Abstract: Gamma rays are applied to a suspension which includes water and a catalyst having an element of platinum group metal carried on a semiconductor, thereby decomposing the water so as to produce hydrogen. The energy of gamma rays emitted from a nuclear reactor can be utilized to achieve a high-efficient generation of hydrogen.

Abstract: The present invention provides a method for identifying failed fuel elements and the scale of damage accurately, quickly and at low cost without disassembling a fuel assembly and without discharging radioactive waste. Radiation detector(s) for measurement of gamma radiation emitted from surface of the irradiated fuel assembly and the fuel assembly are rotated and translated relative to each other, the dectected data of the radiation emitted from the surface of the fuel assembly is acquired, processed, a tomographic image is constructed from the radiation intensity distribution and is prepared and displayed, and a failed fuel element is finally confirmed from the tomographic image of the fuel assembly cross-section.

Abstract: A diving bell type control rod of sodium bond type. The control rod including a plurality of control elements each comprising a pellet chamber for packing B.sub.4 C pellets and disposed in a cladding tube, an intermediate plug disposed above the pellet chamber, an upper chamber formed above the intermediate plug, a vent tube allowing the pellet chamber to communicate with the upper chamber while penetrating through the intermediate plug, upper and lower vent holes formed in upper and lower two stages in the cladding tube at the upper chamber, a sodium inflow port opening to the upper surface of the intermediate plug, and a sodium introduction tube extending from the sodium inflow port to a position below the lower end surface of the intermediate plug while penetrating through the intermediate plug.

Abstract: A fitting structure of a plurality of rectangular parallelopipedal blocks comprising concavo-convexities formed on the surfaces of each of the blocks. The concavo-convexities are formed on each surface of the block on the basis of a figure which is in symmetry of rotation per 90.degree. round the center of a regular square or is in symmetry of rotation per 180.degree. round the center of a rectangle, and is complementarily in symmetry of axis with respect to a center of the rectangle line passing through the center and being in parallel with a side of the regular square or rectangle. Predetermined congruence is imparted to the figures on the surfaces depending on various shapes of the blocks. Fitting of the concavo-convexities of the surfaces of the adjacent blocks is always ensured when each block is aligned so that its thickness and its length are in conformity. The surfaces of adjacent blocks can be connected without the necessity of considering the direction of each block.

Abstract: A machine for inspecting the surface conditions of structural members within a furnace, particularly within a furnace operating at a high temperature or with a highly radioactive environment, such as a melting furnace for processing radioactive wastes.

Abstract: A continuous denitration apparatus capable of ensuring mass processing of a nitrate solution of a nuclear fuel and a continuous stable operation. By a rotation of screws, uranium nitrate solution supplied from a liquid feed inlet is continuously conveyed. A trough is divided into a concentration zone, a denitration zone and a drying zone. Microwaves emitted from a microwave incident inlet pass through a microwave permeable part provided in a critical shield plate for covering the upper part of the trough and are applied to the uranium nitrate solution of high concentration and high viscosity, conveyed by the screws. The uranium nitrate solution is denitrated to prepare a denitrated product (uranium trioxide). This denitrated product is dried in the drying zone to obtain powder to be discharged from an outlet.

Abstract: In a method of coextracting neptunium and plutonium, a nitric acid solution containing a mixture of neptunium and plutonium is oxidized by irradiation of ultraviolet light. As a result, different valences of neptunium are adjusted all into the valence 6, which can remain in water, and in the meantime, valences of plutonium are adjusted into the valence 4 or 6, which can be extracted in the organic phase. It is therefore possible to coextract neptunium and plutonium without difficulty. The coextracted neptunium and plutonium can be used in forming mixed fuel by blending at least a portion of at least one of neptunium and plutonium which neptunium and plutonium have been formed by separating a nitric acid solution containing neptunium and plutonium by exposing the solution and a reducing agent to ultraviolet radiation to adjust the valences, and extracting the solution using an organic phase to extract plutonium from the solution into the organic phase.

