Abstract: A waste gas generated in the reprocessing of used nuclear fuel is at first subjected to removal of explosive, gaseous substances such as hydrocarbons and nitrogen oxides, and materials capable of forming the explosive gaseous substances, such as oxygen, and condensible substances such as carbon dioxide, water and ammonia from the waste gas, and then to cryogenic distillation, thereby separating and recovering Kr-85 from the waste gas. As the separation and recovery of Kr-85 is carried out by cryogenic separation after the removal of the substances having a possibility to explode in a cryogenic distillation apparatus and also the removal of condensible substances having a possibility to clog a piping system of the apparatus, the operation of the apparatus is ensured. It is also disclosed that the oxygen and nitrogen oxides can be completely removed by catalytic hydrogen reduction.

Abstract: A detergent-containing radioactive liquid waste originating from atomic power plants is concentrated to have about 10 wt. % detergent concentration, then dried in a thin film evaporator, and converted into powder. Powdered activated carbon is added to the radioactive waste in advance to prevent the liquid waste from foaming in the evaporator by the action of surface active agents contained in the detergent. The activated carbon is added in accordance with the COD concentration of the radioactive liquid waste to be treated, and usually at a concentration 2-4 times as large as the COD concentration of the liquid waste to be treated. A powdery product having a moisture content of not more than 15 wt. % is obtained from the evaporator, and pelletized and then packed into drums to be stored for a predetermined period.

Abstract: In the concentration of radioactive combustible waste comprising evaporating and drying a radioactive combustible waste slurry by a thin film drier, the radioactive combustible wastes and an incombustible material, such as sodium sulfate, etc. obtained from a nuclear reactor effluent are mixed together in an amount of not more than 70% by weight, preferably 43 to 70% by weight, of radioactive combustible waste on the basis of a mixture on dry basis, and the mixture is fed to the thin film drier and evaporated and dried therein. A risk of powder explosion and fire is prevented in the drying step thereby.

Abstract: An adsorbing material comprising a porous body having larger pores of a mean pore diameter of 200 to 2000 A and smaller pores of a mean pore diameter of 40 to 200 A on the surfaces of the larger pores, said porous body being impregnated with a metal such as silver, copper, etc., or a salt thereof such as silver nitrate, etc., has excellent adsorbing performance for iodine and/or organic iodine compounds under any degree of humidity.

Abstract: A metallic catalyst of three-layer structure of a carrier metal, an interlayer metal having a heat-insulating property by itself, or an interlayer metal capable of forming an oxide having a heat-insulating property or a catalyst surface area-increasing property, deposited on the entire surface of the carrier metal, and a catalyst metal deposited on the interlayer metal is prepared in a shorter production time at a lower cost through simplified process steps by depositing the interlayer metal and the catalyst metal by plating, if necessary, followed by oxidation, or both oxidation and reduction. The metallic catalyst has an improved catalytic activity, especially at a low temperature, in addition to the high mechanical strength.

Abstract: An iodine adsorbent comprises an alumina carrier having a large number of pores having a mean pore size of 200 to 2,000 A and silver supported on the alumina carrier. The alumina carrier has a pore volume of at least about 0.1 cc/g.High percent iodine removal is obtained in a highly humid atmosphere, and an amount of silver supported on the carrier is much reduced.

Abstract: A cleaning method of an etched disc filter and the system therefor, in which a plurality of discs having grooved surfaces are assembled or piled one on top of another. This filter is used for removing cruds and the like in a nuclear plant. For separating cruds and the like from small flow passages provided between each two of the discs thus assembled, reverse cleaning is applied, with the discs relieved from an assembled or piled condition for providing clearances among the discs.

Abstract: Hydrocarbons are removed from a waste gas including oxygen, hydrocarbons and radioactive Krypton-85 (hereinafter referred to as "Kr-85"), which is generated in a nuclear reactor and a fuel recycling plant without adopting the reduction method of oxygen by adding hydrogen; the resultant gas is caused to pass through an activated charcoal layer and Kr-85 is adsorbed to the activated charcoal layer; the rest of gas is discharged to the atmosphere; further oxygen remaining in the activated charcoal layer is returned to a process of removing hydrocarbons; and thereafter Kr-85 adsorbed to the activated charcoal layer is desorbed, condensed and recovered.

Abstract: In an apparatus for treating an exhaust gas from a nuclear plant which comprises a container and a cryogenic distillation apparatus disposed in the container for liquefying and separating a radioactive gas therefrom, an adsorbent such as an active carbon is filled in the container to surround the cryogenic distillation apparatus whereby leakage of the radioactive gas on the occasion of an accident can be removed.