis is acentrically arranged with respect to the optical axis of the projection lens. The acentricity or eccentricity of a graded, rotationally symmetric, reflective coating with respect to the optical axis of the entire system provided by the invention yields an additional degree of freedom for optimizing the optical characteristics of the projection lens that is lacking in conventional systems, where due account should be taken of the fact that the design, or optical layout, of an EUV-projection system may be roughly segregated into two, consecutive, stages. The first stage is optimizing the layout and designs of the uncoated mirror substrates using a computer and suitable optical-design software, duly allowing for the traditional criteria, such as wavefront aberrations, distortion, assembly conditions, fabrication conditions, etc. Their reflective coatings are then computed and the design recomputed, duly taking account of their reflective coatings. The coatings are effectively “stuck onto” the uncoated substrates, which generally results in imaging performance that is much worse than that of the system with uncoated optics, which, as a rule, will be intolerable unless the system is subsequently reoptimized. Among other things, that reoptimization should take account of wavefront aberrations and wavefront apodizations caused by the reflective coatings. The competing effects involved are primarily total system transmittance and field uniformity. It has been found that these key properties are usually affected in opposite manners by the sorts of design modifications available. Good compromise solutions that provide adequate total transmittance combined with adequate field uniformity may be particularly favorably obtained using acentric, rotationally symmetric, reflective coatings, where it has generally been found that providing acentric, graded, reflective coatings is particularly beneficial to total transmittance. Field uniformity, on the other hand, is benefited by reflective coatings that are centered on the optical axis. Angular-range computations for the individual reflective surfaces, from which, in particular, the area of each mirror that is actually utilized (their “footprints”), the average angle of incidence at every point on their surface and the angular bandwidths, or ranges of angles of incidence, at each point on their surfaces may be derived, usually serve as the starting point for this reoptimization. The particularly important items of that data are the average angles of incidence and the ranges of angles of incidence (angular bandwidths). Since the primary purpose of the reflective coatings employed on EUV-systems is reflecting as much of incident electromagnetic radiation as possible, designs may be optimized for maximum reflectance, where the average angles of incidence at every point obtainable from angular-range computations may be called upon and used as a basis for computing the film thicknesses needed for optimizing reflectance. The manner in which this proceeds will be largely determined by the shape of the object field, which, in the case of the preferred embodiment, is an annular segment. It has proven beneficial to provide that at least that mirror that has the largest range of angles of incidence, i.e., the largest angular bandwidth, has an acentric, graded, reflective coating. The invention is based on the recognition that employment of constant film thicknesses causes enormous reflectance losses on systems where angles of incidence vary widely over their reflective sections, since films that have constant thicknesses may be optimized for a specially selected angle of incidence, or for a narrow range of angles of incidences, only. This is particularly a problem on high-aperture systems, e.g., systems for which NA>0.2), since angles of incidence on their mirrors are largely determined by their numerical aperture. Once those mirrors that have the largest range of angles of incidence have been identified, design modifications, such as shifting a rotationally reflective coating off-axis, will allow highly effectively tailoring the system's imaging characteristics. In the case of a preferred embodiment, the range of angles of incidence of that mirror that has the largest range of angles of incidence extends to angles less than 5° to 10° and angles exceeding 10° to 15°. The range of angles of incidence involved may, for example, range from about 1° to about 17°. In cases where a reflective system is to be optimized for extremely high total transmittance and field uniformity is either unimportant or plays a minor role, it may be beneficial to employ at least one of those mirrors having the largest range of angles of incidence has an acentric, graded, reflective coating whose film-thickness gradient may be optimized in the radial direction such that they will have high reflectance for the radiation employed over the full range of angles of incidence involved. However, in cases where complex optimizations are involved, it may turn out that employing coatings that have been optimized for high reflectance will displace the system so far from an original local minimum that had been reached that that minimum will no longer be automatically locatable, which might result in a new design, instead of a reoptimized design. Since employing a single, acentric, graded, reflective coating on a reflective system may, in addition to the desired beneficial effects, also adversely affect imaging performance, a preferred embodiment has a mirror that has a first, acentric, graded, reflective coating and at least one other mirror that has a second, acentric, graded, reflective coating whose acentricities, film-thickness gradients, etc., have been adapted to suit one another such that the contributions of their reflective coatings to certain imaging errors are at least partially compensated, where distortion along the cross-scan direction (the x-direction) will be particularly critical, since, for this sort of distortion, there is no compensating effect along the orthogonal y-direction due to the scanning. In the case of preferred embodiments, the acentricities of their reflective coatings are thus configured such that their coating axis is acentric with respect to the projection lens' optical axis along a y-direction, which, in the case of a scanner, corresponds to the scanning direction. It has proven beneficial to provide that the film thicknesses, d, of their rotationally symmetric film-thickness gradients have the following form: d = d 0 ⁢ ∑ i = 0 n ⁢ c 2 ⁢ i ⁡ ( r - r 0 ) 2 ⁢ i , ( 1 ) where d0 is the optimal film thickness for normal incidence (0° angle of incidence), r0 is the acentricity of the coating axis relative to the system's optical axis in the x-y plane, r is the current radial coordinate in the x-y plane, the parameters, c are polynomial coefficients, and n is an integer. The preferred film-thickness gradient may thus be described by a second-order polynomial lacking any odd-powered terms, in particular, lacking a linear term, that may, in the simplest case, be, for example, a parabola. A preferred projection lens that will be described in detail in conjunction with a sample embodiment has six mirrors between its object plane and image plane. The fifth mirror following its object plane is that mirror that has the largest range of angles of incidence. In the case of a system that has been optimized for maximum reflectance, this mirror may have a centered, graded, reflective coating. In the case of other embodiments, several of their mirrors are provided with centered, graded, reflective coatings that have been adapted to suit one another such that their pupil-irradiance distributions are substantially rotationally symmetric. Preferred here are two, and no more than four, such mirrors, since lateral film-thickness gradients are difficult to deposit. At least this fifth mirror is provided with an acentric, graded, reflective coating in order to allow simultaneously optimizing several quality criteria, in particular, total transmittance and distortion. The projection lens may have an image-side numerical aperture, NA of greater than or equal to 0.15, or more specifically, greater than or equal to 0.2. Particularly beneficial results are achieved when at least one of those mirrors that precede the fifth mirror, for example, the third or fourth mirror, also has an acentric, graded, reflective coating, where the axes of rotation of both film-thickness gradients of the cascaded, graded, reflective coatings are acentrically displaced parallel to the optical axis such that their respective contributions to distortion along the cross-scan direction at least partially compensate one another. The foregoing and other characteristics will be apparent, both from the claims and from the description and the drawings, where the individual characteristics involved may represent characteristics that are patentable alone or in the form of combinations of subsets thereof in an embodiment of the invention and in other fields. In the following description of the major principles of the invention, the term “optical axis” shall refer to a straight line or a sequence of straight-line segments passing through the paraxial centers of curvature of the optical elements involved, which, in the case of embodiments described here, consist exclusively of mirrors that have curved reflecting surfaces. In the case of those examples presented here, the object involved is a mask (reticle) bearing the pattern of an integrated circuit or some other pattern, such as a grating. In the case of those examples presented here, its image is projected onto a wafer coated with a layer of photoresist that serves as a substrate, although other types of substrate, such as components of liquid-crystal displays or substrates for optical gratings, may also be involved. A typical layout of an EUV-projection lens 1 based on a preferred sample embodiment is shown in FIG. 1. It serves to project an image of a pattern on a reticle or similar arranged in an object plane 2 onto an image plane 3 aligned parallel to that object plane on a reduced scale, for example, a scale 4:1. Imaging is by means of electromagnetic radiation from the extreme-ultraviolet (EUV) spectral region, in particular, at an operating wavelength of about 13.4 nm. A total of six mirrors 4–9 that have curved reflecting surfaces, and are thus imaging mirrors, are mutually coaxially arranged between the object plane 2 and image plane 3 such that they define a common optical axis 10 that is orthogonal to the image plane and object plane. The substrates of those mirrors 4–9 have rotationally symmetric, aspherical, surface figures whose symmetry axes coincide with their common physical axis 10. This six-mirror system, which has been designed for operation in step-and-scan mode and operates with an off-axis annular field, achieves a numerical aperture, NA, of NA=0.25 for an annular field with typical field dimensions of 2 mm×26 mm. As may be seen from FIG. 1, light from an illumination system (not shown) that includes a soft-X-ray light source initially strikes a reflective mask arranged in the object plane 2 from the side of the object plane 2 opposite the image. Light reflected by the mask strikes a first mirror 4 that has a concave reflecting surface facing the object that reflects it, slightly narrowed down, to a second mirror 5. This second mirror 5 has a concave reflecting surface facing the first mirror 4 that reflects the radiation toward a third mirror 6, in the form of a convergent beam. This third mirror 6 has a convex reflecting surface that reflects the off-axial incident radiation to a fourth mirror 7 that is utilized in a mirror section situated far away from the optical axis and reflects incident radiation to a fifth mirror 8 arranged in the vicinity of the image plane 3, while forming a real intermediate image 11. The latter mirror has a convex reflecting surface facing away from the image plane that reflects the incident, divergent, radiation toward a sixth mirror 9 that has a concave reflecting surface facing the image plane 3 that reflects incident radiation and focuses it on the image plane 3. All reflecting surfaces of the mirrors 4–9 have reflectance-enhancing reflective coatings deposited on them. In the case of preferred embodiments, these coatings are stacks of, for example, about forty alternating pairs of layers, each of which includes a layer of silicon and a layer of molybdenum. As related to FIGS. 17–19, the several imaging mirrors of the EUV projection lens 1 of FIG. 1 have reflective coatings and define an optical axis of the projection lens. The relation of these several mirrors to the optical axis 10 of the projection lens is illustrated in FIG. 17, where exemplary mirrors 101 and 102 have curvature surfaces 101a and 102a with axes coaxial with optical axis 10. As shown in FIG. 1, the several mirrors are arranged between the object plane and the image plane, and at least one of those mirrors has an acentric, graded, reflective coating (such as coating 105b of mirror 105, FIG. 19 ) that has a film-thickness gradient that is rotationally symmetric with respect to a coating axis (such as coating axis 105c, FIG. 19 ), wherein that coating axis is acentrically arranged with respect to the optical axis 10 of the projection lens. As shown by exemplary mirror 105 of FIG. 19, the coating axis 105c of the coating 105b is offset from the optical axis 10 by a distance yde. Table 1 summarizes the design shown in tabular form, where its first row lists the number of the reflective, or otherwise designated surfaces, involved, its second row lists the radius of those surfaces [mm], and third row lists the distance between the respective surface involved and the next surface [mm]. The algebraic signs of the radii have been chosen such that a positive sign corresponds to a center of curvature of the reflecting surface that lies on the image-plane side. Its fourth through ninth rows, which are designated “A” through “E,” list the aspheric coefficients of the aspherical reflecting surfaces. It may be seen that all reflecting surface are spherically curved. Their aspherical surfaces may be computed using the following equation:p(h)=[((1/r)h2)/(1+SQRT(1−(1+K)(1/r)2h2)]+Ah4+Bh6+ . . . ,where 1/r is their curvature and h is the distance of a point on their surface from the optical axis. p(h) thus represents the radial distance of a point on their surface from the inflection point of their surface along the z-direction, i.e., along the optical axis. The constants K, A, B, etc., are listed in Table 1. The coefficients, C0, C2, xde, and yde, listed in the rows that follow describe the film-thickness gradients for the reflective coatings that, in the case of a preferred embodiment, are applied to the respective mirrors, in accordance with the formula appearing in Eq. 1, which has been explained above, where r0=√{square root over (xde2+yde2)}. The effects that the reflective coatings chosen have on the imaging performance of the projection lens will now be discussed in several stages. Computerized design of those reflective coatings was conducted under the boundary condition that each of the coating designs employed should be allowed to distort the transmitted wavefront only to the point where the entire system would not be displaced from a local minimum of its characteristics that was found when the system's basic design was developed for the case of uncoated substrates, where higher-order wavefront errors hardly occurred at all. The major effects are distortion and defocusing. In addition to the wavefronts, described by, for example, Zemike coefficients and distortion along the scanning direction, the y-direction, and the cross-scan direction, the x-direction, the quality criteria that apply to such coating designs are field uniformity and pupil apodization. System design and fabrication characteristics remain virtually unchanged compared to the those of the basic design with uncoated substrates. We shall start off by describing a projection lens, all of whose reflective coatings have constant film thicknesses, where it is useful to compute an average angle of incidence from the computations of ranges of angles of incidence for all mirrors, where their average angles of incidence should be computed over their entire utilized surfaces. The associated, optimal, film thicknesses are then computed, based on these global average angles of incidence, and inserted into an associated coating design in a known manner. The major effect of these uniformly thick films is a constant image offset along the scanning direction, accompanied by a readily recognizable defocusing. This first-order error may be corrected by a reoptimization. Wavefront aberrations, which are designated by their rms-values, were about 20% worse than those for designs with uncoated mirrors. FIGS. 2 and 3 present plots of the irradiance distribution at the projection lens' circular exit pupil for two field points, where FIG. 2 plots the distribution for a field point lying on the system's symmetry axis and FIG. 3 plots the distribution for a field point at the edge of its annular field. The percentages stated designate fractions of the irradiance at the entrance of the projection lens. In keeping with the rotational symmetry of the system and the coatings employed, which are rotationally symmetric with respect to any axis parallel to the optical axis due to their constant film thicknesses, these two irradiance distributions differ only in a rotation about the exit pupil's axis. The rotation angle involved results from the location of the field point in the object plane or image plane. These schematic representations show that a pronounced pupil apodization occurs. The irradiance level varies from about 3% to 14% over the pupil. Those areas having differing pupil irradiances are indicated by contours of constant intensity in FIGS. 2 and 3. The special form of these distributions, whose center lies outside the exit pupil, would cause large differences (h-v-differences) between the critical dimensions (CD-values) for horizontal and vertical features. FIG. 4 schematically depicts the transmittance distribution over the field. Although the variations along the scanning direction, which correspond to the plot's y-axis, have no significant adverse effects due to the integrating effect of scanning, the nonuniformities normal to the scanning direction, i.e., the cross-scan direction, or x-direction, are responsible for CD-variations over the field. However, weighting the irradiation distribution with the irradiance distribution at the reticle will allow achieving a dynamic uniformity of around 1%, which may be adequate for many types of applications. In the case of the example shown, the average transmittance is about 13%, which represents a very high value, in view of simple reflective coatings employed. In the case of the design shown in FIG. 1, the fifth mirror 8 near the image is the mirror that has the largest variation of average angle of incidence over its utilized reflective surface, where “angle of incidence” is defined as the angle between the direction at which incident radiation is incident and the normal to its reflecting surface at the location where radiation strikes that surface. The angles of incidence involved range from about 1° to 17°. Coating this mirror with coatings that have a constant thickness will cause relatively high reflection losses. A beneficial compromise between high reflectance and acceptable wavefront corrections may be achieved by providing that at least this mirror 8 has a rotationally symmetric, graded, reflective coating whose film-thickness gradient may be described by Eq. 1. It has been found that in order to significantly improve reflectance it may be sufficient to adapt the film-thickness gradient along the symmetry axis to suit the average angle of incidence involved. This will usually be a linear gradient and may be well-adapted using the polynomial of Eq. 1, provided that a corresponding acentricity (r0≠0) may be tolerated. FIGS. 5 and 6 present plots of intensity distributions at the exit pupil that yield a high average transmittance of, for example, 13.7%, with a variance of from about 12% to about 14%, which is thus much less than for the multilayer coatings with constant film thicknesses described above. However, the field uniformity shown in FIG. 7, which has a variance of about 2.5%, is somewhat worse than for the case of coatings with constant film thickness. However, multilayer coatings of this type, which have lateral film-thickness gradients, are suitable for use in exceptional cases only due to their relatively high distortion along the cross-scan direction (the x-direction), since scanning generates no effects that will compensate for this distortion. We have been able to show that this distortion along the cross-scan direction is largely attributable to the acentricity of the graded reflective coating on the fifth mirror 8. This effect can thus be reduced by keeping the acentricity involved small or arranging the graded reflective coating such that it is rotationally symmetric with respect to the optical axis. Typical optical characteristics of a design that employs a centered, graded, reflective coating on the fifth mirror are shown in FIGS. 8 through 10. It may be seen that pupil apodization, which is about 8% in the vicinity of the pupil's axis and about 14% at the edge of the pupil, is relatively large. However, it is rotationally symmetric with respect to the pupil's axis and therefore also independent of field point, which then also immediately yields the near-perfect uniformity (<0.4%) over the entire field shown in FIG. 10. The total transmittance, 12%, is less than that for the design under consideration. Another embodiment that has been optimized to yield a rotationally symmetric pupil apodization will now be described, based on FIGS. 11 through 13. In the case of this embodiment, centered, graded, reflective coatings have been applied to two mirrors, namely, to the fifth mirror 8, which has the largest range of angles of incidence, and to the sixth mirror 9 that is arranged ahead of it in the optical path. The centered film-thickness gradients of these mirrors are adapted to suit one another such that the pupil apodization is largely rotationally symmetric, as in the case of the embodiment shown in FIGS. 8 through 10. However, unlike that embodiment, in this case, the pupil apodization exhibits smaller absolute variances over the exit pupil, which significantly improves the uniformity of the illumination compared to the case where a single, centered, graded, reflective coating is employed. As may be seen from FIGS. 11 through 13, the irradiance variances at the exit pupil, which only range from about 13.4% to about 15.6%, are much less than the corresponding variances for an embodiment that employs just a single, centered, graded, reflective coating (cf. FIGS. 8 through 10). Furthermore, its total transmittance,which is about 14.7%, is much better than the latter embodiment and its field uniformity, which is less than 0.4%, is nearly perfect (cf. FIG. 13). Its rotationally symmetric exit pupil is achieved by tailoring the film-thickness gradients of the coatings on its third and fifth mirrors. This example shows that employing several, centered, graded, reflective coatings whose film-thickness gradients have been suitably adapted to suit one another will allow achieving substantially rotationally symmetric pupil-irradiance distributions. An embodiment that allows a compromise between total transmittance and field uniformity will now be described, based on FIGS. 14 through 16. In order to correct for the distortion along the cross-scan direction caused by employment of acentric multilayer coatings mentioned above, it is preferentially foreseen that that the film-thickenss gradients of the coatings on several, i.e., at last two, mirrors will be acenric and their respective acentricities will have been adapted to suit one another such that they partially, or fully, compensate for their contributions to distortion. FIGS. 14 through 16 present the characteristics of a design wherein, in addition to the fifth mirror 8 and sixth mirror 9, the third mirror 6, also has an acentric, graded, reflective coating. In addition to correcting for distortion along the cross-scan direction (residual distortions are typically less than 1 nm) and acceptable wavefront corrections (typical rms variances of less than 30 mλ), the system has a very high total transmittance of about 13.6% and an acceptable static field uniformity, which is plotted in FIG. 16, of about 1.6%. The field uniformity, as integrated by scanning motions, should be even less, around 1% or less, and thus much better. It may be seen from FIGS. 14 and 15 that these coatings generate a gradient in the irradiance distribution at the pupil that is somewhat worse than for the case where centered, graded, reflective coatings are employed (cf. FIGS. 8 and 9). The variances involved range from about 9% to 14%. However, the apodization is neither complete nor rotationally symmetric, which may adversely affect telecentricity and the processing window. To specialists in the field, it will be clear from the explanation of the fundamental principles of the invention that, in the case of projection lenses designed for use in EUV-microlithography, employing suitably applied and, if necessary, combined, acentric, graded, reflective coatings will allow good compromises between total transmittance and field uniformity. Particularly beneficial therefor are designs that employ several, acentric, graded, reflective coatings, since employment of suitable relative arrangements of such coatings allows compensating for their adverse effects on imaging errors, such as distortion, while largely retaining their good total transmittance. If necessary, any intolerable residual errors may still be eliminated by employing additional, acentric, graded, reflective coatings. For example, an acentric grading may be applied to the first mirror in order to minimize the acentricity at the pupil recognizable in FIGS. 14 and 15, without significantly reducing total transmittance The above description of the preferred embodiments has been given by way of example. From the disclosure given, those skilled in the art will not only understand the present invention and its attendant advantages, but will also find apparent various changes and modifications to the structures and methods disclosed. It is sought, therefore, to cover all changes and modifications as fall within the spirit and scope of the invention, as defined by the appended claims, and equivalents thereof. TABLE 1Surface No.ObjectM1M2M3M4M5M6ImageRadius−10704.66651058.26338355.429333565.293287549.218427535.96002Distance763.156811−508.895688592.994217−263.021453857.514737−437.185791481.268511K0.129826−0.0002420.0003280.7993550.0002270.000006A 5.01967E−10−8.68517E−11−8.94789E−10−6.05680E−10 5.28599E−096.69253E−11B−3.60955E−15−8.37923E−16 1.08954E−14−1.14820E−15 1.32773E−133.07601E−16C 4.75929E−20−7.38993E−21−1.55248E−18−3.64576E−20−2.91744E−181.31588E−21D−1.15371E−24−2.26675E−25 1.19824E−22 2.50168E−25 6.32401E−221.28668E−27E 2.35510E−29−8.68225E−30−3.89134E−27−1.67219E−30−6.82763E−267.45365E−32C0 1.005E+00 1.007E+00 1.577E+00 1.010E+00 1.035E+00 1.002E+00C2 0.000E+00 0.000E+00 −5.062E−08 0.000E+00 −6.996E−06 0.000E+00xde000000yde003159.89014.55380
	abstract	Various embodiments of a power source and a method of forming such power source are disclosed. The power source can include an enclosure, a substrate disposed within the enclosure, and radioactive material disposed within the substrate and adapted to emit radioactive particles. The power source can further include a diffusion barrier disposed over an outer surface of the substrate, and a carrier material disposed within the enclosure, where the carrier material includes an oxide material.
	description	This application is a National Stage under 35 U.S.C. §371 of International Application No. PCT/IB2005/050738, filed Mar. 1, 2005, which claims the benefit of South African Patent Application No. 2004/1667, filed Mar. 1, 2004, the entirety of each of which is incorporated by reference. Field of the Invention This invention relates to nuclear fuel. More particularly, the invention relates to a method of preparing a nuclear fuel, to a nuclear fuel particle and to a nuclear fuel element. Description of Related Art In a nuclear reactor of the high temperature gas-cooled type, use is made of fuel comprising a plurality of spherical fuel elements. The fuel elements include a core comprising fuel particles, each having a kernel of fissile material, dispersed in a matrix. The spherical fuel elements are known as pebbles and the nuclear reactor of this type is generally known as a pebble bed reactor. According to one aspect of the invention, there is provided a method of preparing a nuclear fuel, which method includes the step of depositing a coating which includes fluorine, or at least one compound thereof, around a kernel of fissile material. More particularly, the method may include depositing a mixture of silicon and silicon carbide around a kernel of fissile material followed by fluorinating the silicon and silicon carbide. The method may include the step of introducing magnesium into the fluorinated silicon and silicon carbide around the kernel. The method may include the prior step of depositing silicon-nitride-bonded-silicon-carbide around the kernel of fissile material. Depositing the silicon-nitride-bonded-silicon-carbide may include the steps of depositing a mixture comprising silicon and silicon carbide around the kernel and nitriding the silicon and silicon carbide mixture. By “nitriding” is to be understood treating the nuclear fuel particle in an atmosphere capable of supplying nitrogen to a surface of the fuel particle kernel such that nitrogen diffuses into the surface and combines with nitride-forming elements therein. Depositing the silicon-nitride-bonded-silicon-carbide may include the further step of introducing carbon into the nitrided silicon and silicon carbide mixture. The method may include the step of depositing diamond around the kernel. Depositing the diamond may include depositing silicon carbide around the kernel and at least partly reducing the silicon carbide to carbon, more particularly, to the carbon allotrope of diamond. Preferably, the silicon carbide deposited will be beta polytype silicon carbide. Reducing the silicon carbide may include reacting the silicon carbide with hydrogen chloride or chlorine. Naturally, however, any other suitable reducing agent may be used. Preferably, the method includes the steps of, during a continuous process and whilst maintaining a temperature of between about 1 300 degrees Celsius and about 1 950 degrees Celsius, in sequence, depositing stoichiometric beta polytype silicon carbide followed by a mixture of silicon and silicon carbide around the kernel of fissile material, nitriding the silicon and silicon carbide mixture, introducing carbon into the nitrided silicon and silicon carbide mixture, depositing a further amount of mixture of silicon and silicon carbide, fluorinating the further amount of silicon and silicon carbide mixture, and optionally introducing magnesium into the fluorinated silicon and silicon carbide mixture. The method may include the further step of thereafter, during the continuous process and whilst maintaining the temperature, depositing stoichiometric silicon carbide and reducing the silicon carbide at least partly to diamond by reacting the silicon carbide with chlorine or other suitable reducing agent. According to another aspect of the invention, there is provided a method of preparing a nuclear fuel, which method includes the step of providing a composite coating comprising at least two elements or compounds selected from the group consisting of fluorine or derivatives thereof, silicon nitride, silicon carbide and magnesium around a kernel of a fissile material. The composite coating may have a thickness of between about 6 micrometers and about 120 micrometers, preferably about 60 micrometers. According to still another aspect of the invention, there is provided a method of preparing a nuclear fuel, which method includes the step of depositing by chemical vapor deposition techniques a coating which includes magnesium, or at least one compound thereof, around a kernel of a fissile material. The method may be conducted at a temperature of between about 1 300 degrees Celsius and about 1 950 degrees Celsius. The method may be carried out at a pressure of between about 0.4 kPa and about 10 kPa, preferably about 1.6 kPa. The method may include the prior step of forming a plurality of nuclear fuel particle kernels by atomising a uranyl nitrate solution to form microparticles, followed by baking the microparticles at high temperature to provide a kernel of fissile material. Typically the particles are about 0.5 mm in diameter. According to yet another aspect of the invention, there is provided a coated nuclear fuel particle, which includes a kernel of a fissile material and a coating which includes fluorine, or at least one compound thereof, deposited around the kernel. According to a further aspect of the invention, there is provided a coated nuclear fuel particle, which includes a kernel of a fissile material and a composite coating comprising at least two elements or compounds selected from the group consisting of fluorine or derivatives thereof, silicon nitride, silicon carbide and magnesium deposited around the kernel. The kernel may be of size about 500 micrometers. The kernel may be of uranium dioxide. The composite coating may have a thickness of between about 20 micrometers and about 270 micrometers, preferably about 240 micrometers. More particularly, the coated nuclear fuel particle may have deposited around the kernel, stoichiometric silicon carbide, silicon nitride bonded silicon carbide, fluorinated mixture of silicon and silicon carbide, optionally impregnated with magnesium, and diamond. According to a still further aspect of the invention, there is provided a nuclear fuel element which includes a plurality of coated nuclear fuel particles as hereinbefore described dispersed in a matrix. The invention will now be described, by way of example, with reference to the accompanying diagrammatic drawing and the following Example: A plurality of nuclear fuel particle kernels was formed by atomisation of uranyl nitrate to form microspheres. The microspheres were then gelled and baked at a high temperature, ie. calcinated, to yield uranium dioxide particles, each to provide a kernel of fissile material for a coated nuclear fuel particle. A plurality of nuclear fuel particle kernels was formed by atomisation of uranyl nitrate to form microspheres. The microspheres were then gelled and baked at a high temperature, ie. calcinated, to yield uranium dioxide particles, each to provide a kernel of fissile material for a coated nuclear fuel particle. A batch of uranium dioxide particles was suspended in a fluidised bed type deposition chamber of a chemical vapor deposition reactor, the deposition chamber having an argon environment. The deposition chamber was heated to a temperature of approximately 1000 degrees Celsius and all depositions were carried out a pressure of between 1.5 kPa and 1.7 kPa. First, stoichiometric silicon carbide was deposited on the surface of the uranium dioxide particles to a thickness of at least 4 micrometers. Whilst maintaining the temperature and as this thickness of stoichiometric silicon carbide was attained, the source gases for deposition were switched to methylchlorosilane to deposit a mixture of silicon and silicon carbide around each kernel by the decomposition of the methylchlorosilane. The silicon and silicon carbide mixture was then nitrided by fumacing in a nitrogen atmosphere at a temperature of 1820 degrees Celsius and a pressure of 1.6 kPa to yield a mixture of silicon carbide and silicon nitride crystals. The fuel particles were treated in the nitrogen atmosphere for 1.5 hours to permit nitrogen to permeate the full depth of the silicon and silicon carbide layer to yield silicon-nitride-bonded-silicon-carbide. The deposition source gases were thereafter switched to carbon-enriched gas and carbon was introduced into yield silicon-nitride-bonded-silicon-carbide to bond to free silicon remaining within the yield silicon-nitride-bonded-silicon-carbide. Whilst maintaining the temperature, the source gases for deposition were again switched to methylchlorosilane to deposit further mixture of silicon and silicon carbide. The silicon and silicon carbide mixture was fluorinated by the addition of fluorine gas to the methylchlorosilane and the deposition was carried out at a pressure of between 1.5 kPa and 1.7 kPa. While still maintaining the temperature, the fluorine source was disconnected and a magnesium source gas was connected to the inlet end of the deposition chamber thereby to introduce magnesium into the silicon and silicon carbide mixture. Magnesium was introduced for a period of between 30 minutes and 40 minutes in as much as possible to avoid the formation of a magnesium nanolayer. The source gases for deposition were then switched to deposit further stochiometric silicon carbide to a thickness of at most 9 micrometers around the kernel at a deposition temperature of 1780 degrees Celsius and a deposition pressure of 1.6 kPa. A chlorine (Cl2) source was then connected to an inlet end of the deposition chamber whilst maintaining the temperature between 1020 and 1050 degrees Celsius and the silicon carbide layer was reduced to diamond. Reference is made to FIG. 1 of the drawings, which shows a part-sectional perspective view of a coated nuclear fuel particle in accordance with the invention. In FIG. 1, reference numeral 10 refers generally to a coated nuclear fuel particle, prepared in accordance with the above Example. The coated fuel particle 10 includes a kernel 12 comprised of a uranium dioxide particle. A coating, generally indicated by reference numeral 14, is deposited on the kernel 12. The coating 14 includes stoichiometric silicon carbide yield silicon-nitride-bonded-silicon-carbide, a fluorinated mixture of silicon and silicon carbide, magnesium and diamond. FIG. 1 is for illustrative purposes only and it is to be appreciated that, as a result of the coating/deposition process being carried out whilst at all times maintaining a high temperature, ie. not permitting the temperature to drop below 1000 degrees Celsius, boundaries between different compounds/materials deposited are not clearly defined such that a composite coating is formed. Discussion Preferably the stoichiometric silicon carbide initially deposited will be beta polytype silicon carbide. The deposition steps of the method of the invention are carried out as part of a continuous process during which the high temperature of deposition is at all times maintained and no intermediate cooling is permitted. A composite layer 14 comprising silicon carbide, silicon nitride, silicon fluoride, magnesium, silicon and carbon is thus deposited on the kernel 12 of fissile material. No nano-layer of magnesium should be formed during the deposition process. The Applicant believes that the coated nuclear fuel particles 10 of the invention will exhibit improved retention of fission products, particularly of silver and caesium by-products of nuclear fission. It is believed that the diffusion of these contaminants will be greatly reduced for temperatures between 0 and 1850 degrees Celsius. Fluorine, in particular, affords a barrier to diffusion of fission products, is very hard and can withstand high working temperatures. It is believed that the coated nuclear fuel particles of the invention will exhibit gas tightness and retain gaseous fission products at temperatures of less than 1900 degrees Celsius where the particle burn up is at most 18%.
061472743	summary	FIELD OF THE INVENTION This invention relates to the field of decontamination procedures. More specifically, the present invention relates to the field of decontamination procedures for removing radioactive contamination from nuclear power plants. BACKGROUND OF THE INVENTION Decontamination of sub-systems of LWR plants has now become relatively common in the United States and is important as a useful contributor to the reduction of radiation exposure of workers at these plants. Sub-system decontamination involves exposing a part of the reactor circuit to chemical decontamination solutions which dissolve radioactive deposits which have accumulated on process equipment which includes piping. The spent decontamination solutions may then be treated by ion exchange to retain the chemical and radioactive burden of the decontamination solution on the resin, while clean water is returned to the system. An example of such a process is the LOMI process, described in U.S. Pat. No. 4,705,573. One of the purposes of decontamination is to remove the radioactive deposits which can represent a danger to plant workers. Decontamination of plant components which are intended to be returned to service should avoid any damage to materials exposed to the process. Such damage could occur due to corrosion resulting from the process or from normal operating conditions of the nuclear plant subsequent to decontamination. Certain processes which attempt to avoid damage do not attack base metal and operate by dissolving the overlying layer of corrosion product metal oxides. Although effective in lowering or reducing the amount of radiation to which workers are exposed, such processes do not remove all radioactivity from treated surfaces and are therefore not capable of allowing the plant items to be treated as non-radioactive waste. In order to sufficiently decontaminate radioactive items to be able to classify them as non-radioactive, it is necessary to remove a thin layer of the underlying base metal, so as to release radioactivity trapped in fissures in the metal (occurring, for example, as a result of mild intergranular attack of the metal surface.) For decommissioning a reactor, restrictions concerning plant damage are not as stringent since the plant items are not required for further operational duty. The only requirement with regard to damage is that the plant items maintain their integrity against leakage during the operation of the process while remaining structurally sound. Although the removal of a thin layer of base metal is consistent with these requirements, removal of too much metal may cause a problem concerning the amount of radioactive waste generated. Several processes have been described for removal of base metal. For example, U.S. Pat. No. 4,828,759 is directed to a process for using fluoroboric acid as a decontaminating reagent. The reagent is capable of dissolving a wide variety of metals and metal oxides. The patent details several methods for using the acid to minimize radioactive waste, for example, recovering the acid by distillation. The process described may be convenient for treating components which are immersed or sprayed in a bath for decontamination. The concentration of acid stated (0.05 to 50 moles per liter) is sufficiently great to avoid the complications of ineffectiveness referred to below. In some instances, using a dilute chemical system may be advantageous when decontaminating large components of nuclear plants, such as steam generators. The purchase and handling of chemicals is difficult and expensive if concentrated chemical solutions are used, and it is difficult to manage the wastes in a minimum volume. Although a process described in U.S. Pat. No. 4,828,759 overcomes many of these difficulties, the type of equipment proposed is not commonly used in a temporary manner in nuclear plant decontamination, and the process does not easily allow the benefits of exposing the items to be decontaminated to a progressively cleaner decontamination solution. Use of progressively cleaner decontamination solutions is useful for obtaining high decontamination effectiveness in a large convoluted system of plant items contaminated on inaccessible internal surfaces. Another decontamination solution capable of dissolving base metal involves cerium salts in an acid solution (e.g. German Patent No. DE-PS 2, 714,245). The oxidizing action of cerium (IV) in conjunction with a mineral acid such as nitric acid causes the metals to be dissolved. The cerium (III) resulting from oxidation of the metal can be reoxidized to cerium (IV) by the action of an oxidizing chemical such as ozone. The problem with systems based on cerium as oxidant is that cerium is cationic and is removed and depleted along with metals and radioactivity by ion exchange. It is therefore difficult to provide a system that allows continuous removal of cationic radioactive metals without consequent removal of cerium. The desired objective of treating the system with a progressively cleaner decontamination solution cannot therefore be accomplished conveniently. SUMMARY OF THE INVENTION The present invention provides a process for decontaminating a contaminated material which includes providing a solution containing from about 1 to about 50 millimoles of fluoroboric acid per liter, contacting the solution with a material which causes the oxidation potential (Eh) of the fluoroboric acid solution to range from about 500 to about 1200 mV versus a Standard Calomel Electrode, and contacting the fluoroboric acid solution with the contaminated material and removing a contaminant by contacting the fluoroboric acid solution with a cation exchange resin. The present invention also provides a process for removing metal from a substrate which includes providing a solution containing from about 1 to about 50 milli-moles of fluoroboric acid per liter, contacting the solution with a material which causes the oxidation potential (Eh) of the fluoroboric acid solution to range from about 500 to about 1200 mV. 1200 mV versus a Standard Calomel Electrode, and contacting the fluoroboric acid solution with the substrate and removing metal from the substrate. The metal is removed or recovered from the fluoroboric acid solution by contacting it with a cation exchange resin. In one aspect, it is an object of the invention to provide decontamination by progressively removing deposits and/or a layer of base metal from a surface in an even and controlled manner, thereby releasing radioactive contamination. In another aspect, it is an object of the invention to allow the surface to be treated with a progressively cleaner decontamination solution as the process proceeds. In yet another aspect, it is an object of the invention to create a minimum volume of radioactive waste from the process.
	summary
	description	1. Field of the Invention This invention relates to a stripping foil preferably usable for a charged particle accelerator, and a method and an apparatus for fabricating the stripping foil. 2. Description of the Prior Art Conventionally, a stripping foil has been employed to extract from a negative ion beam introduced from an external ion source. With the stripping foil, an electron of the ion beam is scattered and ionized by the coulomb force from an atomic nucleus of the substance constituting the stripping foil, and thus, a desired charged particle such as a proton can be injected while the ion beam is penetrated through the stripping foil. FIG. 1 is a schematic view showing a charged particle accelerator including a stripping foil, and FIG. 2 is a structural view showing the stripping foil. As is shown in FIG. 1, a negative ion beam is penetrated through a stripping foil to be converted into a given positive charged particle, which is introduced into a charged particle accelerator. Then, the charged particle interflows with another charged particle introduced previously and is accelerated with circulating orbit. On the other hand, as shown in FIG. 2, the stripping foil is formed very thin in a rectangular shape, so that it is required that the three side edges of the stripping foil without the side edge exposing to the circulating orbit are supported in order to maintain the stripping foil stably. At present, in order to increase the number of charged particles to be accelerated in a charged particle accelerator, a phase space painting to introduce the charged particles dispersed vertically and laterally in a given degree has been planned. In this case, a large amount of charged particles are introduced and penetrated through the same stripping foil, the stripping foil may be deformed and damaged by excess heating or the like. In this point of view, in order to decrease the number of charged particles to be introduced into the same stripping foil, such an attempt is made as to reduce the size of the stripping foil almost equal to the diameter of the charged particle or to change and shift the circulating orbits of the charged particles with a pulsed electromagnet. With the stripping foil of which the three side edges are supported as shown in FIG. 2, all of the charged particles circulating their respective orbits are introduced into and penetrated through the stripping foil, so that the above-mentioned problems are posed on the stripping foil. In this point view, various stripping foil-supporting structure are proposed. Concretely, as shown in FIG. 3 is proposed a supporting structure where the two side edges of a stripping foil are supported, and as shown in FIG. 4, is proposed a supporting structure where a stripping foil is supported by thin wire set up vertically from a supporting frame. With the corner foil structure shown in FIG. 3, the number of charged particles can be reduced almost half, compared with the three side edge supporting structure shown in FIG. 2. However, since the circulating orbits of the charged particles are always set on the stripping foil, the number of the charged particles are not reduced per unit area of the stripping foil. As a result, with the corner foil structure, the stripping foil is deformed and damaged in the same degree as with the three side edge supporting structure. With the wire supporting structure as shown in FIG. 4, since the wire are located in the circulating orbits of the charged particles, the charged particles are scattered by the wire, resulting in the damage of the wire. It is an object of the present invention to provide a new stripping foil to mitigate the above-mentioned problems such as deformation and damage, and a method and an apparatus for fabricating the stripping foil. In order to achieve the above object, this invention relates to a stripping foil comprising a rectangular outer shape and a curved surface shape, which is supported by itself. FIG. 5 is a schematic view showing a stripping foil according to the present invention. As shown in FIG. 5, the stripping foil is formed rectangularly so that the surface is curved. Specifically, the stripping foil is a rectangular foil that has a curved surface, such that two non-adjacent side edges of the rectangular foil define a curve that supports the stripping foil. In this case, the stripping foil can be supported by itself if one curved side edge of the stripping foil is supported by a frame. In other words, since the stripping foil is formed so that the surface is curved, it can be supported by itself at the one curved side edge. In the present invention, since the supporting structure is simplified as shown in FIG. 5, the operationality of the stripping foil can be developed. In a paint to introduce charged particles dispersed vertically and laterally in order to increase the number of charged particles to be accelerated in an accelerator, if the stripping foil as mentioned above is appropriately arranged and the size of the stripping foil is controlled, only the injected beam can be penetrated through the stripping foil and the circulating particles can not be almost penetrated. Therefore, the circulating particles can not be almost scattered at the stripping foil, and the stripping foil can not be almost deformed and damaged. FIGS. 6 and 7 are cross sectional views of the stripping foil shown in FIG. 5, taken on line “A-A”. As mentioned above, although it is required that the surface of the stripping foil is curved, concretely, the surface may be waved as shown in FIG. 6 and curved as shown in FIG. 7. For practical use, it is preferable that the weight per unit area of the stripping foil is set within a range of 5 μg/cm2−1 mg/cm2. In other words, it is preferable that the stripping foil is made of a material having a weight per unit area within the above-mentioned range. Concretely, the stripping foil may be made of carbon. The fabricating method and the fabricating apparatus for the stripping foil will be described in detail, hereinafter. In the present invention, it is required as shown in FIG. 5 that the stripping foil is formed rectangularly so that the surface is curved and thus, the stripping foil can be supported by itself at the one side edge thereof. The stripping foil may be fabricated as follows, by utilizing the fabricating method and the fabricating apparatus of the present invention. FIG. 8 is an elevational view showing a jig substrate of the fabricating apparatus, and FIG. 9 is a side view of the jig substrate shown in FIG. 8, taken on line “B-B”. The jig substrate 10 includes the folding plate 1, the foil forming-supporting plate 2, the supporting plate 3 provided opposite to the supporting plate 2, the foil substrate 4-1 provided with joined to the supporting plate 2, the foil substrate 4-2 provided with joined to the supporting plate 3, and the foil acceptor 5. These constituent elements are supported by the supporting member 6 with the angle controlling shaft 7. The supporting member 6 is held by the frame 8. FIGS. 10-14 are process views showing the fabricating method for the stripping foil of the present invention. First of all, the foil 40 is formed of carbon or the like in a predetermined thickness on a given substrate by means of deposition. Then, the substrate including the foil 40 thereon is sunk in the water 30 charged in the tank 20 from the edge portion, as shown in FIG. 10. The foil 40 is peeled off of the substrate by means of a peeling member and then, floated on the water surface. In the water 30, the jig substrate 10 shown in FIGS. 8 and 9 is sunk and provided. Then, when the surface level of the water 30 is decreased, as shown in FIG. 11, the foil 40 is contacted with the folding plate 1 of the jig substrate 10, then, folded and deformed along the supporting plate 2 and 3. In this case, the two surfaces of the foil 40 opposing each other via the supporting plates 2 and 3 are laminated within the laminate region R at the same time when the foil 40 is folded. The thus obtained laminated foil 41 is deformed in a waving shape or a curving shape commensurate with the surface shapes of the supporting plates 2 and 3. In the laminating process of the foil 40, it is desired that the tangent line of the surface of the supporting plate 2 is set almost parallel to the folding direction of the foil 40 by means of the angle controlling shaft 7 so that the two surfaces of the foil 40 is set almost parallel to the folding direction and thus, laminated vertically. In this case, since the horizontal components of surface tensions in the two surfaces of the foil 40 to be laminated is removed, the laminating operation can be performed precisely without deformation and damage. For example, in the case that the two surfaces of the foil 40 is laminated at the point X of the supporting plate 2 of the jig substrate 10, the tangent line of the supporting plate 2 at the point X is inclined from the folding direction (vertical direction) by a angle of θ in FIG. 9. In this condition, therefore, the horizontal components of the surface tensions of the surfaces to be laminated is created. Accordingly, if the supporting member 6 is rotated leftward by the angle of θ, the tangent line is set almost parallel to the folding line, so that the laminating process can be performed precisely at the point X of the supporting plate 2 without the horizontal components of the surface tensions. Even at another point of the supporting plate 2, it is desired that the laminating process is performed by controlling the angle controlling shaft 7 so that the laminating direction is set almost equal to the folding direction (vertical direction). The bottom of the laminated foil 41 is held at the foil acceptor 5, as shown in FIG. 12. Thereafter, the laminated foil 41 is dried and annealed by means of radiant heat except the area in the vicinity of the supporting plate 2. Then, as shown in FIG. 13, the laminated foil 41 is peeled off along the folding plate 1, the supporting plate 3 and the foil acceptor 5, and then, as shown in FIG. 14, A wave-shaped charge conversion foil 50 can be obtained. As is apparent from FIG. 14, the supporting plate 2 is intervened between the laminated foil 41, and thus, the stripping foil 50, is supported by the foil substrate 4-1 via the foil substrate 2. In other words, the foil substrate serves as a supporting member for the stripping foil 50, so that the stripping foil 50 can be supported by itself at one side edge to which the foil substrate 4-1 is attached. Although the present invention was described in detail with reference to the above examples, this invention is not limited to the above disclosure and every kind of variation and modification may be made without departing from the scope of the present invention. For example, although in the above embodiment relating to FIGS. 10-14, the wave-shaped stripping foil is fabricated, a curved stripping foil may be fabricated by adjusting the surface shape of the foil forming-supporting plate, as shown in FIG. 7. In addition, the foil 40 may be peeled off of the substrate directly by an experimenter or a given appliance. As mentioned above, according to the present invention, a new stripping foil of which the size can be freely controlled. The stripping foil described herein can be used without a supporting frame that supports at least two edges of the stripping foil, but instead can be used with a supporting frame that supports only one curved edge of the stripping foil. and thus extreme operationality can be provided.
