A comparison of the acid digestion of spent ion exchange resins using H 2SO 4-HNO 3 and H 2SO 4H 2O 2

Abstract

An alternative acid digestion system, H 2SO 4H 2O 2, to a conventional reaction system, H 2SO 4HNO 3, has been proposed to reduce the volume of spent ion exchange resins generated at nuclear power plants. A comparative study on both reaction systems has been carried out to obtain the relationship between the reaction conditions and the conversion of the resins, the coprecipitation behavior of 60Co and 137Cs, and the release rate of the radionuclides from a reaction vessel, and to elucidate the feasibility of the system proposed. The mole ratio of an oxidant and carbon contained in the resins, required to digest the resins, was comparable between both systems, while the H 2SO 4H 2O 2 system gave higher conversion than the H 2SO 4HNO 3 system. Some degradation products of an anion exchange resin were relatively stable against the oxidation, and required excessive amounts of the oxidant and a higher reaction temperature to digest, especially in the H 2SO 4HNO 3 system. The coprecipitation behavior of the radionuclides in both systems was almost identical; 60Co coprecipitated effectively with Fe(III) sulfate while 137Cs did not coprecipitate. The release rates of the radionuclides were on the order of 10 −3%/hr.