STATIC AND DYNAMIC SIMFUEL DISSOLUTION STUDIES UNDER OXIC CONDITIONS

The dissolution behavior of an unirradiated chemical analogue of spent nuclear fuel (SIMFUEL) has been studied in the presence of two different synthetic groundwaters at 25-degrees-C and under oxic conditions. The release of U, Mo, Ba, Y and Sr was monitored during static (batch) dissolution experiments of long duration (about 250 days). Preliminary results from continuous flow-through reactor experiments are also reported. The results obtained indicate the usefulness and limitations of SIMFUEL in the study of the kinetics and mechanism of dissolution of the minor components of spent nuclear fuel. In the batch experiments, Mo, Ba and Sr showed a trend to congruent dissolution with the SIMFUEL matrix after a higher initial fractional release. Y release has been found to be solubility controlled under the experimental conditions. A clear dependence of the rates of dissolution of uranium on the partial pressure Of O2 has been observed.