Abstract: A function ally gradient composite material containing copper and carbon as main components and having a predetermined shape, in which the composition ratio of the copper to the carbon in the material continuously varies in at least one predetermined direction. The material is manufactured, for example, by impregnating carbon felt with a resin and thermo-compressively molding the impregnated felt (step S101), carbonizing the resin by baking (step S102) to provide a preformed carbon material (step S104). Pyrolytic carbon is thereafter deposited in the preformed carbon material by the CVI method (step S105) to provide a carbon material having the bulk density varying in a predetermined direction (step S107). After the wettability of the carbon material against copper is improved by siliconization (step S108), pores of the carbon material are impregnated with copper (step S109) to obtain a functionally gradient composite material of copper and carbon.

Abstract: A method of separating exothermic elements of Cs and Sr from a high-level radioactive liquid waste. The method comprises a denitration step wherein formic acid is added to the high-level liquid waste so as to adjust its pH to about 5, thereby causing most of the elements other than Cs and Sr to precipitate in the high-level liquid waste to obtain a denitrated liquid waste containing Cs and Sr in high concentrations. The denitrated liquid waste is then subjected to a pH adjustment step wherein ammonia is added to the denitrated liquid waste so as to adjust its pH to about 7.5 to 9, thereby removing by precipitation the elements other than Cs and Sr remaining in the denitrated liquid waste. When the thus resulting precipitate freed of Cs and Sr is vitrified, the waste content in the vitrified waste can be increased.

Abstract: An object material to be melted (radioactive liquid waste and glass material) 16 is charged into the interior of a cold-crucible induction melting apparatus 10, and a conductor 18 the melting point of which is higher than that of the glass material is inserted into a melting furnace 12. A high-frequency current is supplied to a coil 14 so as to generate heat in the conductor and indirectly heat the glass material. The conductor is withdrawn after a part of the glass material has been put in a molten state. The glass material as a whole is thereafter kept in a molten state while maintaining the induction heating by the molten glass material. The conductor inserted into the melting furnace is, for example, a silicon carbide rod. The surface of the molten material which contacts the inner surface of the melting furnace turns into a solid layer (skull) due to cooling, so that the molten material does not directly contact the refractories.

Abstract: A method of vitrifying a high-level radioactive liquid waste comprising removing a precipitate composed mainly of Mo and Zr from the high-level liquid waste, mixing the resulting high-level liquid waste with a raw glass material having a chemical composition wherein the B.sub.2 O.sub.3 /SiO.sub.2, ZnO/Li.sub.2 O and Al.sub.2 O.sub.3 /Li.sub.2 O ratios are at least 0.41, at least 1.00 and at least 2.58, respectively, and melt-solidifying the mixture to thereby form a vitrified waste. By using such a raw glass material, there can be obtained a vitrifled waste having the waste content of about 45% by oxide weight in which the same leaching rate as that of a conventional vitrified waste having the waste content of 25% by oxide weight is ensured without suffering from yellow phase separation.

Abstract: A method of separating and purifying a spent solvent generated in a nuclear fuel cycle and containing a higher hydrocarbon and a phosphate. This method comprises applying to the spent solvent a pressure high enough for allowing the crystallization of the higher hydrocarbon to thereby crystallize the higher hydrocarbon, and separating under pressure a resulting solid mainly composed of the higher hydrocarbon from a remaining solution containing the phosphate in a higher concentration. The remaining solution may further be subjected to low-temperature vacuum distillation to separate the solution into the phosphate and a deterioration product thereof contained in the solution.

Abstract: Fission noble metals contained in an insoluble residue and/or a high-level radioactive liquid waste generated in the step of reprocessing spent nuclear fuels are dissolved in nitric acid to prepare a palladium-containing nitric acid solution, which is then brought into liquid-liquid contact with an extracting solvent containing a dialkyl sulfide in which each alkyl group has 4 to 10 carbon atoms as an extractant to extract the palladium component into the extracting solvent. The palladium-containing extracting solvent is brought into liquid-liquid contact with an aqueous thio compound solution or aqueous ammonia solution to strip the palladium component into the aqueous solution. A borohydride compound in added to the palladium-containing aqueous solution to precipitate palladium from this solution by reduction, and metallic palladium is recovered by separating the precipitate from the aqueous solution.

