PRODUCTION AND REGENERATION OF SILVER(2) USED FOR DECONTAMINATION OF FACILITIES CONTAMINATED BY PUO2 AND DECOMPOSITION OF RADIOLOGICAL ORGANIC WASTE

摘要

A solution, which consists of Ag2+ ion and nitric acid is a very aggressive oxidant to PuO2 and organic compounds. Facilities contaminated by PuO2 can be decontaminated by this kind of solution when Pu4+ in PuO2 is oxidized by Ag2+ to Pu6+ and then PuO2 is dissolved into the solution. The radiological organic compounds can be decomposed by the solution of Ag2+ ion and nitric acid into CO2 and H2O, so the organic wastes are destroyed and the volume of organic wastes are reduced greatly. The method is very useful, but the key problem is the production and regeneration of Ag2+ ion, and it is difficult. In our experiments, a special electrochemical oxidization cell was designed and it is better than single compartment cell and membrane cell to produce and regenerate Ag2+ ion. The cell consists of two compartments as cathode compartment and anode compartment respectively. The two compartments are connected by a specially designed connector, so the solution can be interlinked. The solution in the anode compartment can be Ag+ and nitric acid, and nitric acid in cathode compartment. In the anode compartment, Ag+ is oxidized into Ag2+ and in cathode compartment, H+ is reduced into H2. During production of Ag2+, the reducing agent occurring in the cathode surface will be H2 mostly, and it will not consume the Ag2+. Consequently, Ag2+ is produced as desired. During regeneration of Ag2+, even other reducing agent occurred upon the surface of cathode because of introduced chemicals during the process of decontamination or decomposition, they will enter into anode compartment less and just consume a little of Ag2+. So the Ag2+ can be regenerated. In order to produce and regenerate Ag2+ in the anode compartment, several variables must be considered like structure of cell, length and diameter of the connector, solution composition in the cathode compartment, material of cathode and anode, current density, and the temperature of the solution. The optimum parameters are selected through our experiments to achieve high rate of production and regeneration of Ag2+ at low cost.