A Study on the Oxidative-dissolution Leaching of Fission Product Oxides in the carbonate solution

This study was carried out to investigate the characteristics of an oxidativedissolution leaching of FP co-dissolved with U in a carbonate solution of Na2CO3- H2O2 and (NH4)2CO3-H2O2, respectively. Simulated FP-oxides which contained 12 components have been added to the solution to examine their oxidative dissolution characteristics. It was found that H2O2 was an effective oxidant to minimize the dissolution of FP in a carbonate solution. In 0.5M Na2CO3-0.5M H2O2 and 0.5M (NH4)2CO3-0.5M H2O2 solution, some elements such as Re, Te, Cs and Mo seem to be dissolved together with U. It is revealed that dissolution rates of Re, Te and Cs are high (completely dissolved within 10∼20 minutes) due to their high solubility in Na2CO3 and (NH4)2CO3 solution regardless of the addition of H2O2, and independent of the concentrations of Na2CO3 and H2O2. However, Mo was slowly dissolved by an oxidative dissolution with H2O2. It is found that the most important factor for the oxidative dissolution of FP is the pH of the solution and an effective oxidative dissolution is achieved at a pH between 10∼12 for Na2CO3 and a pH between 9∼10 for (NH4)2CO3, respectively, in order to minimize the dissolution of FP