Abstract: A low-temperature Raman laser apparatus that avoids an increase in the pump light power, which would otherwise be needed under room temperature conditions, and eliminates the problems of instability of the equipment and complicatedness of the operation under liquid nitrogen cooling conditions and also lowers the cost, which has heretofore been high due to the consumption of liquid nitrogen, and that is capable of stably and efficiently effecting Raman conversion. The low-temperature Raman laser apparatus has a Raman cell (1) filled with a Raman conversion medium to convert the wavelength of incident pump light by the Raman conversion action of the Raman conversion medium. A heat absorbing member (2) or (3), through which a brine cooled by a brine refrigerator (4) circulates, is provided around the Raman cell (1) to cool the Raman conversion medium to a temperature in the range of from 200.degree. K. to 300.degree. K.

Abstract: In a method of separating neptunium and plutonium, a nitric acid solution containing a mixture of neptunium and plutonium is oxidized by irradiation of ultraviolet light in the presence of a reducing agent. As a result, different valences of neptunium are adjusted all into the valence 5, which can remain in water, and in the meantime, valences of plutonium are adjusted into the valence 4 or 6, which can be extracted in the organic phase. It is therefore possible to separate neptunium and plutonium from each other without difficulty.

Abstract: Neptunium of minor actinide nuclides separated from spent fuel is added to fuel of reactor cores (inner reactor cores and/or outer reactor cores) of a fast reactor and americium of the separated minor actinide nuclides and rare earth elements are added to either or both of radial and axial blankets of the fast reactor for burning. Thus, the minor actinide nuclides with long half-lives can be burnt with the fast reactor core with the minimized effects of the rare earth elements. For a burner reactor, americium and rare earth elements may be added to shields for burning. Curium may be added together with americium and rare earth elements. Neptunium is added in amount of 2% to 5% by weight based on the weight of the fuel and the rare earth elements are added in an amount of 50% by weight or less based on the weight of the fuel. A Purex process is used to separate neptunium and a Truex process is used to separate americium and curium.

Abstract: A radiation scanning mechanism is capable of increasing an observable range by eliminating a restriction on a scannable range of a conventional scanning mechanism for a radiation TV set for scanning an observation object by a directional radiation detector to display the distribution state of a radioactive material as an image. In the radiation scanning mechanism, an inner frame having a rotary shaft provided with a directional gamma-ray detector is attached to an outer frame having a rotary shaft so that the rotary shaft of the inner frame may perpendicularly and rotatably intersect the rotary shaft of the outer frame, and the rotary shaft of tile outer frame is rotatably supported by an outer frame support base.

Abstract: A method of separating and recovering Pu and Np from a Pu- and Np-containing nitric acid solution. The method comprises the steps of subjecting a nitric acid solution containing Pu and Np to valence adjustment by adding a reducing agent consisting of hydroxylamine nitrate and hydrazlne to said nitric acid solution so as to reduce Pu and Np in said nitric acid solution to Pu (III) and Np (IV), respectively; adjusting a nitric acid concentration of said nitric acid solution after said valence adjustment to 6 to 8 M; bringing said nitric acid solution after said nitric acid concentration adjustment into contact with a strong basic anion exchange resin so as to cause Np to be selectively adsorbed by said resin and to separate and recover Pu as a plutonium nitrate solution; and eluting said adsorbed Np (IV) by using diluted nitric acid of 1 M or below so as to recover Np as a neptunium nitrate solution.

Abstract: Particles contained in a suspension are separated in accordance with their magnetic susceptibility and based on the variation in flow velocity of suspension. In order to achieve this magnetic separation, a pair of wall plates having at least one flat surface in which a plurality of ferromagnetic narrow wires are buried in parallel are positioned in parallel to each other with a small distance therebetween so that the flat surfaces are opposed to each other to form a channel. The suspension flows in a laminar state with different flow velocities through the channel in the longitudinal direction of the ferromagnetic wires. A magnetic field is externally applied to the channel in the direction perpendicular both to the flow direction and the wall plates. Particles are separated in accordance with their magnetic susceptibility and based on variation in flow velocity which interacts with the magnetic susceptibility.

Abstract: An extractant for selectively extracting strontium from an aqueous solution containing the same, which comprises a 1,2-benzenebis(1,4-dioxanonyl-6,8-dionato)metal complex of the following structural formula: ##STR1## wherein M represents a metal ion of Cu (II), Zn (II) or Ni (II).