055725627	description	DETAILED DESCRIPTION OF THE INVENTION According to the invention, electromagnetic radiation of shorter, or of significantly shorter, wavelength than visible light is used for lithography of integrated circuits. Given the inherent resolution problems associated with conventional visible light and near-visible light photolithographic techniques (discussed hereinabove), the use of shorter wavelength radiation sources is highly desirable. However, due to the failure of conventional optics to perform at these short wavelengths, it is necessary to employ near-field or direct-write, afocal imaging techniques (non-focusing or non-converging optically) with short wavelength radiation sources. In this manner, by avoiding the inherent resolution problems associated with the relatively long wavelengths of light, finer (smaller) features can be defined on a semiconductor wafer. For example, fine lines can be patterned in a layer of photoresist material on the wafer and, subsequently, lines can be etched into a layer underlying the photoresist. The invention takes advantage of the situation that the apparent `resolutions` (if you will) of etching techniques are typically much (e.g., orders of magnitude) finer than the resolution of light. Generally, "resolution" is the ability of a given medium to create patterns on another medium. As used herein, the term "lithography" means any technique of creating patterns on a semiconductor wafer (or on a photoresist layer on the wafer). By providing higher (than light) resolution lithography techniques, the invention affords the opportunity to create finer, more densely packed features and devices on a semiconductor device. For example, more transistors can be formed on a die of given area, and more conductive lines (e.g., polysilicon or metal) can be provided in a given area. The size (width) of conductive lines is a measure of process resolution (sometimes called "process geometry"). Present photolithographic techniques, limited as they are by the relatively long wavelengths of light, are limited to approximately 0.5 .mu.m. By using the techniques disclosed herein, which involve employing radiation of shorter or significantly shorter wavelengths than light, conductive lines that are smaller, and much smaller than 0.5 .mu.m can be created-on semiconductor devices. For example, lines having a width of less than "w" microns can readily be fabricated on semiconductor devices, where "w" is below 0.5, 0.4, 0.3, 0.2, 0.1, and smaller. Current densities in such "fine" lines evidently needs to be controlled (or limited). In order to increase the current-carrying capability of such fine lines, it is also contemplated herein that the height (above the surface of the wafer) of such lines must be maximized For example, a line having a width of 0.1 .mu.m can be formed that has a height "h" of 0.2 .mu.m, in which case the h:w "aspect ratio" of the line would be on the order of 2:1. According to an aspect of the invention, which is provided herein mainly as a "rule of thumb", fine conductive lines have a height:width (h:w) aspect ratio of at least "x", where "x" is 1.2:1, 1.3:1, 1.4:1, 1.5:1, 1.6:1, 17:1, 1.8:1, 1.9:1, 2:1, 2.5:1, 3.0:1, 3.5:1, 4.0:1, 4.5:1 or 5.0:1. Preferably, "x" is at least 2.0:1. In contrast to a technique that provides only narrow lines, without allowing for increased line density (see, e.g., U.S. Pat. No. 5,139,904, described above), the present invention allows for both finer lines and for packing fine lines close together. In one embodiment of the invention, integrated circuit (semiconductor) lithography is performed using X-ray emissions as the actinic source. As described hereinabove, the use of short-wavelength radiation sources, such as X-rays, for semiconductor lithography is less wavelength resolution-limited than light for fabricating small-geometry (sub-micron cd) integrated circuits. The short wavelength (10.sup.-8 -10.sup.-11 meters) of X-ray radiation is well suited to providing the resolution required for the formation of very small sub-micron semiconductor features in semiconductor devices. Some efforts have been made to use X-ray lithography. However, such efforts are plagued with difficulties. Present image mask substrate materials include silicon carbide, polyimide, and silicon dioxide. These masking substrate materials suffer from a number of shortcomings relative to X-ray lithography. Among these are: 1) present X-ray image mask substrates exhibit extremely poor transparency to X-rays, yielding masks which provide poor contrast; PA1 2) the poor transparency of present X-ray mask substrate materials forces the use of extremely thin substrates, resulting in very fragile image masks; PA1 3) present X-ray mask substrate materials are subject to humidity-induced distortions, yielding image masks of poor stability, and causing unpredictable critical dimensions and feature positions in a resist material exposed by such image masks; PA1 4) the expansion and adhesion characteristics of the opaque materials patterned on present mask substrates result in pattern-dependent distortions of the thin image mask substrates; and PA1 5) present X-ray image mask substrate materials have poor "windows of transparency" (ranges of wavelengths for which they are transparent) which do not include the wavelength of the most desirable (shortest) X-ray wavelengths and the most intense available X-ray sources. PA1 1) good transparency to X-rays; PA1 2) viability of formation into thicker (than present) mask substrates due to its good X-ray transparency; PA1 3) insensitivity to moisture-induced distortion; PA1 4) excellent Young's modulus to resist distortion; PA1 5) expansion characteristics more compatible with those of available opaque masking materials and carrier materials. PA1 6) a wide window of transparency, permitting the use of high-intensity X-ray sources of the shortest wavelengths possible. PA1 1. extremely high source brightness (intensity), due to the extreme intensity of naturally occurring gamma-ray sources such as Cobalt-60, which is a passive source requiring no power; PA1 2. high inherent resolution, due to short wavelength; PA1 3. large depth of field, due to short wavelength; PA1 4. resist materials can be fabricated (as discussed in greater detail hereinbelow) which exhibit a high cross section (absorptivity) with respect to gamma-rays, and the resist materials can be applied to a semiconductor wafer; Further, an image mask formed from these substrate materials is subject to an overall distortion within the "carrier" to which it is mounted due to different rates of thermal expansion between the image mask and the carrier. When heated, present X-ray image masks distort to an unacceptable level, thereby requiring exotic processing techniques. According to the invention, Beryllium metal (chemical symbol Be) is used as an X-ray image mask substrate. Beryllium has many desirable characteristics which make it quite suitable for use as an X-ray image mask substrate. These desirable qualities of beryllium include: According to the present invention, a Beryllium substrate is used as a planar image mask substrate upon which a patterned layer of X-ray opaque material is disposed. In conjunction with the use of a beryllium substrate for the X-ray exposure mask, the following materials make excellent X-ray opaqueing materials, for forming patterns on the image mask: gold (chemical symbol Au), tungsten (chemical symbol W), platinum (chemical symbol Pt), barium (chemical symbol Ba), lead (chemical symbol Pb), iridium (chemical symbol Ir), and rhodium (chemical symbol Rh). These materials have excellent opacity to X-rays, are relatively insensitive to moisture and are highly corrosion resistant. Further, these materials will adhere adequately to a beryllium substrate, thereby making the combination of these materials patterned on a beryllium substrate ideal for X-ray lithography of semiconductor devices. The thickness of the masking material can be empirically determined for each material (e.g., for gold) and based upon the parameters of the specific X-ray source employed. The mask pattern should be substantially opaque to the X-ray emissions, thereby providing high contrast on the image mask. Since, like beryllium, these masking materials (e.g., gold) are all metals, their thermal coefficients of expansion are highly compatible (substantially equal) to the thermal coefficient of expansion of the beryllium image mask substrate. This serves to reduce the amount of thermally-induced pattern-dependent mask distortion as compared to that experienced with present mask and substrate materials. The insensitivity of the inventive combination of masking materials and substrate to humidity serves to substantially eliminate pattern-dependent mask distortion due to humidity. According to the present invention, an X-ray mask is formed by providing a substantially planar beryllium substrate, and disposing upon the substrate a patterned opaque (to X-rays) layer of gold, tungsten, platinum, barium, lead, iridium or rhodium. The patterned layer may be disposed on either the "upstream" (towards the X-ray source) side of the beryllium substrate or on the "downstream" (towards the semiconductor wafer) side of the substrate. The mask is positioned in close proximity "upstream" of a sensitized wafer (a wafer with a layer of X-ray sensitive resist). The wafer is then exposed to an upstream X-ray source through the mask, causing a downstream "shadow" image of the mask to be formed on the surface of the resist. The close proximity of the image mask to the substrate sufficiently avoids dispersion of the illuminating radiation so that a "copy" of the image mask pattern is imaged onto the sensitized (e.g., with a layer of photoresist) wafer. The X-ray radiation is actinic with respect to the resist, and causes exposed areas of the resist to become chemically converted. After exposure to X-ray radiation, the unconverted areas of the resist (those areas of the resist which were "shadowed" by the mask) are chemically removed. (This described a "negative" mode of resist development. It is also possible to employ a "positive" resist chemistry, for which only the exposed areas of the resist are chemically removed). FIG. 2a is a cross-sectional view of semiconductor lithography apparatus, according to the present invention, showing an X-ray mask assembly 200a comprising an image mask 215a and a carrier 210 for the image mask 215a, according to the invention. A patterned opaque layer 230 of an X-ray masking material (e.g., gold), as described hereinabove, is disposed on the "upstream" surface (left hand surface, as shown in the Figure) of a planar beryllium substrate 220 to form the image mask 215a. The image mask 215a is fastened to the carrier 210 in any suitable manner. Preferably, the carrier 210 has a coefficient of expansion similar, or substantially identical, to that of the beryllium substrate 220. This is quite feasible since the beryllium itself is a metal. For example, the carrier 210 is also made of beryllium so that its expansion characteristics are identical to that of the beryllium substrate 220, effectively eliminating any thermally induced distortion of the mask 215a. The image mask 215a is positioned a "near field" distance "d" upstream of a front (left, as viewed in the Figure), sensitized (e.g., with photoresist) surface of a semiconductor wafer "W" such that the plane of the image mask 215a is substantially parallel to the front surface of the wafer "W". The sensitized wafer "W" has a layer of X-ray sensitive resist (not shown) disposed upon its front surface. The wafer "W" is exposed to actinic (relative to the resist) X-ray radiation 240, which first passes through the image mask. Preferably, the distance "d" is between 0.5 and 3.0 .mu.m, so that the image mask is sufficiently close to the front surface of the wafer to cause a pattern formed in the masking material 230 to be imaged onto the photosensitive material on the front surface of the wafer "W". At greater distances from the wafer, the imaging ability of the image mask would suffer, unless the irradiating energy were perfectly collimated. In contrast to the present invention, for photolithography using light as the irradiating source, employing a taking lens (see 124, FIG. 1) is effectively the only practical way of faithfully replicating a pattern from the image mask onto the surface of the wafer. FIG. 2b is a cross-sectional view of an alternate embodiment of an X-ray mask assembly 200b comprising an image mask 215b and carrier 210, according to the invention. A patterned opaque layer 230 of an X-ray masking material, as described hereinabove, is disposed on the "downstream" surface (right hand surface, as shown in the Figure) of a planar beryllium substrate 220 to form the mask 215b. As in the embodiment of FIG. 2a, the mask 215b is fastened to the carrier 210. In this case, however, this patterned opaque layer 230 is on the wafer side (downstream side) of the mask 215b. As described hereinabove with respect to FIG. 2a, the carrier 210 preferably has a coefficient of expansion similar to that of the beryllium substrate 220. As with the previous embodiment (of FIG. 2a), the image mask 215b is positioned a distance "d" upstream of the front surface of a sensitized semiconductor wafer "W" such that the plane of the mask is parallel to the front (planar) surface of the wafer. The sensitized wafer "W" has a layer of X-ray sensitive resist (not shown) disposed upon its front surface. The wafer "W" is exposed to actinic (relative to the resist) X-ray radiation 240 through the mask. Preferably, the distance "d" is between 0.5 and 3.0 .mu.m, so that the pattern formed by the masking material 230 is faithfully reproduced into the sensitized layer (e.g., of photoresist) on the semiconductor wafer "W". The near-field, afocal, imaging (shadow imaging) technique described hereinabove with respect to FIGS. 2a and 2b is analogous to photographic contact printing, in that the mask (analogous to a negative) is placed almost directly on the wafer (analogous to photographic paper) to faithfully reproduce an image from the image mask onto the wafer, without using optics (i.e, without focusing). In the case of semiconductor device fabrication, the image on the wafer creates a pattern in a photosensitive layer on the wafer, which through subsequent removal of all but the image portions of the photosensitive layer is used to create (e.g., by etching) patterns (e.g., lines) in underlying layers (not shown) on the wafer (such as an underlying layer of polysilicon). The term "photosensitive layer" is used herein to mean a layer of material that chemically reacts (converts) in the presence of actinic (chemical conversion causing) radiation, such as X-rays. Although the use of X-rays for semiconductor lithography is advantageous in terms of its inherent higher resolving ability (i.e., higher than light), inter alia, high-quality, fluent X-ray sources tend to be very expensive and consume a great deal of power. Hence, according to the present invention, gamma-rays can be employed (rather than X-rays) as illuminating sources for semiconductor lithography. As mentioned above, gamma-rays are even shorter in wavelength than X-rays. Hence, gamma-rays are even less resolution-limited than X-rays. Materials are available that are relatively transparent to gamma rays, and materials which are substantially opaque with respect to gamma rays. It is contemplated by this invention that these materials could be substituted for the materials described above, for making a gamma-ray based image mask for near field lithography (using a gamma ray source for illumination instead of an X-ray source). The structures and methods described herein with respect to FIGS. 2a and 2b, with such different materials, would be usable and are contemplated for gamma-ray, instead of X-ray lithography. In the main hereinbelow, the use of gamma-rays (radiation) for direct write lithography, rather than near field lithography is discussed. Generally, the use gamma-rays for lithography of integrated circuits has certain significant advantages, including: 5. materials are available which are not only highly opaque to gamma rays, but which also emit secondary emissions (primarily in the form of photons) which can be used with conventional photoresist materials (as discussed in greater detail hereinbelow); 6. numerous chemistries are available which can be exploited to create gamma-ray sensitive resist materials (discussed in greater detail hereinbelow); 7. mechanisms are available (according to the present invention) for beam modification (as discussed in greater detail hereinbelow) and shuttering (as discussed in greater detail hereinbelow. The use of gamma-rays as an exposure (illumination) source for integrated circuit lithography depends, of course, on the use of suitable materials for the resist process. In lithographic processes, a resist layer on the surface of a semiconductor wafer is exposed through a mask to an actinic radiation (illumination) source. The resist responds, in the areas where it is exposed (illuminated), by chemically converting. The unconverted areas are then chemically removed. (This is a "negative" process. "Positive" processes also exist whereby the exposed areas are chemically removed. Both positive and negative type processes are contemplated.) The result is a patterned etch resistant layer. Conventional photolithography uses one of a number of organic resist materials (e.g., polystyrene, phenolformaldehyde, polyurethane, etc.). These materials are photo-sensitive (convert chemically when exposed to visible light radiation) and have good etch resist characteristics for subsequent wafer etching. These conventional organic resist materials are suitable for gamma-ray lithography in all respects except that their intrinsic absorbance of gamma-rays is very low. As is well known in the art, silicon integrated circuits, including CMOS circuits, have a finite tolerance to gamma-ray exposure. Excessive exposure to gamma-rays can cause field inversion in MOS FETs (Metal-Oxide-Semiconductor Field Effect Transistors) leading to excessive current leakage or outright device failure, and various other serious problems. It is necessary, therefore, to provide a gamma-sensitive resist material which either: a) requires very short exposure times, or b) provides a sufficiently high cross-section to gamma-rays (absorbs gamma-rays well enough) so that the underlying wafer is effectively "shielded" from the gamma radiation by the resist material itself. According to the present invention, it is recognized that gamma radiation, being an ionizing radiation, is capable of causing secondary emissions in various materials. For example, when tungsten is exposed to gamma radiation, gamma radiation is effectively completely absorbed by the tungsten, and the energy of the gamma radiation causes electrons to be "ripped" from their ordinary orbits (shells) in the atomic structure of the tungsten, thereby causing the tungsten to become ionized. In the process, the change of energy levels causes the ionized tungsten to emit photons of energy at a different wavelength (secondary emissions). As will be evident from the discussion hereinbelow, these secondary emissions are compatible with (actinic with respect to) essentially conventional photoresist materials. Tungsten, having a high inherent cross-section (absorptivity) with respect to gamma radiation, i.e., gamma radiation does not pass through it particularly well, makes an effective gamma radiation shield when present over the surface of a semiconductor device. For example, by applying a layer of tungsten over a conventional organic resist layer (on the upstream side of the resist), the secondary emission properties of the tungsten in response to gamma radiation may be utilized to "expose" the resist, while simultaneously shielding the underlying wafer from gamma radiation. The organic resist materials have a high cross-section to the secondary radiation. Various combinations of conventional photoresist materials with tungsten added into or onto the photoresist are disclosed hereinbelow (with respect to FIGS. 3a-3d), and for purposes of this discussion are termed "compound resists". They are all effectively converted when exposed to incident gamma radiation, and can all be formulated to effectively shield the underlying semiconductor device (if necessary). FIG. 3a is a cross-sectional view of a sensitized semiconductor wafer 300a illustrating an embodiment of a gamma-sensitive compound resist. A front surface "S" of a semiconductor wafer 310 is coated with a layer 320a of photoresist, for example conventional organic photoresist material such as polystyrene, phenolformaldehyde, polyurethane, etc. Preferably, the layer of photoresist is applied as a planar layer, in any suitable manner. A layer 330a of a material with a high cross-section to gamma radiation, such as tungsten, boron or bromine, is disposed over the resist layer 320a. This may be referred to as a "secondary resist layer"--together the layers 320a and 330a forming a "compound resist" sensitizing the front surface "S" of the wafer 310 to incident gamma radiation. Preferably, the secondary resist layer 330a is formed as a film of tungsten, and is preferably of sufficient thickness to absorb all incident gamma radiation. However, the layer 330a must also be fairly thin, to allow secondary emissions to enter the underlying resist layer 320a. Gamma radiation 340, impinging upon the secondary-resist layer 330a ionizes the material of the secondary resist layer 330a, causing scattered secondary photons emissions 345a having a different (generally longer) wavelength than that of the gamma radiation to be emitted into the resist layer 320a. The secondary emissions 345a are preferably of substantially shorter wavelength than visible light, and are employed to convert the underlying resist material 320a. In this manner, the lithography technique of the present invention is not as resolution bound as conventional photolithography. Preferably, the secondary emissions 345a are substantially shorter in wavelength than visible light, and are nevertheless capable of converting (acting actinically with respect to) the underlying photoresist 320a. The resist material 320a is highly absorbent of the secondary emissions 345a and thereby limits the exposure of the resist layer 320a to the secondary emissions 345a to a small area 360a about the point where the gamma radiation 340 strikes the secondary resist layer 330a. After chemically (or mechanically) stripping the secondary resist layer 330a, the unconverted areas of the resist layer 320a are removed, leaving an "island" of etch-resistant resist material over an area 350a of the semiconductor wafer 310. This describes forming a point feature on the wafer. A layer to be patterned, such as a layer of polysilicon underlying the resist is omitted for illustrative clarity (in all of FIGS. 3a-3d). With a finely collimated gamma beam in fixed position, the wafer 310 can be "walked around" so that the beam 340 can describe and convert a line of photoresist. This would be a so-called "direct write" technique for semiconductor lithography. In the case that the gamma radiation were to impinge on the sensitized wafer 300a through a mask (not shown), two dimensional patterns could be formed directly on the photoresist 320a. This would be "near-field" semiconductor lithography (compare FIGS. 2a and 2b). As shown in FIG. 3a, the secondary emissions 345a tend to scatter, in other words be emitted in directions at an angle to the incident beam 340. This causes a limited amount of "blooming" (or de-focusing of a pattern through an image mask). However, the intensity and direction of the gamma radiation 340 cause the bulk of the secondary emissions 345a to be emitted substantially in the direction of travel of the incident gamma beam 340. Further, high absorbency of the resist layer relative to the secondary emissions limits the amount of blooming. Further, since the secondary emissions do not travel any significant distance, their divergence from the path of the incident gamma beam is relatively insignificant (they do not have an opportunity to go in the "wrong" direction for very far). By controlling the beam diameter (in direct write applications), or by adjusting the mask pattern (in near field applications), to compensate for any blooming, it is possible to accurately control the feature size (area 350a). Vis-a-vis direct write lithography techniques, evidently the photoresist can be patterned with a fineness--having a critical dimension (cd)--substantially approaching the diameter of the beam. Techniques for creating an extremely small diameter, collimated beam of gamma radiation are discussed hereinbelow. Another approach to making a gamma-sensitive resist from conventional organic resist materials is to make use of the same secondary emission property of a secondary material in a slightly different way. The compound gamma-resist material shown and described with respect to FIG. 3a was formed by depositing an overlying, upstream layer of a secondary emitter (330a) with a high cross-section to gamma radiation over the organic resist (320a). If instead the organic resist material is doped with the secondary emitter, a homogenous, gamma-sensitive, compound resist can be formed. FIG. 3b is a cross-sectional view of a sensitized semiconductor wafer 300b employing a doped type of gamma-sensitive compound resist. As in FIG. 3a, an underlying layer of material to form semiconductor features (such as a layer of polysilicon) is omitted for illustrative clarity. Beginning with a base of substantially conventional, preferably organic photoresist material 320b, the photoresist 320b is doped with particles of a material which will absorb gamma rays and emit secondary emissions. A representative particle 325b is illustrated, and functions in a manner similar to the layer 345a of FIG. 3a. Preferably, the doped, base resist layer 320b is a conventional organic resist material, such as polystyrene, phenolformaldehyde, polyurethane, etc., and it is doped with a secondary emitting dopant (e.g., dopant particle 325b) with a high cross-section to gamma radiation, such as tungsten, boron, or bromine. Gamma radiation 340 is shown impinging upon a representative secondary emitter dopant particle 325b, causing it to become ionized, resulting in scattered secondary photon emissions 345b having a different wavelength than that of the gamma radiation. The "base" (undoped) resist material is highly absorbent of the secondary emissions 345b and thereby limits the exposure of the resist layer 320b to the secondary emissions 345b to a small area 360b about the point where the gamma radiation 340 strikes the particle 325b. After exposure, the unconverted areas of the doped resist layer 320b are removed, leaving areas (points or lines) of converted compound resist over an underlying layer (e.g., polysilicon) on the front surface "S" of the wafer 310. The number of particles (e.g., 325b) required to be "mixed" into the base photoresist is determined by the intensity of the incident gamma radiation. The particles (e.g., 325b) may be uniformly distributed throughout the base photoresist, for example by mixing the particles into the photoresist material prior to applying the photoresist material to the surface of the wafer. On the other hand, the particles can be "implanted" into the surface of photoresist already applied to the surface of the wafer, in which case there will be a concentration gradient of particles more concentrated towards the surface of the photoresist (away from the wafer). Other gradients or non-uniform concentrations of particles are also contemplated. Although the base photoresist is most sensitive to the secondary emissions (345a, 345b), it bears mention that the base photoresist may also be somewhat sensitive to the direct effects of gamma-ray irradiation. However, it is preferred that the process parameters be adjusted so that little or no gamma radiation reachs the underlying semiconductor wafer 310. Hence, the dopant concentration (or thickness of the film 330a, in FIG. 3a), as well as the transparency of the photoresist with respect to gamma radiation, as well as the sensitivity of any underlying structures to gamma radiation must be taken into account when performing the semiconductor lithography techniques of the present invention. Again assuming that the gamma radiation reaches the sensitized wafer 300b through a mask (not shown), forming patterns of intense gamma radiation on the surface of the doped resist layer 320b, the scattering of the secondary emissions 345b causes a certain amount of "blooming" or de-focusing of the pattern, for the reasons described hereinabove. As before, the intensity and direction of the gamma radiation 340 cause the bulk of the secondary emissions 345b to be emitted substantially in the direction of travel of the gamma radiations. Even though the secondary emitter (particle 325b) is disposed within the organic resist as a dopant, it still has a high cross-section to gamma radiation and effectively shields the semiconductor wafer 310 from excessive exposure. Both of these embodiments of gamma-sensitive resist, i.e., the two-layer compound resist described with respect to FIG. 3a and the doped compound resist described with respect to FIG. 3b, provide the desired characteristics of sensitivity to gamma radiation and inherent gamma-ray shielding, thereby acting as an effective resist while preventing excessive exposure of the underlying semiconductor wafer to gamma rays. In the two-layer gamma-sensitive resist embodiment shown and described with respect to FIG. 3a, the secondary resist layer (330a) is not generally chemically sensitive to the incident radiation (340). It simply serves as a secondary emitter which serves to simultaneously block the incident gamma-radiation and to convert the incident radiation to another type of radiation which is actinic with respect to a resist layer (or base resist) and of which the underlying integrated circuitry (on wafer 310) is more tolerant. There are materials, however, suitable for use as a secondary emitter which are themselves chemically sensitive to exposure to gamma radiation. Further, some organic (and inorganic) resist materials are at least somewhat chemically sensitive to exposure to gamma radiation. Accordingly, it is possible to form multilayer gamma-sensitive resist coatings where the top layer (overlayer) provides secondary emissions and is also chemically converted by exposure to gamma-radiation. If the bottom layer (underlayer, between the overlayer and the wafer) is gamma-sensitive, then the use of an overlayer which does not completely block gamma radiation permits exposure of the underlayer by both direct (leaked through the overlayer) gamma radiation and by secondary emissions in the overlayer. Several benefits are derived from the use of multilayer gamma-sensitive resist. First, the use of dual chemistries in combination permits considerably greater flexibility and versatility in determining overall resist characteristics. Second, a multilayer resist tends to permit better planarization of the resist surface. (Planar layers in semiconductor devices are generally sought-after objectives.) It is well known in the art that a truly planar surface is more easily obtained in two steps (i.e., an extremely planar surface is easier to form on top of a surface which is already substantially planar) than in one step. Improved surface planarity of a resist coating tends to enhance the linewidth uniformity of patterns created by incident radiation. (Linewidth uniformity in semiconductor layers is a generally sought-after objective.) FIGS. 3c and 3d illustrate two embodiments of multilayer, gamma-sensitive, compound resists, according to the present invention. FIG. 3c is a cross-sectional view of a sensitized semiconductor wafer 300c employing a multi-layer gamma-sensitive resist (320c/330c). A front surface "S" of the semiconductor wafer 310 is coated with a primary resist layer 320c, which is sensitive to both gamma radiation and secondary emissions. On top of this primary layer 320c is disposed a secondary gamma-sensitive resist layer 330c of a material with a relatively high cross-section to gamma radiation, but which permits some gamma radiation to pass through it. Gamma radiation 340 impinging upon the secondary resist layer 330c ionizes the material of the secondary resist layer 330c, causing scattered secondary (photon) emissions 345c which enter the primary resist layer 320c with, generally, a different wavelength than that of the gamma radiation being emitted into the secondary resist layer 330c. A portion 340' of the incident gamma radiation 340 (indicated by dashed line and arrow) passes through the secondary resist 330c and into the primary resist 320c. The primary resist material is highly reactive to the secondary emissions 345c and thereby limits the exposure of the primary resist layer 320c to the secondary emissions 345c to a small area 360c about the point where the gamma radiation 340 strikes the secondary resist layer 330c. The primary resist 320c is also chemically sensitive to the "leaked" gamma radiation 340' (gamma radiation is actinic to the primary resist), a factor which enhances the chemical conversion of the primary resist 320c, improving contrast. After chemically "developing and stripping the unconverted areas of the primary and secondary resist layers 320c and 330c, respectively, an "island" of etch resist remains over an area 350c of the semiconductor wafer 310 as shown. Complete patterns may be formed on the resist layers, in the manner described above, and the resist pattern may be transferred to an underlying layer (not shown) as described above. FIG. 3d shows another arrangement of a sensitized semiconductor wafer 300d employing a multilayer gamma-sensitive resist. Again, a front surface "S" of semiconductor wafer 310 is coated with a primary resist layer 320d. Preferably, the resist layer 320d is a conventional organic resist material, such as polystyrene, phenolformaldehyde, polyurethane, etc. A secondary gamma-sensitive resist layer 330d of a gamma-sensitive material with a high cross-section to gamma radiation is disposed over the resist layer 320d. Gamma radiation 340, impinging upon the secondary resist layer 330d simultaneously chemically convents and ionizes an area of the material of the secondary resist layer 330d, causing scattered secondary (photon) emissions 345d, generally having a different wavelength than that of the gamma radiation 340 being emitted into the secondary resist layer 330d. The secondary resist material 330d is highly absorbent of the secondary emissions 345d and thereby limits the exposure of the primary resist layer 320d to the secondary emissions 345d to a small area 360d about the point where the gamma radiation 340 strikes the secondary resist layer 330d. The high cross-section of the secondary resist layer 330d to gamma radiation prevents leakage of gamma radiation 340 through the secondary resist layer 330d into the primary resist layer 320d and the underlying wafer 310, thereby limiting the exposure of the wafer 310 to gamma radiation. After chemically developing and stripping the unconverted areas of the primary and secondary resist layers 320d and 330d, an "island" of etch resist remains over an area 350d of the semiconductor wafer 310 as shown. Patterning and processing is performed as described above. The compound resists described above With respect to FIGS. 3a-3d are useful for either near field or direct write lithography, both of which processes are afocal. Near field lithography utilizes an image mask in close proximity to the sensitized surface of the wafer, as described with respect to FIGS. 2a and 2b, and is preferably performed with X-ray radiation. Direct Write lithography is preferably performed with gamma-rays, and requires a tightly focused or collimated beam of radiant energy directed to specific locations of a resist layer, thereby exposing and chemically converting those areas and forming patterns for processing lines and the like in layers underlying the resist layer. However, both X-ray and gamma-ray radiation may be used for either direct-write or near-field lithography, such combinations being contemplated herein as within the scope of the present invention. Because of the high inherent resolution capability of gamma radiation (short wavelength), the prospect of direct-write gamma lithography is very attractive. In order to accomplish this, however, it is necessary to provide, in addition to the gamma-sensitive resists described hereinabove, means for generating a tightly focused or collimated beam of gamma radiation, and means for "shuttering" or gating the beam. Suitable means for collimating and shuttering are described hereinbelow with respect to FIGS. 4 and 5a-c, respectively. According to the invention, a broad incident beam of radiation (or a radiant point source) can be concentrated and collimated, providing a very narrow, intense beam of radiation useful over a range of distances. This is accomplished by using a hollow, horn-shaped (or conical) afocal concentrator of the type schematically depicted in FIG. 4. FIG. 4 is a diagrammatic view of an afocal concentrator 400 for providing a very narrow, collimated beam of radiation. The afocal concentrator 400 has a tapered input (upstream) section 410 and an optional cylindrical output (downstream) section 450. The tapered section has a broad upstream mouth 420 (analogous to the bell of a trumpet) and a narrow opening 425 at an opposite downstream end thereof. The cylindrical section 450 has a diameter "do" equal to the diameter of the narrow opening 425, and is preferably formed contiguously therewith (i.e., the tapered and cylindrical sections are preferably formed as a unit structure). A relatively broad incident beam of radiation (e.g., gamma radiation) enters the mouth 420 of the tapered portion 410. (Such a beam could be generated by any suitable means including by a chemical radiant source, with or without a backing reflector.) The radiation beam is indicated by representative rays 440a and 440b entering opposite outer peripheral (circumferential) portions of the mouth 420. In the tapered section 410 as shown, the taper is approximately exponential, however any tapered form (e.g., a linear taper forming a conical shape), may be employed. An inner surface 415 of the afocal concentrator 400 is reflective of the incident radiation, and serves to reflect and concentrate the incident radiation towards the narrow opening 425 of the tapered section 410. For example, the tapered section could be formed of aluminum, nickel or chromium, or plated with the same on its inner surface (bore), to reflect and concentrate gamma rays. The cylindrical section 450, which should also have a highly reflective bore, serves to further collimate this concentrated radiation beam, providing an intense, narrow, collimated output beam 460 at an output end 455 thereof. In practice, the output beam 460 is not perfectly collimated and will diverge to some degree. However, over a first distance, d1, the output beam 460 remains roughly converged to within approximately the diameter `do` of the output end 455 of the cylindrical section 450 (or of the narrow opening 425 if the cylindrical section 450 is not Used). Assuming a maximum useful (for direct write lithography) beam diameter "dm", the output beam 460 is useful over a distance of up to "d2" (d2>d1, as shown here) from the output end 450 of the cylindrical section (or of the narrow opening 425 if the cylindrical section 450 is not used). The longer the afocal concentrator 400, especially the longer the tapered portion of the concentrator, generally the better the collimation of the output beam 460 can be (i.e., long taper=less beam divergence). The dimension "d2" represents the useful effective (for direct write lithography) depth of field of the concentrator 400. In practice, for direct write semiconductor lithography, a radiant source, such as a pellet of Cobalt-60, is placed as close to the mouth of the concentrator as possible. As mentioned hereinabove, the emissions from the source can be directed more-or-less exclusively towards the mouth of the concentrator 400 by providing a reflector (compare 114, FIG. 1) upstream of the source (compare 112, FIG. 1). The resultant output beam 460 exiting the concentrator 400 is intense, adequately collimated, highly fluent (given a fluent source such as Cobalt-60), and very highly homogenous (minimal or negligible hot spots in the cross section of the beam 460 due to the many reflections experienced by the beam in the concentrator 400). Exemplary dimensions for the concentrator, for semiconductor lithography are: Preferably, the mouth of the concentrator is between 50 .mu.m and 60 .mu.m in diameter, and the output diameter "do" is less than 0.5 .mu.m in diameter. The output diameter "do" can be made as small as desired, for example 0.1 .mu.m, for converting extremely small areas of resist material on a semiconductor wafer (compare 360a-d in FIGS. 3a-d). Evidently, to form converted lines in the resist material, in a direct-write application, one or the other of the concentrator 400 or the semiconductor wafer must "walk around" in the plane of the wafer surface (or the appropriate differential angle may be utilized to target areas without perpendicular beam impingement). Given the relative complexities of walking around the concentrator or the wafer, it is preferred that the concentrator remain stationary and that the wafer be moved around in a plane (X-Y positioning). High resolution positioning platforms are available for "walking" the wafer around. Given a "passive" gamma source such as Cobalt-60, it is evident that a mechanism must be provided for gating (turning on and off) the output beam (460). Else, walking around the wafer would produce an endless line. A shutter mechanism for gating the output beam is described below with respect to FIGS. 5a-c. Although the rays 440a and 440b are shown in FIG. 4 as parallel rays entering the "bell" (mouth 420) of the concentrator 400, the rays of the incident beam need not be parallel (collimated). The concentrator will collimate input rays that are not parallel. However, the less parallel the input rays, the more collimation must be performed by the collimator. These factors need to be taken into account in the design of an overall lithography system. The better the initial collimation of the incident beam, the better the ultimate collimation of the output beam. One way to improve the input collimation is to position the source of the incident beam distant from the mouth of the concentrator (relative to the size of the concentrator. This serves to make the rays of the incident beam that actually enter the mouth of the concentrator more parallel with one another, thereby improving output collimation. If the source is positioned far away from the mouth of the collimator, it is also possible to use a cylindrical pipe (not shown) between the source and the mouth of the concentrator to help collect and direct radiation from the source. For example, a Cobalt-60 pellet could be placed in a closed end of a cylindrical tube, the closed end serving as=an upstream reflector. The tube would be oriented coaxial to the concentrator, with its downstream open end placed adjacent the mouth of the concentrator. The inside surface of the tube would be highly reflective. In this manner, emissions of gamma radiation into the environment (other than towards the wafer) could be minimized. Although the instant application of the afocal concentrator 400 is to concentrate a gamma radiation beam, the same technique is applicable to any form of radiation source, including X-rays, UV light, and visible light. A major difference between such afocal concentrators for different radiation sources would be the material of which the inner surface of the concentrator (e.g., 415) is formed (or plated). The main requirement for the material of the inner surface of the concentrator is that it be reflective of the range of wavelengths in the incident beam. Aluminum is reflective of many different radiation wavelengths, including gamma radiation, and is suitable for gamma lithography. Nickel and Chromium are also suitably reflective materials. It is within the spirit and scope of the present invention that the afocal concentrator described hereinabove be applied to concentrate any suitable radiation source. The bore size of the concentrator also depends on the desired size of the output beam. Extremely small bore diameters can be formed by etching, ion milling, and other "machining" techniques which are known. Although the concentrator may be somewhat expensive to manufacture with precision, its cast will readily be amortized over the course of fabrication for a great number of semiconductor devices. And, as mentioned hereinabove, a passive source, such as Cobalt-60, provides a great deal of energy without consuming any external power. A shutter mechanism for gating the output beam from the concentrator is described hereinbelow with respect to FIGS. 5a-c. According to the invention, a surface acoustic wave (SAW) device operating as a shallow angle reflecting/scattering surface, can operate as a shutter element for X-ray or gamma-ray (or other) radiations. A thin, reflective film of, for example, aluminum, nickel, or chromium, is disposed over the surface of a Surface Acoustic Wave (SAW) device. Assuming that the SAW device is not activated, the reflective surface is substantially planar, and reflects any incident energy (e.g., a beam of gamma rays) at an angle equal and opposite to its angle of incidence. A tightly collimated beam approaching at a known shallow angle, will be reflected off of the reflective surface of the unactivated SAW device at a predictable shallow angle. If the SAW device is activated, however, the surface of the SAW device becomes distorted and deflects or scatters the incident beam. By providing a beam stop or an aperture, and positioning the beam stop or aperture such that radiation from the incident beam will pass the beam stop or aperture only when shallow-angle-reflected off of the surface of the SAW device, an effective shutter mechanism can be implemented. FIGS. 5a-c illustrate the operation of this Surface Acoustic Wave shutter device, as exemplary of a shallow-angle-reflection, distortable-surface shutter mechanism. SAW devices are generally known for other (than the shallow angle shutter disclosed herein) purposes, such as for imposing propagation delays on travelling waves, allowing particular wavefronts to be selectively "picked off" from the end of the SAW device. FIG. 5a is a side view of a shutter mechanism 500 employing a SAW device in its unactivated (planar, non-deformed surface) state. The shutter is formed of a Surface Acoustic Wave device 510 with a planar top surface upon which a reflective film 510a is disposed, and a strategically positioned beam-stop (or "knife edge") 520. A collimated (directional) incident beam 540 approaches the reflective surface 510a of the Surface Acoustic Wave device 510 at a shallow angle, and is reflected by the reflective surface 510a at an equal and opposite angle, forming a reflected beam 540a. The trajectory of the reflected beam is such that it misses the beam stop 520 and continues traveling along the same trajectory. FIG. 5b is a side view of the shutter mechanism 500 of FIG. 5a, with the Surface Acoustic Wave device in an activated (surface-deformed) state. Electrical stimulation of the Surface Acoustic Wave device causes surface Waves 530 or distortions (shown greatly exaggerated) to be formed on the reflective surface 510b. For the same shallow angle incident beam 540 (compare FIG. 5a), these surface distortions 530 cause the reflected beam 540b to be scattered or diverted relative to the position of the reflected beam 540a from the unactivated Surface Acoustic Wave device 510. In other words, the beam 540b is reflected at a different angle off the distorted surface than the beam 540a is reflected from the undistorted surface of the SAW device. As a result, the reflected beam strikes the beam stop 520 and is blocked thereby such that the reflected beam does not exit the Surface Acoustic Wave shutter 500. By selectively energizing (activating) the SAW device, the beam 540 is effectively gated (turned on and off). This allows discrete lines (e.g., of converted resist material) to be formed on the surface of a semiconductor device. FIG. 5c is a greatly enlarged (magnified) view of a portion of the Surface Acoustic Wave shutter device 510, in the surface-distorted state shown in FIG. 5b, showing the point of reflection. As before, the distortions are shown greatly exaggerated. A reference line 550 indicates the location and angle of the undistorted surface (see, e.g., 510a). A tangent line 560 indicates the angle of the reflective surface 510b at the point of reflection. The incident beam 540, approaches the reflective surface 510b of the Surface Acoustic Wave device 510 at a shallow incident angle .THETA.ih relative to the horizontal (i.e., relative to the reference line 550). However, due to the distortion of the reflective surface 510b, the effective angle of incidence relative to the tangent line 560 is a steeper angle, shown as .THETA.i, where .THETA.i>.THETA.ih (as shown). As a result, the incident beam 540 is reflected as a reflected beam 540b at a reflection angle of .THETA.r=.THETA.i relative to the tangent line 560. The effective reflection angle .THETA.rh of the reflected beam 540b relative to the reference line 550 (horizontal plane) is even greater (as shown). By this mechanism, the incident beam 540 can be reflected such that it is either blocked or passed by a beam stop or aperture under electrical control. Note that the beam stop 520 effectively forms an "aperture" with the surface 510a of the Surface Acoustic Wave device 510. Alternatively, an aperture may be provided instead of a "knife-edge" style of beam stop 520. It is not necessary, according to the invention that the incident beam 540 be "cleanly" reflected in any particular direction. It is only necessary that the reflected beam 540b be reflected anywhere other than past the beam stop or aperture 520. It will readily be apparent to one of ordinary skill in the art that a magnetostrictive device may be substituted for the Surface Acoustic Wave device 510 to accomplish a similar result (directing and diverting a beam of incident radiation). Both magnetostrictive and Surface Acoustic Wave devices act as a sort of "surface distortion device" for the purposes of the present invention. Any device that can reflect an incident beam at one angle in one energized state (e.g., not energized), and reflect an incident beam at another angle in another energized state (e.g., energized), in conjunction with a beam stop or aperture allowing a reflected beam to pass only at a critical angle, can be employed in the instant inventive shutter mechanism. An advantage of using a surface distortion device, rather than a device which must physically be positioned, is that the response time of such surface distortion devices is relatively quick. This enables such a device, in conjunction with a beam stop or aperture, to be used as a high-speed shutter (e.g., no moving parts). It will also be readily apparent to one of ordinary skill in the art that this type of shutter device may be applied to radiation of a variety of wavelengths, including gamma-rays, X-rays, UV light, etc. It is within the spirit and scope of the present invention that the SAW (or magnetostrictive) shutter device described hereinabove be applied as a high-speed shutter to any suitable form of radiation beam. FIGS. 6a and 6b are block diagrams of (gamma-ray) direct-write lithographic apparatus employing the techniques described hereinabove with respect to FIGS. 3a-d, 4, and 5a-c; or for a near-field lithographic apparatus employing the techniques described hereinabove with respect to FIGS. 2a-b, 3a-d 4 and 5a-c. FIG. 6a is a block diagram of a direct-write (or energy source for near-field; gamma-ray, x-ray or other radiation) lithography (lithographic) apparatus 600a, according to the present invention. A radiation source 610 provides a source of intense directional gamma-ray (or x-ray, or other radiation, collectively herein called "gamma-ray") radiation. A suitable passive gamma radiation source is Cobalt-60 which passively radiates intense gamma-ray radiation. A reflector (such as that shown and described as 114 with respect to FIG. 1) may be employed to improve the directionality and intensity of the source 610. Given any shutter 630, or other "on/off" mechanism, the beam 640 need not be very well collimated. Given a shutter 630 such as was described with respect to FIGS. 5a-5c, a collimator similar to that shown in FIG. 4 could be employed to direct the beam 640 into the shutter 630. Incident gamma-ray radiation 640 from the gamma-ray radiation source 610 enters a shutter device 630, such as the Surface Acoustic Wave shutter device shown and described as 500 with respect to FIGS. 5a-5c. The shutter device 630 serves to selectively gate (block or pass) the incident beam 640, resulting in a controlled gamma-ray beam 640a. The controlled gamma-ray beam 640a enters the mouth of an afocal concentrator 620, such as that shown and described (400) with respect to FIG. 4. The afocal concentrator narrows and intensifies the controlled beams 640a to provide a collimated beam 640b. A semiconductor wafer 650 is positioned a distance "d3" from the output of the afocal concentrator 620 such that the collimated beam impinges upon the front surface 655 thereof. The front surface 655 of the wafer 650 is coated with a layer 660 of gamma-sensitive resist, such as that shown and described as 320a-d (and optionally 330a, c-d) with respect to FIGS. 3a-3d, respectively. Preferably, the wafer is mounted to a movable carriage (not shown) for direct-write application, by which means the wafer 650 may be positioned such that the collimated beam 640b may be caused to impinge on any point on the resist layer 660. The on/off state of the collimated beam 640b may be effectively controlled by selectively activating and de-activating the shutter device 630. Preferably, the distance "d3" is approximately 5 .mu.m. Preferably, the distance "d3" should be no greater than the distance "d2" shown in FIG. 4. FIG. 6b is a block diagram of an alternate embodiment of a direct-write gamma-ray (or x-ray or similar radiation, collectively herein called "gamma-ray") lithographic apparatus 600b, according to the invention. As before, a radiation source 610, such us Cobalt-60, provides a source of intense directional gamma-ray radiation. A reflector (such as that shown and described as 114 with respect to FIG. 1) may be employed to improve the directionality and intensity of the source 610. Incident gamma-ray radiation 640 from the gamma-ray radiation source 610 enters the mouth of an afocal concentrator 620, such as that shown and described (400) with respect to FIG. 4. The afocal concentrator narrows and intensifies the incident gamma-ray radiation 640 to provide a collimated gamma-ray beam 640a'. The collimated gamma-ray beam 640a' enters a shutter device 630, such as the Surface Acoustic Wave shutter device shown and described as 500 with respect to FIGS. 5a-5c. The shutter device serves to selectively gate (block or pass) the collimated gamma-ray beam 640a', resulting in a collimated, controlled gamma-ray beam 640b'. A semiconductor wafer 650 is positioned a distance "d3" from the output of the afocal concentrator 620 such that the controlled collimated beam 640b' impinges upon the front surface thereof. The front surface 655 of the wafer 650 is coated with a layer 660 of gamma-sensitive resist, such as that shown and described as 320a-d (and optionally 330 a, c-d) with respect to FIGS. 3a-3d, respectively. Preferably, the wafer 650 is mounted to a movable carriage (not shown) for direct-write application, by which means the wafer 650 may be positioned such that the collimated controlled beam 640b' may be caused to impinge on any point on the resist layer 660. The on/off state of the collimated controlled beam 640b' may be effectively controlled by selectively activating and de-activating the shutter device 630. In this configuration, the shutter device 630 is between the output of the concentrator 620 and the wafer 650. Hence, the shutter 630 must be made small. Small SAW (or magnetostrictive) devices can be fabricated to meet this criteria. It is also possible (in any of the examples set forth herein) that the beam may be reflected off a suitable reflecting surface (not shown) so that it initially approaches the wafer 650 at an angle (e.g., parallel, or between parallel and normal) to the surface of the wafer) and is reflected by the reflector to ultimately impact the wafer at ninety degrees (normal) to the surface of the wafer. It is within the spirit and scope of the present invention that the inventive techniques described hereinabove be used either alone or in combination. By employing these techniques, viable forms of short-wavelength (e.g., gamma-ray or X-ray) afocal lithography may be realized. It should also be recognized that many of the techniques described hereinabove may be applied to other types of radiation, such as UV light or visible light.
