[en] Upon separation of uranium, plutonium, fission products and transuranium elements by solvent extraction in a reprocessing of spent nuclear fuels, it has been found that they can be processed by using an organic solvent, similar to that used in an existent reprocessing, that is a mixture of tributyl phosphate (TBP) and dodecane. When a solution containing spent nuclear fuels dissolved in nitric acid is extracted by the solvent described above, a solvent of 30% TBP/70% dodecane has been used in order to extract uranium and plutonium at high purity. In the present invention, the concentration of TBP is increased to extract transuranium elements and a portion of fission products together with uranium and plutonium. Since this can suppress intrusion of transuranium elements into liquid extraction residues, that is, high level liquid wastes, the amount of the transuranium element having a long half-decay time and a high toxicity can be minimized, to facilitate the processing and disposal. (T.M.)

[en] Purpose: To effectively adsorb to remove radioactive nuclides in waste water by the combined use of activated carbon incorporated with oxine (8-hydroxyquinoline) and zeolite incorporated with copper ferrocyanide. Method: For adsorbing to remove radioactive nuclides in waste water issued from radioactive material handling facilities, activated carbon incorporated with oxine (8-hydroxyquinoline) capable of adsorbing to remove transition metals such as Co, Iron, Cr, Mn and zeolite incorporated with copper ferrocyanide having a property of taking Cs, Sr and the like selectively into the lattice are used together. This enables to effectively adsorb to separate and remove those nuclides such as radioactive Co, radioactive Iron, radioactive Cr, radioactive Mn, radioactive Cs and radioactive Sr from the liquid wastes containing various coexistent salts such as of sodium issued from nuclear power plants or the likes. (Seki, T.)

[en] A sealed radiation source is disposed at the periphery or the inside of a facility in the processing system of low level liquid wastes formed from nuclear fuel reprocessing. A nitrate solution is radiolized by radiation rays generated from the sealed radiation source to form NO₂ and HNO₂. Then, nuclear fission products (FP) such as highly oxidative ruthenium tetraoxide formed by the oxidizing effect of nitric acid at high temperature and high concentration react with nitrous acid (HNO₂) formed by the radiolysis at an extremely high rate and is reduced to lose its corrosion acceleration effect. Accordingly, irradiation of radiation rays to the nitric acid liquid wastes can provide similar effect as that of adding NO_x from the outside. This can suppress the corrosion of the facilities in liquid waste processing system at a relatively low radioactive level safely and efficiently. (T.M.)

[en] Purpose: To enable selective and efficient removal of transition element such as cobalt from high-temperature water such as reactor water. Constitution: Porous titanium metal and water are filled in an autoclave. After tightly closing the autoclave, heating treatment is applied, by which the surface of the porous titanium metal is converted into titanium oxide. After washing the oxide with water and then drying, adsorbents can be obtained. When the adsorbents are filled in a reactor-water purifier and brought into direct contact with the reactor-water at high-tenperature, the adsorbents adsorb metal ions in the high-temperature water. Accordingly, since there is no requirement for cooling the reactor-water, metals ions can be removed with no heat loss. In addition, the amount of radioactivity in the reactor can be decreased. (Kawakami, Y.)

[en] An ion exchaner having at least one phosphorus atom in an ion exchange group or the substrate of the ion exchanger in which an entire or most part of a substrate (matrix) of the ion exchanger comprises an aliphatic hydrocarbon, is brought into contact with a solution containing metal ions, to capture and separate the metal ions in the solution to any of the ion exchangers. If an ion exchanger mostly comprising the aliphatic hydrocarbon is used instead of generally used ion exchangers comprising aromatic hydrocarbons, the pyrolysis temperature of the ion exchanger can be lowered from 750degC to 300degC. If the pyrolysis temperature is lowered, the pyrolytic processing can be facilitated, in addition, scattering of easily evaporating metals can be prevented. In view of the above, it is possible to separate metals or polyvalent metals in radioactive liquid wastes or liquid wastes generated from industrial plants and homes and further put the ion exchangers used to pyrolytic decomposition. (T.M.)

[en] Purpose: To decrease the leaching of radioactive waste in marine environment. Method: Fillers are placed between a drum can and an inner cage for charging radioactive wastes in order to prevent the leakage of the radioactive wastes from the drum can. Leaching inhibitors for radioactive materials are mixed with the fillers made of organic substance such as asphalts and plastics. The leaching inhibitors are made of materials in the similar chemical form to that of the radioactive materials in the wastes and mixed into the fillers to the saturation limit of dissolution. For the radioactive wastes containing spent adsorbents for iodine, the inhibitors are made of silver nitrates. (Ikeda, J.)

[en] Purpose: To greatly decrease the volume of spent inorganic adsorbents with ease while preventing the scattering of radioactive materials, and convert them into a state suitable to disposal. Method: Titanium type spent inorganic adsorbents are supplied to a reactor and, after evacuation, hydrogen is supplied to the inside of the reactor. At the same time, the inside of the reactor is heated by a heater to hydrogenate the inorganic adsorbents. After the hydrogenation, hydrogen is discharged to reduce the pressure inside the reactor. After the completion of the hydrogen removal, the powder of the inorganic adsorbents deposited at the bottom of the reactor is supplied to a compression molding device to form the powder into compression molding products. (Yoshino, Y.)

[en] Purpose: To remove solid contaminants deposited in a cold trap by only dry process, without use of chemicals. Method: Solid products (such as UO₂F₂ and UF₄) deposited at the bottom or the like part of a cold trap are subjected to a jet of inert gases, such as nitrogen and argon. Pulverized and scrapped contaminants are then converted into aerosol form before removed by suction. (Aizawa, K.)

[en] Purpose: To increase the efficiency of removing radioactive cesium from radioactive liquid waste by employing zeolite affixed to metallic compound ferrocyanide as an adsorbent. Method: Regenerated liquid waste of a reactor condensation desalting unit, floor drain and so forth are collected through respective supply tubes to a liquid waste tank, and the liquid waste is fed by a pump to a column filled with zeolite containing a metallic compound ferrocyanide, such as with copper, zinc, manganese, iron, cobalt, nickel or the like. The liquid waste from which radioactive cesium is removed is dried and pelletized by volume reducing and solidifying means. (Yoshino, Y.)

[en] Purpose: To lighten the disposal trouble about secondary wastes such as cladding exfoliated from nuclear reactor equipments and pipeways upon decontamination substance to radiation-contaminated metal materials. Method: Particles of sublimating substance such as solid carbon dioxide and naphthalene are sprayed to the wall surfaces of nuclear reactor equipments and pipeways to exfoliate the claddings deposited on the wall surfaces. The mixture of the claddings and the sublimating particles are collected in filters and the sublimating substance particles are sublimated in a hot blow gases, which is to be checked by radiation monitors. By the use of the particles of sublimating substance, the amounts of the secondary wastes can be reduced to 1/20 of those in the conventional methods. (J.P.N.)