[en] Purpose: To provide a protective metal layer in the inner surface of a nuclear fuel cladding tube thereby to prevent stress corrosion cracks of the cladding tube and to remove iodine from the atmosphere of the inner part of the cladding tube. Method: A composite cladding tube comprises a cladding tube, and a protective metal layer made of at least a member selected from the group consisting of Zr, Sn, Mg, Ca, Cr, Fe, Cu, Ni and Zn, and metallurgically bonded to the inner surface of said cladding tube. In manufacturing the composite cladding tube, the inner surface of a long hollow billet which is a raw material of the cladding tube is subjected beforehand to extrusion processing thereby to form vertical grooves therein, and a hollow sleeve of the protective metal layer separately manufactured is inserted therein as a inner layer, thereafter copper coating being applied thereon. Then, the composite tube is subjected to hot unitary extrusion processing, and then the copper coating is exfoliated and subjected to cold extrusion. (Nadamura, S.)

[en] Purpose: To prevent radioactive leaching and to attain excellent heat-dissipating and mechanical performances of radioactive wastes. Method: Solution or powder of radioactive wastes is dispersed, for example, into molten borosilicate glass or phosphate glass of about 70 to 30 % by weight per the dried oxides of the wastes and then molded into glass spheres of 2 - 50 mm in diameter. The surface of the glass solidified particles are made with electroconductive membranes by way of electroless plating, sputtering, vapor deposition, paste sintering or the like, thereafter, formed with membranes of metals such as copper, nickel, iron and silver by way of electroplating. The particles are sintered at a temperature between glass-softening point and metal-melting point. (Horiuchi, T.)

[en] Purpose: To enable substantially permanent storage for radioactive wastes, by solidifying the wastes with metals and then coating them with metals in multi-layers. Method: Calcination products of radioactive wastes such as spent nuclear fuels and various radioactive liquid wastes or those pretreated materials containing the calcination products are solidified by compression molding together with metals such as copper powder or by injection of molten metals in an inner vessel made of an alloy consisting at least one of metal elements such as iron, aluminum and nickel. Then, one or more of such inner vessels are embedded in a storage container made of iron, titanium or nickel or alloys thereof together with embedding metals such as copper, iron and aluminum by melting-cooling solidification, compression or the like. The radioactive wastes are thus coated in a multi-layer manner with metals to be improved with mechanical and chemical stability and enabled for longer and safe storage. (Horiuchi, T.)

[en] Purpose: To enable substantially permanent wastes storage by calcinating radioactive wastes, storing them in the recesses of metal plates and laminating and pressurizing the metal plates in a container to solidify them. Method: Radioactive wastes are calcinated and stored in the recesses formed in metal plates. The metal plates are made of a metal, i.g., lead metal, having a good fittability to the calcinated products and the recesses are formed corresponding to the configuration of the calcinated products. Then, the metal plates are moved laterally and vertically so that the metal plates containing the calcinated products in their recesses may be laminated in the most compacted structure, and the entire contents are compressed to solidify. Accordingly, the calcinated products are disposed in the metal matrix, can be stored with safe for a long time and the volume reduction ratio can be decreased significantly. (Yoshino, Y.)

[en] Purpose: To prepare filter materials having high adsorption performance for cobalt in reactor water, with no risk of leaching into the reactor water and good fabricability even in a reactor water at high temperature and high pressure. Constitution: The surface of steel containing Cr (9 to 20 % by weight), Mn (9 to 25 %), C (less than 0.5 %), N (less than 1 %), and Si (less than 2 %) is oxidized, to which cobalt can be selectively adsorbed. Thus, the adsorbing performance for cobalt in the reactor water can be increased. (Yoshihara, H.)

[en] Purpose: To attain man-power saving and effective processing in the cleaning and administrating steps of working cloths in a radioactive material handling facility. Method: Radiation monitors, chute, conveying bags, storage lines, auxiliary charging chute, finishing equipments, automatic classifying circle conveyors and the likes are disposed to the up- and down-stream of a dry cleaner step, and the information processings and operation controls for each of the equipments are adapted to be carried out systematically. The specific items for the information to be handled are the amount of cloths to be cleaned, accumulation amount of conveying bags, operation states of the dry cleaner, contamination degree of cloths, operation states of the finishing equipments, storage amount of cloths in the storage area and the like. As the administrative function, administration of working cloths, control of secondary wastes, and preparation of operation recordings for each of the equipments are carried out. (Kamimura, M.)

[en] Purpose: To compression mold, sinter and solidify the calcined bodies of radioactive wastes together with a metal, thereby to form solidified bodies having good heat conductivity and excellent mechanical strength, thermal shock resistance, and mechanical shock resistance, and durable in permanent storage. Method: Powders of calcined bodies of radioactive wastes and metal powders (Pb, Zn, Sn, Cu, Ag, Al, Fe and Ni or alloys of these metals) of more than 10% in apparent volume are mixed with each other and thereafter the mixtures are compression molded into a compression density of more than 40%. Subsequently, the compression molded bodies are sintered at a temperature of below 600⁰C. Alternatively, the powders of the calcined bodies are granulated and sintered beforehand, and metal coated layers are formed on the surfaces of particles by the non-electrolytic plating method, evaporating method or the like. If necessary, metal powders may be mixed therein, and thereafter the mixtures may be compression molded and sintered in the reducing atmosphere. (Sekiya, K.)

[en] With regard to the Japanese high-level radioactive waste management, Power Reactor and Nuclear Fuel Development Corp. (PNC) plays a leading role in the whole area of research and development covering vitrification, storage and final disposal. The vitrification technology development in PNC including construction of the Tokai Vitrification Facility for plant scale demonstration is described. Quality control as for the vitrification process and products is described. The geological isolation research focussing assessment of multibarrier systems to demonstrate long term isolation from biosphere in the Japanese domestic deep geological environment is also discussed. (orig.)

[en] As to the reprocessing techniques for the fuel of FBRs, the present status in foreign countries is briefly reported, and the present status of the technical development in Japan, which has been carried out for the past ten years, is described through the FBR fuel recycling test facility of pilot scale, of which the conceptual design has been finished recently. In FBRs, it is necessary to recover plutonium from the spent fuel and recycle it an new fuel. It is indispensable to complete the reprocessing techniques for FBR fuel. In Power Reactor and Nuclear Fuel Development Corp., the full scale development was started in fiscal year 1975, and the various equipment was developed, and the cold and hot tests were carried out. The main problems of FBR fuel recycling techniques, the present status of the reprocessing technique development in USA, UK, West Germany and Japan, and the conceptual design of the FBR fuel recycling test facility are described. In the recycling test facility, the remote maintenance techniques were positively adopted, and the treatment is carried out for 100 days/year at 120 kg/day. (Kako, I.)

[en] A chemical bond generated by the interaction between low energy ion and base was investigated by ab initio molecular orbital method. The effects of ion charge were studied by calculation of this method. When carbon ion approached to graphite base (C₂₄H₁₂), the positive ion and the neutral atom covalently bonded, but the negative ion did not combine with it. When carbon ion was injected into h-BN base (B₁₂N₁₂H₁₂, hexagonal system boron nitride), the positive ion and the neutron atom formed covalent bond and the van der Waals binding, and the negative ion interacted statically with it. (S.Y.)