	summary
	claims	1. A method for irradiating a target with a beam of energetic radiation formed by electrically charged particles, comprising:providing a pattern definition system having a plurality of apertures transparent to said radiation,illuminating said pattern definition system using an illuminating wide beam, which traverses the pattern definition system through said apertures thus forming a patterned beam including a corresponding plurality of beamlets,forming said patterned beam into a pattern image on the location of the target, said pattern image comprising the images of at least part of the plurality of apertures imaged onto a corresponding number of image pixels on the target, andgenerating a relative movement between said target and the pattern definition system producing a movement of said pattern image on the target along a path over a region where a beam exposure is to be performed, which defines a number of stripes covering said region in sequential exposures, each of said stripes comprising a plurality of image pixels on the target wherein within each stripe the image pixels have non-overlapping nominal positions on the target,wherein within each stripe the movement of said pattern image on the target is parallel to the direction of relative movement between the target and the pattern definition system,wherein the stripes at their boundaries to adjacent stripes comprise overlap margins, each of said overlap margins being located at a stripe boundary oriented parallel to the movement of said pattern image on the target and comprising a plurality of image pixels, wherein said plurality of image pixels is a subset of the image pixels within the respective stripe, and each overlap margin in a stripe is brought into spatial overlap with a corresponding overlap margin of an adjacent stripe wherein nominal positions of image pixels in the overlap margin are overlapping with nominal positions of corresponding image pixels in the corresponding overlap margin,wherein, during the exposure of an overlap margin, a first subset of image pixels in said overlap margin are exposed and a second subset of image pixels in said overlap margin are not exposed, whereas during the exposure of a corresponding overlap margin, image pixels in said corresponding overlap margin which correspond to image pixels in said first subset are not exposed, and image pixels in said corresponding overlap margin which correspond to image pixels in said second subset are exposed. 2. The method of claim 1, wherein the first and second subsets are complementary with regard to the numbers of image pixels in a pixel pattern to be generated on the target within an overlap margin. 3. The method of claim 1, wherein the ratio formed between the number of image pixels in the first subset and the sum of numbers of image pixels in the first and second subsets is decreasing towards an outer boundary of the overlap margin along a direction transverse to the direction of the path defining the respective stripe. 4. The method of claim 3, wherein said ratio decreases in a stepwise manner in a sequence of consecutive sub-regions in the overlap margin. 5. The method of claim 4, wherein the number of said consecutive sub-regions is at least two. 6. The method of claim 5, wherein the number of said consecutive sub-regions is n2 −1, where n≧2. 7. The method of claim 5, wherein the number of said consecutive sub-regions is 22i−1, where i≧1. 8. The method of claim 4, wherein said ratio is expressed with regard to sampling cells of uniform size within the respective overlap margin or sub-region. 9. The method of claim 3, wherein said ratio has at least two different values greater than 0 and smaller than 1. 10. The method of claim 9, wherein said ratio has at least n2−1 values greater than 0 and smaller than 1, where n≧2. 11. The method of claim 9, wherein said ratio has at least 22i−1 values greater than 0 and smaller than 1, where i≧1. 12. The method of claim 3, wherein said ratio is expressed with regard to sampling cells of uniform size within the respective overlap margin or sub-region. 13. The method of claim 9, wherein the sampling cells are blocks of adjacent image pixels. 14. The method of claim 1, wherein the spatial overlap between an overlap margin and a corresponding overlap margins such that nominal positions of image pixels in the overlap margin are substantially coinciding with nominal positions of corresponding image pixels in the corresponding overlap margin. 15. The method of claim 1, wherein the images of apertures formed on the target have a width that is greater than the distance between neighboring positions of image pixels within each stripe. 16. The method of claim 15, wherein said width of the images of apertures, when expressed in terms of the distance between neighboring image pixel positions, has an integer part which is at least 2. 17. The method of claim 16, wherein said width of the images of apertures, when expressed in terms of the distance between neighboring image pixel positions, has an integer part that is 2N where N≧1.
	claims	1. A truss-reinforced nuclear fuel rod spacer grid comprising:a truss structure in which horizontal trusses formed by horizontally weaving a plurality of truss members are vertically disposed at regular intervals; andan external plate joined with ends of the horizontal trusses and surrounding the truss structure to vertically join the horizontal trusses to each other,wherein:the truss structure includes vertical trusses, which are vertically fastened to vertically corresponding truss intersections of the horizontal trusses to vertically support the horizontal trusses at regular intervals within an interior of the spacer grid;the horizontal trusses are shaped around a hexagon shaped space; andthe horizontal trusses are configured to deform outwardly and apply a frictional force on a nuclear fuel rod upon insertion of the nuclear fuel rod. 2. The truss-reinforced spacer grid as set forth in claim 1, wherein the truss structure includes unit trusses, each of which has a shape of a hexagon in the center thereof and a shape of a triangle outside corresponding sides of the hexagon. 3. The truss-reinforced spacer grid as set forth in claim 2, wherein the truss structure is configured to support said fuel rods inserted into the unit trusses. 4. The truss-reinforced spacer grid as set forth in claim 1, wherein the truss structure includes a guide tube hole configured for a guide tube wherein the guide tube is configured to accept a control rod. 5. The truss-reinforced spacer grid as set forth in claim 4, wherein the guide tube is surrounded by a cylindrical sleeve, the sleeve and the guide tube being welded. 6. The truss-reinforced spacer grid as set forth in claim 1, wherein each truss member is formed of a wire. 7. The truss-reinforced spacer grid as set forth in claim 1, wherein the hollow cylindrical pipe has an outer diameter of 0.5 mm to 2.0 mm. 8. The truss-reinforced spacer grid as set forth in claim 1, wherein each truss member has a linear shape. 9. The truss-reinforced spacer grid as set forth in claim 1, wherein each truss member has a circular shape curved at a predetermined curvature. 10. The truss-reinforced spacer grid as set forth in claim 1, wherein each truss member has an angled shape bent at a predetermined angle. 11. A method of manufacturing the truss-reinforced spacer grid of claim 1, the method, comprising:a first step of horizontally weaving said plurality of truss members to form said horizontal trusses;a second step of fastening said vertical trusses to the horizontal trusses to form said truss structure; anda third step of joining said ends of the horizontal trusses to said external plate surrounding the truss structure to form the truss-reinforced spacer grid. 12. The method as set forth in claim 11, wherein the first step includes:a process of weaving the truss members to form unit trusses; anda process of joining the unit trusses using brazing to form the horizontal trusses. 13. The method as set forth in claim 11, wherein the second step includes:a process of vertically disposing the horizontal trusses at the same separation height; anda process of vertically fastening the vertical trusses to vertically corresponding truss intersections of the horizontal trusses to form the truss structure. 14. The method as set forth in claim 11, wherein the third step includes joining the horizontal trusses to the external plate using brazing. 15. The method as set forth in claim 11, further comprising a fourth step of inserting a guide tube into the truss structure. 16. The method as set forth in claim 15, wherein the fourth step includes:a process of forming a guide tube hole in the truss structure, the guide tube hole having a diameter greater than that of the guide tube;a process of inserting a cylindrical sleeve into the guide tube hole; anda process of inserting the guide tube into the cylindrical sleeve and welding the sleeve and the guide tube. 17. The method as set forth in claim 11, further comprising a fifth step of inserting fuel rods into the truss structure. 18. A truss-reinforced nuclear fuel rod spacer grid comprising:a truss structure in which horizontal trusses formed by horizontally weaving a plurality of truss members are vertically disposed at regular intervals, wherein:the horizontal trusses are shaped around a hexagon shaped space;the horizontal trusses are configured to deform outwardly and apply frictional force on a nuclear fuel rod upon insertion of the nuclear fuel rod; andan external plate joined with ends of the horizontal trusses and surrounding the truss structure and wherein the truss structure includes a cut guide tube hole configured for a guide tube wherein the guide tube is configured to accept a control rod. 19. The truss-reinforced spacer grid as set forth in claim 18, wherein the guide tube is surrounded by a cylindrical sleeve, the sleeve and the guide tube being welded. 20. A truss-reinforced nuclear fuel rod spacer grid comprising:a truss structure in which horizontal trusses formed by horizontally weaving a plurality of truss members are vertically disposed at regular intervals, wherein:the horizontal trusses are shaped around a hexagon shaped space;the horizontal trusses are configured to deform outwardly and apply frictional force on a nuclear fuel rod upon insertion of the nuclear fuel rod; andan external plate joined with ends of the horizontal trusses and surrounding the truss structure and wherein each truss member is formed of a hollow cylindrical pipe. 21. The truss-reinforced spacer grid as set forth in claim 20, wherein the hollow cylindrical pipe has an outer diameter of 0.5 mm to 2.0 mm.
056195460	summary	BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is generally related to a nuclear steam supply system (NSSS) resistance temperature detector (RTD) nozzle mechanical clamp seal assembly and blowout retainer designed to prevent leakage from or around an RTD nozzle and blowout of the nozzle from its joint or seat in NSSS piping. 2. General Background The resistance temperature detectors measure the nuclear reactor coolant temperature in both the "hot" and "cold" legs of the NSSS. The RTD's are installed through the welded penetrations in the Reactor Coolant System (RCS) piping. The penetrations are susceptible to cracking and leakage caused by primary water stress corrosion cracking (PWSCC) of the, typically, Inconel 600 stainless steel nozzles. The present repair method for these nozzles requires a lengthy and expensive welding procedure which increases the amount of work and time required to restore the NSSS to operation once this type of cracking and deterioration occurs. Examples of this type of technique in repairing pressurized heater sleeve penetration nozzles which involve analogous pressure boundary welding procedures are disclosed in U.S. Pat. No. 5,094,801 dated Mar. 10, 1992 by Dixon et al., U.S. Pat. No. 5,091,140 dated Feb. 25, 1992 by Dixon et al., and U.S. Pat. No. 4,255,840 dated Mar. 17, 1991 by Cook et al. The RTD nozzle mechanical clamp seal of the invention prevents reactor coolant leakage at the RTD nozzles without the necessity of such a welding procedure. In U.S. Pat. No. 4,655,483, filed May 14, 1984, entitled "Boundary Seal for Pressure Penetration", and assigned to the assignee of the present invention, a connector device provides a primary pressure boundary between a nozzle and a column concentrically disposed therein. The connector device includes a closure member for compressing a seal ring against the end of a nozzle. The closure member includes a hub portion which defines an annular space between the closure member and the column. Packings are inserted in this annular space and compressed by means of a drive unit which includes a drive sleeve and an actuator nut threaded to an upper portion of the sleeve. A split-ring type collar is clamped to the column to provide support for the column. Rotation of the actuator nut loads the column thus causing it to be longitudinally displaced relative to the closure member until a tight connection is made. Continued actuation of the nut advances the drive sleeve along the annular space to compress the gasket to thereby complete the fluid-tight connection. While the boundary seal of the referenced prior art application can be installed in a relatively short time when compared to previous devices of like character, it nevertheless requires substantial effort to install the connector, particularly the collar clamp which has eight bolts to tighten. Further, this boundary seal assembly does not completely insure against the column assembly accidentally moving upwardly or downwardly during the assembly process. In U.S. Pat. No. 4,723,795 filed May 5, 1996, entitled "Instrument Penetration For High Pressure Vessels", and assigned to the assignees of the present invention, an assembly provides a fluid-tight connection between a nozzle and a concentric tubular column supported in the nozzle. The nozzle is provided with an interior flange while a ledge extends from the exterior of the column at a point which will be displaced from the nozzle flange when the column is disposed in the nozzle. A seal assembly, which comprises an annular packing or sealing ring, is positioned on the flange and surrounds the column for establishing a seal between the nozzle and the column. A drive sleeve is received within the nozzle. The drive sleeve has a first end, which bears against the seal assembly, and a drive shoulder. A spacer sleeve is threadedly received in the nozzle for axial positioning relative thereto. A first end of the spacer sleeve is configured for engagement with the column ledge. A clamp assembly is mounted to the column at a fixed axial position relative to a first end of the nozzle. The clamp assembly includes an adjustable means for axially displacing the column relative to the nozzle so that the column ledge firmly engages the lower end of the spacer sleeve to fix the axial position of the column relative to the nozzle. A drive means, which comprises a nut threaded to the nozzle, is engageable with the drive shoulder of the drive sleeve to axially force the drive sleeve first end toward the nozzle flange to compress the sealing assembly into sealing engagement with the column and the nozzle to prevent fluid leakage therebetween. This prior art assembly provides a fluid-tight connection between a nozzle, which has an interior flange, and a column, which is concentrically supported within the nozzle Further background and prior art information is provided by a paper "Repair Method for Control Rod Drive Stub Tube Using a Mechanical Graphite Seal" by C. W. Ruoss, Jr. et al, presented at the EPRI and EPRI NDE Center Sponsored BWR Reactor Pressure Vessel & Internals Inspection & Repair Workshop, Jul. 16-18, 1991, Charlotte, N.C. SUMMARY OF THE INVENTION It is an object of the present invention to provide a mechanical clamp designed to prevent leakage from the resistance temperature detector nozzles on nuclear reactor coolant system piping which can be readily installed by bolting without the need of extensive welding. It is a further object of the invention to provide a mechanical clamp seal designed with split sections to allow installation over a resistance temperature detector. It is a further object of the invention to provide a graphite seal at a nozzle to pipe interface to prevent leakage from the nozzle annulus. It is a further object of the invention to provide a mechanical clamp seal which includes a blowout retainer to prevent ejection of the nozzle in the event of a weld failure. The above objects are accomplished in a fluid tight mechanical clamp seal for nuclear reactor coolant system hot and cold leg pipe resistance temperature detector nozzles which has a split an annular compressible graphite seal ring surrounding the nozzle at a pipe and nozzle joint. The mechanical clamp seal has an annular split ring made up of plural sections surrounding and confining the periphery of the split annular seal ring into which is telescopically received an annular split load sleeve made up of plural sections to compress axially the seal ring against the pipe, thereby also to expand radially the seal ring against the nozzle and the seal confirming annular split ring. A reaction plate having a first surface shaped to engage the pipe, a second and annular surface to peripherally engage and to confine radially the split ring and a third surface to confine axially the split ring against the pipe is bolted to the pipe by means of threaded blind holes provided in the pipe. The third surface has an opening sufficiently great to allow its installation without disassembly of the resistance temperature detector or nozzle to pipe joint. A load ring has a central opening and surrounds, and has a surface which axially abuts against, the split load sleeve. Bolts are threadedly connected to holes in the reaction plate and pass through openings in the load ring to provide an axial driving and compressing force through the load ring surface axially abutting against the split load sleeve to compress the annular seal ring and provide an effective seal at the pipe and nozzle joint. The load ring central opening has an internally threaded portion and receives a split blowout retainer made up of plural sections threaded therein. The central opening is surrounded by a peripheral inwardly directed flange for engaging a radially directed surface provided on the nozzle to prevent the nozzle's ejection from the pipe in the event of a weld failure at the nozzle pipe joint.
	description	This is a Continuation-In-Part application of application Ser. No. 14/109,072, filed Dec. 17, 2013, entitled FLOATING NUCLEAR POWER REACTOR WITH A SELF-COOLING CONTAINMENT STRUCTURE. 1. Field of the Invention This invention relates to a floating nuclear power reactor and more particularly to a floating nuclear power reactor wherein the containment structure of the reactor is self-cooling. This invention relates even more particularly to an emergency heat exchange system for the nuclear power reactor. 2. Description of the Related Art In most nuclear power reactors, a primary electrically operated water pump supplies cooling water to the reactor. In many cases, a secondary or back-up water pump is provided in case the primary water pump becomes inoperative. However, should the electrical power source for the water pump or water pumps be disrupted such as in a tsunami, a typhoon or an earthquake, the water pumps are not able to pump cooling water to the reactor which may result in a dangerous meltdown. Further, in some situations, the pipes supplying cooling water to the reactor may fail due to natural causes or a terrorist attack. Currently, there are land based reactor cooling systems available which store water in a tank above the level of the reactor which will passively feed the reactor in case of pump or electricity failure. These tanks are designed to have enough water to cool the system for three days until help can arrive and more water can be pumped in from outside. The problem is that water stored in these tanks is of finite quantity. The tanks will work in case of an emergency shut down like in Fukushima, Japan, but will not work in the case of a pipe breakdown leaking a huge amount of water to the exterior. The reactor core will heat the water supplied from the tank and steam will escape via the pipe breakdown and the water will run out. Once the water runs out, the reactor core will melt due to overheating and explode. It is therefore necessary to be able to supply an infinite amount of water to compensate for lost water via a leaking pipe. Further, current day reactors are protected by huge containment structures but this is not the answer to pipe breakdown outside or inside the containment chambers. A terrorist attack on the turbine room outside the containment structure is probably more dangerous than an attack on the containment structure since such an attack would result in multiple pipes breaking down, thereby breaking the water circuit between the reactor, turbine and condenser. Such an attack could also result in a breakdown of electrical control systems. This would result in the loss of circulating water to the reactor with the emergency stored water being unable to compensate for all the leaking pipes. In such a situation, the reactor will overheat without heat removal and explode. The invention of the co-pending parent application represents a major improvement in the art. The instant invention represents a further improvement in the art. This Summary is provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description. This Summary is not intended to identify key aspects or essential aspects of the claimed subject matter. Moreover, this Summary is not intended for use as an aid in determining the scope of the claimed subject matter. A floating nuclear power reactor is disclosed. A nuclear power reactor is mounted or positioned on a floating barge-like vessel with the barge-like vessel having an upper end positioned above the water level of a body of water and a lower end positioned beneath the water level of the body of water. Side walls extend between the lower and upper ends of the floating vessel. The nuclear power reactor is positioned on the bottom of the barge-like vessel. The nuclear power reactor includes an upstanding concrete containment structure having a lower end, an upstanding sidewall, and an upper end. The confinement structure defines a sealed interior compartment. The lower end and a lower portion of the side wall of the containment structure are positioned below the water level of the body of water. An upstanding cylindrical, metal wall structure extends around the outer side of the concrete containment structure. A cover closes the upper end of the metal wall structure. The relationship of the metal wall structure, the upper outer portion of the containment structure and the cover define a vent chamber. The vent chamber is filled with a filter material such as stones or rocks, chemicals and water. One or more steam exhaust pipes extend outwardly from the upper end of the vent chamber through the cover to the atmosphere. A reactor vessel, having upper and lower ends, is positioned in the interior compartment of the containment structure with the reactor vessel being positioned below the water level of the body of water. The reactor vessel includes an interior compartment having upper and lower ends. One or more steam exhaust pipes extend through the containment structure so that one end thereof is in communication with the upper end of the interior compartment thereof and so that the other end thereof is in communication with the vent chamber. One or more return pipes are associated with the reactor vessel so that one end thereof is in communication with the upper end of the interior compartment of the reactor vessel and so that the other end is in communication with the lower end of the interior compartment of the reactor vessel. In the preferred embodiment, one of the return pipes is of the closed loop type. A portion of the return pipe is positioned in the interior compartment of the containment structure. The return pipes form a heat exchanger system. A steam exhaust pipe extends from the upper end of the interior compartment of the reactor vessel outwardly through the containment structure to a turbine. A steam by-pass pipe extends from the steam exhaust pipe, which extends to the turbine, to the vent chamber. A normally closed first valve is imposed in the steam by-pass pipe. A normally open second valve is imposed in the steam exhaust pipe, which extends to the turbine, outwardly of the containment structure. A first water passageway, having inner and outer ends, extends through the bottom of the floating vessel and the bottom of the containment structure with the outer end of the first water passageway being in fluid communication with the body of water. The inner end of the first water passageway is in fluid communication with the interior compartment of the containment structure. A spring-loaded first hatch is movably mounted on the exterior of the side wall of the vessel at the outer end of the first water passageway. The first hatch is movable between a closed position and an open position. The first hatch, when in its closed position, closes the outer end of the first water passageway. The first hatch, when in its open position, permits water from the body of water to flow inwardly through the first water passageway into the interior compartment of the containment structure to cool the reactor vessel. A first latching means is associated with the first hatch with the first latching means being movable between a latched position and an unlatched position. The first latching means, when in its latched position, maintains the first hatch in its closed position. The first latching means, when in its unlatched position, permits the first hatch to move from its closed position to its open position. A first condition responsive actuator is associated with the first latching means to move the first latching means from its latched position to its unlatched position upon the condition, either temperature or pressure, in the containment structure reaching a predetermined level. Although a single first water passageway is disclosed, a plurality of first water passageways could be utilized. A second water passageway, having inner and outer ends, extends through the bottom of the vessel, through the bottom of the containment structure, and into the interior compartment of the reactor vessel. A second hatch is movably mounted in the second water passageway. The second hatch is movable between a closed position and an open position. The second hatch closes the outer end of said second water passageway when in its closed position. The second hatch, when in its open position, permits water from the body of water to flow inwardly into the interior compartment of the reactor vessel to cool the reactor vessel. A second latching means is associated with the second hatch which is movable from a latched position to an unlatched position. The second latching means, when in its latched position, maintains the second hatch in its closed position. The second latching means, when in its unlatched position, permits the second hatch to move from its closed position to its open position. A condition, either temperature or pressure, responsive actuator is associated with the second latching means to move the second latching means from its latched position to its unlatched position upon the condition within the interior compartment of the reactor vessel reaching a predetermined level. Although a single second water passageway is disclosed, a plurality of second water passageways could be utilized. It is therefore a principal object of the invention to provide an improved floating nuclear power reactor. It is another object of the invention to provide an infinite supply of cooling water to the reactor in case of the reactor overheating A further object of the invention is to provide a floating nuclear power reactor which is self-cooling upon the temperature or pressure reaching a predetermined level in the containment structure or reactor vessel of the nuclear power reactor. A further object of the invention is to provide a self-cooling nuclear power reactor including an emergency heat exchange system. A further object of the invention is to provide a self-cooling nuclear power reactor including a filtered containment venting system. These and other objects will be apparent to those skilled in the art. These and other objects will be apparent to those skilled in the art. Embodiments are described more fully below with reference to the accompanying figures, which form a part hereof and show, by way of illustration, specific exemplary embodiments. These embodiments are disclosed in sufficient detail to enable those skilled in the art to practice the invention. However, embodiments may be implemented in many different forms and should not be construed as being limited to the embodiments set forth herein. The following detailed description is, therefore, not to be taken in a limiting sense in that the scope of the present invention is defined only by the appended claims. The numeral 10 refers to a floating vessel such as a barge as shown in the co-pending application Ser. No. 14/109,072, filed Dec. 17, 2013, entitled FLOATING NUCLEAR POWER REACTOR WITH A SELF-COOLING CONTAINMENT STRUCTURE. Barge 10 could be a ship hull or other floating structure. The details of the barge will not be described other than to say that the barge includes a bottom 12, upstanding ends, and upstanding sides. One of the ends 14 of the barge is shown in the drawings. Barge 10 may be constructed of any suitable material such as steel, concrete, etc. Barge 10 is shown as floating in a body of water 16 such as a lake, ocean, etc. For reference purposes, the body of water 16 will be described as having a water level 18. As seen, the upper end of barge 10 is positioned above the water level 18 with a majority of the barge 10 being submerged in the body of water 16. A nuclear power reactor 22 is positioned on the barge 10 as shown. Normally, a second power reactor would also be positioned on the barge 10 such as shown in the co-pending application. Reactor 22 includes a cylindrical metal housing 24 which includes the end wall 14, which extends upwardly from bottom 12 and which has an open upper end 26 positioned above the water level 18. A cover or lid 28 closes the open upper end 26 of housing 24. Reactor 22 includes an upstanding containment structure 30 constructed of concrete and which includes a bottom 32, an upstanding side wall 34, and an upper end 36 which defines a sealed interior compartment 38. A reactor vessel 40 is positioned in compartment 38 and includes an open bottom 42, side wall 44 and upper end 46 which define a sealed interior compartment 48. As seen, the bottom 42 of reactor vessel 40 is positioned on the upper end of bottom 32 of containment structure 30. As seen, a portion of the exterior of side wall 34 of containment structure 30 engages the interior of housing 24 to create a vent chamber 50. Vent chamber 50 is filled with rocks, chemicals and water to define a filtered containment venting system. A steam exhaust pipe 52 has its inner end in communication with vent chamber 50 and has its outer end in communication with the atmosphere as shown in FIG. 1. A steam exhaust pipe 54 has its inner end in communication with vent chamber 50 and has its outer end in communication with the atmosphere. Although two steam exhaust pipes 52 and 54 are shown and described, any number of steam exhaust pipes may be utilized. The numeral 56 refers to a steam exhaust pipe which extends through containment structure 30 adjacent the upper end thereof so that the inner end of steam exhaust pipe 56 is in communication with the upper end of compartment 38 and so that the outer end of steam exhaust pipe 56 is in communication with vent chamber 50. A steam exhaust pipe 58 extends through containment structure 30 adjacent the upper end thereof so that the inner end of steam exhaust pipe 58 is in communication with compartment 38 and so that the outer end of steam exhaust pipe 58 is in communication with vent chamber 50. Although two steam exhaust pipes 56 and 58 are shown and described, any number of those steam exhaust pipes could be utilized. The numeral 60 refers to a return pipe having pipe portions 62, 64, 66 and 67. Pipe portion 62 extends outwardly from compartment 48 adjacent the upper end of side wall 44 thereof. Pipe portion 64 extends downwardly from the outer end of pipe portion 62 in interior compartment 38, as seen in the drawings. Pipe portion 66 extends inwardly from the lower end of pipe portion 64, through side wall 44 into compartment 48 at the lower end thereof. Pipe portion 67 extends upwardly from the inner end of pipe portion 66 to the inner end of pipe portion 62 to form a closed-loop return pipe. Return pipe 60 is filled with a suitable coolant material such as water, sodium or the like. Although a single return pipe 60 is shown, more than one return pipes 60 could be utilized. The numeral 68 refers to a steam return pipe having pipe portions 70, 72 and 74. Pipe portion 70 extends outwardly from interior compartment 48 adjacent the upper end of side wall 44 of reactor vessel 40. Pipe portion 72 extends downwardly from the outer end of pipe portion 70, as seen in the drawings, so that pipe portion 72 is in interior compartment 38 of containment structure 30. Pipe portion 74 extends inwardly from the lower end of pipe portion 72 through side wall 44 into compartment 48 at the lower end thereof. If desired, the inner ends of pipe portions 70 and 74 could be connected together by a pipe so that the return pipe is a closed loop system. Although a single steam return pipe 68 is shown and described, any number of the steam return pipes 68 could be utilized. A water passageway 76 extends upwardly through bottom 12 of barge 10 and through bottom 32 of containment structure 30. The inner end of passageway 76 communicates with a larger water passageway 78, which communicates with the interior compartment 48 of reactor vessel 40. A spring-loaded hatch 80, which is identical to that shown and described in the co-pending application, is positioned in water passageway 78 to close water passageway 76. Hatch 80 includes a spring (not shown) which urges hatch 80 to its open position. A latching means (not shown), which is identical to that shown in the co-pending application, is associated with the hatch 80 with the latching means being movable between a latched position and an unlatched position as described in the co-pending application. The latching means, when in its latched position, maintains the hatch 80 in its closed position. The latching means, when in its unlatched position, permits the hatch 80 to move from its closed position to its open position. A condition responsive actuator 82, identical to that shown and described in the co-pending application, is associated with the latching means to move the latching means from its latched position to its unlatched position upon the condition, either pressure or temperature, in the interior compartment 48 of reactor vessel 40 reaching a predetermined level. A water passageway 84 extends upwardly through bottom 12 of barge 10 and through bottom 32 of containment structure 30. The inner end of passageway 84 communicates with a larger passageway 86, which communicates with the interior compartment 38 of containment structure 30. A spring loaded hatch 88, which is identical to that shown in the co-pending application, is positioned in the water passageway 86 to close water passageway 84. Hatch 88 includes a spring (not shown), which urges hatch 88 to its open position. A latching means, identical to that shown in the co-pending application, is associated with the hatch 88 with the latching means being movable between a latched position and an unlatched position. The latching means, when in its latched position, maintains the hatch 88 in its dosed position. The latching means, when in its unlatched position, permits the hatch 88 to move from its closed position to its open position. A condition responsive actuator 92, which is identical to that shown and described in the co-pending application, is associated with the latching means to move the latching means from its latched position to its unlatched position, upon the condition, either temperature or pressure, in the interior compartment 38 of containment structure 30 reaching a predetermined level. The numeral 94 refers to a steam exhaust pipe which extends from the upper end of interior compartment 48 of reactor vessel 40 to a conventional turbine. As seen, steam pipe 94 extends outwardly through side wall 44 of reactor vessel 40, through interior compartment 38, through containment structure 30, and through housing 24. A steam by-pass or vent pipe 96 extends upwardly from steam exhaust pipe 94 and passes through housing 24 into the lower end of vent chamber 50 as seen in the drawings. A normally open valve 97, which is manually or electrically operated, is imposed in pipe 94. A normally closed valve 98 is imposed in vent pipe 96. The instant invention functions as will be described. FIG. 1 illustrates the instant nuclear power reactor in its normal operating mode. In that mode: (1) hatches 80 and 88 are closed; (2) the return pipes 60 and 68 will not be functioning since pipe portions 64 and 72 are not being cooled by any surrounding coolant (water) and will stay at the same temperature as the reactor coolant; (3) valve 97 will be open and valve 98 will be closed; (4) steam exhaust pipes 56 and 58 will be inactive; (5) and the core of the reactor vessel will heat the water in the interior compartment thereof so that steam is created and passed to the turbine through steam exhaust pipe 94. The condition responsive actuator 92, upon sensing a predetermined level of pressure or temperature in interior compartment 38, will unlatch the latching means associated with hatch 88, to open hatch 88 thereby creating a temporary pool of water in interior compartment 38 of containment structure 30. The temporary pool of water in interior compartment 38 surrounds reactor vessel 40 to cool reactor vessel 40. Reactor vessel 40 is further cooled by the return pipe 60. As the material in pipe portion 67 is heated by the core of the reactor vessel 40, the material will rise in pipe portion 67 and will pass outwardly through pipe portion 62 and thence downwardly through pipe portion 64. The material in pipe portion 64, as it moves downwardly in pipe portion 64, will be cooled since pipe portion 64 is surrounded by the flood water in interior compartment 38. The cooled material will then pass from the lower end of pipe 64 into the interior compartment 48 of reactor vessel 40. As the cooled material in pipe portion 67 cools the core of the reactor vessel as the material in 67 is heated, the material will rise upwardly through pipe portion 67 and thence again move outwardly through pipe portion 62. The heating and cooling of the material in return pipe 60 causes a continual flow of the material through the heat exchanger system created by return pipe 60. The return pipe 68 functions similarly to return pipe 60 except that return pipe 68 is an open return system rather than a dosed loop system as is pipe 60. Steam from interior compartment 48 exits outwardly therefrom by way of pipe portion 70. The steam then passes downwardly through pipe portion 72 which is cooled by the flood water in interior compartment 38. As the steam moves downwardly in pipe portion 72, it is cooled and turns to liquid, with the cooled liquid being returned to the interior compartment 48 of reactor vessel 40 to cool the reactor vessel. The water in interior compartment 38 gets hot in this process and evaporates or turns into steam. This heated water has not been in contact with radioactive material. However, to be safe, the steam in interior compartment 38 is vented into chamber 50 and is filtered by the filter material in chamber 50 and is passed to the atmosphere by way of the steam exhaust pipes 52 and 54. This process is continued until the temperature in the reactor vessel 40 comes down. The trigger point set to open hatch 88 will be much lower than the trigger point set to open the hatch 80. In this way, there is no sea water entry into the reactor vessel. In the very unlikely scenario that the above described process is unable to cool the core of the reactor vessel 40, and the temperature in the reactor vessel rises, the trigger point to open the hatch 80 would become operational (at the upper safety margins). When water enters reactor vessel, it will evaporate and steam goes into steam exhaust pipe 70 and to the turbine. By opening valve 98, steam passes into the vent chamber 50 where it is filtered and then vented to the atmosphere by way of steam pipes 52 and 54. The filter material in vent chamber 50 and the venting of the steam thereof functions as a filtered containment venting system. In the event that there is a pipe breakage or leakage in pipe 94 downstream of the reactor, valve 97 may be closed and valve 98 opened so that the steam from the upper end of interior compartment will be vented through pipe 96 and passed through the filter material in vent chamber 50 and thence to the atmosphere by way of steam exhaust pipes 56 and 58. Although the foregoing description explains the hatches and the actuation of those hatches in detail, it should be noted that the hatches could be opened by means other than that shown. For example, the hatches could be operated by electrical means or by other mechanical means. Further, the barge could be submerged so that the bottom thereof rests on the floor of the body of water. In that case, the hatches would be formed in the side of the barge as disclosed in the co-pending application. FIG. 4 illustrates a modified form of the reactor which is of the pebble bed type. In the pebble bed type reactor of FIG. 4, the interior compartment of the containment structure can be flooded so that the fluid filled closed-loop heat exchanger 60 will be cooled by the water in the interior compartment of the containment structure upon the interior compartment being flooded by way of the water passageway and hatch being opened. Thus it can be seen that the invention accomplishes at least all of its stated objectives. Although the invention has been described in language that is specific to certain structures and methodological steps, it is to be understood that the invention defined in the appended claims is not necessarily limited to the specific structures and/or steps described. Rather, the specific aspects and steps are described as forms of implementing the claimed invention. Since many embodiments of the invention can be practiced without departing from the spirit and scope of the invention, the invention resides in the claims hereinafter appended.
	summary
048636380	abstract	A process for containment of hazardous waste is disclosed including initially encasing the waste material into a plurality of containment vessels each of which includes a coding on the exterior thereof to indicate the type of hazardous waste therein retained. The containment vessels are then secured with respect to one another into a grouping of 2 to 8 such vessels. The grouping is then entombed within a plastic casing to further prevent leaking of hazardous waste material outwardly from the vessels. Finally a handling device is attached with respect to the plastic casing to facilitate movement thereof. The individual containment vessels preferably are metal cylindrical drums and can be lead lined to facilitate retaining of low level radioactive waste therein. Preferably the grouping of containment vessels are banded together with steel banding. A support means may be included secured to the lower surface of the plastic casing such as a plurality of cylindrically shaped support legs to facilitate stability of the plastic casing after placement thereof. Preferably the casing support and the handling device is biodegradable and the plastic casing is seamless.
	description	The present description relates generally to systems for and methods of attenuating radiation during radiographic imaging of an object. More particularly, the present description relates to systems for and methods of shielding the object and/or persons near the object from primary and/or secondary radiation during lateral radiographic imaging of the object of a type utilized during kyphoplasty and vertebroplasty procedures, among others. Lateral radiographic imaging refers to radiographic imaging wherein radiation is emitted at a lateral side of an object (e.g., a patient, etc.) and directed through an opposite lateral side of the object for purposes of generating an internal image of the object. Often, in lateral radiographic imaging, the primary radiation beam is emitted in a direction that is relatively horizontal and substantially parallel to a ground surface or a support surface for the object. Such an imaging technique is distinct from the more common imaging technique of emitting radiation into either the front or back of the object and directing it through the other of the front or back of the object in a vertical direction that is substantially perpendicular to the ground surface or the support surface for the object. Several medical procedures utilize lateral radiographic imaging of a patient to visualize and/or monitor the procedure. An example of such a medical procedure is vertebroplasty, sometimes referred to as percutaneous vertebroplasty. Percutaneous vertebroplasty involves the injection of a bone cement or other suitable biomaterial into a vertebral body via a percutaneous route under radiographic imaging guidance (e.g., fluoroscopy, Computed Tomography, etc.). The cement is injected as a semi-liquid substance through a delivery device (e.g., needle, syringe, cannula, etc.) that has been passed into the vertebral body, generally along a transpedicular or posterolateral approach. Percutaneous vertebroplasty is intended to provide structural reinforcement of a vertebral body through injection, by a minimally invasive percutaneous approach, of bone cement into the vertebral body. Percutaneous vertebroplasty can result in increased structural integrity, decreased micromotion at the fracture site and possibly a destruction of pain fibres due to the heat of the bone cement as it polymerizes and sets. Generally, when performing vertebroplasty, the delivery device is passed down the pedicle until it enters the vertebral body and reaches the junction of the anterior and middle thirds. The delivery device must be inserted at a suitable angle and pass through the periosteum, down the pedicle and into the vertebral body. A suitable cement is prepared and injected through the delivery device and into the vertebral body. Guidance of the delivery device and monitoring of the cement injection is provided via a lateral radiographic imaging technique, such as fluoroscopy. The injection is stopped as the cement starts to extend into some unwanted location such as the disc space or towards the posterior quarter of the vertebral body, where the risk of epidural venous filling and hence spinal cord compression is greatest. The injection is also discontinued if adequate vertebral filling is achieved. During a vertebroplasty procedure, medical personnel (e.g., technicians, assistants, nurses, physicians, surgeons, etc.) are often positioned near the patient undergoing the procedure. For example, the procedure usually requires someone (typically the physician) to hold the delivery device in position. This is normally required since the delivery device should be stabilized and oriented in the desired position in order for the intended target to be reached. As such, someone is likely to be positioned near the patient as the patient during the procedure. Medical personnel positioned near the patient during a vertebroplasty procedure are susceptible to radiation since the patient is being irradiated so that the procedure can be monitored. Specifically, medical personnel positioned near the patient are susceptible to exposure to primary beam radiation and scatter radiation. Scatter radiation is a secondary radiation generated when the primary radiation interacts with the object being impinged. Scatter radiation has a frequency range lower than the primary radiation beam and generally moves in a variety of uncontrollable directions. Scatter radiation, like primary radiation, can cause damage to living tissue. The amount of scatter radiation present during a vertebroplasty procedure is increased since the radiographic image is being taken in a lateral (e.g., horizontal relative to a support surface of the patient table, partially lateral or oblique relative to the support surface, etc.) and the primary radiation beam is likely to scatter after impinging a lateral side of the patient, the patient table and/or walls or other objects within the procedure room. As such, known radiation attenuating safeguards, such as table drapes or standard patient shields used during more common radiographic imaging techniques, may not provide the medical personnel with a desired level of protection from the scatter radiation. This issue of scatter radiation is not limited to vertebroplasty procedures, as it becomes an issue for any procedure utilizing lateral radiographic imaging. Thus, there is a need for a radiation attenuation system for and method of shielding an object from primary beam radiation during lateral radiographic imaging of the object. There is also a need for a radiation attenuation system that is configured to shield persons positioned near an object undergoing lateral radiographic imaging from primary beam radiation. There is further a need for a radiation attenuation system that is configured to shield an object or persons positioned near the object undergoing lateral radiographic imaging from scatter radiation. Yet further, there is a need for a radiation attenuation system that is multifunctional so that it can be used effectively with more common radiographic imaging techniques and can also be used effectively with lateral imaging techniques. There is further a need for a radiation attenuation system that is reconfigurable (e.g., positionable, collapsible, adaptable, etc.) so that it can be effectively used in various applications and/or so that it can adapt to changing conditions that may occur during a procedure. There is also a need for a radiation attenuation system that can be easily shipped and/or stored. There is further a need for a radiation attenuation system having a configuration that may reduce the tension or stress experienced by a patient during a radiological procedure. There is further a need for radiation attenuation system addressing these and/or any other need. One exemplary embodiment relates to a radiation attenuation system for attenuating radiation during lateral radiographic imaging of an object. The system includes a first radiation attenuating barrier that is substantially conformable to the object and configured to at least partially cover the object. The first radiation attenuating barrier has a fenestration area defining at least one opening. The system further includes a second radiation attenuating barrier coupled to the first radiation attenuation barrier. The second radiation attenuating barrier is selectively movable between a collapsed position and a generally upright position relative to the first radiation attenuating member. Another exemplary embodiment relates to a shield for attenuating radiation during lateral radiographic imaging of a patient. The shield includes a drape formed of a first radiation attenuating material and substantially conformable to the patient. The drape is configured to at least partially cover a non-target area on the patient. The shield also includes a flap formed of a second radiation attenuating material and coupled to the drape. The flap is supported at a generally upright position relative to the drape. The flap is configured to attenuate scatter radiation during lateral radiographic imaging of the patient. Another exemplary embodiment relates to a method of attenuating radiation during lateral radiographic imaging of a patient. The method includes the step of providing a radiographic device configured to emit a primary radiation beam at a first lateral side of the patient towards a second lateral side of the patient in a direction that is substantially perpendicular to a longitudinal axis of the patient. The method also includes the steps of positioning a first radiation shield at least partially over a non-target area on the patient, aligning a fenestration area of the first radiation shield with a target area on the patient, positioning a second radiation shield at an orientation that is substantially upright relative to the first radiation shield. The first radiation shield is substantially conformable to the patient. The second radiation shield is coupled to the first radiation shield and configured to attenuate scatter radiation during lateral radiographic imaging of the patient. Referring to FIGS. 1 through 11, a radiation attenuation system 20 and components thereof are shown according to exemplary embodiments. Generally, radiation attenuation system 20 includes one or more radiation shields or barriers supported in a manner and at a position that may be useful in attenuating (e.g., blocking, reflecting, absorbing, etc.) primary beam radiation and/or secondary or scatter radiation generated during lateral radiographic imaging of an object (e.g., patient, etc.). For purposes of the present disclosure, the phrase “lateral radiographic imaging,” unless expressly stated otherwise, is used broadly to refer to not only literal lateral imaging of an object (i.e., side-to-side wherein the primary radiation beam is emitted in a horizontal direction that is substantially parallel to a ground surface or a support surface for the object), but also partially lateral or oblique imaging of the object (i.e., wherein the primary radiation beam is emitted at an angle (e.g., 20, 30 or 40 degrees, etc.) relative to a ground surface or a support surface for the object). Radiation attenuation system 20 generally includes a first radiation shield or barrier provided in the form of a cover or drape and a second radiation barrier provided in the form of a supplemental member or flap coupled to the first radiation barrier and extending upwardly from the first radiation barrier. It should be noted that for purposes of this disclosure, the term “coupled” is used broadly to mean the joining or combining of two or more members (e.g., portions, layers, materials, components, etc.) directly or indirectly to one another. Such joining or combining may be relatively stationary (e.g., fixed, etc.) in nature or movable (e.g., adjustable, etc.) in nature. Such joining or combining may be achieved with the two members or the two members and any additional intermediate members being integrally formed as a single unitary body with one another (e.g., one-piece, etc.) or with the two members or the two members and any additional intermediate member being attached to one another. Such joining or combining may be intended to be relatively permanent in nature or alternatively may be intended to be relatively detachable or removable in nature. The first radiation barrier is configured to at least partially cover an area of a patient during a procedure (e.g., a non-target area, etc.), and is intended to protect the patient from unnecessary radiation exposure (both primary beam radiation and scatter radiation) during the procedure. In addition to protecting the patient, the first radiation barrier may also be useful in protecting one or more individuals present during the procedure (e.g., technicians, assistants, nurses, physicians, surgeons, etc.), referred to generally herein as medical personnel. Medical personnel present during the radiographic imaging of the patient may also be susceptible to radiation exposure from the primary radiation beam (e.g., during a fluoroscopy procedure, etc.), but are more likely to be susceptible to radiation exposure from secondary or incidental scatter radiation. The first radiation barrier protects against scatter radiation by absorbing at least a portion of the primary radiation beam and scatter radiation. The first radiation barrier includes a fenestration area which provides medical personnel (typical a physician) with access to an area of interest on the patient (e.g., target area, etc.) through an aperture or opening. During a procedure, a radiographic visualization or imaging device (e.g., fluoroscope, etc.) will likely be positioned such that a radiation emitter of the device is located at a first lateral side of the patient and a corresponding radiation receiver of the device is located at an opposite second lateral side with the fenestration area of the first radiation barrier provided therebetween. One or more medical personnel are likely to be positioned near the patient and, in particular, near the fenestration area during the procedure, and as such, are likely to be positioned in the path of, or closely adjacent to, the primary radiation beam (i.e., between the emitter and receiver) and/or an area likely to be exposed by scatter radiation. To provide further protection against radiation for the patient and/or medical personnel, the second radiation barrier is provided. The second radiation barrier is provided near the fenestration area and extends upwardly from the first radiation barrier. For example, the second radiation barrier may extend upwardly in a direction that is substantially perpendicular to the first radiation barrier and laterally across at least a portion of the first radiation barrier in a direction that is substantially parallel with the primary radiation beam originating at the radiation emitter of the radiographic imaging device. In such a position, the second radiation barrier is positioned between the medical personnel attending to the fenestration area and the primary radiation beam (and/or scatter radiation). According to an exemplary embodiment, the second radiation barrier is selectively movable (e.g., reconfigurable, adjustable, repositionable, formable, etc.) between a first position (e.g., stowed position, retracted position, collapsed position, flattened position, etc.) and a second position (e.g., use position, upright position, attenuating position, etc.). An example of the first position is shown in FIG. 1, while an example of the second position is shown in FIG. 2. In the first or non-extended position, the second radiation barrier is shown as overlapping a portion of the first radiation barrier and orientated substantially parallel thereto. Such positioning of the second radiation barrier may be useful for shipping and/or storing of radiation attenuation system 20. Such positioning may also allow the radiation attenuation system 20 to be used as a more conventional patient drape or shield (e.g., during a non-lateral radiographic imaging technique, etc.). Configuring the second radiation barrier as a selectively movable member may advantageously provide medical personnel with flexibility during the procedure. For example, while it may be beneficial to use the second radiation barrier throughout a procedure, at certain times the second radiation barrier may interfere with one or more medical personnel and/or for various reasons become unneeded. Further, it may be desirable to change the orientation and/or positioning of the second radiation barrier in the extended position to precisely position it response to the position of the medical personnel. By providing a second radiation barrier that is selectively movable, medical personnel can control when the second radiation barrier is used and, if used, the position of it during use (e.g., height, angle, etc.). The second radiation barrier is also self-supportive in the extended position, meaning that medical personnel does not have to hold the second radiation barrier in the desired position in order to retain it in this position. As detailed below, the second radiation barrier may be supported by a support structure fixedly coupled between the first radiation barrier and the second radiation barrier (e.g., one or more adjustable bands, etc.), by a support structure removably coupled to the second radiation barrier (e.g., an L-shaped bracket, etc.), or by any other suitable support technique. The “self-supportive” feature may advantageously allow the medical personnel to conduct other tasks during the procedure and/or may eliminate the number medical personnel required around the patient. It should be noted that while the exemplary embodiments are described and illustrated herein as a radiation attenuation system for shielding medical personnel (and possibly the patient) during lateral radiographic imaging of the patient, the radiation attenuation system may be configured to shield medical personnel (and possibly the patient) during any radiological procedure. For example, radiation attenuation system 20 is suitable for use with diagnostic procedures (i.e., procedures allowing non-invasive examination or investigation of a patient such as x-ray examinations, Computed Tomography scanning procedures, or the like), therapeutic procedures (i.e., procedures wherein anatomical regions of a patient are irradiated as a treatment), and/or various invasive procedures in addition to those mentioned herein. Also, radiation attenuation system 20 may be used regardless of the position of the patient. For example, the patient may be provided in a supine position wherein the patient is positioned on his or her back with the legs of the patient being straight or bent, a prone position wherein the patient is positioned face down, and/or a lateral position wherein the patient is positioned on one side. With a patient in the lateral position, lateral radiological imaging of the patient, as that phrase is defined herein, would involve emitting the primary radiation beam towards the front or back of the patient. Further still, radiation attenuation system 20 is suitable for use with procedures other than kyphoplasty and vertebroplasty, wherein lateral radiographic imaging is utilized for visualization and/or monitoring of the procedure. For example, radiation attenuation system 20 may be used during various pain management procedures (such as spinal procedures) and can be used during any procedure wherein it would be beneficial to use a radiation attenuation system having a selectively movable flap. FIG. 1 is a top planar view showing radiation attenuation system 20 according to an exemplary embodiment and in a relatively flattened or non-extended position. Radiation attenuation system 20 generally comprises a first radiation shield (e.g., primary barrier, patient shield, cover, blanket, etc.), shown as a drape 30, and a second radiation shield (e.g., scatter radiation barrier, supplemental member, etc.), shown as a flap 50, coupled to drape 30. Drape 30 is shown in the form of a rectangular or rectilinear member configured to be placed over an area of a patient undergoing the procedure or otherwise susceptible to unnecessary radiation exposure (e.g., a non-target area, etc.). Drape 30 is defined by a first lateral side edge, shown as a right edge 32, a second lateral side edge, shown as a left edge 34, an upper lateral edge, shown as a top edge 36, and a lower lateral edge, shown as a bottom edge 38. Right edge 32, left edge 34, top edge 36 and bottom edge 38 are all shown as continuous linear edges, but alternatively, may be curvilinear edges or discontinuous edges having both linear and curvilinear portions. For example, drape 30 may be contoured to conform to various portions of a patient and/or to better drape over a patient in the areas for which shielding is sought. By way of example only, top edge 36 may include a curvilinear cutout portion configured to receive the neck of a patient when drape 30 is positioned over the patient. The size, shape, and configuration of drape 30 may be provided in any number of forms depending on various design criteria such as type of procedure, typical size of patient, type of radiographic imaging device being used, etc. Drape 30 could be of sufficient width and length to span entirely across the patient and a patient table, or alternatively could be configured only span across a portion of the patient. According to an exemplar embodiment, drape 30 is sized to cover a substantial portion of the patient, with top edge 36 intended to be positioned near the head of the patient, bottom edge 38 intended to be positioned near the feet of the patient, right edge 32 intended to drape over the left side of the patient, and left edge 34 intended to drape over the right side of the patient. Drape 30 is characterized by an ability to attenuate radiation while possessing the ability to be relatively lightweight and highly conformable to the patient. Drape 30 includes one or more radiation attenuating members (e.g., sheets, films, pads, inserts, etc.) made of a radiation attenuating material. These radiation attenuating members may span across the entire drape 30, or alternatively, may be provided in certain key areas on drape 30 (e.g., areas likely to cover non-target areas on the patient that are susceptible to radiation exposure, etc.). According to an exemplary embodiment, the radiation attenuating material is generally light and flexible to maximize workability for bending, folding, reconfiguring, etc., or otherwise manipulating drape 30. The attenuating material may be formable (e.g., deformable) or compliant, and/or relatively “stretchable” (e.g., elastic). According to alternative embodiments, the attenuating material used may be generally rigid and inflexible, and/or substantially weighted. According to an exemplary embodiment, the compliant nature of the radiation attenuating member allows drape 30 to reside closely next to the body of the patient. Drape 30 is comfortable and fits positively against the undulating surface of the patient thus improving its stability during the procedure. The coefficient of friction between drape 30 and the surface of the patient may add to that stability, preventing movement of drape 30 during the procedure and further obviating the need to take extraordinary measures to prevent slippage or movement of drape 30. The radiation attenuating member may be fabricated of any radiation attenuation material including, but not limited to, bismuth, barium, lead, tungsten, antimony, copper tin, aluminum, iron, iodine, cadmium, mercury, silver, nickel, zinc, thallium, tantalum, tellurium, and uranium. Anyone of the aforementioned radiation attenuation materials alone or in a combination of two or more of the radiation attenuation materials may provide the desired level of radiation attenuation. According to an exemplary embodiment, the radiation attenuating material is comprised of a polymeric matrix charged with an attenuating filler. Examples of suitable radiation attenuation materials are disclosed in U.S. Pat. No. 4,938,233, entitled “Radiation Shield,” and U.S. Pat. No. 6,674,087, entitled “Radiation Attenuation System,” both of which are hereby incorporated by reference in their entirety. It should be noted that the radiation attenuating member is not limited to such radiation attenuating materials, and according to the various alternative embodiments, may be formed of any suitable radiation attenuating material including more conventional attenuating materials (e.g., lead-based materials, etc.). The radiation transmission attenuation factor of the radiation attenuating member may vary depending upon the intended application of radiation attenuation system 20 and/or the number of layers of the attenuating members is provided. According to one exemplary embodiment, the radiation attenuating member has a radiation transmission attenuation factor of a percent (%) greater than about 50%, suitably greater than about 75%, suitably greater than about 90%, suitably greater than about 95% (with reference to a 90 kVp x-ray beam). According to various alternative embodiments, radiation attenuating member may have a radiation transmission attenuation factor of a percent less that 50% such as 10-50% or 10-20%. The radiation attenuating member may also at least partially attenuate gamma rays, and may have a gamma ray attenuation factor of at least 10% of a 140 keV gamma radiation source. Referring further to FIG. 1, drape 30 is further shown as including a fenestration area defined by one or more apertures (e.g., slits, missing portions, keyway, cut-out, etc.), shown as an opening 40. Opening 40 provides an entry point to an area of interest on the patient (e.g., target area, etc.) for conducting various invasive procedures, such as fluoroscopic guidance and/or manipulation of instruments during exploratory or surgical procedures. According to an exemplary embodiment, opening 40 is located at a position on drape 30 that provides medical personnel with relatively unobstructed access to the spine of a patient. Such positioning of opening 40 may be useful during a variety of spinal procedures such as a vertebroplasty procedure. In such an example, opening 40 is sized to receive a delivery device used in the vertebroplasty procedure to deliver cement to a vertebral body. Opening 40 of the fenestration area is shown as being a rectangular opening having a width 42 that is between approximately 2 inches and approximately 8 inches and a length 44 that is between approximately 4 inches and approximately 18 inches. According to one exemplary embodiment, opening 40 has a width 42 of approximately 4 inches and a length 44 of approximately 9 inches. According to the various exemplary embodiments, opening 40 may have any of a variety of shapes (e.g., circular, triangular, non-uniform, square, etc.) provided in any of a number of sizes. For example, opening 40 may be tapered at one or more ends to further limit the amount of the patient that is exposed to radiation. Drape 30 further includes a covering 46 disposed about or containing the radiation attenuating member. Covering 46 may enhance processability, provide softness or comfort to a patient, and/or may allow radiation attenuation system 20 to be more easily cleaned and/or sanitized. Covering 46 is preferably made of a fabric material such as that of a surgical drape, but can also be made of a non-fabric material such as a plastic sheet, non-woven paper material, or any other material suitable for covering the radiation attenuating member. According to an exemplary embodiment, covering 46 is constructed from a front sheet and a back sheet which are coupled together at the periphery to enclose the radiation attenuating member. Covering 46 may be configured so that it permanently encloses the radiation attenuating member, or alternatively may be configured so that the radiation attenuating member may be selectively removed. According to an alternative embodiment, drape 30 may include a radiation attenuating member that is not enclosed by a covering 46. According to another alternative embodiment, drape 30 may include a covering 46 that is integrally formed with a radiation attenuating member. Referring still further to FIG. 1, radiation attenuation system 20 is also shown as including flap 50 and a corresponding support structure (e.g., frame, etc.), shown as a plurality of support members 60, which are used to provide rigidity to flap 50 and/or to support or move flap 50 to the extended position. According to the embodiment illustrated, flap 50 is a substantially rectangular member having a width 52 that is between approximately 6 inches and approximately 20 inches and a length 54 that is between approximately 6 inches and approximately 30 inches. According to one exemplary embodiment, flap 50 has a width 52 of approximately 11 inches and a length 54 of approximately 14 inches. According to the various exemplary embodiments, flap 50 may have any of a variety of shapes (e.g., circular, triangular, non-uniform, square, etc.) provided in any of a number of sizes. Like drape 30, flap 50 includes one or more radiation attenuating members (e.g., sheets, films, pads, inserts, etc.) made of a radiation attenuating material. According to an exemplary embodiment, flap 50 is formed of the same radiation attenuating material forming drape 30. As such, flap 50 is generally light and flexible member capable of being bent, folded, reconfigured, etc., or otherwise manipulated. In addition, like drape 30, flap 50 may include a covering which encloses or encapsulates at least a portion of the radiation attenuating member. Flap 50 is coupled to drape 50 and includes a first region 56 that is intended to be coupled to drape 30 and a second region 58 that is configured to be movable relative to drape 30. Flap 50 may be coupled to drape 30 using any known or otherwise suitable technique. For example, flap 50 may be coupled to drape 30 using mechanical fasteners (hook and loop fasteners, grommets, pins, snaps, clips, etc.), adhesives, welding, bonding, fusing, stitching, etc. According to an exemplary embodiment, first region of flap 50 is glued to a top or outer surface of drape 30 using a relatively permanent adhesive. A fold line 62, spanning the width of flap 50, functionally separates first region 56 from second region 58. Fold line 62 constitutes the location on flap 50 wherein second region 58 can move relative to first region 56 and/or drape 30. Fold line 62 may be defined, at least in part, by the technique used to couple flap 50 to drape 30 (e.g., a glue seam, a stitched edge, etc.) and/or the support structure detailed below. According to the embodiment illustrated, fold line 62 is orientated to be substantially parallel to the intended path of the primary radiation beam emitted during lateral radiographic imaging of the patient. According to the various alternative embodiments, fold line 62 may extend at any orientation relative to the likely path of the primary radiation beam (e.g., 45 degrees, 90 degrees, etc.). Further, while fold line 62 is shown as a substantially continuous linear line, this line may have a curvilinear configuration, a combination of linear and curvilinear segments, or any other suitable configuration. Flap 50 may be located at any of a number of positions relative to drape 30, but is preferably positioned where the medical personnel conducting the procedure is likely to be positioned. According to the embodiment illustrated, flap 50 is positioned near the fenestration area such that fold line 62 of flap 50 is adjacent and parallel with a lower edge of opening 40, and an outer side edge of flap 50 is adjacent and parallel to a side edge of opening 40. According to an exemplary embodiment, flap 50 is configured to move between the first or non-extended position (shown in FIG. 1) and a second or extended position (shown in FIG. 2). Configuring flap 50 as a member that can be substantially flattened or collapsed may facilitate more efficient shipping and/or storing of radiation attenuation system 20. In the first position, flap 50 is shown as overlapping a portion of drape 30. Further, configuring flap 50 as a member that can be substantially flattened or collapsed may increase the usefulness of radiation attenuation system 20 by allowing it to be used in other radiological procedures for which is may be unnecessary or otherwise undesirable to make use of an auxiliary radiation shield extending outwardly from a primary radiation shield. To facilitate the movement of flap 50 relative to drape 30, to support flap 50 in the extended position, and/or to otherwise provide rigidity to flap 50, one or more support members 60 are provided. Support members 60 allow flap 50 to be self-supportive. According to the embodiment illustrated, support members 60 are malleable (e.g., adjustable, flexible, impressible, pliable, etc.) members that can be configured and reconfigured with minimal effort by medical personnel so that flap 50 can be selectively arranged in a position that is desirable for the particular procedure being conducted or for the particular preferences of person conducting the procedure. Support members 60 can also be selectively reconfigured throughout the procedure to accommodate changes dictated by the procedure, the medical personnel, and/or the patient, etc. For example, it may be desirable to start a procedure with flap 50 in a position that is substantially perpendicular to drape 30 and later move (e.g., bend, shape, etc.) it to an orientation wherein flap 50 is partially collapsed so that it does not substantially interfere with the particular radiological procedure. According to an exemplary embodiment, support members 60 are strips or bands that can be folded or bent into any of a number of positions and can then be returned to a substantially flattened positioned for storage and/or disposal of radiation attenuation system 20. The strips or bands may be formed of metal, plastic, or any other suitable material. According to various alternative embodiments, support members 60 may be provided by a variety of know or otherwise suitable components that can support radiation attenuation system 20 in the in-use position. For example, support members 60 may be generally rigid and inflexible members which have been set in a non-adjustable in-use position. Alternatively, support members 60 may be generally rigid and inflexible members coupled to each other at one or more hinges which allow for the selective movement of flap 50 between the flattened position and the extended position. According to a further alternative embodiment, support members may be unnecessary if flap 50 (e.g., cover 42, etc.) is formed of a material that can sufficiently support radiation attenuation system 20 in the in-use position without requiring additional support. Referring further still to FIG. 1, radiation attenuation system 20 is shown as having three support members 60 spaced apart laterally and extending in a longitudinal direction relative to drape 30 and a fourth support member 60 extending in a lateral direction relative to drape 30 and the other support members 60. The longitudinal support members 60 are shown extending between first region 56 and second region 58 of flap 50. According to an alternative embodiment, separate support members 60 may be provided for first region 56 and second region 58 and those separate support members may be coupled to each other using a suitable technique (e.g., a hinge, etc.). The lateral support member 60 may extend over all of the lateral support members 60 (as shown) or alternatively may extend only partially therebetween. Support members 60 are shown as being provided along a back surface of flap 50, by alternatively may be sandwiched between layers of the radiation attenuating material and/or covering. Support members 60 may be coupled to each other and/or portions of flap 50 using any of a variety of known or otherwise suitable techniques including, but not limited to, mechanical fasteners (e.g., hook and loop, clips, snaps, etc.), adhesives, welding, bonding, fusing, stitching, etc. FIG. 2 is a perspective view showing radiation attenuation system 20 in the extended position. As illustrated, flap 50 has been selectively reconfigured so that it is substantially perpendicular to at least a portion of drape 30. Such a position is obtained by manipulating (e.g., bending, shaping, etc.) support members 60 until the desired position is achieved. It should be noted that flap 50 can be supported at positions other than a substantially perpendicular position while in the extended position. Specifically, flap 50 is configured to be retained at a variety of extended or generally upright positions. For purposes of this disclosure, the phrase “generally upright” is used broadly to define any extended position in which flap 50 may be moved to that is suitable for shielding medical personnel and/or a patient. Design criteria and application parameters may affect the definition of “generally upright.” For example, “generally upright” may describe flaps that have a linear and/or a non-linear trajectories, that extend outward and/or upward in a substantially vertical direction, and/or that extend outward and/or upward at any angle ranging from approximately 0 degrees to approximately 180 degrees. Accordingly, all such definitions of “generally upright” are included in the scope of the appended claims. FIGS. 4 through 7 are perspective views showing radiation attenuation system 20 being used with a patient P who is positioned on a patient support structure, shown as a patient table 100. Referring to FIGS. 4 and 5 in particular, drape 30 is shown as being disposed about patient P in manner and at a position intended to reduce the amount of scatter radiation received by certain non-target areas on patient P during a radiological procedure and so that the fenestration area, specifically opening 40, is positioned over the area of interest on patient P. In these FIGURES, flap 50 is shown in a flattened positioned wherein flap 50 is collapsed onto drape 30 and lying substantially parallel thereto. A fluoroscope is shown having a radiation emitter provided at a first lateral side of patient table 100 and a radiation receiver provided at a second lateral side of patient table 100. The fluoroscope is positioned such that it will emit a primary radiation beam in a relatively horizontal direction through patient P between the radiation emitter and the radiation receiver. Referring to next to FIGS. 6 and 7, flap 50 is shown in a generally upright position. As illustrated, flap 50 is substantially perpendicular to drape 30 and patient P. Flap 50 has been folded about fold line 62 which is positioned substantially parallel to the intended path of the primary radiation beam. The method of using radiation attenuation system 20 is described herein with reference to FIGS. 4 through 7 and with reference to a vertebroplasty procedure. Prior to the vertebroplasty procedure a member of the medical personnel obtains radiation attenuation system 20. When first obtained, radiation attenuation system 20 is likely to have flap 50 in a relatively flattened or non-extended position. The medical personnel then places drape portion over patient P, with the side of drape 30 having flap 50 facing outward and/or upward, and aligns opening 40 so that it is over the area of interest on patient P (i.e., the target area). For the vertebroplasty procedure, wherein patient P is likely to being lying on his or her stomach, opening 40 is provided near the spine of patient P. The medical personnel then selectively moves (e.g., adjusts, reconfigures, etc.) flap 50 relative to drape 30 into a generally upright position by manipulating support members 60 until a desirable position for flap 50 is achieved. As illustrated, this position may be approximately 90 degrees relative to drape 30. During the vertebroplasty procedure, medical personnel standing near patient P inserts a delivery device (e.g., needle, syringe, cannula, etc.) into the pedicle until it enters the vertebral body and reaches the junction of the anterior and middle thirds. Movement of the delivery device is monitored by lateral radiographic imaging provided via fluoroscopy. The primary radiation beam is applied through patient P to generate the guidance images for the medical personnel. As the primary radiation beam is applied to patient P, scatter radiation is generated due to the interaction of the primary beam with patient P, patient table 100, and/or any other object in the path of the primary radiation beam. The scatter radiation tends to be directed in all directions. Drape 30 shields certain non-target areas on patient P from this scatter radiation, while flap 50 shields medical personnel from the scatter radiation. Medical personnel assisting during the procedure may selectively adjust/reconfigure the positioning of flap 50 to provide more effective shielding and/or to prevent flap 50 from interfering with the range of movement of the medical personnel conducting the procedure. Once the delivery device is in position, a cement is prepared and injected through the delivery device and into the vertebral body. Monitoring of the cement injection is also provided via lateral radiographic imaging. Referring next to FIG. 8, radiation attenuation system 20 is shown according to another exemplary embodiment. Radiation attenuation system 20 of FIG. 8 is similar to radiation attenuation system 20 of FIGS. 1 through 7, but is shown as including a flap 50 that is detachably coupled to drape 30. The detachable coupling of flap 50 may be provided by any of a number of techniques. According to an exemplary embodiment, a first component of a hook and loop fastener is provided along fold line 62 of flap 50 and a corresponding second component 48 of the hook and loop fastener is provided on drape 30. According to the various alternative embodiments, more than one corresponding second component may be provided about drape 30, and may be provided at more than one orientation. Such an embodiment would accommodate a variety of scenarios wherein it may be desirable to relocate flap 50 relative to drape 30. Referring to FIG. 9, radiation attenuation system 20 is shown according to another exemplary embodiment. Radiation attenuation system 20 of FIG. 9 is similar to radiation attenuation system 20 of FIGS. 1 through 7, but is shown as including a more than one flap 50. Use of multiple flaps 50 may not only provide further shielding for medical personnel, but may also provide shielding for the patient. For example, as illustrated, flap 50 is positioned as it is in the exemplary embodiment illustrated in FIGS. 1 through 7, and a second flap 50′ is provided on drape 30. Second flap 50′ is positioned near the top of drape 30 and may be useful for at least partially protecting the head of the patient from scatter radiation. Like flap 50, second flap 50′ is intended to be manipulated and is configured to move between a generally flattened and a generally upright position. Referring to FIG. 10, radiation attenuation system 20 is shown according to another exemplary embodiment. Radiation attenuation system 20 of FIG. 10 is similar to radiation attenuation system 20 of FIGS. 1 through 7, but is shown as having a flap 50 with a fold line 62 that is provided at an orientation that is likely to be angled relative to a path of a primary radiation beam during lateral imaging of a patient. For example, fold line 62 and the path of the primary radiation beam may create an angle that is between approximately 0 degrees and approximately 90 degrees, and more particularly between approximately 20 degrees and approximately 60 degrees. According to the various alternative embodiments, fold line 62 may be curvilinear or partially curvilinear. Referring to FIG. 11, which is a cross-sectional view of a patient P, radiation attenuation system 20 is shown according to another exemplary embodiment. Radiation attenuation system 20 of FIG. 11 is similar to radiation attenuation system 20 of FIGS. 1 through 7, but utilizes a separate support frame, shown as a support bracket 70 to support flap 50 in the generally upright position. According to the embodiment illustrated, bracket 70 is a substantially rigid, L-shaped bracket having a first portion 72 (e.g., a first leg, horizontal segment, etc.) configured to be positioned under a patient cushion 80 on a patient table and a second portion 74 (e.g., second leg, vertical segment, etc.) configured to support flap 50 in the extended or open position. Bracket 70 may be selectively added to radiation attenuation system 20 when in it is desirable to utilize flap 50 in an upright position. When use of flap 50 is not required or undesirable, bracket 70 can be removed from radiation attenuation system 20 and stowed in a convenient location (e.g., cabinet, etc.). According to the embodiment illustrated, flap 50 is provided in a generally upright position wherein flap 50 extends outward at a lateral side of the patient to shield medical personnel. To support flap 50 in the generally upright position, flap 50 is coupled to the second portion 74 of bracket 70. In order to maintain a sterile field during the radiological procedure, a cover, such as a sterile bag or wrap, can be applied to bracket 70. Flap 50 may be coupled to bracket 70, and/or to a sterile cover applied to bracket 70, using any of a variety of fastening techniques mentioned throughout this disclosure or any other suitable technique. Bracket 70 may have any of a number of shapes which allow flap 50 to be supported at any of a number of positions. For any of the embodiments described herein, one or more of the components of radiation attenuation system 20 (e.g., drape 30, flap 50, etc.) may be generally disposable in whole or in part, thereby minimizing ancillary sources of contamination that may arise from multiple uses. According to another suitable embodiment, one or more of the components of radiation attenuation system 20 are generally non-toxic, recyclable, and/or biodegradable. According to an alternative embodiment, one or more of the components of radiation attenuation system 20 may be reusable. According to a preferred embodiment, one or more of the components of radiation attenuation system 20 may be sterilized between uses to minimize the likelihood of bacteriological or virus contamination. Sterilization may be performed in any convenient manner, including gas sterilization and irradiation sterilization. It is important to note that the construction and arrangement of the elements of the radiation attenuation system as shown in the illustrated embodiments is illustrative only. Although only a few embodiments of the present inventions have been described in detail in this disclosure, those skilled in the art who review this disclosure will readily appreciate that many modifications are possible (e.g., variations in sizes, dimensions, structures, shapes and proportions of the various elements, values of parameters, mounting arrangements, use of materials, colors, orientations, etc.) without materially departing from the novel teachings and advantages of the subject matter recited. For example, elements shown as integrally formed may be constructed of multiple parts or elements shown as multiple parts may be integrally formed, the operation of the interfaces may be reversed or otherwise varied, or the length or width of the structures and/or members or connectors or other elements of the system may be varied. It should be noted that the elements and/or assemblies of the system may be constructed from any of a wide variety of materials that provide sufficient strength or durability, in any of a wide variety of colors, textures and combinations. For example, the radiation attenuation material may be a relatively flexible material, or alternatively, may be a relatively rigid material. Further, drape 30 may not include the fenestration area if drape 30 is not going to be used for invasive procedures. Further, while lateral radiographic imaging is used above with reference to a primary radiation beam that is generally parallel to a patient table, the angle at which the primary radiation beam may emitted relative to a patient table during lateral radiographic imaging may be up to approximately 45 degrees (or any other degree of obliquity) relative to the patient table. Accordingly, all such modifications are intended to be included within the scope of the present inventions. Other substitutions, modifications, changes and omissions may be made in the design, operating conditions and arrangement of the preferred and other exemplary embodiments without departing from the spirit of the present inventions. The order or sequence of any process or method steps may be varied or re-sequenced according to alternative embodiments. In the claims, any means-plus-function clause is intended to cover the structures described herein as performing the recited function and not only structural equivalents but also equivalent structures. Other substitutions, modifications, changes and omissions may be made in the design, operating configuration and arrangement of the preferred and other exemplary embodiments without departing from the spirit of the inventions as expressed in the appended claims.
	abstract	A method for treating nuclear sludge comprising subjecting the nuclear sludge to a plasma treatment in a plasma chamber to melt at least some of the inorganic components of the sludge, wherein the plasma chamber comprises a crucible having a cooled inner surface, this surface cooled sufficiently such that the inorganic components in contact with the inner surface are in a solid state and form a barrier between the part of surface of the crucible with which they are in contact and the molten inorganic components of the sludge.
056152450	summary	BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a spectroscope which is installed in an X-ray beam line using an undulator as a light source in high luminance radiant beam facilities for synchrotron, and particularly to a monochromator for radiant X-rays which is used as part of apparatus for X-ray analysis of structure and material evaluation. 2. Prior Art According to a conventional monochromator, as shown in FIG. 14, one surface of a plate-like monochromator or a plate crystal serves as a reflecting surface, and another surface serves as a cooling surface. The reflecting surface is heated, and the cooling surface is cooled by a cooling material or a coolant such as water or liquid metal. In a certain type of monochromator, the cooling surface is finned or processed likewise so as to increase a cooling efficiency. However, in such plate type monochromators, heat applied to the reflecting surface causes stress deformation, and thus the surface of a crystal thermally deforms with a resultant problem of the scattering of emissive X-rays. FIG. 1 shows typical thermal deformations of a monochromator crystal. As shown in FIG. 1(a), when the entire surface of the plate crystal is irradiated with incident X-rays and thus heated uniformly and also when the other surface is cooled, only a grating constant expands uniformly, while planes of atoms remain uninclined. Thus, a uniform expansion (lattice expansion) occurs in which an expansion reduces as it goes downward. In this case, a warp (bowing) (FIG. 1(c)) occurs with the heated surface being convexed. If a local zone is irradiated, only the irradiated portion swells like a knot or a bump (FIG. 1(b)). These thermal deformations of a plate crystal cause a pencil of emissive X-rays to diverge as represented with E' and E" when the surface of a crystal is irradiated with a parallel pencil of incident X-rays. That is, X-rays are reflected in nonparallel, causing a marked deterioration in spectroscopic performance (energy resolution and intensity) of X-rays. Particularly, in designing a beam line in high-luminance radiant beam facilities most of which are occupied by an insertion light source, the aforesaid thermal deformation of a crystal is a most serious problem. Various devices have been adopted, but most of them are intended to physically improve a cooling capability. A monochromator with practical specifications has not been obtained yet. Too much emphasis is rather placed on an improvement of cooling capability, leading to a problem of instability at a lower accuracy, difficulty in use, higher costs, complicated maintenance and the like. FIG. 2 shows an inclined crystal monochromator which has been developed for use with APS, U.S.A. (Advanced Photon Source, U.S.A.; energy 7.0 GeV; characteristic photon energy 19.0 KeV; 34 beam lines +.alpha.; circumferential length 1104 m). An angle between incident X-rays and lattice planes can never be changed, but the surface of a crystal can have an arbitrary angle. As shown in FIG. 2, (111) lattice planes (crystallographic planes related to spectroscopy) of a single crystal of silicon are laid horizontally, and the single crystal is cut at an angle of near 90 degrees from crystallographic planes to obtain an inclined surface. When X-rays impinge on the inclined surface, their shadow is cast long thereon, and thus a heat flux per unit area becomes smaller, whereby generated heat can be reduced. This means that the shadow should be cast long so as to reduce generated heat, denoting a need for a large crystal. FIG. 3 shows measurements of a ratio of an irradiated area on the surface of a crystal to the orthogonal cross-sectional area of a beam as an angle of inclination of a crystal from incident X-rays is varied. As seen from FIG. 3, as the angle of inclination increases, the ratio increases. That is, as the angle of inclination of a crystal from a pencil of incident X-rays increases, an area of shadow of incident X-rays expands on the surface of a crystal, whereby a heat flux per unit area reduces. Also, in this geometry, a direction of thermal deformation mostly falls on crystallographic planes of a crystal, thereby producing an advantage that lattice planes related to diffraction are free from large distortion. However, in spite of these advantages, the inclined crystal monochromator is said to have the following disadvantages: (1) a large crystal needs to be used so as to reduce generated heat; (2) adjustment is difficult to make (an adjustment error is greatly amplified); and (3) a fluctuation in the position of an incident beam causes instability of the position of an emissive beam. Thus, problems with respect to practical use remain to be solved. SUMMARY OF THE INVENTION An object of the present invention is to provide a monochromator for radiant X-rays which minimizes a thermal deformation of a crystal, thereby overcoming the aforesaid difficulties involved in conventional apparatus; it also solves the problems with respect to practical use. Specifically, an object of the present invention is to provide a monochromator for radiant X-rays which uses a small crystal and minimizes thermal deformation of the crystal by increasing the cooling capability, allows easy adjustment, suppresses a fluctuation in the position of a pencil of incident X-rays, provides a stable pencil of emissive X-rays, i.e., useful light at high accuracy, is easy to use and economical, and allows easy maintenance. In accordance with the present invention, X-rays which are emitted from an X-ray source and enter a first crystal are called incident X-rays (or incident beam), X-rays which reflect from the first crystal and enter a second crystal are called reflected X-rays (or reflected beam), and X-rays (monochromatic X-rays) which exit the second crystal are called emissive X-rays (or emissive beam). A monochromator for radiant X-rays of the present invention is characterized by comprising a first crystal which has a surface of incidence having a shape of a concave letter V-shaped groove and cooling means for flowing a cooling material behind the surface of incidence along the letter V-shaped groove, and a second crystal which has a letter V-shaped convex having a convex letter V-shape to fit the concave letter V-shaped groove. The bottom portion of the concave letter V-shaped groove of the first crystal, i.e., a most acute-angled portion is largest in terms of the volume of a pencil of incident X-rays. As a result, the center of heat generation (i.e., the portion which receives the most intense heat, or an intensely heated zone) is formed at the bottom portion. In the first crystal, inclined surfaces of the letter V-shaped groove surround the periphery of the center of heat generation, and thus a lattice distortion due to a thermal deformation can be suppressed by the peripheral volume of the crystal. A pencil of radiant X-rays which has impinged on the concave letter V-shaped groove of the first crystal reflects therefrom, and thus reflected X-rays impinge on the letter V-shaped convex of the second crystal. The reflected X-rays are rearranged on the second crystal to the same size as that of a pencil of incident X-rays. Thus rearranged X-rays exit the second crystal as a pencil of emissive X-rays. Accordingly, to accurately obtain a pencil of emissive X-rays, it is preferable that the first and second crystals be set within a slight range of error. Specifically, it is most preferable that the bottom portion of the concave letter V-shaped groove of the first crystal and the letter V-shaped convex of the second crystal align with each other along a centerline. However, a deviation of 0.01 mm or less is acceptable between them. The aforesaid cooling means is provided behind the surface of incidence along the letter V-shaped groove so as to promote thermal diffusion within the first crystal. Preferably, the cooling means is provided behind the surface of incidence along the letter V-shaped groove with a starting point thereof located just under the center of heat generation. More preferably, a transport pipe is directed toward the intensely heated zone from the bottom portion of the fist crystal, branches off in opposite directions with a starting point thereof located just under the center of heat generation, and allows the cooling material to flow behind the surface of incidence along the letter V-shaped groove. Stainless steel or Teflon (registered trademark of Dupont) is preferably used as material for the transport pipe in view of heat resistance and pressure resistance and so as to use as the cooling material water and/or liquid metal such as liquid gallium or the like having high cooling efficiency. The operations of the above-mentioned structure will be described below. (1) As X-rays impinge on an inclined surface of a letter V-shaped groove, the shade of X-rays can elongate on a surface of incidence, whereby a heat flux can be made smaller. (2) Unlike conventional inclined crystal monochromators having one inclined surface, two inclined surfaces which form a letter V-shape are provided, whereby a size in a longitudinal direction can be reduced (half the size of conventional inclined crystal monochromators). (3) A heat flux is intensest at the bottom portion of a letter V-shaped groove to form the center of heat generation. However, heat generated at the center of heat generation diffuses radially along the peripheral inclined surfaces of the letter V-shaped groove and toward the inside of a crystal underneath the groove, whereby the diffusion of heat is promoted within the crystal. (4) Since a crystal surrounds the center of heat generation, generated thermal stresses cancel each other, whereby a distortion of the crystal due to heat (thermal deformation) can be suppressed. (5) Cooling means is provided behind a surface of incidence along the letter V-shaped groove, whereby heat whose generation is caused by incident X-rays can be cooled efficiently. (6) When cooling means is in the form of a transport pipe formed of stainless steel or Teflon, as cooling material water and/or liquid metal such as liquid gallium or the like can be used intact. (7) By adopting the letter V-shaped groove which allows generated stresses to cancel each other out, a water jet which otherwise is likely to cause a local deformation of a crystal can be used as cooling means.
043269176	claims	1. A method of controlling the power output of a nuclear reactor comprising the steps of: providing a variable average reactor coolant temperature set point having a constant temperature portion and a decreasing temperature portion for controlling the reactor power by control rod movement; providing a control range of average reactor coolant temperatures below said variable temperature set point for controlling the reactor power in response to variable feedwater flow; and switching control between said variable coolant temperature set point and said control range of temperatures whenever a large change in reactor power output is required. providing an output signal indicative of required power output of the reactor; converting said output signal into a reactor coolant temperature signal according to a predetermined function relating required power output to reactor coolant temperature wherein said function provides a substantially constant temperature for the middle range of reactor power output and a range of substantially decreasing temperatures for the high range of reactor power output; providing a signal indicative of actual reactor coolant temperature; comparing said converted output to said signal indicative of actual reactor coolant temperature to establish a control signal thereby; and utilizing said control signal to control the reactor power output. providing a control range of temperatures below said variable temperature converted output signal; and switching control of the reactor from said variable temperature converted set point to said control range of temperatures. preventing reactor control rod movement; and allowing increased feedwater flow to increase reactor power output. 2. A method as set forth in claim 1 wherein said variable temperature set point is a function of reactor power demand. 3. A method as set forth in claim 2 wherein said variable temperature set point is constant over the middle portion of said reactor power demand and is linearly decreasing in the high power end of said reactor power demand. 4. A method as set forth in claim 3 wherein said control range of coolant temperatures has a constant temperature lower limit over the middle and high power end of said reactor power demand. 5. A method as set forth in claim 4 wherein said step of switching control is done whenever the required change in reactor power output is substantially in the range of five percent full power per minute. 6. A method as set forth in claim 5 wherein said step of switching control comprises the manual actuation of control signals preventing the movement of reactor control rods and enabling the variation of feedwater flow to decrease coolant temperature below said variable temperature set point. 7. A method as set forth in claim 6 further including the step of automatically switching reactor control back to said variable temperature set point control of the reactor control rods whenever reactor coolant average temperatures drop below the lower limit said range of coolant temperatures. 8. A method of controlling the power output of a nuclear reactor comprising the steps of: 9. A method as set forth in claim 8 wherein the control of the reactor power output utilizing said control signal is done by reactor control rod movement. 10. A method as set forth in claim 9 including the steps of: 11. A method as set forth in claim 10 wherein said step of switching control includes the steps of:
	summary
	abstract	An object is to provide a sample holder and a sample mount which allow observation of a sample from many directions in an electron microscope. A sample holder (10) is made for use in a transmission electron microscope (TEM). In the TEM, an electron beam is incident in the Z direction. A sample mount (17) and a sample (SA) affixed on it can be rotated by a motor (12) in the range of 0 to 360xc2x0 on an axis extending in the Y direction which differs from the direction of the electron beam incidence. Therefore the electron beam can enter the observed sample (SA) from many directions, thus allowing observation of the sample (SA) from many directions. It is also possible to FIB-process the sample (SA) in many directions without removing the sample (SA) from the sample holder (10), which facilitates the handling in the FIB processing.
	summary
	abstract	The present disclosure provides a stopped cooling system including: a steam line connecting portion connected to a steam line so as to receive cooling water through the steam line connected to an outlet of a steam generator; a stopped cooling heat exchanger for receiving cooling water that enters the stopped cooling system through the steam line connecting portion, and discharging same through a passage of the heat exchanger; a stopped cooling pump activated to perform stopped cooling of the nuclear reactor upon normal stoppage of the nuclear reactor after primary cooling of the nuclear reactor cooling system or when an accident occurs, and for forming a circulating flow of cooling water that circulates between the steam generator and the stopped cooling heat exchanger; and a water supplying pipe connecting portion connected to the heat exchanger passage and a water supplying pipe, which is connected to the inlet of the steam generator, so as to supply the cooling water cooled in the stopped cooling heat exchanger to the steam generator through the water supplying pipe.
	abstract	The present invention is used to reduce thermal load itself, being the cause to generate stress, which develops near liquid surface in a nuclear reactor wall and to contribute to further improvement of safety. A partition member (5) is arranged above a coolant liquid surface (9) in an annulus space (3) between a reactor vessel (1) and a guard vessel (2), a low-temperature gas is circulated through the annulus space above the partition member to cool down, the gas is circulated through the annulus space from under the coolant liquid surface to the partition member, and the high-temperature gas heated under the coolant liquid surface is used to raise the temperature above the coolant liquid surface.
	description	This application is a divisional application of and claims priority to U.S. application Ser. No. 12/393,577, filed on Feb. 26, 2009, which claims priority to U.S. Provisional Patent Application Ser. No. 61/115,614, filed on Nov. 18, 2008. The entire contents of both applications are hereby incorporated by reference in its entirety. The invention relates to the field of nuclear power generation, including systems designed to cool a reactor core. In nuclear reactors designed with passive operating systems, the laws of physics are employed to ensure that safe operation of the nuclear reactor is maintained during normal operation or even in an emergency condition without operator intervention or supervision, at least for some predefined period of time. A nuclear reactor 5 includes a reactor core 6 surrounded by a reactor vessel 2. Water 10 in the reactor vessel 2 surrounds the reactor core 6. The reactor core 6 is further located in a shroud 122 which surrounds the reactor core 6 about its sides. When the water 10 is heated by the reactor core 6 as a result of fission events, the water 10 is directed from the shroud 122 and out of a riser 124. This results in further water 10 being drawn into and heated by the reactor core 6 which draws yet more water 10 into the shroud 122. The water 10 that emerges from the riser 124 is cooled down and directed towards the annulus 123 and then returns to the bottom of the reactor vessel 2 through natural circulation. Pressurized steam 11 is produced in the reactor vessel 2 as the water 10 is heated. A heat exchanger 135 circulates feedwater and steam in a secondary cooling system 130 in order to generate electricity with a turbine 132 and generator 134. The feedwater passes through the heat exchanger 135 and becomes super heated steam. The secondary cooling system 130 includes a condenser 136 and feedwater pump 138. The steam and feedwater in the secondary cooling system 130 are isolated from the water 10 in the reactor vessel 2, such that they are not allowed to mix or come into direct contact with each other. The reactor vessel 2 is surrounded by a containment vessel 4. The containment vessel 4 is designed so that water or steam from the reactor vessel 2 is not allowed to escape into the surrounding environment. A steam valve 8 is provided to vent steam 11 from the reactor vessel 2 into an upper half 14 of the containment vessel 4. A submerged blowdown valve 18 is provided to release the water 10 into suppression pool 12 containing sub-cooled water. Water 10 circulates through the reactor vessel 2 as a result of temperature and pressure differentials that develop as a result of heat generation through reactor operation and through heat exchange with the secondary cooling system 130. Accordingly, the efficiency of the circulation depends on the thermal properties of the reactor module 5 as well as its physical design and geometry. Conventional nuclear reactors include certain design features that tend to provide less than optimal coolant circulation, and must therefore rely on increased coolant volume or redundant components to ensure sufficient performance. The present invention addresses these and other problems. A power module is herein disclosed as comprising a reactor vessel containing a coolant, and a reactor core located near a bottom end of the reactor vessel. A riser section is located above the reactor core, wherein the coolant circulates past the reactor core and up through the riser section. The power module further comprises a coolant deflector shield including an ellipsoidal or other flow-optimized surface, wherein the flow-optimized surface directs the coolant towards the bottom end of the reactor vessel. A nuclear reactor module is herein disclosed as comprising a reactor vessel including an upper end and a lower end, a pressurizer located near the upper end of the reactor vessel, and a reactor core located near the bottom end of the reactor vessel. The nuclear reactor module further comprises a baffle assembly located between the reactor core and the pressurizer, and a reactor housing the directs coolant flow through the reactor core. The reactor housing comprises an inward facing portion that varies a flow pressure of the coolant and promotes a circulation of the coolant past the baffle assembly and towards the bottom end of the reactor vessel. A method of cooling a reactor core is herein disclosed as comprising circulating a primary coolant through a reactor housing comprising an upper riser, and directing a flow of the coolant down a reactor vessel and around the reactor housing, wherein an ellipsoidal shaped lower end of the reactor vessel promotes coolant flow through the reactor core. An ellipsoidal or flow-optimized surface shaped deflector shield located above the upper riser promotes coolant flow around the reactor housing. The invention will become more readily apparent from the following detailed description of a preferred embodiment of the invention which proceeds with reference to the accompanying drawings. Various embodiments disclosed or referred to herein may be operated consistent, or in conjunction, with features found in co-pending U.S. application Ser. No. 11/941,024 which is herein incorporated by reference in its entirety. FIG. 2 illustrates a power module assembly 25 comprising an internally dry containment vessel 54. The containment vessel 54 is cylindrical in shape, and has ellipsoidal, domed, concave or hemispherical upper and lower ends. The entire power module assembly 25 may be submerged in a pool of water 16 which serves as an effective heat sink. The pool of water 16 and the containment vessel 54 may further be located below ground 9 in a reactor bay 7. The containment vessel 54 may be welded or otherwise sealed to the environment, such that liquids and gas do not escape from, or enter, the power module assembly 25. The containment vessel 54 may be supported at any external surface. In one embodiment, the containment vessel 54 is suspended in the pool of water 16 by one or more mounting connections 180. A reactor vessel 52 is located or mounted inside the containment vessel 54. An inner surface of the reactor vessel 52 may be exposed to a wet environment including a coolant 100 or liquid, such as water, and an outer surface may be exposed to a dry environment such as air. The reactor vessel 52 may be made of stainless steel or carbon steel, may include cladding, and may be supported within the containment vessel 54. The power module assembly 25 may be sized so that it can be transported on a rail car. For example, the containment vessel 54 may be constructed to be approximately 4.3 meters in diameter and approximately 17.7 meters in height (length). Refueling of the reactor core 6 may be performed by transporting the entire power module assembly 50 by rail car or overseas, for example, and replacing it with a new or refurbished power module assembly which has a fresh supply of fuel rods. The containment vessel 54 encapsulates and, in some conditions, cools the reactor core 6. It is relatively small, has a high strength and may be capable of withstanding six or seven times the pressure of conventional containment designs in part due to its smaller overall dimensions. Given a break in the primary cooling system of the power module assembly 25 no fission products are released into the environment. Decay heat may be removed from the power module assembly 25 under emergency conditions. The reactor core 6 is illustrated as being submerged or immersed in a primary coolant 100, such as water. The reactor vessel 52 houses the coolant 100 and the reactor core 6. A reactor housing 20 comprises a shroud 22 in a lower portion and a riser 24 in an upper portion of the reactor housing 20. The riser 24 may be substantially cylindrical in shape. The shroud 22 surrounds the reactor core 6 about its sides and serves to direct the coolant 100 (shown as coolant flow 26, 28) up through the center of the riser 24 located in the upper half of the reactor vessel 52, then back down the annulus 23, as a result of natural circulation of the coolant 100. In one embodiment, the reactor vessel 52 is approximately 2.7 meters in diameter and includes an overall height (length) of approximately 13.7 meters. The reactor vessel 52 may include a predominately cylindrical shape with ellipsoidal, domed, concave, or hemispherical upper and lower ends. The reactor vessel 52 is normally at operating pressure and temperature. The containment vessel 54 is internally dry and may operate at atmospheric pressure with wall temperatures at or near the temperature of the pool of water 16. The containment vessel 54 substantially surrounds the reactor vessel 52 and may provide a dry, voided, or gaseous environment identified as containment region 44. Containment region 44 may comprise an amount of air or other fill gas such as Argonne. The containment vessel 54 includes an inner surface or inner wall which is adjacent to the containment region 44. The containment region 44 may include a gas or gases instead of or in addition to air. In one embodiment, the containment region 44 is maintained at or below atmospheric pressure, for example as a partial vacuum. Gas or gasses in the containment vessel may be removed such that the reactor vessel 52 is located in a complete or partial vacuum in the containment region 44. During normal operation, thermal energy from the fission events in the reactor core 6 causes the coolant 100 to heat. As the coolant 100 heats up, it becomes less dense and tends to rise up through the riser 24. As the coolant 100 temperature reduces, it becomes relatively denser than the heated coolant and is circulated around the outside of the annulus 23, down to the bottom of the reactor vessel 52 and up through the shroud 22 to once again be heated by the reactor core 6. This natural circulation causes the coolant 100 (shown as coolant flow 26, 28) to cycle through the heat exchanger 135, transferring heat to a secondary coolant, such as the secondary cooling system 130 of FIG. 1, to generate electricity. FIG. 3 illustrates a cross sectional view of an embodiment of a power module assembly 30 comprising a reactor vessel deflector shield 35. Reactor vessel 52 contains a reactor core 6 located near a bottom end 55 of the reactor vessel 52. A riser section 24 is located above the reactor core 6, wherein coolant circulates past the reactor core 6 to become high-temperature coolant TH and then continues up through the riser section 24 where it is directed back down the annulus and cooled off by a heat exchanger 135 (FIG. 1) to become low-temperature coolant TC. The reactor vessel deflector shield 35 comprises a flow-optimized ellipsoidal, domed, concave, or hemispherical shaped portion 35A, wherein the flow-optimized portion 35A directs the coolant (shown as coolant flow 26) towards the bottom end 55 of the reactor vessel 52. The ellipsoidal portion 35A may come into direct contact with and deflect the coolant that exits the riser section 24. The ellipsoidal portion 35A operates to reduce a flow resistance or turning loss of the coolant flow 26, as compared to an interaction of the coolant with a flat, or irregular surface, or plenum region without a solid interface. In one embodiment, the reduction in turning loss is by a factor of four or five compared to systems without a deflector shield. The reactor vessel deflector shield 35 may be made of stainless steel or other materials which may be formed into an ellipsoidal or optimized shaped surface. In one embodiment, the bottom end 55 of the reactor vessel 52 comprises a second flow-optimized ellipsoidal, domed, concave, or hemispherical portion 55A, wherein the second ellipsoidal portion 55A directs the coolant (shown as coolant flow 28) towards the reactor core 6. The ellipsoidal portion 35A and second ellipsoidal portion 55A increase flow rate and promote natural circulation of the coolant through the reactor core 6. An optimization of the coolant flow 26 may be obtained according to a ratio of the distance Ho between the top of the riser section 24 and the center of the reactor vessel deflector shield 35 and the relative distance Do between the walls of the riser section 24, wherein the dimension La represents the distance between the outside of the riser 24 and the inside surface of the reactor vessel 52. In one embodiment, the distance Do equals the diameter of the riser section 24. The flow area inside the riser is Ao, the flow area inside the annulus is Aa. The optimized coolant flow ratios may be represented as Ho/Do and Aa/Ao. In one embodiment, the optimized coolant flow ratio Ho/Do comprises a value 0.1 and 2.0, and the flow ration and Ao/Aa comprises a value between/approximately 1 and 10. Further optimization of the coolant flow 26 may be obtained by modifying the radius of curvature of the surface of ellipsoidal portion 35A to eliminate/minimize boundary layer separation and stagnation regions. The reactor vessel deflector shield 35 is illustrated as being located between the top of the riser section 24 and a pressurizer region 15. The pressurizer region 15 is shown as comprising one or more heaters 17 and a spray nozzle 19 configured to control a pressure, or maintain a steam dome, within an upper end 56 of the reactor vessel 52. Coolant located below the reactor vessel deflector shield 35 may comprise relatively sub-cooled coolant TSUB, whereas coolant in the pressurizer region 15 in the upper end 56 of the reactor vessel 52 may comprise substantially saturated coolant TSAT. A fluid level of the coolant is shown as being above the reactor vessel deflector shield 35, and within the pressurizer region 15, such that the entire volume between the reactor vessel deflector shield 35 and the bottom 55 of the reactor vessel 52 is full of coolant during normal operation of the power module assembly 30. FIG. 4 illustrates a partial view of an example power module assembly 40 comprising a reactor vessel deflector shield 35 supported by one or more control rod guide tubes or instrumentation structures 45. The one or more control rod guide tubes or instrumentation structures 45 may be attached to an upper end of the reactor vessel 52, and serve to guide control rods that are inserted into, or removed from, the reactor core 6, or provide support for instrumentation devices located inside the reactor vessel 52. By attaching or suspending the reactor vessel deflector shield 35 from the one or more control rod guide tubes or instrumentation structures 45, the reactor vessel deflector shield 35 may be free from contacting the sides of the reactor vessel 52. By isolating the reactor vessel deflector shield 35 from the reactor vessel walls 52, the reactor vessel deflector shield 35 is protected from changes in rates of thermal expansion of the different materials and structures of the power module assembly 40, or from any movement of components that might otherwise damage the reactor vessel deflector shield 35 or the reactor vessel 52. The riser section 24 is illustrated as comprising an inward facing portion 65 that varies a flow pressure of the coolant to reduce a turning loss of the coolant 26 circulating by the reactor vessel deflector shield 35. In one embodiment, the cross section of the inward facing portion 65 approximates a cross section of an airplane wing in shape, but with a smaller cross sectional area, for example. The cross-section blunt end of the inward facing portion 65 may face the top of the vessel or the bottom, or be blunt on both ends. The inward facing portion 65 may be continuously located around a perimeter of an upper end of the reactor housing 20 or riser section 24 (e.g. FIG. 9). The inward facing portion 65 may effect a change in pressure and accompanying loss of turning resistance of the coolant 26 about the entire perimeter of the riser section 24. In one embodiment, the inward facing portion 65 comprises multiple portions (e.g. FIG. 8) located around a perimeter of the upper end of the reactor housing 20 or riser section 24. The inward facing portion 65 may be understood to affect the coolant flow 26 or fluid pressure similar to the aerodynamics of an airplane wing, in that the flow is preferentially directed to minimize regions of separation and the related losses. FIG. 5 illustrates a partial view of an example power module assembly 150 comprising a baffle assembly 50 and a coolant flow augmentation mechanism comprised of inward facing portion 65. The reactor vessel 52 includes an upper end 56 and a lower end 55 (FIG. 3). Pressurizer region 15 is located near the upper end 56 of the reactor vessel 52, whereas the reactor core 6 is located near the bottom end 55 of the reactor vessel 52. Baffle assembly 50 is shown illustrated as being located between the reactor core 6 and the pressurizer region 15. The reactor housing 20 (FIG. 3) directs coolant flow 28 through the reactor core 6, wherein the reactor housing 20 comprises inward facing portion 65 that varies a flow pressure of the coolant and promotes a circulation of the coolant (illustrated as coolant flow 26) to by-pass the baffle assembly 50 and towards the bottom end 55 of the reactor vessel 52. The baffle assembly 50 comprises an upper baffle plate 62 and a lower baffle plate 64. A hot/cold liquid interface Lo due to stratification in the baffle region may exist between the upper and lower baffle plates 62, 64 separating the subcooled coolant TSUB from the saturated coolant TSAT. The liquid interface Lo provides a medium in which the first fluid entering the pressurizer region when flow is into the pressurizer, is hot fluid, and afterwards the subcooled coolant TSUB entering the pressurizer heats up (or mixes together with saturated coolant TSAT) before entering the pressurizer region 15. The baffle assembly 50 operates to impede a flow of the subcooled coolant TSUB from entering the pressurizer region 15, comprising substantially saturated coolant TSAT. The baffle assembly 50 helps maintain or create a thermal trap between the upper and lower baffle plates 62, 64. A steam dome may be maintained in pressurizer region 15, or the upper end 56 of the reactor vessel 52. If the subcooled coolant TSUB is allowed to enter the pressurizer region 15 too quickly, it may result in a loss of reactor vessel pressure or collapse of the steam dome. The baffle assembly 50 effectively increases a flow path length from the subcooled coolant TSUB on a first side of the baffle assembly 50 to the saturated coolant TSAT on a second side of the baffle assembly 50. Coolant flow (illustrated as F1) entering the baffle assembly 50 is allowed to flow around or by the lower baffle plate 64. The coolant flow (illustrated as Fo) next maneuvers around one or more internal baffles 72, 74 before exiting into the pressurizer region 15 as coolant flow F2, through or by the upper baffle plate 62. The flow path made by the baffles directs the flow F1 past the structure of the baffle assembly 50 that is heated from the pressurizer region 15. Directing of the flow F1 past the relatively hot structure heats this fluid, and additionally mixes the fluid with the Tsat region, effectively heating it previous to it entering the pressurizer region 15. FIG. 6 illustrates an example baffle assembly 60 comprising a reactor vessel deflector shield 66. The reactor vessel deflector shield 66 comprises a flow-optimized ellipsoidal region or concave portion 66A having a diameter D1 or width that is larger than a distance Do between the inward facing portions 65 of the reactor housing 20 or riser section 24. In one embodiment, the diameter D1 of the lower baffle plate 66 is approximately equal to the width or diameter of the reactor vessel 52. The pressurizer region 15 is located at the upper end of the reactor vessel 52. The baffle assembly 60 is located between the pressurizer region 15 and the riser section 24. The baffle assembly 60 comprises one or more baffles 72, 76 located between an upper baffle plate 62 and the reactor vessel deflector shield 66. The one or more baffles 72, 76 impede a flow of the sub-cooled coolant TSUB into the pressurizer region 15. The baffle assembly 60 may be understood to operate similarly as a pressurizer surge line of a typical pressurized water reactor design. The baffle assembly 60 may prevent an insurge of coolant from the reactor vessel 52 from entering the pressurizer region 15 too suddenly or at too low of a temperature. In one embodiment, the baffle assembly 60 operates to control a rate of insurge of the coolant into the pressurizer region 15, and increases the temperature of the insurge flow by structure heat addition and mixing with hot fluids. The baffle assembly 60 includes an upper portion which comprises the upper baffle plate 62. The upper baffle plate 62 may include, or be attached to, one or more baffles 72. The baffle assembly 60 further includes a lower portion which comprises the reactor vessel deflector shield 66. The reactor vessel deflector shield 66 may include, or be attached to, one or more baffles 76. The baffle assembly 60 may comprise one or more heaters 79. The one or more heaters 79 may be provided intermediate the upper and lower baffle plates 62, 66. In one embodiment, the one or more heaters 79 are provided within the upper baffle plate 62 to warm the coolant. In another embodiment the one or more heaters 79 are provided in the liquid interface Lo. Coolant that passes through the baffle assembly 70 may become heated to at, or near, saturation temperatures TSAT while being transferred into the pressurizer region 15. The baffle assembly 60 may be understood to both isolate the pressurizer region 15 from the subcooled coolant TSUB, as well as promote increased flow rate of the coolant (illustrated as flow 26) in the reactor vessel 52. In one embodiment, a width or diameter of the reactor vessel deflector shield 66 is less than a width or diameter of the reactor vessel 52 forming a pathway or channel 68 about the perimeter of the reactor vessel deflector shield 66. The channel 68 provides a path for the coolant flow (illustrated as F1) to pass by or through the reactor vessel deflector shield 66. Coolant continues to flow (illustrated as Fo) around the one or more baffles 72, 76 before exiting by or through the upper baffle plate 62 as coolant flow F2. Coolant that passes through the baffle assembly 60 may become heated to at, or near, saturation temperatures TSAT while being transferred through the pathway or channel 68 and being heated by the upper baffles 72. FIG. 7 illustrates a partial view of an example power module assembly 75 comprising a baffle assembly 70 and coolant flow augmentation mechanism comprised of inward facing portion 65. The baffle assembly 70 comprises an upper baffle plate 62 and a lower baffle plate 77 including one or more flow-optimized ellipsoidal, domed, hemispherical or concave surfaces 77A and a divider 77B. The flow-optimized concave surface 77A of the lower baffle plate 77 directs the coolant 26 down around the riser section 24 of the housing 20 to the bottom of the reactor vessel 52. The flow-optimized concave surface 77A of the lower baffle plate 77 may be understood to operate the same or similar to the flow-optimized ellipsoidal region or concave portion 66A of the reactor vessel deflector shield 66 of FIG. 6. Divider 77B further facilitates coolant 26 to flow in an outward direction from the center of the baffle plate 77. Divider 77B may be shaped similar to a bullet tip. Baffle plate 77 minimizes pressure loss of coolant flow based on an optimized position and geometry above the exit of the riser section 24. The baffle assembly 70 is located between the pressurizer region 15 and the riser section 24. The baffle assembly 70 comprises one or more baffles 72, 78 located between the upper baffle plate 62 and the lower baffle plate 77. The one or more baffles 72, 78 impede a flow of the sub-cooled coolant TSUB into the pressurizer region 15. An upper portion of the baffle assembly 70 comprises the upper baffle plate 62. The upper baffle plate 62 may include, or be attached to, one or more baffles 72. A lower portion of the baffle assembly 70 comprises the lower baffle plate 77. The lower baffle plate 77 may include, or be attached to, one or more baffles 78. A pathway or channel may be formed through one or all of the baffles 72, 78. The channel provides a path for the coolant flow (illustrated as F1) to pass by or through the lower baffle plate 77. Coolant continues to flow (illustrated as Fo) through the one or more baffles 72, 78 before exiting by or through the upper baffle plate 62 as coolant flow F2. The baffle assembly 70 may comprise one or more heaters 79. The one or more heaters 79 may be provided intermediate the upper and lower baffle plates 62, 77. In one embodiment, the one or more heaters 79 are provided within the upper baffle plate 62 to warm the coolant entering the pressurizer region during an insurge. In another embodiment the one or more heaters 79 are provided in the temperature variation layer proximate to the liquid interface Lo. Coolant that passes through the baffle assembly 70 may become heated to at, or near, saturation temperatures TSAT while being transferred into the pressurizer region 15. The baffle assembly 70 may be understood to both isolate the pressurizer region 15 from the subcooled coolant TSUB, as well promote increased flow rate of the coolant (illustrated as flow 26) in the reactor vessel 52. In one embodiment, the inward facing portion 65 has a cross section which approximates an inverted teardrop. The inward facing portion 65 has a cross section which generally increases in thickness towards an upper end of the riser region 24. The upper end of the reactor housing 20, or riser section 24, comprises a perimeter characterized by a rounded rim of the inverted teardrop. FIG. 8 illustrates a plan view of an embodiment of the coolant flow augmentation mechanism 65 comprising a plurality of inward facing portions 85. The coolant flow augmentation mechanism 65 is illustrated as comprising four inward facing portions 85 located about the perimeter of the top of the riser 24, however it is understood that different numbers and types of inward facing portions 65 may be provided for. Partial views of the riser 24 and inward facing portion 65 illustrated in FIGS. 4, 5, and 7 may be understood as comprising a cross sectional view C-C of the coolant flow augmentation mechanism 85. FIG. 9 illustrates an elevated side view of an embodiment of the coolant flow augmentation mechanism 65 comprising a continuous inward facing portion 95. The inward facing portions 95 is illustrated as being located about the perimeter of the top of the riser 24. Partial views of the riser 24 and inward facing portion 65 illustrated in FIGS. 4, 5, and 7 may be understood as comprising a cross sectional view D-D of the coolant flow augmentation mechanism 65. FIG. 10 illustrates coolant flow 26 around a coolant flow augmentation mechanism 65. A fluid pressure Po of the coolant flow 26 exiting the riser 24 is varied as fluid pressure P1 when it passes around the coolant flow augmentation mechanism 65. Coolant flow augmentation mechanism 65 increases an effective path of the coolant flow 26, which results in the varied fluid pressure P1, as the velocity of the coolant flow 26 varies. Varying the fluid pressure of the coolant operates to reduce a flow resistance or turning loss of the coolant flow 26 by preventing or minimizing boundary layer separation of the flow 26 from the riser 24. This is accomplished by providing a smooth transition for the flow exiting the riser section 24 and entering into the annulus flowing back towards the bottom of the reactor vessel 52. FIG. 11 illustrates a novel method of cooling a reactor core using a reactor vessel deflector shield. The method may be understood to operate with, but not limited by, various embodiments illustrated herein as FIGS. 1-10. At operation 210, a primary coolant is circulated through a reactor housing comprising an upper riser. At operation 220, a fluid pressure of the coolant in the reactor housing is varied by directing a coolant flow around an inward facing portion of the upper riser. At operation 230, a flow-optimized ellipsoidal, domed, concave or hemispherical shaped deflector shield forms a lower portion of a baffle system that inhibits the flow of coolant into a pressurizer region. In one embodiment, the flow-optimized ellipsoidal deflector shield is located between the upper riser and the pressurizer region, wherein the pressurizer region is located in an upper end of reactor vessel. At operation 240, a flow of the coolant is directed down the reactor vessel and around the reactor housing. A flow-optimized ellipsoidal, domed, concave or hemispherical shaped lower end of the reactor vessel promotes coolant flow through the reactor core, and the flow-optimized ellipsoidal deflector shield located above the upper riser promotes coolant flow around the reactor housing. Although the embodiments provided herein have primarily described a pressurized water reactor, it should be apparent to one skilled in the art that the embodiments may be applied to other types of nuclear power systems as described or with some obvious modification. For example, the embodiments or variations thereof may also be made operable with a boiling water reactor. The rate of fluid flow about the reactor housing, the rate of insurge and outsurge flows within the baffle assemblies, and the variation in pressure of the fluid moving about flow augmentation devices, as well as other rates and values described herein are provided by way of example only. Other rates and values may be determined through experimentation such as by construction of full scale or scaled models of a nuclear reactor fluid system. Having described and illustrated the principles of the invention in a preferred embodiment thereof, it should be apparent that the invention may be modified in arrangement and detail without departing from such principles. We claim all modifications and variation coming within the spirit and scope of the following claims.
	claims	1. A micro testing and assembly device comprising: A) a scanning electron microscope; B) an operating chamber having walls and within which said scanning electron microscope operates; C) a linear motion feedthrough device that includes a linear motion feedthrough device shaft having a terminal end; D) attached to the terminal end and within said operating chamber a tool; E) in the vicinity of said tool and controlled via stage controls a manipulable platform; F) a scanning electron microscope stage mounted on said stage platform; and G) a testing/assembly stage mounted on said scanning electron microscope stage. 2. The micro testing and assembly device of claim 1 wherein said linear motion feedthrough device is located within said operating chamber. claim 1 3. The micro testing and assembly device of claim 1 wherein said tool is a microgripper. claim 1 4. The micro testing and assembly device of claim 1 further including intermediate said scanning electron microscope stage and said testing stage a hot stage for controllably heating said assembly stage and any parts or materials located thereon. claim 1 5. The micro testing device of claim 1 further including intermediate said tool and said terminal end, a load cell for the measurement of load applied to said tool during assembly or testing. claim 1 6. The micro testing and assembly device of claim 1 further including an acoustic emission sensor for detecting contact between parts being assembled or tested. claim 1 7. The micro testing and assembly device of claim 1 further including an alignment guide for said linear motion feedthrough device. claim 1 8. The micro testing and assembly device of claim 1 further including a piezoelectric positioner located intermediate said linear motion feedthrough device shaft and said tool. claim 1
046801669	claims	1. In a large-area cell containing equipment for reprocessing irradiated nuclear fuels, the equipment having a stationary conduit with an end flange connectable to a removable conduit unit also having an end flange, said end flanges having respective rotational axes and conjointly defining an interface when disposed one next to the other, the large-area cell being equipped with remote handling apparatus for moving the removable flanged conduit unit relative to the stationary conduit, a centering and manipulating arrangement for facilitating the remotely manipulated connection of the end flange of the removable flanged conduit unit to the end flange of the stationary conduit, the arrangement comprising: an upwardly open guide cradle attached to the peripheral edge of one of said end flanges, said cradle being mounted laterally on said one end flange and parallel to the rotational axis of said one end flange; said guide cradle including a catch ring disposed thereon at a predetermined location rearward of the interface of the end flanges; and, a guide pin fixedly mounted on the other one of said end flanges so as to be received in said guide cradle so as to extend through said catch ring when said end flanges are connected to each other. 2. The large-area cell of claim 1, wherein said guide cradle is attached to the peripheral edge of said end flange of said stationary conduit and said guide pin is fixedly mounted on said end flange of said removable flanged conduit unit. 3. The large-area cell of claim 1, further comprising barb means formed on said guide pin for holding said removable flanged conduit unit in position on said stationary unit after the connection holding said end flanges together has been disengaged. 4. The large-area cell of claim 1, wherein said removable flanged conduit has a lug for receiving a load hook therein whereby said removable flanged conduit can be lifted and moved in said large-area cell.
	summary
	summary
052767205	claims	1. In a nuclear boiling water reactor (BWR) facility wherein housed within a sealed annular drywell is a reactor pressure vessel (RPV) which contains a nuclear core and a condensible heat transfer fluid for circulation in heat transfer relationship with said core, and which is fluid communicable in an emergency situation with said drywell for passage thereinto of gaseous phase heat transfer fluid and any noncondensibles in said RPV; an annular sealed wetwell which houses said drywell; and a pressure suppression pool of liquid which is disposed in said wetwell and is connected to said drywell by submerged vents, an improved emergency cooling system which comprises: (a) a containment condenser (b) a water pool in heat transfer relationship with said containment condenser for conducting heat away from said containment condenser. (a) passing at least a portion of said heat transfer fluid and said noncondensibles from said RPV into said drywell for mixing with heat transfer fluid and noncondensibles from a later step of the method; (b) passing the mixed heat transfer fluids and noncondensibles from said drywell through a containment condenser for condensing at least a portion of the heat transfer fluid; (c) passing the condensed heat transfer fluid of step (b) from said containment condenser to said RPV; (d) passing the noncondensed balance of the heat transfer fluid and the noncondensibles of step (b) into said drywell for mixing in step (a) with said heat transfer fluid and said noncondensibles from said RPV. a shroud defining a plenum which is in fluid communication with said RPV; a steam dome; and a plurality of tubes running from said stream dome to said plenum for passage therethrough in step (b) of said mixed heat transfer fluids and noncondensibles from said drywell, said tubes having annular centers and inner surfaces, at least a portion of the heat transfer fluid condensing in said tubes and flowing through said tubes along said inner surfaces. 2. The improved emergency cooling system of claim 1, wherein said containment condenser additionally comprises: 3. The improved emergency emergency cooling system of claim 2, wherein said tubes are disposed at an angle of from between about 20.degree. and 40.degree. with respect to vertical. 4. The improved emergency cooling system of claim 2, wherein said tubes are disposed vertically. 5. The improved emergency cooling system of claim 2, wherein said tubes are linear. 6. The improved emergency cooling system of claim 2, wherein said tubes are helical coils. 7. The improved emergency cooling system of claim 2, wherein the length of said plenum is about twice the length of said tubes. 8. The improved emergency cooling system of claim 4, wherein flowtrips are incorporated into said tubes for dropletizing the condensed portion of said heat transfer fluid flowing through said tubes along said inner surfaces and for directing the droplets produced by said dropletizing to said annular centers of said tubes. 9. The improved emergency cooling system of claim 8, wherein said flowtrips are fins which extend inwardly from said inner surfaces of said tubes. 10. The improved emergency cooling system of claim 8, wherein said flowtrips are a plurality of V-shaped flutes terminating a cylindrical channel circumscribed into said inner surfaces of said tubes. 11. The improved emergency cooling system of claim 3, wherein flowtrips are incorporated into said tubes adjacent said shroud for dropletizing the condensed portion of said heat transfer fluid flowing through said tubes along said inner surfaces. 12. The improved emergency cooling system of claim 11, wherein said flowtrips are fins which extend inwardly from said inner surfaces of said tubes. 13. The improved emergency cooling system of claim 11, wherein said flowtrips are a plurality of V-shaped flutes terminating a cylindrical channel circumscribed into said inner surfaces of said tubes. 14. The improved emergency cooling system of claim 1, wherein said heat transfer fluid and said noncondensibles are passed from said RPV to the drywell and then through said containment condenser by negative pressure differentials. 15. A method for removing heat from a reactor pressure vessel (RPV) in emergency cooling situations, said RPV being part of a nuclear boiling water reactor (BWR) facility wherein housed within a sealed annular drywell is said reactor pressure vessel (RPV) which contains a nuclear core and a condensible heat transfer fluid for circulation in heat transfer relationship with said core, and which is fluid communicable in an emergency situation with said drywell for passage thereinto of gaseous phase heat transfer fluid and any noncondensibles in said RPV; an annular sealed wetwell which houses said drywell; and a pressure suppression pool of liquid which is disposed in said wetwell and is connected to said drywell by submerged vents, which comprises: 16. The method of claim 15 wherein said containment condenser is provided to comprise: 17. The method of claim 16, wherein said tubes are disposed at an angle of from between about 20.degree. and 40.degree. with respect to vertical. 18. The method of claim 16, wherein said tubes are disposed vertically. 19. The method of claim 16, wherein said tubes are provided to be linear. 20. The method of claim 16, wherein said tubes are provided as helical coils. 21. The method of claim 16, wherein the length of said plenum is provided to be about twice the length of said tubes. 22. The method of claim 18, wherein flowtrips are incorporated into said tubes for dropletizing the condensed portion of the heat transfer fluid flowing through said tubes along said inner surfaces and for directing the droplets produced by said dropletizing to said annular centers of said tubes. 23. The method of claim 22, wherein said flowtrips are provided as fins which extend inwardly from said inner surfaces of said tubes. 24. The method of claim 22, wherein said flowtrips are a plurality of V-shaped flutes terminating a cylindrical channel circumscribed into said inner surfaces of said tubes. 25. The method of claim 17, wherein flowtrips are incorporated into said tubes adjacent said shroud for dropletizing the condensed portion of the heat transfer fluid flowing through said tubes along said inner surfaces. 26. The method of claim 25, wherein said flowtrips are provided as fins which extend inwardly from said inner surfaces of said tubes. 27. The method of claim 25, wherein said flowtrips are a plurality of V-shaped flutes terminating a cylindrical channel circumscribed into said inner surfaces of said tubes. 28. The method of claim 15 wherein in step (a), said heat transfer fluid and said noncondensibles from said RPV are passed into said drywell by negative pressure differentials. 29. The method of claim 15 wherein in step (b), said mixed heat transfer fluids and noncondensibles are passed from said drywell into said containment condenser by negative pressure differentials. 30. The method of claim 15 wherein a water pool is disposed in a heat transfer relationship with said containment condenser for conducting heat from said containment condenser.
053512774	claims	1. A method of constructing a top slab of a nuclear reactor container having a sleeve with a flange and a prefabricated doughnut-shaped steel reinforcement structure wherein the outermost diameter of said flange is greater than the innermost diameter of said prefabricated doughnut-shaped steel-reinforcement structure, comprising the steps of: placing a container sleeve separate from said flange, at a position where said top slab is to be constructed; lifting said prefabricated doughnut-shaped steel reinforcement structure and placing this structure at a position where it forms said top slab; and welding said flange to said container sleeve for mounting a top head of said nuclear reactor container on said flange. prefabricating a structure integrating a top slab liner, a container sleeve, separate from said flange, fixed to the inner periphery of said top slab liner substantially orthogonal to said top slab liner, and said prefabricated doughnut-shaped steel reinforcement structure on said top slab liner, and lifting and mounting said prefabricated doughnut-shaped steel reinforcement structure to a position where said top slab is to be constructed; and welding said flange to said container sleeve for mounting a top head of said nuclear reactor container on said flange. a bottom-equipped cylindrical portion for containing a nuclear reactor therein: a top slab provided on top of said cylindrical portion and composed of a doughnut-shaped steel reinforcement structure and concrete placed integrally with said doughnut-shaped steel reinforcement structure, said top slab having a central bore; a container sleeve outlining said central bore of said top slab; and a flange fixed by welding to said container sleeve and said flange having its outermost diameter greater than the innermost diameter of said doughnut-shaped steel reinforcement structure; and a top head attached to said flange. 2. A method according to claim 1, wherein said prefabricated doughnut-shaped steel reinforcement structure has a cylindrical auxiliary plate integrated therewith and located near the innermost circumference of said prefabricated doughnut-shaped steel-reinforcement structure. 3. A method according to claim 2, wherein said welding said flange to said container sleeve is conducted simultaneously with pouring concrete in and solidifying the same on the outer diameter side of said cylindrical auxiliary plate, followed by pouring concrete in and solidifying the same on the inner diameter side of said cylindrical auxiliary plate, bounded by said container sleeve and said cylindrical auxiliary plate. 4. A method of constructing a top slab of a nuclear reactor container having a sleeve with a flange and a prefabricated doughnut-shaped steel reinforcement structure wherein the outermost diameter of said flange is greater than the innermost diameter of said prefabricated doughnut-shaped steel reinforcement structure, comprising the steps of: 5. A method according to claim 4, wherein said prefabricated doughnut-shaped steel reinforcement structure has a cylindrical auxiliary plate integrated therewith and located near the innermost circumference of said prefabricated doughnut-shaped steel reinforcement structure. 6. A method according to claim 5, wherein welding said flange to the container sleeve is conducted simultaneously with pouring concrete in and solidifying the same on the outer diameter side of said cylindrical auxiliary plate, followed by pouring concrete in and solidifying the same on the inner diameter side of said cylindrical auxiliary plate, bounded by said container sleeve and said cylindrical auxiliary plate. 7. A nuclear reactor container, comprising: 8. A nuclear reactor container according to claim 7, wherein a cylindrical auxiliary plate is integrated with said doughnut-shaped steel reinforcement structure near the innermost circumference thereof.
056595905	abstract	In a pressure vessel of a nuclear reactor containing a core assembly enclosed within a core shroud, the core shroud spaced radially inwardly of a side wall of the pressure vessel with an annular pump deck located in an annular radial space between the core shroud and the side wall of the pressure vessel, the improvement wherein the shroud is removably secured to an annular support leg extending upwardly from the bottom of the pressure vessel; and further wherein the annular pump deck is provided in the form of a plurality of removable segments.
	abstract	An electron gun that serves to reduce the quantity of electron stimulated desorption and accomplishes vacuum evacuation efficiently with a sufficient degree of vacuum. An electron source 1 and an extraction electrode 6 are provided for emitting an electron beam 7 from the electron source 1. A first vacuum chamber 16 containing the electron source 1 is connected to a second vacuum chamber 9 via an aperture 8 provided in the extraction electrode 6. Each vacuum chamber is differentially evacuated with an independent vacuum evacuation means, and the generation of electron stimulated desorption gas 11 is reduced by securing a wide route of vacuum evacuation around the electron source 1 and intercepting the procession of back scattered electrons 12 emitted from the area with the electron beam 7 on the extraction electrode 6 by using a shielding electrode 22 given a prescribed potential.
	claims	1. A method for separating and recovering uranium from a nuclear fuel element, the method comprising:(a) immersing a nuclear fuel element having a nuclear fuel and a cladding in a molten metal wherein the molten metal is molten magnesium or molten lithium, the nuclear fuel including uranium, wherein the cladding is selectively dissolved from the nuclear fuel element when contacted by the molten metal thereby leaving the nuclear fuel;(b) loading the nuclear fuel into a permeable basket, the permeable basket is electrically configured as an anode of an electrolytic cell, the electrolytic cell having a molten salt electrolyte and a cathode; and(c) applying an electric charge across the electrolytic cell thereby causing the molten salt electrolyte to selectively transfer uranium from the anode to the cathode. 2. The method of claim 1 wherein the nuclear fuel is a monolithic uranium-molybdenum nuclear fuel. 3. The method of claim 1 wherein the nuclear fuel is a high enriched uranium fuel. 4. The method of claim 1 wherein the nuclear fuel is a mixture of uranium and other fission products. 5. The method of claim 1 wherein the cladding contains aluminum. 6. The method of claim 1 wherein the nuclear fuel element further includes a zirconium interface layer located between the nuclear fuel and the cladding. 7. The method of claim 1 wherein the nuclear fuel remains in a metallic state following the separation of the cladding. 8. The method of claim 1 wherein the molten metal has a melting point approximately at or below the melting point of the cladding. 9. The method of claim 1 wherein the electrolyte is molten LiCl—KCl—UCl3. 10. The method of claim 1 wherein the uranium transferred to the cathode is free of other fuel constituents. 11. The method of claim 1 wherein the uranium transferred to the cathode is free of fission products. 12. The method of claim 1 additionally comprising the step of:(a) drying residual molten metal from the nuclear fuel after immersing the nuclear fuel element into a molten metal. 13. The method of claim 1 additionally comprising the step of:a) using the uranium recovered at the cathode for fabrication into a low enriched uranium nuclear fuel. 14. A method for separating and recovering uranium from a nuclear fuel element, the method comprising:(a) immersing a nuclear fuel element having nuclear fuel, an interlayer, and a cladding in molten magnesium, the nuclear fuel being a uranium-molybdenum alloy fuel, the interlayer including zirconium, the cladding including aluminum, wherein the cladding is selectively dissolved from the nuclear fuel element when contacted by the molten magnesium thereby leaving the nuclear fuel and interlayer intact;(b) loading the nuclear fuel and interlayer into a permeable basket, the permeable basket is electrically configured as an anode of an electrolytic cell, the electrolytic cell having a LiCl—KCl—UCl3 electrolyte and a cathode; and(c) applying an electric charge across the electrolytic cell thereby causing the electrolyte to selectively transfer uranium from the anode to the cathode. 15. The method of claim 1 wherein the molten magnesium has a melting point approximately equal to the melting point of the cladding. 16. The method of claim 1 additionally comprising the step of:(e) drying residual molten magnesium from the nuclear fuel and interlayer after immersing the nuclear fuel element into the molten magnesium. 17. The method of claim 14 additionally comprising the step of:e) using the uranium recovered at the cathode for fabrication into a low enriched uranium nuclear fuel.
	summary
054955114	summary	TECHNICAL FIELD The present invention relates to a device for preventing the formation of a flammable mixture of hydrogen and oxygen in the reactor containment of a nuclear power plant in the event of an accident involving the release of hydrogen with a simultaneous rise in temperature. BACKGROUND ART During the build-up leading to a serious accident in a nuclear power plant chemical processes of various natures cause hydrogen to be produced. This can lead to the formation of flammable gas mixtures in the reactor containment. If hydrogen is released and concentrated over a longer period of time, mixtures capable of detonation can be formed. This means that the integrity of the reactor containment, the last barrier for the retention of fission products, will be jeopardized. (The term "reactor containment" is used here as a generic term for all compartments in which the problem described may arise and must thus be solved). Known in the art are measures for the prevention of the danger arising from such a flammable gas mixture that are aimed at eliminating the hydrogen in the compartments of a reactor containment. These measures include the use of igniters, as well as the catalytic recombination into water of the hydrogen with the oxygen present in the reactor containment (e.g., EP-A-0 303 144). Especially promising is the use of catalytic recombiners, which meanwhile have become known in the art in various designs (EP-A-0416 143, DE-A-36 04 416, EP-A-0 303 144, DE-A-40 03 833), although these are not fully capable of eliminating the danger of a detonation or even a deflagration, for reasons that will be explained in the following. Depending on the steam content of the atmosphere within the compartments of a reactor containment, the deflagration limit may be reached even with a local concentration of hydrogen of as little as 4%. It is a known fact that steam has an inerting property, which is to say that with a higher steam content the deflagration limit is not reached until higher concentrations of hydrogen are generated. (The term "inerting," which is translated from the German word "Inertisierung," is used herein to mean decreasing the danger of explosion of an explosive gas mixture by reducing the concentration of explosive components in the gas mixture.) From model tests it is known that at the beginning of a nuclear core melt-down accident steam is released first while hydrogen is not released until after a certain delay. The composition of the gas mixtures in the different compartments of a reactor containment can, however, vary from one another very extensively and can change continuously during the further progression of the accident. The reaction speed of the catalytic recombiners (catalysts) increases exponentially with the temperature. The catalysts heat up until an equilibrium is reached between the heat that is produced and the heat that is carried off. It is only after higher catalyst temperatures have been reached that the reduction of hydrogen will accelerate and the convection resulting from the increase in temperature will cause mixing of the surrounding atmosphere. If the supply of hydrogen within a given compartment proceeds faster than it is eliminated, an increased hydrogen concentration will result within the gas mixture. The steam content, which at first will not necessarily be equal in all compartments of the reactor containment, will be reduced during the continued course of the process by condensation at the cold walls, thereby reducing its inerting effect. The so-called detonation cell size constitutes a measure for the propagation of a detonation as well as for the sensitivity of a gas mixture to detonation. The smaller the cell size, the greater will be the susceptibility of the gas mixture to detonation. It is known that dilution of the gas mixture containing hydrogen by the use of steam and even more by CO.sub.2 causes an increase in the detonation cell size. This is true for both lower and higher temperatures. In a gas mixture at 100.degree. C. with a stoichiometric composition, the detonation cell size will be increased fivefold or 34-fold by the addition of 10% or 20% by volume of CO.sub.2, respectively (fourfold or sixfold in the case of steam), compared to that without the addition of CO.sub.2 (or steam). Nothing has been demonstrated so far about what the effect would be of diluting the gas mixture simultaneously with steam and CO.sub.2. It may be assumed, however, that the effect would be at least additive. The detonation cell size of a gas mixture of like composition will be reduced through an increase in temperature and pressure. During an accident situation a temperature of around 100.degree. C. will prevail in the compartments of the reactor containment. Opposing this, a significantly lower temperature in the gas mixture can result in the immediate vicinity of a cold concrete wall. This will cause an increase in the detonation cell size. However, the detonation cell size of the gas mixture will potentially tend to decrease at the same time because of a reduction in the steam content owing to condensation. Consideration has been given to the possibility of making use of the inerting effect of CO.sub.2 to prevent the danger of detonation during an accident situation in a reactor containment. In conjunction with this, a distinction has been made of a so-called pre-inerting and a so-called post-inerting. In pre-inerting the compartments of the reactor containment of the nuclear power plant are filled with nitrogen (N.sub.2) so that when an accident begins to occur, no oxygen would be available to form a flammable gas mixture with the hydrogen that would then be produced. But such a type of pre-inerting involves such practical problems that no actual significance attaches to it. It is sufficient to merely mention that problems would arise with accessing a reactor containment containing a pure nitrogen atmosphere during normal operation. By post-inerting is meant an injection of liquid CO.sub.2 into the reactor containment that is triggered only at the onset of an accident. This post-inerting represents an active safety measure and for this reason in itself is not very realistic. The word "active" means that some sort of device has to be present which senses the fact that an accident has occurred and which activates the introduction of CO.sub.2. Every type of active measure suffers from the fact that it cannot be relied on one hundred per cent to function properly in an emergency. In addition, serious problems arise from feeding in cold CO.sub.2 of -78.degree. C. Feeding in this cold gas would cause a drastically increased condensation of the steam present in the reactor containment and cancel its inerting effect. In addition, this injection would of necessity lead to a subsequent increase in pressure, which, as explained above, would reduce the detonation cell size. Finally, it is very uncertain what the effect would be of the low temperatures involved in supplying cold gas on the relevant safety devices in the reactor containment. The catalytic recombiners, which are passive safety devices, represent mechanisms contributing considerably to reduce the risks involved in an accident situation as described, but they do not eliminate the danger. The possibilities of both pre-inerting and post-inerting do not appear to be practicable. SUMMARY OF THE INVENTION The object of the present invention is to create a device of the type indicated at the beginning which in case of an accident would have the effect of making the atmosphere in the reactor containment inert without being encumbered with the problems described for pre-inerting and post-inerting. This object is achieved in accordance with the present invention by a device as described in claim 1. Preferred embodiments of the invention are set forth in the dependent claims. The present invention offers the possibility for a passive inerting that does not require any auxiliary energy. To achieve this passive inerting, chemical substances are employed as inerting materials, which triggered by the rise in temperature that sets in when an accident occurs, release an inerting gas or gas mixture, e.g., CO.sub.2 and/or steam, into the reactor containment. This can involve two different types of chemical substance, those which are allowed to react with one another when a certain temperature is reached (temperature of reaction) or materials which disintegrate, releasing the inerting gas or gas mixture when a certain temperature of reaction is reached. The first of the above types includes substances which, when coming into contact with one another, will also react with one another even at much lower temperatures than the temperatures considered as temperatures of reaction in the instance under discussion here. These substances must obviously not come into contact with one another until the onset of an accident. But this can be accomplished in a passive manner by using, say, a membrane to keep the substances separated from one another, which membrane liquefies when a target temperature is reached or otherwise releases the chemical substances into direct contact to react with one another. Examples of materials which can be made to react when a certain temperature is reached to release an inerting gas or gas mixture (here CO.sub.2 and steam) are calcium bicarbonate in conjunction with hydrochloric acid and potassium permanganate in conjunction with a mixture of oxalic acid and some sulfuric acid. The following compounds are examples of inerting materials which, when a certain temperature is reached, will disintegrate, releasing CO.sub.2 and/or steam and can be used for purposes of the present invention: Smithsonite (ZnCO.sub.3) exists in the form of a white powder with a density of approximately 4 g/cm.sup.3. This compound has a disintegration temperature of 300.degree. C., at which gaseous CO.sub.2 is released. The portion of CO.sub.2 in the molecular weight of this compound is 49%. Zinc oxide (ZnO) remains as a reaction product following the reaction and has a high melting point of 1260.degree. C. Iron(II) oxalate (FeC.sub.2 O.sub.4.2H.sub.2 O) exists in the form of yellowish crystals with a density of some 2 g/cm.sup.3. This compound disintegrates at a temperature of 190.degree. C. into FeO+CO.sub.2 +CO+2H.sub.2 O. The portion of CO.sub.2 and water of crystallization in this compounds is 25% and 20%, respectively. This means that, given 100 g of this compound at 190.degree. C., 25 g of CO.sub.2 and 20 g of steam can be released for inerting. The FeO remaining after disintegration reacts with the oxygen present in the air and transforms into a higher form of oxide. This brings the additional advantage of lowering the partial pressure of oxygen inside the reactor containment, thus also contributing to the inerting process. Iron(II) carbonate (FeCO.sub.3), which is found in nature and is known as siderite, disintegrates into iron oxide (FeO) and carbon dioxide (CO.sub.2) at approximately 300.degree. C. The portion of CO.sub.2 in the molecular weight of this compound is 38 g. In this case the occurrence of iron oxide resulting from disintegration also reacts with the oxygen present in the atmosphere of the reactor containment. Borax (Na.sub.2 B.sub.4 O.sub.7.10H.sub.2 O) is found in nature under the name of tincal. In its pure state, borax is formed of large, colorless, transparent crystals superficially efflorescent in dry air, which when heated to 350.degree. to 400.degree. C. transform into anhydrous Na.sub.2 B.sub.4 O.sub.7 with a melting point of 878.degree. C. The portion of water of crystallization in the molecular weight is 47%. Potassium aluminum sulfate (KAl(SO.sub.4).sub.2.12H.sub.2 O) is found in nature. Of the 12 molecules of water, six are in a loose bonding with the potassium and the other six in tight bonding with the aluminum. This means that when a temperature of 100.degree. C. is reached, first, half the water of crystallization is released in the form of steam and later, at a higher temperature, the remaining half. The portion of the water of crystallization in the molecular weight is 45.5%. The compound [Mg(MgCO.sub.3).sub.4 ](OH).sub.2 5H.sub.2 O exists in the form of a white powder and is known in the industry as "magnesia alba" or "magnesium carbonate". The portion of CO.sub.2 and H.sub.2 O in the molecular weight of this compound amounts to 51% and 23%, respectively. The use of inerting elements according to the present invention offers, among others, the following substantial advantages: inerting is completely passive, i.e., no auxiliary source of energy is required that might fail to function in case of an accident; inerting does not take place until it is needed, i.e., during normal operation of the reactor the compartments protected in accordance with the present invention can be accessed without any added hindrance whatsoever; by the selection of the quantity and type of the inerting materials with their respective temperatures of reaction, the degree of inerting can be achieved that, depending on the expected quantity of hydrogen that will be released, is necessary for avoiding a deflagration or detonation; the inerting process controlled to meet the need does not cause any excessive increase in pressure; after the initial inerting process, catalytic recombiners also present can operate at higher temperatures and thus be more effective, without this higher temperature posing a risk. The passive inerting according to the present invention as a rule is employed in addition to the use of catalytic recombiners. According to a preferred embodiment, additional advantages can be achieved by exploiting the synergistic effects of the two measures. As already mentioned at the beginning, the catalyst structures used as catalytic recombiners heat up because of an exothermic reaction. If the chemical substances used in accordance with the present invention are placed in the vicinity of a catalyst structure, then the heat developed from the latter can be exploited to start the reaction or disintegration desired, which means that the choice of chemical substances is not restricted to those that have a temperature of reaction for reaction or disintegration in the range of 100.degree. C. It is also possible, especially, to employ various substances with different temperatures of reaction to achieve a passive inerting effect staggered in time according to increases in temperature. The arrangement of the substances in the vicinity of the catalysts offers the added advantage that the released CO.sub.2 and/or steam can rapidly mix in with the surrounding atmosphere due to the convection currents caused by the heated-up catalyst structure. The heat resulting from the catalysts can thus be exploited to great advantage for purposes of passive inerting. On the other hand, the withdrawal of heat that this involves will prevent the temperature in the catalysts rising too high, which otherwise could cause the gas mixture to ignite.
	summary
048184799	abstract	The invention relates to a nuclear reactor spacer grid member for use in a liquid cooled nuclear reactor and to a ductless core component employing a plurality of these spacer grid members. The spacer grid member is of the egg-shell type and is constructed so that the walls of the cell members of the grid member are formed of a single thickness of metal to avoid tolerance problems. Within each cell member is a hydraulic spring which laterally constrains the nuclear material bearing rod which passes through each cell member against a hardstop in response to coolant flow through the cell member. This hydraulic spring is also suitable for use in a water cooled nuclear reactor. A core component constructed of, among other components, a plurality of these spacer grid members, avoids the use of a full length duct by providing spacer sleeves about the sodium tubes passing through the spacer grid members at locations between the grid members, thereby maintaining a predetermined space between adjacent grid members.
	claims	1. A radiation beam therapy system comprising:an assembly of treatment devices, including:a charged-particle accelerator that provides a beam of energetic charged particles;a treatment station that allows positioning of a patient to receive at least a portion of the beam of charged particles; anda beam delivery system that delivers the beam of charged particles to the patient positioned at the treatment location;a database component that stores subsets of parameters associated with selected treatment devices, wherein the parameters comprise instructional information that can be used to configure the selected treatment devices for operation;an interface component that allows a user to modify the subsets of parameters associated with selected treatment devices stored in the database wherein the system is configured so that changes to the stored subsets of parameters in the database component can only be made through the interface component; anda management component that extracts subsets of parameters from the database and generates data storage elements comprising the extracted subsets of parameters in a format recognizable by the selected treatment devices, wherein the data storage elements permit configuration of the selected treatment devices based, at least in part, on the instructional information comprised therein, the management component further distributes the data storage elements to the selected treatment devices to thereby permit the selected treatment devices to operate independently of the database component. 2. The system of claim 1, wherein the beam of charged particles comprises a beam of protons. 3. The system of claim 2, wherein the treatment station comprises a rotatable gantry that allows delivery of the beam of protons to the positioned patient from a plurality of angles. 4. The system of claim 1, wherein the subsets of parameters include treatment data, configuration parameters, operational parameters, and control settings for the selected treatment devices. 5. The system of claim 4, wherein the selected treatment devices are software controlled instruments that require at least one of the subsets of parameters for operation and treatment. 6. The system of claim 1, wherein the database component comprises a centralized database server, which stores configuration and operational information, such as data, parameters, and control settings, for the selected treatment devices in a manner so as to provide easy access to the stored configuration and operational information, wherein parameter retrieval and modification are easily performed by the centralized database server via requests from the interface component. 7. The system of claim 6, wherein the centralized database server provides configuration management activities, which includes record keeping and version/revision control. 8. The system of claim 1, wherein the interface component only permits changes to the stored parameters during time periods when the management component is not extracting subsets of parameters from the database and distributing such extracted parameters to the selected treatment devices. 9. The system of claim 1, wherein the management component reduces the occurrence of single point failures by generating appropriate data storage elements and distributing the data storage elements to the selected treatment devices. 10. The system of claim 9, wherein the distribution of data storage elements by the management component affords the selected treatment devices operational independence from the database component due to the associated reliance on the data storage elements for parameter retrieval and operational configuration. 11. The system of claim 1, further comprising at least one communication link between the management component and the selected treatment devices so as to distribute the generated data storage elements to the selected treatment devices. 12. The system of claim 1, wherein the subsets of parameters are stored in the database component in at least one of database table structures, records, and values. 13. The system of claim 1, wherein the data storage elements are arranged in a consolidated information set that is recognizable by the selected treatment devices. 14. The system of claim 13, wherein the consolidated information set exploits the native functionality of the selected treatment devices in a manner such that an additional numerical or supplemental program or application is unnecessary for the selected treatment devices to recognize the configuration parameter values from the data storage elements. 15. The system of claim 1, wherein the data storage elements comprise a data type that is stored and accessed in a file-oriented manner as is suitable for each selected treatment devices. 16. The system of claim 1, wherein the data storage elements comprise a data type that is stored and accessed in an address-oriented manner as is suitable for each selected treatment devices. 17. The system of claim 1, wherein the data storage elements comprise one or more volatile or non-volatile system control files. 18. The system of claim 1, wherein the data storage elements comprise one or more system control files. 19. The system of claim 18, wherein the one or more system control files include one or more flat files. 20. The system of claim 1, wherein the management component sends configurable parameters to each treatment device, and wherein a selected treatment device retrieves usable parameters from the configurable parameters. 21. The system of claim 1, wherein the management component selectively sends configurable parameters to each treatment device representing usable parameters by each treatment device. 22. A radiation beam therapy system comprising:a plurality of distributed functional components that operate to provide a radiation beam to a patient;a database component that stores a plurality of parameters associated with the distributed functional components,an interface component that allows a user to select an operational mode for which the database component identifies appropriate subsets of parameters that are associated with the distributed functional components and generates at least one system control file containing an appropriate subset of parameters used to configure a selected distributed functional component to operate in a selected manner wherein the subsets of parameters can only be changed via the interface component; anda control file distribution component that provides each of the distributed functional components with the appropriate system control file such that the functional components are able to operate substantially independently of the database component to thereby reduce the likelihood of a single point failure of the radiation beam therapy system and wherein changes to the subsets of parameters can only be made when system control files are not being distributed. 23. The system of claim 22, wherein the distributed functional components are software controlled instruments that require at least one of the plurality of parameters for operation.
	claims	1. A nuclear-fuel sintered pellet based on oxide manufactured using an oxide to which at least one of a group including uranium (U), plutonium (Pu), gadolinium (Gd), and thorium (Th) is added, the nuclear-fuel sintered pellet comprising:a precipitate material generated due to a sintering additive during a sintering process in a microstructure of nuclear-fuel sintered pellet thereof,wherein the precipitate material is uniformly dispersed in a circumferential direction, and wherein the precipitate material forms a donut-shaped two-dimensional precipitate cluster. 2. The nuclear-fuel sintered pellet of claim 1, wherein the precipitate material is disposed along a crystal grain boundary. 3. The nuclear-fuel sintered pellet of claim 1, wherein the precipitate material has a length of 3 to 30 μm and a thickness of 1 to 10 μm. 4. The nuclear-fuel sintered pellet of claim 1, wherein an addition amount of the sintering additive is 0.5 to 10.0 wt % based on the oxide for the nuclear-fuel sintered pellet. 5. The nuclear-fuel sintered pellet of claim 1, wherein the sintering additive includes at least one of a group including copper (I) oxide (CuO), copper (II) oxide (Cu2O), chromium carbide (Cr23C6), molybdenum dioxide (MoO2), molybdenum trioxide (MoO3), molybdenum carbide (Mo2C), and molybdenum disilicide (MoSi2). 6. The nuclear-fuel sintered pellet of claim 5, wherein the sintering additive further includes titanium dioxide (TiO2). 7. The nuclear-fuel sintered pellet of claim 6, wherein a content of the titanium dioxide (TiO2) is 0.05 to 0.70 wt % based on an oxide for the nuclear-fuel sintered pellet. 8. The nuclear-fuel sintered pellet of claim 5, further comprising:a metal aluminum (Al) powder. 9. The nuclear-fuel sintered pellet of claim 8, wherein a content of the metal aluminum powder is 0.01 to 0.10 wt % based on an oxide for the nuclear-fuel sintered pellet. 10. A method of manufacturing an oxide nuclear-fuel sintered pellet in which a plate-type fine precipitate material is dispersed in a circumferential direction, the method comprising:mixing an oxide powder, including at least one of a group including uranium (U), plutonium (Pu), gadolinium (Gd), and thorium (Th), with a sintering additive powder, thus manufacturing a mixed powder (first step);manufacturing a granulated powder using a sieve after pre-compaction and crushing the mixed powder (second step);uniaxially compressing the granulated powder at 300 to 500 MPa, thus manufacturing a nuclear-fuel green pellet (third step);performing primary sintering of the manufactured nuclear-fuel green pellet in a hydrogen-containing reducing gas atmosphere at a sintering temperature of about 700 to 1100° C. (fourth step); andperforming secondary sintering in a hydrogen-containing reducing gas atmosphere at a sintering temperature of 1700 to 1800° C. successively after the primary sintering is completed,wherein the nuclear-fuel sintered pellet comprises:a precipitate material generated due to a sintering additive during a sintering process in a microstructure of nuclear-fuel sintered pellet thereof,wherein the precipitate material is uniformly dispersed in a circumferential direction, and wherein the precipitate material forms a donut-shaped two-dimensional precipitate cluster. 11. The method of claim 10, wherein, in the secondary sintering, after completion of the primary sintering, sintering is performed at a condition of 1700 to 1800° C. for 60 to 240 minutes at a heating rate of 1 to 10° C./min without cooling so that a sintering additive in a liquid state is precipitated into a plate-type fine precipitate material and is then disposed homogeneously in a circumferential direction while crystal grains of a nuclear-fuel sintered pellet based on oxide grow. 12. The method of claim 10, wherein a hydrogen-containing reducing gas contains at least one of a group including carbon dioxide, nitrogen, argon, and helium gases. 13. The method of claim 10, wherein a hydrogen-containing reducing gas contains only a hydrogen gas. 14. The method of claim 10, wherein the sintering additive powder includes at least one of a group including copper (I) oxide (CuO), copper (II) oxide (Cu2O), chromium carbide (Cr23C6), molybdenum dioxide (MoO2), molybdenum trioxide (MoO3), molybdenum carbide (Mo2C), and molybdenum disilicide (MoSi2). 15. The method of claim 14, wherein a sintering additive further includes titanium dioxide (TiO2). 16. The method of claim 15, wherein a content of the titanium dioxide (TiO2) that is added is 0.05 to 0.70 wt % based on an oxide for a nuclear-fuel sintered pellet. 17. The method of claim 15, wherein a metal aluminum (Al) powder is further added. 18. The method of claim 10, wherein in the primary sintering, heating is performed at a heating rate of 1 to 10° C./min so that sintering is performed at a condition of 300 to 1100° C. for 30 to 120 minutes, thereby maintaining a sintering additive in a liquid state. 19. The method of claim 18, wherein, when a sintering additive powder is copper (I) oxide (CuO) or copper (II) oxide (Cu2O), in the primary sintering (fourth step), a sintering temperature is 300 to 500° C. and a sintering time is 30 to 120 minutes.
	summary
	description	1. Field of the Invention The present invention relates to spacer grid spring that increases the conformal contact area with a fuel rod and, more particularly, to spacer grid spring that increases the conformal contact area with a fuel rod, in which the spacer grid spring of the grid strap, which is in contact with the fuel rod, is optimized in shape, thereby the elasticity of the spacer grid spring contacting the fuel rod is increased, the conformal contact area with a contact portion of the spacer grid spring contacting the fuel rod when the fuel rod is inserted into each cell of a spacer grid spring is expanded to realize uniform stress distribution, and excessive plastic deformation of the spacer grid spring can be reduced, and in which magnitude and distribution of contact pressure between the fuel rod and the spacer grid spring are improved, thereby reducing the possibility of fretting wear caused by contact between the fuel rod and the spacer grid spring. 2. Description of the Related Art In general, spacer grids is one of the components constituting a nuclear fuel assembly in a nuclear reactor, and functions to arrange and support nuclear fuel rods, which constitute unit grid cells thereof, at designated positions by mutually connecting a plurality of straps, each of which has a spacer grid spring and dimples. FIG. 1 is a perspective view schematically illustrating a conventional nuclear fuel assembly. FIG. 2 is a plan view schematically illustrating spacer grids applied to a conventional nuclear fuel assembly. FIG. 3 is a perspective view schematically illustrating spacer grids applied to a conventional nuclear fuel assembly. FIG. 4 is a perspective view schematically illustrating spacer grid spring for spacer grids applied to a conventional nuclear fuel assembly. FIG. 5 schematically illustrates deformation of spacer grid spring, which is applied to spacer grids of a conventional nuclear fuel assembly, caused by one nuclear fuel rod. As illustrated in the figures, the conventional nuclear fuel assembly 2 to which spacer grids 110 are applied has a plurality of guide tubes 113 fitted between a top end piece 111 and a bottom end piece 112. Here, the spacer grids 110 supporting nuclear fuel rods 125 form the nuclear fuel assembly 2 by means of welding with the guide tubes 113 in the longitudinal direction of the guide tubes 113 at regular intervals. Meanwhile, the spacer grids 110 is usually formed of zircaloy, and includes nuclear fuel rod cells 123 that support the nuclear fuel rods 125, and guide tube cells 124 into which the guide tubes 113 are inserted, wherein each nuclear fuel rod cell 123 is designed such that two spacer grid springs 118 and the total of four dimples 119, which are each located on a top side and a bottom side of each spacer grid spring 118, contact and support each nuclear fuel rod 125 at six supporting points. Thus, when the spacer grid springs 118 are in contact with the nuclear fuel rods 125 and are deformed by the nuclear fuel rods 125, two supports 121 of each spacer grid spring 118 are pressed by each nuclear fuel rod 125. Here, because the rigidity of each support 121 is similar to that of a central curvature 122, which is connected with the two supports 121 and is contact with each nuclear fuel rod 125, each support 121 is simultaneously subjected to bending 131 and twisting 132 due to a load 130 applied by each nuclear fuel rod 125, as illustrated by arrows in FIG. 5. When these bending and twisting deformations act on each support at the same time, each nuclear fuel rod 125 is unstably supported, and thus slight sliding occurs between the nuclear fuel rod 125 and the central curvature 122 contacting the nuclear fuel rod 125. As a result, desired conformal surface contact does not occur, thus causing stress concentration. This stress concentration makes the spacer grid spring vulnerable to fatigue, so that each nuclear fuel rod 125 has a high possibility of increasing the fretting wear thereof. Further, the deformation of the central curvature 122 provides a high possibility of losing the original surface contact profile, and thus exerts an influence on stress distribution and magnitude of peak stress. Meanwhile, the spacer grid spring 118 and the dimples 119 of each grid strap 115 have the same radius of curvature as the nuclear fuel rods 125, and thus are in conformal surface contact with the nuclear fuel rods 125 from the beginning. Thereafter, when the spacer grid spring 118 receives the load of each nuclear fuel rod 125, the central curvature 122 contacting respective nuclear fuel rod 125, and its support 121 are deformed at the same time. Further, when spring force of the spacer grid spring 118 and dimples 119 of each grid strap 115 is too weak, the nuclear fuel rods 125 cannot be arranged at designated positions, and thereby have a possibility of losing sound supporting performance. When the spring force is too high, each nuclear fuel rod 125 undergoes defects such as scratching on the surface thereof due to excessive frictional resistance when inserted into the spacer grid 110. Further, during operation of the nuclear reactor, the nuclear fuel rods 125 experience longitudinal growth by means of irradiation of neutrons. This longitudinal growth is not properly accepted, and thus the nuclear fuel rods 125 are bent. In this manner, when the nuclear fuel rods are bent, the neighboring nuclear fuel rods become too near each other or contact each other. Thus, the coolant channel between the neighboring nuclear fuel rods becomes narrow or is blocked. As a result, heat generated from the nuclear fuel rods is not effectively transmitted to the coolant, thereby increasing the temperature of the nuclear fuel rods. As such, the possibility of generating departure from nucleate boiling (DNB) is increased, which is mainly responsible for the reduction of nuclear fuel output. In order to solve the above-described problems, recent nuclear fuel development has focused on high combustion and zero defects. In particular, to develop high-combustion nuclear fuel, the thermal performance of the nuclear fuel for promoting heat transmission from the nuclear fuel rods to the coolant must be increased. To this end, a method of improving the flow of the coolant flowing around the nuclear fuel rods is required. Here, as the method of improving the flow of the coolant flowing around the nuclear fuel rods, a method of changing the geometry of the spacer grid is employed, and may include the attachment of a hybrid vane or a change in its design, or effective construction of a fluid channel. However, most concepts for raising this thermal performance are based on the principle that the flow of the coolant flowing around the nuclear fuel rods is very turbulent, the flow has a high Reynolds number. In this manner, the turbulence of the coolant flow around the nuclear fuel rods is mainly responsible for, flow induced vibration of the nuclear fuel rods. The flow induced vibration of the nuclear fuel rods is a factor generating mutual relative motion, in which the nuclear fuel rods slide on the contact surfaces with the spacer grid springs or the dimples of the grid straps. For this reason, the contact surfaces of the nuclear fuel rods are subjected to local wear, which incurs “fretting damage to the nuclear fuel rods”, in which the nuclear fuel rods are gradually damaged. In other words, the contact surfaces between the nuclear fuel rods and the spacer grid springs or dimples of the grid straps are worn, so that the nuclear fuel rods are locally damaged. When this damage becomes serious, the nuclear fuel rods can be broken. Therefore, the method of raising the thermal performance of the nuclear fuel in order to develop high-combustion nuclear fuel leads instead in damage to the nuclear fuel rods. As described above, the spacer grids serving to support the nuclear fuel rods must be able to maintain reliable supporting performance during the lifetime of the nuclear fuel rods, and to inhibit the possibility of fretting wear of the nuclear fuel rods. In this manner, in order to allow the nuclear fuel rods to maintain reliable supporting performance for the lifetime of the nuclear fuel rods, the spacer grid springs must be able to support the nuclear fuel rods with sufficient spring force for the lifetime of the nuclear fuel rods, and to maintain at least enough spring force to support the nuclear fuel rods, which can be variously changed in the nuclear reactor up to the lifetime of the nuclear fuel rods, by expanding the elastic behavior region of the spacer grid springs. However, during the operation of the nuclear reactor, the spacer grid springs and dimples gradually lose the initial spring force applied to the nuclear fuel rods due to the irradiation of the neutrons. As a result, a gap can develop between the nuclear fuel rods and their supports, and reliable supporting performance of the nuclear fuel rods can be lost by means of the load acting on the nuclear fuel rods in an arbitrary direction due to the flow of the coolant. Further, in order to inhibit the possibility of the fretting wear of the nuclear fuel rods, the causes of fretting wear must be reduced. These causes generate the gap between the nuclear fuel rods and the supports of the spacer grids due to reduction of the spring force caused by the neutron irradiation, thermal expansion difference between the nuclear fuel rods and the spacer grids, diametrical reduction of the nuclear fuel rods caused by the elongation of the nuclear fuel rods, and so on. The nuclear fuel rods are vibrated by the turbulent flow caused by the coolant flow, and thus fretting wear is accelerated. Accordingly, the present invention has been made keeping in mind the above problems occurring in the prior art, and an object of the present invention is to provide spacer grid spring that increases the conformal contact area with a fuel rod, in which the spacer grid spring of the grid strap, which is in contact with the fuel rod, is optimized in shape, thereby the elasticity of the spacer grid spring contacting the fuel rod is increased, the conformal contact area with a contact portion of the spacer grid spring contacting the fuel rod when the fuel rod is inserted into each cell of a spacer grid spring is expanded to obtain uniform stress distribution, and excessive plastic deformation of the spacer grid spring can be reduced, in which the magnitude and distribution of contact pressure between the fuel rod and the spacer grid spring are improved, thereby reducing the possibility of fretting wear caused by contact between the fuel rod and the spacer grid spring, and in which a elastic behavior region of the spacer grid spring is expanded, so that the fuel rod can be stably supported until the lifetime of the fuel rod expires despite changes in the supporting conditions of the fuel rod. In order to achieve the above object, according to the present invention, there is provided grid strap for spacer grids including upper and lower plates having dimples protruding on one side respectively, and a spacer grid spring which connects the upper and lower plates and is in direct contact with a fuel rod, wherein the spacer grid spring includes upper and lower bases that vertically extend from the middle of the lower end of the upper plate and the middle of the upper end of the lower plate respectively, upper left-hand and right-hand supports and lower left-hand and right-hand supports that branch off from the upper and lower bases, respectively, and are symmetrical with each other, bridges that are connected between the upper and lower left-hand supports and between the upper and lower right-hand supports, and a conformal curvature that is connected between the bridges, protrudes in a direction opposite the dimples, is in direct contact with the fuel rod, and is curved inwards to allow upper and lower ends thereof to have a semi-circular form. Preferably, each of the bridges located on opposite sides of the conformal curvature may be curved outwards in a semi-circular form, and may have a wedge shape formed on one end thereof. Here, the spacer grid spring may include connecting pieces that connect the upper and lower plates at proper positions spaced apart from left-hand and right-hand supports in outward directions by a predetermined distance. Reference will now be made in greater detail to an exemplary embodiment of the invention, which is illustrated in the accompanying drawings. Wherever possible, the same reference numerals will be used throughout the drawings and the description to refer to the same or like parts. FIG. 6 is a perspective view illustrating a grid strap having a spacer grid spring that increases the conformal contact area with a nuclear fuel rod in accordance with an embodiment of the present invention. FIG. 7 is a front view illustrating a grid strap having a spacer grid spring that increases the conformal contact area with a nuclear fuel rod in accordance with an embodiment of the present invention. FIG. 8 is a plan view illustrating a grid strap having a spacer grid spring that increases the conformal contact area with a nuclear fuel rod in accordance with an embodiment of the present invention. FIG. 9 is a perspective view schematically illustrating one cell of spacer grids made by using grid straps having a spacer grid spring that increases the conformal contact area with a nuclear fuel rod in accordance with an embodiment of the present invention. FIG. 10 is a perspective view schematically illustrating a spacer grid made using grid straps having a spacer grid spring that increases the conformal contact area with a nuclear fuel rod in accordance with an embodiment of the present invention. As illustrated in the figures, the spacer grid spring 14 that increases the conformal contact area with a fuel rod 3 is provided between upper and lower plates 11a and 11b which have the dimples 12a and 12b, respectively. More specifically, the spacer grid spring 14 of the grid strap 10 of the present invention is provided between a lower end of the upper plate 11a and an upper end of the lower plate 11b, at the centers of which the dimples 12a and 12b protrude toward one side in place. Further, the spacer grid spring 14 connects the upper and lower plates 11a and 11b, and is in direct contact with the fuel rod 3. The spacer grid spring 14 includes upper and lower bases 15a and 15b that vertically extend from the middle of the lower end of the upper plate 11a and the middle of the upper end of the lower plate 11b respectively, upper left-hand and right-hand supports 16a and 16b and lower left-hand and right-hand supports 16a and 16b that branch off from the upper and lower bases 15a and 15b respectively and are symmetrical with each other, bridges 18a and 18b that are connected between the upper and lower left-hand supports 16a and between the upper and lower right-hand supports 16b, and a conformal curvature 17 that is connected between the bridges 18a and 18b, protrudes in a direction opposite the dimples 12a and 12b, and is in direct contact with the fuel rod 3. Here, the conformal curvature 17 of the spacer grid spring 14 is curved inwards to allow upper and lower ends 21a and 21b thereof to have a semi-circular form. In other words, the conformal curvature 17 is designed such that the middle portion and upper and lower ends 21a and 21b thereof contacting the fuel rod 3 are curved inwards in a circular or elliptical form so as to have the same radius of curvature at the same central point as the fuel rod 3 and to be in conformal contact with the fuel rod 3. Thereby, the conformal curvature 17 can expand the contact area with the fuel rod 3, uniformly maintain contact pressure distribution, and reduce the magnitude of peak stress. Each of the bridges 18a and 18b located on opposite sides of the conformal curvature 17 is curved outwards in a semi-circular form, and is formed in a wedge shape 24 on one end thereof. In other words, each of the bridges 18a and 18b, which are located on opposite sides of the conformal curvature 17, has a semi-circular form curved outwards near the conformal curvature 17, and a wedge shape 24 on the end thereof. As described above, the conformal curvature 17 is curved inwards to allow the upper and lower ends 21a and 21b thereof to have the semi-circular form, and the bridges 18a and 18b, which are located on the opposite sides of the conformal curvature 17, are curved outwards in the semi-circular form. Meanwhile, even if pure bending deformation occurs when elastic deformation is caused by pressing the conformal curvature 17 contacting the fuel rod 3, the left-hand and right-hand supports 16a and 16b, which branch off from the upper and lower bases 15a and 15b extending from the centers of the lower and upper ends of the upper and lower plates 11a and 11b, minimize twisting deformation, so that the surface contact between the fuel rod 3 and the conformal curvature 17 can be maintained. To this end, the left-hand and right-hand supports 16a and 16b are adapted to have relatively lower rigidity by bending compared to the rigidity of the conformal curvature 17, thereby being elastically deformed before the conformal curvature 17 is deformed by the load of the fuel rod 3 applied to the conformal curvature 17 of the spacer grid spring 14. As illustrated in FIGS. 9 and 10, the grid strap 10 having the spacer grid spring 14 of the above-mentioned shape and form is designed so that both the conformal curvature 17 of the spacer grid spring 14 and the dimples 12a and 12b are in surface contact with the outer circumference of the fuel rod 3 when the fuel 3 is inserted into each cell of the spacer grids 1. In this manner, the conformal curvature 17 of the spacer grid spring 14, which is in surface contact with the outer circumference of the fuel rod 3, and the bridges 18a and 18b of the spacer grid spring 14 are deformed in shape and form, thereby expanding the conformal contact area with the fuel rod 3. Thus, sliding of the conformal curvature 17 relative to the fuel rod 3 is reduced, so that the fuel rod 3 is reliably held, and the possibility of fretting wear occurring on the surface of the fuel rod 3 is reduced. Further, the conformal curvature 17 of the spacer grid spring 14 is curved inwards to allow the upper and lower ends thereof to have the semi-circular form, thereby preventing a change in the curvature thereof. A change in the relatively minute amount of sliding between the fuel rod 3 and the conformal curvature 17 is minimized, thereby the fuel rod 3 can be stably supported regardless of changes in the supporting conditions of the fuel rod 3. FIG. 11 is a perspective view illustrating a grid strap having a spacer grid spring that increases the conformal contact area with a nuclear fuel rod in accordance with another embodiment of the present invention. FIG. 12 is a front view illustrating a grid strap having a spacer grid spring in accordance with another embodiment of the present invention. FIG. 13 is a plan view illustrating a grid strap having a spacer grid spring in accordance with another embodiment of the present invention. FIG. 14 is a perspective view schematically illustrating one cell of spacer grids made using grid straps having a spacer grid spring in accordance with another embodiment of the present invention. FIG. 15 is a perspective view schematically illustrating spacer grids made by using grid straps having a spacer grid spring in accordance with another embodiment of the present invention. The spacer grid spring is partly changed in shape and form, compared to the previous embodiment. As illustrated in the figures, the spacer grid spring 14, which increases the conformal contact area with a nuclear fuel rod in accordance with the present embodiment, includes connecting pieces 19a and 19b that connect upper and lower plates 11a and 11b at proper positions spaced apart from left- and right-hand supports 16a and 16b, which are provided on left- and right-hand sides of a conformal curvature 17, in outward directions by a predetermined distance. More specifically, the connecting pieces 19a and 19b connect the upper and lower plates 11a and 11b at proper positions located outside the left- and right-hand supports 16a and 16b, which are connected with bridges 18a and 18b on opposite sides of the conformal curvature 17, and predetermined spaces are formed between the connecting pieces 19a and 19b and the left- and right-hand supports 16a and 16b. As illustrated in FIGS. 14 and 15, the grid strap 10 having the spacer grid spring 14 of the above-mentioned shape and form is designed so that both the conformal curvature 17 of the spacer grid spring 14 and the dimples 12a and 12b are in surface contact with the outer circumference of the fuel rod 3 when the fuel rod 3 is inserted into a cell of the spacer grids 1, and so that the connecting pieces 19a and 19b are provided on the opposite sides of the conformal curvature 17 contacting the fuel rod 3. Thereby, the conformal curvature 17 contacting the fuel rod 3 is prevented from being changed in the curvature thereof. Further, a change in the relatively minute amount of sliding between the fuel rod 3 and the conformal curvature 17 is minimized, thereby the fuel rod 3 can be stably supported regardless of a change in the supporting conditions of the fuel rod 3. As is apparent from the above description, according to the present invention, the spacer grid spring of the grid strap, which is in contact with the fuel rod, is optimized in shape, thereby the elasticity of the spacer grid spring contacting the fuel rod is increased, the conformal contact area with the contact portion of the spacer grid spring contacting the fuel rod when the fuel rod is inserted into each cell of the spacer grid spring is expanded to realize uniform stress distribution, and excessive plastic deformation of the spacer grid spring can be reduced. Further, the magnitude and distribution of the contact pressure between the fuel rod and the spacer grid spring are improved, thereby reducing the possibility of fretting wear caused by contact between the fuel rod and the spacer grid spring. The elastic behavior region of the spacer grid spring is expanded, so that the fuel rod can be stably supported until the lifetime of the fuel rod is expired despite changes in the supporting conditions of the fuel rod. In addition, the grid strap can inhibit breakdown caused by wear, fatigue, and vibration between a piping system transporting a fluid and its supporting structure and between elongate rods or pipes and supports for supporting them in the general industrial equipment using a boiler or heat exchanger, and thus can be applied to various fields. Although an exemplary embodiment of the present invention has been described for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims.
058728244	claims	1. A method of studying a sample of material, comprising the steps of: a) placing a fissionable material source in a path of neutrons emitted from a neutron pulse generator, said neutron pulse generator being positioned at a first distance and at a first axial direction with respect to said fissionable material source; b) placing said sample of material at a second distance and at a second axial direction with respect to said fissionable material source; c) generating one or more neutron pulses by said neutron pulse generator, said one or more neutron pulses being of a sufficient energy such that one or more heavy ions is emitted from said fissionable material source as fission fragments, wherein at least one of said fission fragments propagates toward and falls incident upon said sample of material, and wherein at least some of said fission fragments induce desorption of at least one ion off said sample of material into a drift region; d) recording a start time for each of said at least one ion desorbed off said sample of material, wherein said start time denotes a time instant when said one or more neutron pulses are generated; e) recording a stop time for each of said at least one ion desorbed off said sample of material, wherein said stop time denotes a time instant when said at least one ion desorbed off said sample of material arrives at a detector located at an end of said drift region, said detector being positioned at a third distance with respect to said fissionable material source, said third distance being greater than said second distance; and f) determining a mass of said one of said at least one ion desorbed off said sample of material based on a difference between said stop time and said start time. a) placing a 238 isotope of uranium (.sup.238 U) source in a path of neutrons emitted from a neutron pulse generator, said neutron pulse generator being positioned at a first distance and at a first axial direction with respect to said .sup.238 U source; b) placing said sample of material at a second distance and at a second axial direction with respect to said .sup.238 U source; c) generating one or more neutron pulses by said neutron pulse generator, said one or more neutron pulses being of a sufficient energy such that one or more heavy ions are emitted from said .sup.238 U source as fission fragments, wherein at least one of said fission fragments propagate toward and fall incident upon said sample of material, and wherein at least some of said fission fragments induce desorption of at least one ion off said sample of material into a drift region; d) recording a start time for each of said at least one ion desorbed off said sample of material, wherein said start time denotes a time instant when said one or more neutron pulses are generated; e) recording a stop time for each of said at least one ion desorbed off said sample of material, wherein said stop time denotes a time instant when said at least one ion desorbed off said sample of material arrives at a detector located at an end of said drift region, said detector being positioned at a third distance with respect to said .sup.238 U source, said third distance being greater than said second distance; and f) determining a mass of said one of said at least one ion desorbed off said sample of material based on a difference between said stop time and said start time. determining when said each of said secondary ions impinge on said detector and to output a respective digital signal indicative thereof; and providing a signal from a control unit to enable said neutron pulse generator to emit said neutrons at a first time, said control unit receiving said respective digital signal and determining an amount of time between sending of said first signal and receiving of said respective digital signal, wherein said amount of time is directly related to a mass of one of said secondary ions corresponding to said respective digital signal. determining when said each of said secondary ions impinge on said detector and to output a respective digital signal indicative thereof; and providing a signal from a control unit to enable said neutron pulse generator to emit said neutrons at a first time, said control electronics receiving said respective digital signal and determining an amount of time between sending of said first signal and receiving of said respective digital signal, wherein said amount of time is directly related to a mass of one of said secondary ions corresponding to said respective digital signal. a) placing a fissionable material source in a path of output neutrons that are emitted from a neutron pulse generator, said neutron pulse generator being positioned at a first predetermined distance with respect to said fissionable material source, said neutron pulse generator generating a plurality of said output neutrons within a predetermined time interval, to establish a flux of said output neutrons in a direction towards said fissionable material; b) placing said sample of material at a second predetermined distance with respect to said fissionable material source; c) generating said plurality of said output neutrons by said neutron pulse generator in a direction towards said fissionable material source, said plurality of said output neutrons being of a collective energy such that one or more heavy ions is ionized off of said fissionable material source as fission fragments, wherein said second predetermined distance is chosen so that a solid angle of dispersal of said fission fragments ionized off of said fissionable material source results in at least a fixed percentage of said fission fragments falling incident on said sample of material; d) receiving said at least a fixed percentage of said fission fragments at said sample of material, said at least a fixed percentage of said fission fragments inducing desorption of at least one ion off said sample of material into a drift region; e) recording a start time that is associated with each of said at least one ion desorbed off said sample of material, wherein said start time denotes a beginning of said predetermined time interval; f) recording a stop time for each of said at least one ion desorbed off said sample of material due to said plurality of output neutrons, wherein said stop time denotes a time instant when said at least one ion desorbed off said sample of material arrives at a detector located at an end of said drift region, said detector being positioned at a third predetermined distance with respect to said fissionable material source, said third predetermined distance being greater than said second predetermined distance; and g) determining a mass of said one of said at least one ion desorbed off said sample of material based on a difference between said stop time and said start time. 2. A method of studying a sample of material, comprising the steps of: 3. A method as recited in claim 1, wherein said neutron pulse generator has an adjustable repetition rate for generating pulses. 4. A method as recited in claim 1, wherein said neutron pulse generator is part of a heavy ion induced desorption mass spectrometer source. 5. A method as recited in claim 1, further comprising the step of marking times of pulses generated by said neutron pulse generator. 6. A method as recited in claim 1, further comprising the step of correlating pulses emitted from said neutron pulse generator with said desorption of said sample of material and said fission fragments produced from said fissionable material source. 7. A method as recited in claim 1, wherein said detector is positioned at a third axial direction with respect to said fissionable material source, said third axial direction being approximately equal to said second axial direction. 8. A method as recited in claim 1, further comprising the step of providing an electronic voltage from a grid for attracting said secondary ions as they are produced off of said sample of material, wherein said drift region is located between said grid and said detector, and wherein a time it takes each of said secondary ions to traverse through said drift region to impinge on said detector is indicative of a mass of said each of said secondary ions. 9. A method as recited in claim 8, further comprising the steps of: 10. A method as recited in claim 1, wherein said neutron pulse generator outputs a burst of said neutrons of between 5 nanoseconds and 100 nanoseconds, and wherein said burst of said neutrons causes about 10000 fission fragments to be emitted from said fissionable material source. 11. A method as recited in claim 2, wherein said neutron pulse generator has an adjustable repetition rate for generating pulses. 12. A method as recited in claim 2, wherein said neutron pulse generator is part of a heavy ion induced desorption mass spectrometer source. 13. A method as recited in claim 2, further comprising the step of marking times of pulses generated by said neutron pulse generator. 14. A method as recited in claim 2, further comprising the step of correlating pulses emitted from said neutron pulse generator with said desorption of said sample of material and said fission fragments produced from said .sup.238 U source. 15. A method as recited in claim 2, wherein said detector is positioned at a third axial direction with respect to said .sup.238 U source, said third axial direction being approximately equal to said second axial direction. 16. The method as recited in claim 2, further comprising the step of providing an electronic voltage from a grid for attracting said secondary ions as they are produced off of said sample of material, wherein said drift region is located between said grid and said detector, and wherein a time it takes each of said secondary ions to traverse through said drift region to impinge on said detector is indicative of a mass of said each of said secondary ions. 17. A method as recited in claim 16, further comprising the steps of: 18. A method as recited in claim 2, wherein said neutron pulse generator outputs a burst of said neutrons of between 5 nanoseconds and 100 nanoseconds, and wherein said burst of said neutrons causes about 10000 fission fragments to be emitted from said .sup.238 U source. 19. A method of studying a sample of material, comprising the steps of:
	claims	1. A method for treating a nitric aqueous liquid effluent containing nitrates of metals or metalloids, comprising a step for calcination of the effluent in order to convert the nitrates of metals or metalloids into oxides of said metals or metalloids, at least one compound selected from the nitrates of metals or metalloids and the other compounds of the effluent leading upon calcination to a tacky oxide, and a dilution adjuvant leading upon calcination to a non-tacky oxide being added to the effluent prior to the calcination step, wherein the dilution adjuvant comprises aluminium nitrate and at least one other nitrate selected from iron nitrate and rare earth nitrates. 2. The method according to claim 1, wherein the dilution adjuvant comprises aluminium nitrate and at least one other nitrate selected from iron nitrate, lanthanum nitrate, cerium nitrate, praseodymium nitrate and neodymium nitrate. 3. The method according to claim 1, wherein said at least one compound leading upon calcination to tacky oxide(s) is selected from sodium nitrate, phosphomolybdic acid, boron nitrate, and mixtures thereof. 4. The method according to claim 1, wherein the content of compound(s) leading upon calcination to tacky oxide(s) expressed as oxides, based on the total mass of the salts contained in the effluent, expressed as oxides, is greater than 35% by mass. 5. The method according to claim 3, wherein the effluent has a sodium nitrate content, expressed as sodium oxide Na2O, based on the total mass of the salts contained in the effluent, expressed as oxides, greater than 30 % by mass, preferably greater than 50 % by mass. 6. The method according to claim 1, wherein the calcination step is carried out in a heated rotating tube allowing the calcinate to attain a temperature of about 400° C. 7. The method according to claim 1, wherein after the calcination step, a vitrification step is carried out which consists of elaborating a confinement glass from the melting of the calcination produced during the calcination step with a glass frit.
	description	This application is a divisional of application Ser. No. 11/980,423, filed on Oct. 31, 2007, which is a continuation of application Ser. No. 11/314,413, filed on Dec. 22, 2005, now U.S. Pat. No. 7,365,901 which is a continuation of application Ser. No. 10/776,192, filed on Feb. 12, 2004, now U.S. Pat. No. 7,009,753 which is a continuation of application Ser. No. 09/623,195, filed on Aug. 29, 2000 now U.S. Pat. No. 6,747,783, which is a §371 national phase application of International Application No. PCT/SE99/00310, filed Mar. 2, 1999 which claims priority to Swedish Patent Application No. SE 9800665-3. The entire contents of all of the above are incorporated herein by reference The present invention relates to printing of patterns with extremely high precision on photosensitive surfaces, such as photomasks for semiconductor devices and displays. It also relates to direct writing of semiconductor device patterns, display panels, integrated optical devices and electronic interconnect structures. Furthermore, it can have applications to other types of precision printing such as security printing. The term printing should be understood in a broad sense, meaning exposure of photoresist and photographic emulsion, but also the action of light on other light sensitive media such as dry-process paper, by ablation or chemical processes activated by light or heat. Light is not limited to mean visible light, but a wide range of wavelengths from infrared (IR) to extreme UV. Of special importance is the ultraviolet range from 370 nm (UV) through deep ultraviolet (DUV), vacuum ultraviolet (VUV) and extreme ultraviolet (EUV) down to a few nanometers wavelength. EUV is in this application defined as the range from 100 nm and down as far as the radiation is possible to treat as light. A typical wavelength for EUV is 13 nm. IR is defined as 780 nm up to about 20 □m. In a different sense the invention relates to the art and science of spatial light modulators and projection displays and printers using such modulators. In particular it improves the grey-scale properties, the image stability through focus and image uniformity and the data processing for such modulators by application of analog modulation technique. The most important use of the analog modulation is to generate an image in a high-contrast material such as photoresist with an address grid, i.e. the increment by which the position of an edge in the pattern is specified, that is much finer than the grid created by the pixels of the spatial light modulator. It is known in the current art to build precision pattern generators using projection of micromirror spatial light modulators (SLMs) of the micromirror type (Nelson 1988, Kück 1990). To use an SLM in a pattern generator has a number of advantages compared to the more wide-spread method of using scanning laser spots: the SLM is a massively parallel device and the number of pixels that can be written per second is extremely high. The optical system is also simpler in the sense that the illumination of the SLM is non-critical, while in a laser scanner the entire beam path has to be built with high precision. Compared to some types of scanners, in particular electrooptic and acoustooptic ones, the micromirror SLM can be used at shorter wavelengths since it is a purely reflective device. In both references cited above the spatial modulator uses only on-off modulation at each pixel. The input data is converted to a pixel map with one bit depth, i.e. with the values 0 and 1 in each pixel. The conversion can be done effectively using graphic processors or custom logic with area fill instructions. In a previous application by the same inventor Sandström (Sandström et. al. 1990), the ability to use an intermediate exposure value at the boundary of a pattern element to fine-adjust the position of the element's edge in the image created by a laser scanner was described. It is also known in the art to create a grey-scale image, preferably for projection display of video images and for printing, with an SLM by variation of the time a pixel is turned on or by printing the same pixel several times with the pixel turned on a varying number of times. The present invention devices a system for direct grey-scale generation with a spatial light modulator, with a special view to the generation of ultra-precision patterns. Important aspects in the preferred embodiments, are uniformity of the image from pixel to pixel and independence of exact placement of a feature relative to the pixels of the SLM and stability when focus is changed, either with intention or inadvertently. It is therefore an object of the present invention to provide an improved pattern generator for printing of precision patterns. This object is achieved with an apparatus according to the appended claims, providing an analog modulation of the pixels in the SLM. The basis for understanding the invention is the generic arrangement in FIG. 1 which shows a generic projection printer with an SLM. Spatial light modulators based on reflection come in two varieties, the deflection type (Nelson) and the phase type (Kück). The difference between them may in a particular case with micromirrors seem small, but the phase SLM extinguishes the beam in the specular direction by destructive interference, while a pixel in a deflection SLM deflects the specular beam geometrically to one side so that it misses the aperture of the imaging lens as shown in FIG. 1. For ultra-precise printing as performed in the current invention the phase-modulating system as described by Kück 1990 is superior to the deflecting type. First, it has better contrast since all parts of the surface, also hinges and support posts, take part in the destructive interference and total extinction can be achieved. Second, a system that works by deflecting the light to the side is difficult to make symmetrical around the optical axis at intermediate deflection angles, creating a risk of feature instability when focus is changed. In the preferred embodiments the phase type is used, but if one accepts or designs around the asymmetry of the deflection type it could also be used. This is illustrated schematically in FIG. 4. In the first FIG. 4a, a non-deflected micromirror 401 is illuminated, and the reflected light is not directed towards the aperture 402, and, hence, the light does not reach the substrate 403. In FIG. 4b, on the other hand, the mirror is fully deflected, and all the reflected light are directed towards the aperture. In an intermediate position only part of the reflected light will reach the substrate, which is shown in FIG. 4c. However, in this case the light is not symmetrical around the optical axis for the lens 404, and there is an oblique incidence on the substrate. Hereby the distance between the lens and the substrate area becomes very critical, and small changes, such as the one being indicated by the dashed position for area, causes significant displacements of the features on the substrate. A way to solve this problem is indicated by the FIG. 4d-f. Here, a first exposure is made with a first deflection angle for the micromirror, and thereafter a second exposure, preferably with the same light dose, is made for a second deflection angle, being complementary to the first angle. Hereby, the combination of the first and second exposure is symmetrical around the optical axis for the lens. Another way to solve the problem is to use deforming mirror 401′, such as is shown in FIG. 4g, whereby the reflected light is evenly distributed over aperture. This last figure could schematically represent two cases, a phase type SLM (described below) or a deflection SLM, where light is reflected from different parts of the mirror. The phase SLM can be built either with micromachined mirrors, so called micromirrors, or with a continuous mirror surface on a supporting substrate that is possible to deform using an electronic signal. In Kück 1990 a viscoelastic layer controlled by an electrostatic field is used, but it is equally possible, especially for very short wavelengths where deformations of the order of a few nanometer are sufficient, to use a piezoelectric solid disk that is deformed by electric field or another electrically, magnetically or thermally controlled reflecting surface. For the remainder of this application an electrostatically controlled micromirror matrix (one- or two-dimensional) is assumed, although other arrangements as described above are possible, such as transmissive or reflecting SLMs relying on LCD crystals or electrooptical materials as their modulation mechanism, or micromechanical SLMs using piezoelectric or electrostrictive actuation. The invention preferably uses a micromirror where the phase modulation is variable to obtain a variable amount of light reaching the pupil of the projection lens. FIG. 2 shows some multi-element mirrors. The tilts of the various parts of the mirrors are unimportant. In fact one element by itself would direct the light toward the lens while another would direct it outside of the pupil. The correct way to understand the function is to look at the complex amplitude reaching the center of the pupil from each infinitesimal area element of the mirror and integrate the amplitude over the mirror. With a suitable shape of the mirror it is possible to find a deformation where the complex amplitudes add up to almost zero, corresponding to no light reaching the pupil. This is the off-state of the micromirror, while a relaxed state where the mirror surface is flat and the complex amplitudes add in phase is the on-state. Between the on and off-states the amount of light in the specular direction is a continuous but non-linear function of the deformation. The pattern to be written is normally a binary pattern, such as a photomask pattern in chrome on a glass substrate. In this context binary means that there are no intermediate areas: a certain point on the photomask surface is either dark (covered with chrome) or clear (no chrome). The pattern is exposed in photoresist by the projected image from the SLM and the photoresist is developed. Modern resists have high contrast, meaning that a small percentage change in exposure makes the difference between full removal of the resist in the developer and hardly any removal at all. Therefore the photoresist has an edge that is normally almost perpendicular to the substrate surface, even though the aerial image has a gradual transition between light and dark. The chrome etching does further increase the contrast, so that the resulting image is perfectly binary: either opaque or clear with no intermediate areas. The input data is in a digital format describing the geometry of the pattern to be written on the surface. The input data is often given in a very small address unit, e.g. 1 nanometer, while setting pixels in the SLM to either on or off gives a much coarser pattern. If a pixel on the SLM is projected to a 0.1 μm pixel in the image, a line can only have a width that is an integer number of pixels (n0.1 μm where n is an integer). An address grid of 0.1 μm was enough until recently, but the advent of so called optical proximity correction OPC makes a grid of 1-5 nanometers desirable. In OPC the size of features in the mask are modified slightly to compensate for predicted optical image errors when the mask is used. As an example, when a mask with four parallel lines 0.8 μm wide is printed in a modern 4× reduction stepper (a projection printer for semiconductor wafers) they will in a typical case print as lines 0.187, 0.200, 0.200, and 0.187 μm wide although they were intended to have the same width. This can be predicted by simulation of the image formation and the user of the mask may use OPC to compensate in the mask. therefore he wants the first and last line in the mask to be 40.213=0.852 μm instead of 0.800 μm. With an address grid of 0.1 μm he cannot make the correction, but with 5 nm address grid or finer such correction are possible. In FIG. 5 the method for providing data for the SLM is shown in a flow diagram. The first step, S1, is to divide the pattern data for the pattern to be written into separate pattern fields. The pattern data is preferably received in digital form. Thereafter, in step S2, the fields are rasterised, and thereby assigned different exposure values. These values are then corrected for nonlinear response, step S3, and pixel-to-pixel variations, step S4. Finally, the pixel values are converted to drive signals and forwarded to the SLM. The invention preferably uses intermediate values between the off-state and on-state to create a fine address grid, e.g. 1/15, 1/25, 1/50, of the size of a pixel. A printed feature consists of pixels in the on state, but along the edge it has pixels set to intermediate values. This is done by driving the pixels with other voltages than the on and off voltages. Since there are several cascaded non-linear effects (the position of the edge versus exposure at the pixels at the boundary, the exposure vs. the deformation, and the deformation vs. the electric field) a non-linear transformation from the input data to the electric field is needed. Furthermore this transformation is calibrated empirically at regular time intervals. FIG. 3 shows an array of pixels moving up and down like pistons, thereby creating a phase difference. The figure shows how the pixels are controlled to create the reflectivity in the inset. The bright areas have pixels with 0 phase, while dark areas are created by pixels with alternating +90 and −90 degree phase. The oblique boundaries between bright and dark areas are created by intermediate values of phase. This is how an edge can be fine-positioned with a phase-type SLM. However, other types of SLM with intermediate values could be used in the same manner. The imaging properties with the phase SLM driven into intermediate values are complex and it is far from obvious that the edge will be moved in FIG. 3. However, it has been shown by extensive theoretical calculations and experiments by the inventor, that the described effect is real. To create a finer address grid the electronic processing system is adapted to create one type of pixel map inside pattern features, another type of pixel map outside features, and intermediate pixel maps at a boundary, as shown in FIG. 3, where the intermediate pixel map at a boundary is generated in dependence of the placement of the boundary in a grid finer than that of the pixels of the SLM projected on the workpiece. The SLM and the projection system creates one exposure level inside features, another exposure level between features, and an intermediate exposure level at the boundary. The intermediate exposure level is created using the capability of the SLM to modulate to multiple states. The response from driving signals to actual placement of the boundary is characterized and corrected for. It is empirically measured and a calibrating function is computed and stored in the data processing and delivery system. To further improve the address resolution the stage and the SLM are adapted to stitching exposure fields together along a direction not parallel to the coordinate system of the SLM, typically 45 degrees. In particular the continuous movement of the stage or optical system takes place in a direction not parallel to the SLM, but typically at 45 degrees from the coordinate system of the SLM. It is also possible to have an SLM with non-orthogonal axises, in which case it is advantageous to have no axis parallel to the direction of motion. Furthermore, to suppress line errors resulting from imperfections in the column and row drivers of the SLM of line error in the matrix itself it is effective to have the row and column lines at an angle to the direction of stitching, i.e. the vector between the centers of stitched fields. Additional refinement of the address grid is created by the overlaying of at least two exposures with modified data such that the combined exposure has intermediate values not possible to obtain in a single exposure. The Design of the Phase-type SLM A cloverleaf mirror design, shown in FIG. 2c, as used in prior art is possible to drive to intermediate states between on and off states. However, when the integrated complex amplitude is plotted as a function of deflection, it is seen that it never goes to zero completely but circles around zero, therefore having a non-zero minimum reflectivity with a varying phase angle. This is shown schematically by the line 701 in FIG. 7, where 703 indicates a position for a certain deformation value, and □ being the associated phase angle. A thorough analysis of an image with some pixels set to intermediate states shows that the position of the edges in the final image are not stable through focus if the integrated phase angle of the edge pixels is not zero. This is the diffraction effect analogous to the specular one shown in FIG. 4. In a preferred embodiment of the invention a new type of pixels with pivoting elements is used. Examples of such elements are shown in FIG. 2e-h. When the elements pivots one end moves toward the light source and the other end away from it thereby keeping the average phase close to zero. This is shown schematically by the dashed line 702 in FIG. 7. Furthermore the cloverleaf design has a problem of built-in stress created during the fabrication. This stress tends to give a partial deformation without an applied electric field. The built-in deformation is not perfectly the same in every pixel since it depends on imperfections during the manufacturing. In the cloverleaf design this difference from pixel to pixel creates a first-order variation of reflectivity. With pixel cells built from pivoting elements the same effect occurs, but gives a second-order effect. Therefore the uniformity is better in the projected image. The design of the modulating elements and the exposure method are adapted to creating, for differently placed and/or differently oriented edges in the pattern, a symmetry in the aperture stop of the projection system. Inherent assymmetries between edges placed at different positions relative to the pixel grid can be reduced by overlaying at least two images with different placement of the pixel grid relative to the pattern. For a deflection type of SLM the symmetry relates to the intensity distribution in the aperture stop. Best is to have modulating elements that deflect the light symmetrically relative to the center of the aperture stop, or else can overlayed exposures with complementary deflection be used to create symmetry. With modulating elements with steerable deflection it is possible to create a constant geometrical realtion between the deflection at a pixel at an edge and the edge, i.e. directing it in a direction perpendicular to the edge and toward the interior of the feature. With a diffraction type SLM it is possible to create symmetry by overlaying exposures with opposite phase maps. Symmetry can be maintained if the complex amplitude is everywhere real on the SLM, and pixels can be designed with the integrated complex amplitude being essential real with values in the range −1 to 1. Many times it is sufficient with amplitudes in the range −0.5 to 1. This is the case with the square pivoting micromirror elements in FIG. 2e,f,g,h. With access to a small negative amplitude to print in the background areas it is possible for enhance the resolution. In a more complex scheme it is possible to drive groups of adjacent pixels to combine in the image, and after being filtered by the imaging system, to give a desired real amplitude. In order to preserve symmetry it is beneficial to have at least 2-fold symmetry and preferrably 4-fold. Symmetry can be created for pixels not having an inherent rotational symmetry by muple overlayed exposures. Furthermore, with a pixel design or exposure sequence giving a controlled real amplitude can be used for resolution enhancements. Dark lines can be given extra contrast if placed between areas with opposite phase and the edge of a feature can be improved by driving adjacent pixels inside the feature to higher positive amplitudes or adjacent pixels outside to negative ones. Image Enhancements There is a third advantage with a pivoting design: the cloverleaf does not reach full extinction, but a pivoting cell can more easily be given a geometry that gives full extinction, or even goes through zero and comes back to a small non-zero reflection, but with reversed phase. With better extinction there is greater freedom to print overlapping exposures, designing for a small negative value 702 gives better linearity close to extinction. Printing with a weak exposure, approximately 5%, in the dark areas, but with reversed phase can give an increased edge sharpness of 15-30% and the ability to print smaller features with a given lens. This is an analog to so called attenuating phase-shifting masks that are used in the semiconductor industry. A related method of increasing the edge acuity is to set the pixels that are inside a feature a lower value and those near the edge a higher value. This gives a new type of image enhancement not possible with current projection of patterns from masks or by the use of projectors following Nelson and Kück. The combination of a non-zero negative amplitude in the background and an increased exposure along the edges need not conflict with the creation of a fine address grid by driving edge pixels to intermediate values, since the effects are additive or at least computable. When the pixels are substantially smaller than the feature to be printed there exists a combination of pixel values that creates all effects simultaneously. To find them requires more computation than the generation of a fine address grid alone, but in some applications of the invention the ability to print smaller features can have a high value that pays for the extra effort. In the case of a continuous mirror on a viscoelastic layer there is an inherent balancing of the average phase to zero. Simulations have shown that the driving to intermediate values for fine positioning of feature edges work also for the continuous mirror. The non-linearities are smaller than with micromirrors. But for the method to work well the minimum feature has to be larger than with micromirrors, i.e. have a larger number of addressed pixels per resolved feature element is needed. Consequences are a larger SLM device and that for given pattern the amount of data is larger. Therefore the micromirrors have been chosen in a first and second embodiment. In the invention a pixel with rotation-symmetrical deformation (at least two-fold symmetry, in a preferred embodiment four-fold symmetry) is used for two reasons: to give a symmetrical illumination of the pupil of the projection lens and to make the image insensitive to rotations. The latter is important for printing a random logic pattern on a semiconductor wafer. If there is an x-y asymmetry the transistors laid-out along the x axis will have a different delay from those along the y axis and the circuit may malfunction or can only be used at a lower clock-speed. The two requirements of image invariance through focus and symmetry between x and y makes it very important to create and maintain symmetries in the optical system. Symmetry can be either inherent or it can be created by deliberate balancing of asymmetric properties, such as using multiple exposures with complementary asymmetric properties. However, since multiple exposures lead to reduced through-put inherent symmetrical layouts are strongly favored. Preferred Embodiments A first preferred embodiment is a deep-UV pattern generator for photomasks using an SLM of 2048×512 micromirrors. The light source is an KrF excimer laser with a pulsed output at 248 nanometers, pulse lengths of approximately 10 ns and a repetition rate of 500 Hz. The SLM has an aluminum surface that reflects more than 90% of the light. The SLM is illuminated by the laser through a beam-scrambling illuminator and the reflected light is directed to the projection lens and further to the photosensitive surface. The incident beam from the illuminator and the exiting beam to the lens are separated by a semitransparent beamsplitter mirror. Preferably the mirror is polarization-selective and the illuminator uses polarized light, the polarization direction of which is switched by a quarter-wave plate in front of the SLM. For x and y symmetry at high NA the image must be symmetrically polarized and a second quarter-wave plate between the beamsplitter and the projection lens creates a circularly polarized image. A simpler arrangement when the laser pulse energy allows it is to use a non-polarizing beamsplitter. The quarter-wave plate after the second pass through the beamsplitter is still advantageous, since it makes the design of the beam-splitting coating less sensitive. The simplest arrangement of all is to use an oblique incidence at the SLM so that the beams from the illuminator and to the projection lens are geometrically separated, as in FIG. 1. The micromirror pixels are 20×20 μm and the projection lens has a reduction of 200×, making on pixel on the SLM correspond to 0.1 μm in the image. The lens is a monochromatic DUV lens with an NA of 0.8, giving a point spread function of 0.17 μm FWHM. The minimum lines that can be written with good quality are 0.25 μm. The workpiece, e.g. a photomask, is moved with an interferometer-controlled stage under the lens and the interferometer logic signals to the laser to produce a flash. Since the flash is only 10 ns the movement of the stage is frozen during the exposure and an image of the SLM is printed, 204.8×51.2 μm large. 2 milliseconds later the stage has moved 51.2 μm, a new flash is shot and a new image of the SLM is printed edge to edge with the first one. Between the exposures the data input system has loaded a new image into the SLM, so that a larger pattern is composed of the stitched flashes. When a full column has been written the stage advances in the perpendicular direction and a new row is started. Any size of pattern can be written in way, although the first preferred embodiment typically writes patterns that are 125×125 mm To write this size of pattern takes 50 minutes plus the time for movement between consecutive columns. Each pixel can be controlled to 25 levels (plus zero) thereby interpolating the pixel of 0.1 μm into 25 increments of 4 nanometers each. The data conversion takes the geometrical specification of the pattern and translates it to a map with pixels set to on, off or intermediate reflection. The datapath must supply the SLM with 2048512500 words of data per second, in practice 524 Mbytes of pixel data per second. In a preferred embodiment the writable area is maximally 230×230 mm, giving up to 230/0.0512=4500 flashes maximum in a column and the column is written in 4500/500=9 seconds. The amount of pixel data needed in one column is 9×524=4800 Mb. To reduce the amount of transferred and buffered data a compressed format is used, similar to the one in Sandström at al. 90, but with the difference that a pixel map is compressed instead of segments with a length and a value. A viable alternative is to create a pixel map immediately and use commercially available hardware processors for compression and decompression to reduce the amount of data to be transferred and buffered. Even with compression the amount of data in a full mask makes it highly impractical to store pre-fractured data on disk, but the pixel data has to be produced when it is used. An array of processors rasterise the image in parallel into the compressed format and transfer the compressed data to an expander circuit feeding the SLM with pixel data. In the preferred embodiment the processors rasterise different parts of the image and buffer the result before transmitting them to the input buffer of the expander circuit. A Second Preferred Embodiment In a second preferred embodiment the laser is an ArF excimer laser with 193 nm wavelength and 500 Hz pulse frequency. The SLM has 3072×1024 pixels of 20 * 20 μm and the lens has a reduction of 333× giving a projected pixel of 0.06 μm. There are 60 intermediate values and the address grid is 1 nanometer. The point spread function is 0.13 μm and the minimum line 0.2 μm. The data flow is 1572 Mbytes/s and the data in one column 230 mm long is 11.8 Gb. A third preferred embodiment is identical with the second one except that the matrix of pixels is rotated 45 degrees and the pixel grid is 84 μm, giving a projected pixel spacing along x and y of 0.06 μm. The laser is an ArF excimer laser and the lens the reduction of 240. Because of the rotated matrix the density of pixels in the matrix is less and the data volume is half of the previous embodiment but with the same address resolution. Laser Flash to Flash Variations The excimer laser has two unwanted properties, flash-to-flash energy variations of 5% and flash-to-flash time jitter of 100 ns. In the preferred embodiments both are compensated in the same way. A first exposure is made of the entire pattern with 90% power. The actual flash energy and time position for each flash is recorded. A second exposure is made with nominally 10% exposure and with the analog modulation used to make the second exposure 5-15% depending on the actual value of the first one. Likewise a deliberate time offset in the second exposure can compensate for the time jitter of the first one. The second exposure can fully compensate the errors in the first, but will itself give new errors of the same type. Since it is only on average 10% of the total exposure both errors are effectively reduced by a factor of ten. In practice the laser has a time uncertainty that is much larger than 100 ns, since the light pulse comes after a delay from the trigger pulse and this delay varies by a couple of microseconds from one time to another. Within a short time span the delay is more stable. Therefore the delay is measured continuously and the last delay values, suitably filtered, are used to predict the next pulse delay and to position the trigger pulse. It is possible to make corrections for stage imperfections in the same way, namely if the stage errors are recorded and the stage is driven with a compensating movement in the second exposure. Any placement errors that can be measured can in principle be corrected in this way, partially or fully. It is necessary to have a fast servo to drive the stage to the computed points during the second exposure. In prior art it is known to mount the SLM itself on a stage with small stroke and short response time and use it for fine positioning of the image. Another equally useful scheme is to use a mirror with piezoelectric control in the optical system between the SLM and the image surface, the choice between the two is made from practical considerations. It is also possible to add a position offset to the data in an exposure field, and thereby move the image laterally. The second exposure is preferably done with an attenuating filter between the laser and the SLM so that the full dynamic range of the SLM can be used within the range 0-15% of the nominal exposure. With 25 intermediate levels it is possible to adjust the exposure in steps of 15%*1/25=0.6%. The response varies slightly from pixel to pixel due to manufacturing imperfections and, potentially, also from ageing. The result is an unwanted inhomogeneity in the image. Where image requirements are very high it may be necessary to correct every pixel by multiplication with the pixels inverse responsivity which is stored in a lookup memory. Even better is the application of a polynomial with two, three or more terms for each pixel. This can be done in hardware in the logic that drives the SLM. In a more complex preferred embodiment several corrections are combined into the second corrective exposure: the flash to flash variation, flash time jitter, and also the known differences in the response between the pixels. As long as the corrections are small, i.e. a few percent in each they will add approximately linearly, therefore the corrections can be simply added before they are applied to the SLM. The sum is multiplied with the value desired exposure dose in that pixel. Alternative Illumination Sources The excimer laser has a limited pulse repetition frequency (prf) of 500-1000 Hz depending on the wavelength and type of the laser. This gives large fields with stitching edges in both x and y. In two other preferred embodiments the SLM is illuminated with a pulsed laser with much higher prf, e.g. a Q-switched upconverted solid state laser, and with a continuous laser source scanned over the surface of the SLM, so that one part of the SLM is reloaded with new data while another part is printed. In both cases the coherence properties of the lasers are different from the excimer laser and a more extensive beam-scrambling and coherence control is needed, e.g. multiple parallel light paths with different pathlengths. In some implementations of the invention the light output from a flash lamp is sufficient and can be used as the light source. Advantages are low cost and good coherence properties. In the preferred embodiment with scanning illumination two issues are resolved: the pulse to pulse variation in time and energy, since the scanning is done under full control preferably using an electrooptic scanner such as acoustooptic or electrooptic, and many continuous laser have less power fluctuation that pulsed lasers. Furthermore the use of continuous lasers gives a different selection of wavelengths and continuous lasers are less dangerous to the eye than pulsed lasers. Most important, however, is the possibility of reaching much higher data rates with a matrix with only a few lines since the scanning is non-critical and can be done with 100 kHz repetition rate or higher. Scanning the illumination beam is also a way of creating a very uniform illumination, which is otherwise difficult. In some embodiments it is possible, and feasible, to use a flash lamp as the illumination source. EUV Light sources for EUV are based on radiation from a particle accelerator, a magnetic plasma pinch machine or the heating of a small drop of matter to extreme temperatures with a high-power laser pulse. In either case the radiation is pulsed. The EUV radiation propagates only in vacuum and can only be focused by reflective optics. A typical pattern generator using an SLM has a small exposure field a modest requirement of optical power. The design of the optical system is therefore relaxed compared to that of an EUV stepper, making it possible to use more mirrors and go to higher NA than in a stepper. It is anticipated that a high-NA lens will have a ring-shaped exposure field and it is fully possible to adapt the shape of the SLM to such a field. With a wavelength of 13 nm and an NA of 0.25 it is possible to expose lines that are only 25 nm wide, and, using image enhancement as described below, even below 20 nm. No other known writing technology can match this resolution and a the same time the writing speed that is made possible by the parallel character of an SLM. Edge Overlap Since a two-dimensional field is printed for each flash and the fields are stitched together edge to edge to edge the stitching is very critical. A displacement of only a few nanometers of one field will create pattern errors along that edge that are visible and potentially detrimental to the function of an electronic circuit produced from the mask. An effective way of reducing the unwanted stitching effects is to print the same pattern in several passes but with a displacement of the stitching boundaries between the passes. If the pattern is printed four times the stitching error will occur in four positions, but with only a fourth of the magnitude. In a preferred embodiment of the current invention the ability to create intermediate exposures is used together with an overlap band between the fields. The values are computed during the rasterisation, although it could also be done during the expansion of the compressed data. Edge overlap reduces the stitching errors with much less throughput penalty than multipass printing. Modified Illumination In the first preferred embodiment the illumination of the SLM is done by an excimer laser and a light scrambler such as a fly-eye lens array to create an illumination that resembles that from a circular self-luminous surface in the pupil plane of the illuminator. In order to increase the resolution when printing with a specific projection system it is possible to use a modified illumination. In the most simple cases pupil filters are introduced in the pupil plane of the illuminator, e.g. with a quadrupole-shaped or annular transmission area. In a more complex case the same field is printed several times. Several parameters can be made to vary between the exposures, such as focus in the image plane, illumination pattern, data applied to the SLM and pupil filter in the pupil plane of the projection optics. In particular the synchronized variation of the illumination and a pupil filter can give an increased resolution, most notably if the pupil has and a sector-shaped transmitting area and the illumination is aligned so that the non-diffracted light intercepts an absorbing patch near the apex of the sector Linearization of the Response For linearization of the transfer function from data to edge placement here are essentially three ways to go: taking the non-linearity into account in the data conversion unit and generating an 8 bit (example) pixel values in the data conversion unit and use DACs with the same resolution to drive the SLM. This is shown schematically in FIG. 8a, where R are relay signals and C are capacitors being provided on each matrix element on the SLM. The SLM is indicated by the dashed line. to generate digital values with fewer values, e.g. 5 bits or up to 32 values, and translate them to an 8 bit value in a look-up table (LUT) and then feed the 8 bit values to the DACs. to use a 5 bit value and semiconductor switches to select a DC voltage that is generated by one or several high-resolution DACs. This is shown schematically in FIG. 8b. In either case it is possible to measure an empirical calibration function such that the response on the plate is laniaries, when said function being applied at respectively the data conversion unit, the LUT or in the DC voltages. Which linearization scheme to use depends on the data rate, the precision requirements and also on the available circuit technology that may change over time. At the present time the data conversion unit is a bottleneck and therefore it is not a preferred solution to line arise in the data conversion unit, neither to generate 8-bit pixel values. High-speed DACs are expensive and power-hungry and the most appropriate solution is to generate DC voltages and use switches. It is then possible to use even higher resolution than 8 bits. Description of a Preferred Pattern Generator Referring to FIG. 6, a pattern generator comprises an SLM 601 with individual and multi-value pixel addressing, an illumination source 602, an illumination beam scrambling device 603, an imaging optical system 604, a fine positioning substrate stage 605 with an interferometer position control system 606 and a hardware and software data handling system 607 for the SLM. For proper functionality and ease of operation it also contains a surrounding climate chamber with temperature control, a substrate loading system, software for timing of stage movement and exposure laser triggering to achieve optimum pattern placement accuracy and a software user interface. The illumination in the pattern generator is done with a KrF excimer laser giving a 10-20 nanoseconds long light flash in the UV region at 248 nanometer wavelength with a bandwidth corresponding to the natural linewidth of an excimer laser. In order to avoid pattern distortion on the substrate, the light from the excimer laser is uniformly distributed over the SLM surface and the light has a short enough coherence length not to produce laser speckle on the substrate. A beam scrambler is used to achieve these two aims. It divides the beam from the excimer laser in several beam paths with different path length and then adds them together in order to reduce the spatial coherence length. The beam scrambler also has a beam homogenizer consisting of a lens system containing a set of fly-eye lenses that distributes the light from each point in the laser beam from the excimer laser uniformly over the SLM surface giving a “top-hat” light distribution. This beam scrambling, homogenizing and reduction of coherence is advantageous in all SLM printers. Depending on the actual circumstances implementations using beam-splitters and combiners, diffractive elements, optical fibers, kaleidoscopes, lenslet arrays, prisms or prism arrays or integrating spheres can be used, as well as other similar devices in combinations which split and combines the beams to create a multitude of mutually incoherent light fields impinging on the SLM. The light from the SLM is relayed and imaged down to the substrate on the substrate stage. This is done using a Schlieren optical system described by Kück. A lens l1 with the focal width f1 is placed at the distance f1 from the SLM. Another lens l2 with the focal length f2 is placed at the distance 2×f1+f2 from the SLM. The substrate is then at a distance 2×f1+2×f2 from the SLM. At the distance 2×f1 from the SLM there is an aperture 608 which size determines the numerical aperture (NA) of the system and thereby the minimum pattern feature size that can be written on the substrate. In order to correct for imperfections in the optical system and the substrate flatness there is also a focal system that dynamically positions the lens l2 in the z direction with a position span of 50 micrometers to achieve optimal focal properties. The lens system is also wavelength corrected for the illuminating wavelength of 248 nanometers and has a bandwidth tolerance of the illuminating light of at least ±1 nanometer. The illuminating light is reflected into the imaging optical system using a beamsplitter 609 that is positioned immediately above the lens l1. For a demagnification factor of 250 and an NA of 0.62 it is possible to expose pattern features with a size down to 0.2 micrometers with a good pattern quality. With 32 levels from each SLM-pixel the minimum gridsize is 2 nanometers. The pattern generator has a fine positioning substrate stage with an interferometer position control system. It consists of a moveable air bearing xy table 605 made of zerodur for minimum thermal expansion. A servo system with an interferometer position feedback measuring system 606 controls the stage positioning in each direction. In one direction, y, the servo system keeps, the stage in fixed position and in the other direction, x, the stage moves with continuous speed. The interferometer position measuring system is used in the x-direction to trigger the exposure laser flashes to give uniform position between each image of the SLM on the substrate. When a full row of SLM images are exposed on the substrate the stage moves back to the original position in the x direction and moves one SLM image increment in the y direction to expose another row of SLM images on the substrate. This procedure is repeated until the entire substrate is exposed. The SLM images overlaps with a number of pixels in both the x and y direction and the exposure data pattern is locally modified in the overlap pixels to compensate for the increased number of exposures that result in such overlap areas. Variations in pulse to pulse intensity from the excimer laser is compensated by using two-pass exposure of the pattern where the first pass is done using a nominal 90% intensity of the correct intensity. In the first pass, the actual intensity in each laser flash is measured and stored. In the second pass, the correct intensity for each SLM image exposure is then used based on the measured intensity values from the first pass. In this way it is possible to reduce the influence from pulse to pulse intensity variations from the excimer laser by one order of magnitude. The functionality of the SLM is described extensively elsewhere in this text. It has 2048×256 pixels with pixel size of 16 micrometers and it is possible to address all pixels within 1 millisecond. The SLM is rigidly mounted in a fine stage. This fine stage is moveable 100 microns in the x and y directions with accuracy better than 100 nanometers between each flash exposure. The fine positioning of the SLM is used to correct for position inaccuracy of the substrate positioning stage to further reduce pattern-stitching errors. In addition to the x-y positioning, there is also a rotational possibility of the SLM stage in order to expose a pattern on a substrate with an angle other than the one specified by the substrate stage coordinate system. The purpose for such rotation is to create the possibility of incorporating substrate alignment feasibility for substrates with an already existing pattern where additional features shall be added. It is possible to measure the exact position of the substrate on the stage after loading it using an off axis optical channel and/or a CCD camera looking through the lens to determine the system coordinates for a number of alignment marks existing on the substrate. During exposure, the stage position is then corrected in the x- and y-directions based on the measured positions of the alignment marks. Rotational alignment is achieved by using the stage servo system to follow the rotated coordinate system and also rotating the SLM fine stage as described. The possibility of rotating the SLM makes it also possible to write in a distorted coordinate system, such as to compensate for subsequent warpage of the pattern. An arbitrary data pattern of an arbitrary format is transformed into a compressed rasterized pixel map with 32 (5 bit) gray levels per pixel in a pattern rasterizer 610. Since the grayscale steps of an exposed pixel is not linear in response to the voltage applied to the pixel electrode, the input data is linearized in a pixel linearizer 611 so that the 32 gray levels correspond to a uniform increase in exposure dose for each successive level. This is done using 8-bit digital to analog converters (DAC) 612 where each gray level from the pixel map selects a voltage from the DAC's according to a previously empirically calibrated linearization function. An additional offset in the choice of analog level from the DAC's is made using a lookup table where each value corresponds to an SLM pixel and each such value corrects for anomalies of the corresponding pixel. The calibration values in the lookup table are generated using an empirical calibration procedure where a series of test patterns are sent to the SLM and the resulting exposed patterns are measured and used for individual pixel correction. This means that each gray level in the pixel map selects an analog voltage generating a pixel deformation for every corresponding SLM pixel to give the correct exposure dose.
	description	This application is a continuation of and claims priority to U.S. application Ser. No. 11/868,658, filed on Oct. 8, 2007, now U.S. Pat. No. 7,728,315 which is a continuation of and claims priority to U.S. application Ser. No. 11/183,508 filed on Jul. 18, 2005, now U.S. Pat. No. 7,291,854 and entitled “Radiation Attenuation Corridor”. The present invention relates generally to radiation shielding and particularly to an improved radiation attenuation corridor for radiation treatment facilities. Radiation therapy utilizes several types of ionizing radiation, such as beta-rays, gamma rays and x-rays, as well as high-energy protons and neutrons applied to malignant tissue to prevent and control the spread of cancer. While ionizing radiation is capable of destroying cancerous tissue, it is also capable of damaging healthy tissue inadvertently exposed thereto. Thus, a necessary precondition for treatment is the safeguard of patients and personnel from accidental radiation exposure. Various methods of shielding radiation in rooms and walls are known and in use in hospitals around the world. However, most of these methods are expensive to manufacture and can be complicated to use. Many use complex “radiation mazes” composed of thick leaded walls with multiple 90-degree turns, capped off with a heavy leaded door, often weighing thousands of pounds. Typically, the many walls are composed of thick concrete or other materials known for their ability to absorb or block ionizing radiation. These methods have several drawbacks. The heavy doors require mechanized assistance through automated motors and the like. This is both time consuming and dangerous, as technicians and patients alike can get caught in the door if they are not careful. Furthermore, it is time consuming for a therapist whenever the patient requires adjustment or assistance. Moreover, the closing of a thick lead door has a negative psychological impact on the patient who can feel entombed in the therapy room. Additionally, such a room is expensive and the required footprint is very large, resulting in a lot of unusable space. Finally, it has been known for these heavy doors to become stuck in the closed position due to motor or hinge failure. The patient is then alone in the treatment room and must await for the heavy door to be opened by some other means. Some radiation therapy rooms have been created with a doorless entry system. See, Dawson et al., in “Doorless Entry System”, Medical Physics, fol. 25, No. 2 (February 1998), the entire disclosure and subject matter of which is hereby incorporated herein by reference. While such a system meets some of the above identified challenges, it is desired to increase the radiation attenuation, by improving the system geometry. What is needed therefore is an improved radiation corridor that substantially absorbs ionizing radiation and substantially blocks the transmission of ionizing radiation from inside a room containing a radiation source, takes up as little room as possible, and is cost-efficient. Additionally, it is desirable to avoid the need for a heavy mechanized door. The present disclosure comprises a radiation attenuation corridor coupling a radiation therapy room and a safe area. The safe area is useful as, for instance, a control room wherefrom a therapist can operate radiation therapy controls to administer radiation to a patient, or other common area. A preferred radiation corridor in accordance with the present disclosure basically comprises a corridor which is open at one end to a radiation therapy room and is open at another end to a control room or other site. The corridor comprises a first wall and a second wall, a floor and a ceiling, all made of a material that substantially absorbs ionizing radiation and that substantially blocks the transmission of the ionizing radiation. The first wall and the second wall portions are substantially parallel and diverge from an axis defined by the corridor by from about 10 degrees to about 45 degrees. The corridor thus leads out of the room and makes a 90 degree turn. The corridor then turns at an obtuse angel to traverse laterally across the wall of the therapy room, before turning at a second obtuse angle in the opposite direction of the first. Finally, the corridor makes another 90 degree turn before opening to a safe area. In a preferred embodiment, selected portions of the walls of the corridor are lined with radiation attenuation materials, including, but not limited to, wood, plastics, polyethylene, graphite, wax, water or other suitable materials high in hydrogen concentration. In a further preferred embodiment, the radiation attenuation material is borated polyethylene (BPE). The placement of the angles in the radiation corridor increases the distance radiation must travel, and makes the path more indirect. This increases the contact the radiation emissions with the radiation shielding. In other words, the ionizing radiation bounces between wall sections until it is absorbed before reaching the outer door openings. Coupling this novel geometry with the placement of BPE attenuates the radiation to a point where a door is not necessary for blockage of radiation. Referring now to the drawings, preferred embodiments of the present invention are shown in detail. Although the drawings represent embodiments of the present invention, the drawings are not necessarily to scale and certain features may be exaggerated to better illustrate and explain the present invention. The embodiments set forth herein are not intended to be exhaustive or to otherwise limit the invention to the precise forms disclosed in the following detailed description. Referring now to FIGS. 1 and 2, therapy room 10 includes a radiation source 12, a first wall 14, a second wall 16 a third wall 18 and a fourth wall 20. Fourth wall 20 includes an opening 22 leading to an access corridor 30, which extends along the first wall 14 away from the therapy room 10. Access corridor 30 comprises a therapy room access portion 32, an angular traverse portion 34, and a control room access portion 36, and is defined throughout by a first corridor wall 38a-38e, a second corridor wall 40a-40e, a floor and a ceiling. The first corridor wall 38a-38e, second corridor wall 40a-40e, floor and ceiling are made of materials that substantially absorb ionizing radiation and that substantially block the transmission of the ionizing radiation. In a preferred embodiment, wall section 38a has a length from about 5 ft. to about 22 ft., wall section 38b has a length from about 5 ft. to about 20 ft., wall section 38c has a length from about 3 ft. to about 15 ft., wall section 38d has a length from about 1 ft. to about 5 ft. and wall section 40a has a length from about 2 ft. to about 10 ft., wall section 40b has a length from 1 ft. to about 5 ft., wall section 40c has a length from about 3 ft. to about 12 ft., wall section 40d has a length from about 5 ft. to about 20 ft., and wall section 40e has a length from about 5 ft. to about 20 ft. First corridor wall portions 38a and 38b meet at the junction of the therapy room access portion 32 and the angular traverse portion 34. First corridor wall portions 38a and 38b are lined with BPE, much in the matter that wall insulation is inserted between wall studs. Thy have a preferred length about 4 ft. to about 15 ft. In one preferred embodiment, first corridor wall portions 38a and 38b are lined with BPE for a length of 8 feet. in either direction from their junction point. The therapy room access portion 32 opens at one end into the therapy room 10 along the fourth wall 20, and extends outward from the therapy room 10 a given distance. The therapy room access portion 32 is then coupled with the angular traverse portion 34 of the access corridor 30 at the corner. The angular traverse portion 34 traverses a portion of the fourth wall 20 while angling toward the interior of the therapy room 10. That is, the angular traverse portion 34 forms a first acute angle with the therapy room access portion 32. The angle, α, between axis A and first corridor wall portion 38c may be from 10 to 45 degrees. Similarly, the angle, β, between axis B and second corridor wall portion 40c may be from 10 to 45 degrees. Axis A and axis B are preferably substantially parallel, and relate generally to the axis defined by the corridor. The first corridor wall portion 38c and the second corridor wall portion 40c of the angular traverse portion 34 can be parallel, such that angles α and β are identical, or they can converge, such that angle α is greater than angle β. The angular traverse portion 34 is then coupled with the control room access portion 36 at another corner, and the control room access portion 36 leads further away from the center of the therapy room 10. The angular traverse portion 34 forms a second acute angle with the control room access portion 36. In one preferred embodiment, the first acute angle and the second acute angle are such that the therapy room access portion 32 and the control room access portion 36 are substantially parallel, though other embodiments are contemplated depending on the specific application. In a most preferred embodiment, the distance between opposing walls is a minimum of six fee, to allow for the easy transfer of both patients and equipment into, and out of, the radiation therapy room. In one preferred embodiment, an access door 50 is included at the end of the control room access portion 36 to prevent unauthorized or inadvertent access to the therapy room 10. In such an embodiment, sensors responsive to movement can be integrated with the door 50 to shut off the supply of radiation when someone enters the corridor 30. RepFieldInstantRateEnergySizePhotonsNeutronDoseMU/minGantry(MV)(cm)(μSv/hr)(μSv/hr)[μSv/hr]50001502.307.009.30500015102.407.009.40500015402.004.006.00500901501.704.005.705009015101.903.004.905009015403.701.505.205001801501.905.006.9050018015102.205.007.2050018015401.802.804.605002701502.809.9012.7050027015102.706.008.7050027015402.205.607.80 In a further preferred embodiment, in which the door is absent, one or more proximity sensors (not shown) are located at the junction of the control room and the control room access portion 36 to detect entry into the access corridor 30. Upon detection of entry into the access corridor 30, the system could be set to shut down the radiation, to prevent injury to the entrant. Furthermore, one or more proximity sensors can be employed near the junction of the control room and the control room access portion, such that an audible or a visual warning can be given when someone nears the control room access portion. This can prevent inadvertent access to the control room access portion, thereby preventing the need to shut down the radiation, and save time for the therapist and patient. It is to be understood that the above description is intended to be illustrative and not limiting. Many embodiments will be apparent to those of skill in the art upon reading the above description. Therefore, the scope of the invention should be determined, not with reference to the above description, but instead with reference to the appended claims, along with the full scope of equivalents to which such claims are entitled. The disclosures of all articles and references, including patent applications and publications cited herein are incorporated herein by reference for all purposes. Initial tests done on an embodiment of the doorless radiation attenuation corridor as described above have been performed, and the results are listed in the table below. These results compare favorably with currently mandated “acceptable” radiation levels, and demonstrate the viability of the disclosed system design.
	claims	1. A method of encapsulating biological material in a 3-dimensional hydrogel matrix, said method comprising:providing a hydrogel precursor solution, said solution comprising a hydrogel precursor compound, said biological material, and a divalent cation selected from the group consisting of calcium, barium, strontium, and combinations thereof, dispersed or dissolved in a solvent system;combining said hydrogel precursor solution with alginate to initiate gelation of said alginate and yield core/shell microparticles, each core/shell microparticle comprising an alginate shell and a liquid core comprising said hydrogel precursor solution;crosslinking said hydrogel precursor compound in said liquid core to yield core/shell crosslinked microparticles, each core/shell crosslinked microparticle comprising said alginate shell and a core comprising a 3-dimensional hydrogel matrix and said biological material, said biological material being entrapped in said hydrogel matrix; andremoving said alginate shell to yield self-sustaining hydrogel microbeads, each hydrogel microbead comprising said 3-dimensional hydrogel matrix and biological material entrapped therein. 2. The method of claim 1, wherein said hydrogel precursor compound is a non-alginate compound. 3. The method of claim 1, wherein said hydrogel precursor compound is hyaluronic acid. 4. The method of claim 1, wherein said hydrogel precursor solution further comprises fibronectin, laminin, collagen, extracellular matrix components, or synthetic versions thereof. 5. The method of claim 1, wherein said biological material is selected from the group consisting of populations of cells, cell clusters, tissues, combinations thereof, and fragments thereof. 6. The method of claim 1, wherein, said biological material is selected from the group consisting of islets, hepatocytes, stem cells, endocrine cells, tissues related to islets, hepatocytes, stem cells, endocrine cells, and islet clusters, hepatocyte clusters, stem cell clusters, thyroid clusters, adrenal gland clusters, pituitary clusters, and combinations thereof. 7. The method of claim 1, wherein said hydrogel precursor solution consists essentially said hydrogel precursor compound, divalent cation, and biological material, dispersed or dissolved in the solvent system. 8. The method of claim 1, wherein said hydrogel precursor solution further comprises an optional hydrogel crosslinking agent. 9. The method of claim 1, wherein said alginate is sodium alginate. 10. The method of claim 1, wherein said combining comprises adding said hydrogel precursor solution dropwise to a solution of alginate to yield said core/shell microparticles. 11. The method of claim 10, wherein said adding comprises generating droplets of said hydrogel precursor solution and dropping said droplets into said solution of alginate to yield said core/shell microparticles. 12. The method of claim 11, wherein said droplet has a maximum surface-to-surface dimension of less than about 5 mm. 13. The method of claim 10, wherein the ratio of viscosity of the hydrogel precursor solution to the viscosity of the alginate solution is greater than 1 at room temperature. 14. The method of claim 1, wherein said crosslinking comprises contacting said core/shell microparticles with a hydrogel matrix crosslinker. 15. The method of claim 1, wherein said crosslinking comprises exposing said core/shell microparticles to activating radiation to initiate crosslinking. 16. The method of claim 1, wherein said removing comprises contacting said core/shell, crosslinked microparticles with a chelating agent to weaken, dissolve, or disrupt said alginate shell. 17. The method of claim 16, wherein said chelating agent is selected from the group consisting of citrate, EDTA, EGTA, phosphates, and mixtures thereof. 18. The method of claim 1, wherein said removing comprises physically agitating said core/shell, crosslinked microparticles to break said alginate shell. 19. The method of claim 1, wherein said hydrogel microbead has a maximum surface-to-surface dimension of less than about 5 mm.
	summary
	abstract	A device for generating compressed fluids includes a first process chamber for a first reaction material; a second process chamber for a second reaction material; a third process chamber for a fluid intended for compression; a unit for determining the nebulization and the consequent inlet of the first reaction material into process chamber; a unit intended for determining the emission of radio waves with variable frequencies in the direction of the process chamber, where the radio waves emitted by the unit interact with the first and second reaction material contained in third process chamber, for producing a high-energy plasma warms and thereby compresses the fluid contained in second process chamber.
	abstract	A neutron absorber apparatus for use in restoring reactivity control to a nuclear fuel rack. The apparatus comprises an elongated tubular insert assembly configured for insertion in a storage cell of the rack. First and second absorber plates, each formed of a boron-containing material, are coupled together by upper and lower stiffening bands at the insert extremities and form a longitudinally-extending cavity configured for receiving a fuel assembly. The absorber plates and stiffening bands may have a rectilinear cross sectional configuration in one embodiment. At least one elastically deformable locking protrusion mounted proximate to the lower end of the absorber plates lockingly engages an available lower edge disposed in the cell sidewall above its bottom end. This fixes the tubular insert axially in the cell, thereby preventing its withdrawal after installing the insert. In one embodiment, the edge may be the bottom of existing absorber sheathing in the cell.
	claims	1. A charged particle beam system, comprising:a charged particle beam generator configured to generate a charged particle beam having a beam path;a first lens configured to focus the charged particle beam generated in an object plane;a second lens located downstream of the object plane along the beam path, the second lens having a diffraction plane;a first lens doublet located downstream of the second lens along the beam path, the first lens doublet comprising a third lens and a fourth lens, the first lens doublet being configured to image the diffraction plane into a first intermediate diffraction plane;a first multipole located at the first intermediate diffraction plane;a second lens doublet located downstream of the first multipole along the beam path, the second lens doublet comprising a fifth lens and a sixth lens, the second lens doublet being configured to image the first intermediate diffraction plane into a second intermediate diffraction plane;a second multipole located at the second intermediate diffraction plane;a first deflection system upstream of the object plane along the beam path, the first deflection system being configured to tilt the charged particle beam about the object plane so that the charged particle beam is obliquely incident on the object plane; anda second deflection system located downstream of the third lens along the beam path and upstream of the fourth lens along the beam path, the second deflection system being configured to tilt the charged particle beam to compensate for tilting of the charged particle beam due to the first deflection system. 2. The charged particle beam system according to claim 1, wherein the second and third lenses are configured to image the object plane into an intermediate image plane located downstream of the third lens along the beam path and upstream of the fourth lens along the beam path. 3. The charged particle beam system according to claim 2, wherein the second deflection system is configured to tilt the beam about the intermediate image plane. 4. The charged particle beam system according to claim 2, wherein the fourth and fifth lenses are configured to image the first intermediate image plane into a second intermediate image plane located downstream of the fifth lens along the beam path and upstream of the sixth lens along the beam path. 5. The charged particle beam system according to claim 1, further comprising a tilt controller configured to synchronously control an amount by which the charged particle beam tilts due to the first deflection system and an amount by which the charged particle beam tilts due to the second deflection system. 6. The charged particle beam system according to claim 5, wherein the tilt controller is configured to control the first and second deflection systems so that the amounts of beam tilt generated by the first and second deflection systems change at a frequency greater than 50 Hz. 7. The charged particle beam system according to claim 5, wherein the tilt controller is configured to control the first and second deflection systems so that the amounts of beam tilt generated by the first and second deflection systems change at a frequency greater than 100 Hz. 8. The charged particle beam system according to claim 5, further comprising a corrector controller configured to control at least one element selected from the group consisting of the third lens, the fourth lens, the fifth lens, the sixth lens, the first multipole and the second multipole, wherein the corrector controller comprises a low pass filter configured to control the second deflection system. 9. The charged particle beam system according to claim 8, wherein the low pass filter is configured so that control signals supplied to deflectors of the second deflection system are substantially free of signal components having frequencies greater than 30 Hz. 10. The charged particle beam system according to claim 8, further comprising a switch configured to selectively connect the second deflection system to a member selected from the group consisting of the tilt controller and the corrector controller. 11. The charged particle beam system according to claim 1, further comprising an energy filter located downstream of the seventh lens along the beam path, wherein the energy filter has an entrance pupil plane and an entrance image plane. 12. The charged particle beam system according to claim 11, further comprising an eighth lens located upstream of the energy filter along the beam path, wherein the eighth lens is configured to image the object plane or an intermediate image of the object plane into the entrance pupil plane of the energy filter, and/or wherein the eighth lens is configured to image the diffraction plane or an intermediate image of the diffraction plane into the entrance image plane of the energy filter. 13. The charged particle beam system according to claim 11, wherein:the first deflection system is configured to displace the charged particle beam in the object plane such that a location of incidence of the charged particle beam on the object plane is changed;the charged particle beam system further comprises a third deflection system located upstream of the energy filter along the beam path; andthe third deflection system is configured to deflect the charged particle beam to compensate a change of the location of incidence of the charged particle beam on the object plane generated by the first deflection system. 14. The charged particle beam system according to claim 13, wherein the third deflection system is located upstream of the eighth lens along the beam path, and the third deflection system is configured to tilt the beam about the entrance image plane of the eighth lens. 15. The charged particle beam system according to claim 13, wherein the third deflection system is located downstream of the eighth lens along the beam path and upstream of the energy filter along the beam path, and the third deflection system is configured to tilt the beam about the entrance image plane of the energy filter. 16. The charged particle beam system according to claim 13, further comprising a displacement controller configured to synchronously control an amount by which the charged particle beam tilts due to the first deflection system and an amount by which the charged particle beam tilts due to the second deflection system. 17. The charged particle beam system of claim 1, wherein the charged particle beam generator is configured to generate an electron beam. 18. The charged particle beam system of claim 1, wherein the charged particle beam generator is configured to generate an ion beam. 19. A charged particle system, comprising:a charged particle beam generator configured to generate a charged particle beam having a beam path;a first lens configured to focus the charged particle beam generated in an object plane;a second lens located downstream of the object plane along the beam path, the second lens having a diffraction plane;a first lens doublet located downstream of the second lens along the beam path, the first lens doublet comprising a third lens and a fourth lens, the first lens doublet being configured to image the diffraction plane into a first intermediate diffraction plane;a first multipole located at the first intermediate diffraction plane; a second lens doublet located downstream of the first multipole along the beam path, the second lens doublet comprising a fifth lens and a sixth lens, the second lens doublet being configured to image the first intermediate diffraction plane into a second intermediate diffraction plane;a second multipole located at the second intermediate diffraction plane;a first deflection system upstream of the object plane along the beam path, the first deflection system being configured to tilt the charged particle beam about the object plane so that the charged particle beam is obliquely incident on the object plane;a second deflection system located downstream of the third lens along the beam path and upstream of the fourth lens along the beam path, the second deflection system being configured to tilt the charged particle beam to compensate for tilting of the charged particle beam due to the first deflection system;a tilt controller configured to synchronously control an amount by which the charged particle beam tilts due to the first deflection system and an amount by which the charged particle beam tilts due to the second deflection system; anda corrector controller comprising a low pass filter configured to control the second deflection system,wherein:the second and third lenses are configured to image the object plane into an intermediate image plane located downstream of the third lens along the beam path and upstream of the fourth lens along the beam path;the second deflection system is configured to tilt the beam about the intermediate image plane;the fourth and fifth lenses are configured to image the first intermediate image plane into a second intermediate image plane located downstream of the fifth lens along the beam path and upstream of the sixth lens along the beam path; andthe corrector controller is configured to control at least one element selected from the group consisting of the third lens, the fourth lens, the fifth lens, the sixth lens, the first multipole and the second multipole. 20. A method, comprising:using the charged particle beam according to claim 1 to obtain a diffraction pattern of a sample.
	abstract	A waveguide of the present invention comprises a waveguide main body made of a material selected from a boron nitride or an aluminum oxide, and a thin film made of a titanium nitride to cover an outer peripheral surface of the waveguide main body. The waveguide of the present invention can efficiently guide an electromagnetic wave such as a microwave, and has high physical and chemical durability.
	claims	1. An apparatus for generating monochromatic x-ray radiation comprising:an x-ray source which emits x-rays from a focus, a monochromator, and a slit collimator disposed in succession relative to each other, with said focus said x-ray source and the slit of said collimator in a fixed positional relation to each other, so that x-rays of a specific energy among the x-rays emitted by the x-ray source are reflected at the monochromator and subsequently pass through the slit of the slit collimator, andan adjustment mechanism connected to said monochromator for displacing only said monochromator relative to both said x-ray source and said slit collimator while emitting x-rays from said x-ray source and while substantially maintaining a reflection angle for reflection of said x-rays of said specific energy at said monochromator, for correspondingly displacing an x-ray beam emerging from said slit of said slit collimator through a scanning angle range. 2. An apparatus as claimed in claim 1 wherein said monochromator is a monochromator crystal. 3. An apparatus as claimed in claim 1 wherein said monochromator is a highly oriented pyrolytic graphite crystal. 4. An apparatus as claimed in claim 1 wherein said monochromator is a multi-layer system that reflects said x-rays. 5. An apparatus as claimed in claim 4 wherein said monochromator is a Göbel mirror. 6. An apparatus as claimed in claim 1 wherein said adjustment mechanism displaces said monochromator along a substantially elliptical path. 7. An apparatus as claimed in claim 6 wherein said focus of said x-ray source is disposed substantially at one focus of an ellipse defining said elliptical path, and wherein said slit of said slit collimator is situated substantially in the other focus of said ellipse. 8. An apparatus as claimed in claim 1 wherein said scanning beam is used for conducting an x-ray exposure having a duration, and wherein said adjustment mechanism displaces said monochromator along a displacement path for a duration substantially corresponding to said duration of said x-ray exposure. 9. An apparatus as claimed in claim 1 wherein said scanning beam is used for conducting an x-ray exposure having a duration, and wherein said adjustment mechanism displaces said monochromator along a displacement path for a duration substantially corresponding to a whole-number fraction of said duration of said x-ray exposure. 10. A method for generating monochromatic x-ray radiation comprising:arranging an x-ray source which emits x-rays from a focus, a monochromator, and a slit collimator in succession relative to each other so that x-rays of a specific energy among the x-rays emitted by the x-ray source are reflected at the monochromator and subsequently pass through the slit of the slit collimator; andwhile emitting x-rays from said x-ray source, displacing only said monochromator relative to both said x-ray source and said slit collimator, while maintaining said focus at said x-ray source and the slit of said collimator in a fixed positional relation to each other and while substantially maintaining a reflection angle for reflection of said x-rays of said specific energy at said monochromator, for correspondingly displacing an x-ray beam emerging from said slit of said slit collimator through a scanning angle range. 11. A method as claimed in claim 10 comprising employing a monochromator crystal as said monochromator. 12. A method as claimed in claim 10 comprising employing a highly oriented pyrolytic graphite crystal as said monochromator. 13. A method as claimed in claim 10 comprising employing a multi-layer system that reflects said x-rays as said monochromator. 14. A method as claimed in claim 13 comprising employing a Göbel mirror as said monochromator. 15. A method as claimed in claim 10 comprising displacing said monochromator along a substantially elliptical path. 16. A method as claimed in claim 15 comprising disposing said focus of said x-ray source substantially at one focus of an ellipse defining said elliptical path, and situating said slit of said slit collimator is substantially in the other focus of said ellipse. 17. A method as claimed in claim 10 comprising conducting an x-ray exposure, with said scanning beam, having a duration, and displacing said monochromator along a displacement path for a duration substantially corresponding to said duration of said x-ray exposure. 18. A method as claimed in claim 10 comprising conducting an x-ray exposure, with said scanning beam, having a duration, and displacing said monochromator along a displacement path for a duration substantially corresponding to a whole-number fraction of said duration of said x-ray exposure.
	claims	1. A method of manufacturing a nuclear fuel element configured for use in a high-temperature gas cooled reactor core, the method comprising:forming a base portion of the nuclear fuel element by depositing a powdered matrix material on a substrate, the powder matrix material comprising a mixture of a graphite material and a fibrous material;depositing particles on the base portion in a predetermined pattern to form a first particle layer, by controlling the position of each particle in the first particle layer;depositing the powdered matrix material on the first particle layer to form a first matrix layer;depositing particles on the first matrix layer in a predetermined pattern to form a second particle layer, by controlling the position of each particle in the second particle layer;depositing the powdered matrix material on the second particle layer to form a second matrix layer; andforming a cap portion of the nuclear fuel element by depositing the matrix material comprising a mixture of a graphite material and a fibrous material on a particle layer,wherein the particles comprise nuclear fuel particles. 2. The method of claim 1, wherein:the fibrous material comprises carbon nanotubes, silicon carbide fibers, or a combination thereof; andthe graphite material comprises graphite powder, graphite spheres, or a combination thereof. 3. The method of claim 1, wherein the fibrous material comprises carbon nanotubes and silicon carbide fibers. 4. The method of claim 3, wherein the powdered matrix material comprises, based on the total weight of the matrix material:from about 1 wt % to about 64 wt % of the carbon nanotubes; andfrom about 1 wt % to about 16 wt % of the silicon carbide fibers. 5. The method of claim 1, wherein the powdered matrix material comprises, based on the total weight of the matrix material:from about 20 wt % to about 99 wt % of the graphite material; andfrom about 1 wt % to about 80 wt % of the fibrous material. 6. The method of claim 1, further comprising mixing the graphite material and the fibrous material before depositing the powdered matrix material. 7. The method of claim 1, wherein controlling the position of each particle within the first and second particle layers comprises:loading particles in controlled positions on a deposition head;disposing the deposition head over the base portion or the first matrix layer;releasing the particles from the deposition head; andpressing the particles into the base portion or the first matrix layer,wherein the deposition head is a vacuum deposition head or an electrostatic deposition head. 8. The method of claim 1, wherein:depositing the powdered matrix material on the first particle layer to form a first matrix layer comprises printing a binder on a portion of the deposited matrix material to define the size and shape of the first matrix layer; anddepositing the powdered matrix material on the second particle layer to form a second matrix layer comprises printing a binder on a portion of the deposited matrix material to define the size and shape of the second matrix layer. 9. The method of claim 8, further comprising:pressing the first particle layer before forming the first matrix layer;pressing the first matrix layer before forming the second particle layer;pressing the second particle layer before forming the second matrix layer; andpressing the second matrix layer before forming the cap portion. 10. The method of claim 1, wherein forming a base portion and forming a cap portion each comprise:A) depositing the powdered matrix material comprising a mixture of graphite material and fibrous material;B) pressing the deposited matrix material;C) printing a binder on the pressed matrix material; andrepeating operations A, B, and C; until the corresponding base portion or cap portion has a thickness ranging from 3 mm to 12 mm. 11. The method of claim 1, wherein operation C comprises printing the binder in a pattern having the same shape as a cross-section of the nuclear fuel element. 12. The method of claim 1, wherein the particles deposited in the first matrix layer and the second matrix layer comprise tri-structural-isotropic (TRISO) fuel particles that do not have an overcoat. 13. The method of claim 1, wherein controlling the position of each particle within the first and second particle layers comprises positioning the particles in a fuel zone of the nuclear fuel element that is surrounded by a fuel-free shell of the nuclear fuel element formed of the matrix material. 14. The method of claim 1, wherein the nuclear fuel element is a spherical fuel pebble suitable for use in a pebble bed high temperature gas cooled reactor.
	description	This application claims the priority of U.S. provisional application Ser. No. 60/624,650, filed Nov. 3, 2004. The present application is related to: U.S. patent application Ser. No. 10/896,596, filed Jul. 22, 2004, and having the title of: “Method and apparatus for rapid sample preparation in a focused ion beam microscope;” U.S. patent application Ser. No. 11/186,072, filed Jul. 21, 2005, and having the title of: “Strain detection for automated nano-manipulation;” and, U.S. patent application Ser. No. 11/186,073, filed Jul. 21, 2005, and having the title of: “Method and apparatus for in-situ probe tip replacement inside a charged particle beam microscope.” This application relates to automated processes for the lift-out and preparation of samples inside instruments such as focused ion-beam microscopes. The use of focused ion-beam (FIB) microscopes has become common for the preparation of specimens for later analysis in the transmission electron microscope (TEM). The structural artifacts, and even some structural layers, in the device region and interconnect stack of current integrated-circuit devices can be too small to be reliably detected with the secondary electron imaging in a Scanning Electron Microscope (SEM), or FIB, which offers a bulk surface imaging resolution of approximately 3 nm. In comparison, TEM inspection offers much finer image resolution (<0.1 nm), but requires electron-transparent (<300 nm thick) sections of the sample mounted on 3 mm diameter grid disks. The in-situ lift-out technique is a series of FIB milling and sample-translation steps used to produce a site-specific specimen for later observation in a TEM or other analytical instrument. During in-situ lift-out, a wedge-shaped section (the “lift-out sample”) of material containing the region of interest is first completely excised from the bulk sample, such as a semiconductor wafer or die, using ion-beam milling in the FIB. This lift-out sample is typically 10×5×5 μm in size. Removal of the lift-out sample is then typically performed using an internal nano-manipulator in conjunction with the ion-beam assisted chemical-vapor deposition (CVD) process available with the FIB tool. The process of in-situ lift-out is a procedure of several successive steps, where the starting point is the delivery of a wafer, having the area of interest, and the probe tip inside the FIB vacuum chamber, and the end point is the lift-out sample ready for the TEM investigation. There is a need in the industry to have the entire process automated, thus allowing for fast and safe processing of a lift-out sample without the need to vent the vacuum chamber or to remove the probe and sample through an airlock. The reader should note, however that the field of application is limited neither to automated lift-out systems, nor to semiconductor samples. Other objects of interest could be micro-mechanical systems, or biological specimens. Further, in-situ lift-out can be carried out in an atmosphere instead of a vacuum, when the nature of the specimen permits. The preferred embodiment includes a novel method and apparatus for the fully automated process of in-situ lift-out inside a FIB vacuum chamber using an in-situ probe tip replacement system. Although as stated, the field of application is limited neither to automated lift-out systems, nor to semiconductor samples. FIG. 1 shows schematically the automation system to control the process, comprising a computer (100) running a set of computer-readable instructions, and a set of hardware items for the in-situ probe tip replacement system. Such hardware is typically a nano-manipulator (130), probe tips (140), cassettes (160) for holding probe tips (140). The size of the lift-out sample (150) in FIG. 1 is exaggerated for clarity. A suitable nano-manipulator system is the Omniprobe AutoProbe™ 200 manufactured by Omniprobe, Inc., of Dallas, Tex. Also shown in FIG. 1 are the electron-beam source (170) and ion-beam source (180) that are typical components of a FIB. In the preferred embodiment, the electron beam (170) and the ion-beam sources are operatively connected to the computer (100) so that their imaging and (in the case of the ion-beam) their milling and deposition functions are controlled by the instructions in the computer (100), to assist the lift-out process. FIG. 1 shows that the computer (100) is operatively connected by suitable circuitry (105) to conventional motion controllers (110) inside and outside the FIB chamber (155), thus allowing movement of the specimen stage (120) and the nano-manipulator (130) probe tip (140) in all necessary degrees of freedom. The computer (100) is preferably a general-purpose programmable computer accepting programs stored on computer-readable media, although special-purpose computers having a CPU, memory, and one or more mass storage devices could be built and used. For example, a suitable computer system (100) is a model Dimension XPS 600, by Dell Computers of Austin, Tex., having a National Instruments NI PCI-7354 4-Axis Stepper/Servo Motion Controller for PCI, as well as a keyboard and display (not shown). The computer (100) is preferably connected to the FIB and nano-manipulator hardware by high-speed parallel communication cables, although, depending on the hardware chosen, the circuitry (105) could include serial data transmission. The box in FIG. 1 labeled “Image recognition” represents processes executing in the computer (100) to compute the location of the probe tip (140) from images of it from the differently oriented electron-beam source (170) and ion-beam source (180). The disclosed processes can be implemented in a high-level programming language, such as C++. FIG. 1 also depicts a specimen (125) (usually a wafer) on the specimen stage (120), and the means for detecting contact (115) of the probe tip (140) with a surface (discussed below). In the following description, well-known parts or processes have been shown in block diagram form in order not to obscure the present disclosure in unnecessary detail. For the most part, details concerning timing considerations and the like have been omitted in as much as such details are not necessary to obtain a complete understanding of the present disclosure and are within the skills of persons of ordinary skill in the relevant art. The setup process (200) includes all necessary steps to identify the target position on the specimen (125) at the eucentric position in the microscope, as well as mechanical alignment, initialization of the mechanical automation system, and loading of probe tips (140) and the probe-tip exchange cassette (160). While setting up the system, several approaches can be used. One would be the one-probe tip approach, where a single probe tip (140) is loaded ahead of time in the probe shaft of a nano-manipulator (130) and used for a single lift-out operation. In another approach, a set of probe tips (140) is used. These probe tips (140) fill in the whole length of a hollow probe shaft (not shown), and the extra number of probe tips (140) is loaded ahead of time into an interchangeable magazine (not shown), located outside the FIB, so the supply of the probe tips (140) can be continuous and uninterrupted. Such a system of multiple probe tips is described in co-pending application Ser. No. 11/186,073, cited above. The sample lift-out step (205), described in FIG. 2, includes the means for locating the probe tip (140) by, for example, the parallax method, as is known in the art; contact detection realized by means of strain or optical methods, for example, and the location of an area of interest, using a predetermined list of target locations and image recognition of surface features or added landmarks for registration. The optical method comprises a light detector for measuring the changed intensity of light reflected from a probe tip (140) or a capsule (not shown) attached to the probe tip (140), the probe tip (140) is displaced by surface contact. Novel contact-detection methods are described in co-pending application Ser. No. 11/186,072, described above, and in another co-pending application relating to optical apparatus and methods to be filed, also claiming priority from the provisional application referenced above. As shown in FIG. 3, the sample lift-out process starts when the automated program obtains co-ordinates for the specimen (125) at step (300) and for the probe tip (140) at step (305), according to means just discussed. At step (310), the program computes the coordinate difference and the required motion commands to the motion controllers (110). Step (320) checks to determine if the probe tip (140) is close to the specimen (125) within some pre-determined distance of the desired sample location. When the pre-determined distance is reached, motion continues at a lower speed in step (325) until contact with the sample (150) is detected at step (330) and motion stops at step (335). At step (340) the sample (150) is excised from the specimen (125), attached to a probe tip (140) and lifted out of the specimen (125). After the sample (150) is excised from a specimen (125), a probe tip (140) can be connected to it using, for instance, one of the methods disclosed in U.S. Pat. No. 6,570,170, referred to above. Returning to FIG. 2, the automated process continues after sample lift-out. The sample is either attached to a TEM sample holder (not shown) for subsequent thinning, or it is immediately thinned and then later attached to the TEM sample holder, all as part of the sample lift-out step (205). The location of the sample (150) or probe tip (140) in the specimen chamber can be determined by the parallax method. This method allows bringing the probe tip (140) to the target position on the specimen (125) surface or cassette (160) using incremental movements followed by comparison of consecutive scanned images from at least two perspectives. This comparison of images can be part of an automated process using image recognition. An area of interest on a specimen (125) can be located as follows: The specimen (125) is delivered into a FIB vacuum chamber and placed into a specified location. Special markings previously made around the area of interest, typically by laser or ion beam milling or deposition can be easily detected by the automated system using image recognition. Alternatively, image recognition can be used to locate specific features on the surface of the specimen (125) for navigation to the test point, or CAD (Computer Automated Design) navigation can be used to translate the specimen stage (120) to the target point based on registration marks on the surface of the specimen (125), all as is known in the art. The sample lift-out step (205) can be done by different methods, such as that described in U.S. Pat. No. 6,570,170, referred to above. This procedure can be carried through the step of attachment of the lift-out sample (150) to a TEM sample holder (not shown), or the procedure can be interrupted after the lift-out sample (150) has been attached to the probe tip (140) and lifted out of the specimen (125). The exact extent of completion of the lift-out procedure will depend on the optional method selected for creating the TEM sample; that is combining the lift-out sample (150) with the TEM sample holder. Successful lift-out can be verified as part of the automated process using image recognition. After the sample lift-out process (205) is completed, there are two optional flows for the automated sample lift-out process: one for immediate sample thinning “in-line thinning” (220), using the focused ion beam milling process available at the same in-line FIB, or another flow for thinning later during the course of operation. Alternatively, the thinning can be performed either inside the in-line FIB later on as part of the automated sample lift-out process, or in the off-line FIB after the automated sample lift-out process is finished. If in-line thinning is selected at step (210) to be done later, the tip (140) with sample (150) attached is deposited into a cassette (160) at step 215. If a choice is made at step (245) to commence thinning, this is done at step (250). Either way, the process flows to the decision at step 255 to determine if another sample (150) is to be removed. If so, execution returns to step (200); else, at step 260, the tip (140) and attached sample (150) are removed from the FIB. After removal from the FIB, the tip (140) and attached sample (150) can be joined to a TEM grid or holder as described in one or more of the co-pending applications. If, at step 210, in-line thinning of the sample (150) is selected, such thinning is done at step (220). The sample (150) so thinned may be be optionally subjected to TEM screening at step (225), and then deposited into the cassette (160) at step (230). Decision step (235) decides if a new sample is to be lifted out; if so, execution returns to step (200), if not, the tip (140) and sample (150) can be removed from the FIB at step 240, and further processed as just discussed. Since those skilled in the art can modify the specific embodiments described above, we intend that the claims be interpreted to cover such modifications and equivalents.
	summary
059237201	claims	1. An x-ray spectrometer, comprising: an X-ray source; a curved crystal monochromator which focuses a monochromatic x-ray beam onto a sample surface, the curved crystal monochromator comprising a shape which is substantially identical to a logarithmic spiral and having a width that is tapered along the arclength s of the crystal; and a position-sensitive x-ray detector. at least one single slit positioned between the source and the monochromator. providing an x-ray source comprising an x-ray source, a curved crystal monochromator which focuses a monochromatic x-ray beam onto a sample surface, the curved monochromator comprising the shape of a logarithmic spiral and having a width that is tapered along the arclength s of the crystal, and a position-sensitive x-ray detector; providing a sample comprising a single of multilamellar lipid layer deposited on a flat substrate; and exposing the sampler to the focused x-ray beam of the x-ray spectrometer. a second focusing device positioned so as to focus in the plane substantially perpendicular to the curved crystal monochromator. providing an x-ray spectrometer comprising an x-ray source, a curved crystal monochromator which focuses a monochromatic x-ray beam onto a sample surface, the curved monochromator comprising the shape of a logarithmic spiral and having a width that is tapered along the arclength s of the crystal, and a position-sensitive x-ray detector; and providing a crystallographically oriented sample; exposing the sample to the focused beam of the x-ray spectrometer; and measuring the diffraction intensity at the position-sensitive detector. 2. The x-ray spectrophotometer of claim 1, wherein the size of the focus of the x-ray beam onto the sample surface is less than or equal to about 3.1 microns. 3. The x-ray spectrometer of claim 1, wherein the curved crystal monochromator has a taper selected to minimize a third order difference in arclength s between an ideal logarithmic curve and the curved crystal. 4. The x-ray spectrophotometer of claim 1, wherein the size of the focus of the x-ray beam onto the sample surface is less than 20 microns. 5. The x-ray spectrometer of claim 1, monochromator crystal wherein the taper is less than about 100 milliradians. 6. The x-ray spectrometer of claim 1, wherein a linear position-sensitive proportional detector is used. 7. The x-ray spectrometer of claim 1, wherein the monochromator comprises a single crystal selected from the group consisting of germanium, silicon and lithium fluoride and multilayers thereof. 8. The x-ray spectrometer of claim 1, wherein a linear photodiode array is used. 9. The x-ray spectrometer of claim 1, wherein a linear charge coupled device is used. 10. The x-ray spectrometer of claim 1, wherein a 2-dimensional proportional x-ray detector is used. 11. The x-ray spectrometer of claim 1, wherein a 2-dimensional charge coupled device is used. 12. The x-ray spectrometer of claim 1, further comprising: 13. The x-ray spectrometer of claim 12, wherein a plurality of slits are positioned in front of the monochromator. 14. The x-ray spectrometer of claim 1, wherein the taper is a linear taper. 15. A curved crystal monochromator which focuses a monochromatic x-ray beam onto a sample surface, wherein the width of the curved crystal monochromator is linearly tapered along an arclength s of the crystal. 16. The monochromator of claim 15, wherein the curved crystal monochromator has a taper selected to minimize a third order difference in arclength s between an ideal spiral curve and the curved crystal. 17. The monochromator of claim 15, wherein the monochromator crystal taper is less than about 20 milliradians. 18. A method for measuring electron density in a lipid layer, comprising: 19. The method of claim 18, wherein the sample comprises natural or synthetic lipids. 20. The method of claim 18, wherein the sample comprises natural or synthetic lipids deposited by centrifugation from solution or suspension. 21. The method of claim 18, wherein the sample comprises a lipid deposited by Langmuir-Blodgett deposition. 22. The method of claim 18, wherein the sample comprises a lipid deposited by self-assembly from solution. 23. The x-ray spectrometer of claim 1, further comprising a sample. 24. The x-ray spectrometer of claim 1, wherein the sample comprises an epitaxially grown layer. 25. The x-ray spectrometer of claim 1, wherein the sample comprises a evaporated layer. 26. The x-ray spectrometer of claim 1, wherein the sample comprises an epitaxially grown multilayer or superlattice. 27. The x-ray spectrometer of claim 1, wherein the sample comprises a multilayer deposited by evaporation. 28. The x-ray spectrometer of claim 1, wherein the spectrometer is attached as an accessory to a larger film deposition system. 29. The x-ray spectrometer of claim 28, wherein the film parameters determined by the spectrometer may be used to control the deposition of a film. 30. The x-ray spectrometer of claim 1, wherein the spectrometer is oriented to measure x-ray reflectivity from horizontal surfaces. 31. The x-ray spectrometer of claim 1, wherein the spectrometer is adapted for scanning in the lateral direction. 32. The x-ray spectrometer of claim 1, further comprising: 33. The x-ray spectrometer of claim 32, wherein the second focusing device comprises a curved mirror. 34. The x-ray spectrometer of claim 32, wherein the second focusing device comprises a curved crystal monochromator. 35. A method of measuring diffraction intensities from oriented samples in real time, comprising; 36. The method of claim 18 or 35, wherein the taper is a linear taper.
	claims	1. A position measuring system for detecting an indicated position of a guide rod extending along a rectilinear path being rectilinear relative to a guide system and can be moved along the rectilinear path, the position measuring system comprising:a number of reed contact elements;at least one magnetic element for forming a magnetic field, said magnetic element connected to the guide rod;at least one of said reed contact elements is in each case configured within a detection region to detect the magnetic field whose field strength is greater at a location of said one reed contact element than a predefined threshold value when said at least one magnetic element approaches said one reed contact element, at least one of said reed contact elements disposed in an environment of the rectilinear path;an inductive measuring system for determining a position of the guide rod disposed in the environment of the rectilinear path, said inductive measuring system having a number of electric induction coils; anda circuit configuration having at least one ohmic resistance unit forming a series circuit with at least one of said electric induction coils, and forming a circuit loop with at least one of said reed contact elements. 2. The position measuring system according to claim 1, wherein said magnetic element is a permanent magnet. 3. The position measuring system according to claim 1, wherein said magnetic element has an end connected to the guide rod. 4. The position measuring system according to claim 1, wherein the detection region of at least one of said reed contact elements detects an end of the guide rod disposed in the indicated position. 5. The position measuring system according to claim 1, wherein the guide rod can be moved between a minimum extended position and a maximum extended position. 6. The position measuring system according to claim 1, wherein said at least one ohmic resistance unit is one of two ohmic resistance units forming said series circuit with said electric induction coil, one of said two ohmic resistance units respectively being connected to in each case one end of said electric induction coil, and said series circuit containing a plurality of said reed contact elements, each said reed contact element forming a circuit loop with one of said ohmic resistance units. 7. The position measuring system according to claim 1, further comprising a circuit group for determining an ohmic total resistance of said circuit configuration. 8. The position measuring system according to claim 1, further comprising a control unit containing:a current source for feeding a direct current into said circuit configuration;a first measuring unit for detecting a DC voltage component of a total voltage in said circuit configuration; anda second measuring unit for detecting an AC voltage component of the total voltage in said circuit configuration. 9. The position measuring system according to claim 8, further comprising a further circuit configuration connected to said control unit, said further circuit configuration having an electrical coil and configured to form and control an electric current in said further circuit configuration. 10. The position measuring system according to claim 9, wherein said electrical coil is aligned and disposed parallel to the rectilinear path. 11. A position measuring system for detecting an indicated position of a control rod of a nuclear facility, the position measuring system comprising:a guide system, the control rod extending along a rectilinear path being rectilinear relative to said guide system, said guide system containing a pressure resistant guide tube enclosing the control rod;a number of reed contact elements;at least one magnetic element for forming a magnetic field, said magnetic element connected to the control rod;at least one of said reed contact elements is in each case configured within a detection region to detect the magnetic field whose field strength is greater at a location of said reed contact element than a predefined threshold value, at least one of said reed contact elements connected to said guide system and is disposed in an environment of the rectilinear path;an inductive measuring system for determining a position of the control rod disposed in the environment of the rectilinear path, said inductive measuring system having a number of electric induction coils; anda circuit configuration disposed in the environment of the rectilinear path and having at least one ohmic resistance unit forming a series circuit with at least one of said electric induction coils, and forming a circuit loop with at least one of said reed contact elements.
	summary
058964312	description	DETAILED DESCRIPTION FIG. 1 is a schematic illustration of a section of a boiling water reactor 10 in accordance with one embodiment of the present invention. Boiling water reactor 10 includes a drywell 12, a wetwell 14, and a Gravity Driven Cooling System (GDCS) 16. GDCS 16 is substantially separated from drywell 12 by a GDCS wall 18, and includes a pool of coolant 20, e.g., water, positioned so that when coolant from pool 20 must be supplied to a reactor pressure vessel (not shown in FIG. 1), the coolant flows, under gravity forces, through a GDCS coolant injection line 22 into the reactor pressure vessel. Under normal reactor operating conditions, however, coolant from GDCS 16 does not flow into the RPV. Pool of coolant 20 is movable between an initial level L.sub.1 and a minimum level L.sub.2, which corresponds to the elevation of GDCS injection line 22. Wetwell 14 includes a suppression pool of water 24 and is substantially separated from both drywell 12 and GDCS pool 20. An air space 26 above suppression pool 24 is connected to an air space 28 above GDCS pool 20 via a vent pipe 30. A wall 32 extends between wetwell 14 and drywell 12, and an opening, or spill-over-hole, extends therethrough. A spill-over line 34 extends from suppression pool 24 through the spill-over-hole. Wetwell 14 further includes a main vent 36 filled at least partially with water 38, and suppression pool of water 24 is higher than the main vent water 38 by a pressure differential .DELTA.P.sub.DW/WW, which represents the pressure differential between drywell 12 and wetwell 14. Drywells, wetwells, GDCSes, spill-over-holes, and vent lines are well known. A vacuum breaker assembly 40 including a vacuum breaker 42 and a vacuum breaker condensing system 44 couples wetwell 14 and drywell 12. Vacuum breaker 42 may, for example, be a known vacuum breaker, and is configured to move between an open position, where fluid and steam flow through vacuum breaker 42 between wetwell 14 and drywell 12, and a closed position, where vacuum breaker 42 substantially prevents fluid and steam from flowing between wetwell 14 and drywell 12. Condensing system 44 is coupled to vacuum breaker 42 and includes a condenser 46 and a steam inlet pipe 48. Steam inlet pipe 48 is substantially hollow and includes a first end 50 and a second end 52. First end 50 of steam inlet pipe 48 extends through wall 32 and second end 52 of steam inlet pipe 48 is coupled to vacuum breaker 42. Between first and second ends 50 and 52, respectively, steam inlet pipe 48 further includes a loop seal 54 having a height H. Steam inlet pipe first end 50 is spaced above the spill-over-hole with respect to a floor 56 of drywell 12 so that first end 50 will always be above a drywell pool of water (not shown) which may accumulate during reactor operation. Condenser 46 is positioned in wetwell 14 proximate steam inlet pipe 48 and is configured to substantially condense steam flowing through steam inlet pipe 48. Condenser 46 includes an inlet, or cold leg, 58, an outlet, or hot leg, 60, and a plurality of condenser tubes 62. Condenser inlet 58 and condenser outlet 60 each extend between GDCS pool 20 and wetwell 14, and are configured to draw water from GDCS pool 20 and through condenser tubes 62. During reactor operation, vacuum breaker 42 typically moves to the open position to reduce the pressure differential between wetwell 14 and drywell 12. Particularly, if pressure in wetwell 14 becomes sufficiently great compared to pressure in drywell 12, vacuum breaker 42 opens and noncondensables and steam in wetwell 14 flow through vacuum breaker 42 and into drywell 12 to reduce the differential pressure. Vacuum breaker condensing system 44 substantially prevents steam from flowing from drywell 12 and into wetwell 14 while vacuum breaker 42 is in the open position. If vacuum breaker 42 becomes stuck in the open position for too long, it is possible for the differential pressure between the wetwell 14 and the drywell 12 to reduce so that steam in drywell 12 begins flowing from drywell 12 and through steam inlet pipe 48 toward vacuum breaker 42 and wetwell 14. Condenser inlet 58 supplies cold water from GDCS pool 20 to condenser 46, which circulates such water through condenser tubes 62 to substantially condense any steam flowing through pipe 48. The heated water flowing through condenser tubes 62 is discharged from condensing system 44 via condenser outlet 60 and into GDCS pool 20. Condensed steam, or condensate, 64 accumulates in loop seal 54 and forms a static head column HC of approximately .DELTA.P.sub.DW/WW. Static head column HC substantially seals steam inlet pipe 48 and substantially prevents additional steam and noncondensables from flowing from drywell 12 toward vacuum breaker 42 through steam inlet pipe 48. Condensing system 44 also facilitates maintaining an acceptable drywell 12 to wetwell 14 pressure differential. Particularly, if pressure in wetwell 14 becomes greater than the sum of the pressure in drywell 12 and pressure generated by static head column HC, then such wetwell pressure will discharge condensate 64 from steam inlet pipe first end 50. Accordingly, steam and fluid may flow through open vacuum breaker 42 from wetwell 14 to drywell 12 to reduce the pressure differential between wetwell 14 and drywell 12. If the pressure differential between wetwell 14 and drywell 12 again becomes too small, condensing system 44 condenses steam in pipe 48 to again substantially seal pipe 48 and substantially prevent steam and fluid from flowing directly from drywell 12 to wetwell 14. GDCS pool of water 20 may, for example, have a temperature of approximately 47 degrees Celsius. Steam flowing from drywell 12 toward vacuum breaker 42 through steam inlet pipe 48 may, for example, have a temperature of approximately 132.5 degrees Celsius. Accordingly, an initial temperature difference across condenser 46 may approximate 85.5 degrees Celsius. The above described condensing system 44 substantially prevents steam and noncondensables from flowing from drywell 12 and into wetwell 14 while vacuum breaker 42 is in the open position. Such system 44 also facilitates maintaining an acceptable drywell to wetwell pressure differential. FIG. 2 is a schematic illustration of a section of a boiling water reactor 70 including a vacuum breaker assembly 72 in accordance with another embodiment of the present invention. Reactor 70 includes a drywell 74, a wetwell 76, a Gravity Driven Cooling System (GDCS) 78 and a passive cooling containment system (PCCS) 80. GDCS 78 is substantially separated from drywell 74 by a GDCS wall 82, and includes a pool of coolant 84 positioned so that when coolant from pool 84 must be supplied to a reactor pressure vessel (not shown in FIG. 2), the coolant flows, under gravity forces, through a GDCS coolant injection line 86 into the reactor pressure vessel. Under normal reactor operating conditions, however, coolant from GDCS 78 does not flow into the reactor pressure vessel. Wetwell 76 includes a suppression pool of water 88 and is substantially separated from both drywell 74 and GDCS pool 84. An air space 90 above suppression pool 88 is connected to an air space 92 above GDCS pool 84 via a vent pipe 94. A wall 96 extends between wetwell 76 and drywell 74, and an opening, or spill-over-hole, 98 extends therethrough. A spill-over line 100 extends from suppression pool 88 through spill-over-hole 98. Wetwell 76 further includes a main vent 102 filled at least partially with water 104, and suppression pool of water 88 is higher than the main vent water 104 by a pressure differential .DELTA.P.sub.DW/WW, which represents the pressure differential between drywell 74 and wetwell 76. Drywells, wetwells, GDCSes, spill-over-holes, and vent lines are well known. PCCS 80 includes a set of passive containment cooling condensers (not shown in FIG. 2) positioned in a pool of water, or IC/PCC pool, 106, which is located outside drywell 74. A steam inlet path (not shown in FIG. 2) extends between drywell 74 and the passive containment cooling condensers, and is configured to transport steam from within drywell to such condensers. The passive containment cooling condensers are configured to condense steam received from drywell 74 and remove heat generated within drywell 74. Particularly, the passive containment cooling condensers discharge the condensed steam, or condensate, into drywell 72 and discharge noncondensables into suppression pool 88. Passive cooling containment systems are well known. Vacuum breaker assembly 72 includes a vacuum breaker 108, which couples wetwell 76 to drywell 74, and a vacuum breaker condensing system 110. Vacuum breaker 108 may be a known vacuum breaker, and is configured to move between an open position, where fluid and steam flow through vacuum breaker 108 between wetwell 76 and drywell 74, and a closed position, where vacuum breaker 108 substantially prevents fluid and steam from flowing between wetwell 76 and drywell 74. Condensing system 110 is coupled to vacuum breaker 108 and includes a condenser 112 and a steam inlet pipe 114. Steam inlet pipe 114 is substantially hollow and includes a first end 116 and a second end 118. First end 116 of steam inlet pipe 114 is positioned in drywell 74 and second end 118 of steam inlet pipe 114 is coupled to vacuum breaker 108. Between first and second ends 116 and 118, respectively, steam inlet pipe 114 further includes a loop seal 120 having a height H. Steam inlet pipe first end 116 is spaced above spill-over-hole 98 with respect to a floor 122 of drywell 74. Condenser 112 is positioned in drywell 74 proximate steam inlet pipe 114 and is configured to substantially condense steam flowing through steam inlet pipe 114. Condenser 112 includes an inlet, or cold leg, 124, an outlet, or hot leg, 126, and a plurality of condenser tubes 128. Condenser inlet 124 and condenser outlet 126 each extend between IC/PCC pool 106 and drywell 74, and are configured to draw water from IC/PCC pool 106 and through condenser tubes 128. During reactor operation, vacuum breaker 108 typically moves to the open position to reduce the pressure differential between wetwell 76 and drywell 74. Particularly, if pressure in wetwell 76 becomes sufficiently great compared to pressure in drywell 74, vacuum breaker 108 opens and noncondensables and steam in wetwell 76 flow through vacuum breaker 108 and into drywell 74 to reduce the differential pressure. Vacuum breaker condensing system 72 substantially prevents steam from flowing from drywell 74 and into wetwell 76 while vacuum breaker 108 is in the open position. If vacuum breaker 108 becomes stuck in the open position for too long, it is possible for the differential pressure between the wetwell 76 and the drywell 74 to reduce so that steam in drywell 74 begins flowing from drywell 74 and through steam inlet pipe 114 toward vacuum breaker 108 and wetwell 76. Condenser inlet 124 supplies cold water from IC/PCC pool 106 to condenser 112, which circulates such water through condenser tubes 128 to substantially condense any steam flowing through pipe 114. The heated water flowing through condenser tubes 128 is discharged from condensing system 72 via condenser outlet 126 and into IC/PCC pool 106. Condensed steam, or condensate, 130 accumulates in loop seal 120 and forms a static head column HC of approximately .DELTA.P.sub.DW/WW. Static head column HC substantially seals steam inlet pipe 114 and substantially prevents additional steam and noncondensables from flowing from drywell 74 toward vacuum breaker 108 through steam inlet pipe 114. The above described condensing systems substantially prevent steam and noncondensables from flowing from the drywell and into the wetwell while the vacuum breaker is in the open position. Such systems also facilitate maintaining an acceptable drywell to wetwell pressure differential. From the preceding description of various embodiments of the present invention, it is evident that the objects of the invention are attained. Although the invention has been described and illustrated in detail, it is to be clearly understood that the same is intended by way of illustration and example only and is not to be taken by way of limitation. For example, the above described condensing system was coupled to either the GDCS pool or the IC/PCC pool. However, such condensing system may be coupled to a pool of water, or coolant, other than the GDCS pool or the IC/PCC pool. Accordingly, the spirit and scope of the invention are to be limited only by the terms of the appended claims.

Subsets and Splits

No community queries yet

The top public SQL queries from the community will appear here once available.