A KINETIC-MODEL FOR THE STABILITY OF SPENT FUEL MATRIX UNDER OXIC CONDITIONS

A kinetic model for the UO2-spent fuel dissolution has been developed by integrating all the fundamental and experimental evidence about the odor buffer capacity of the UO2 matrix itself within the methodologic al framework of I; heterogeneous redox reactions and dissolution kinet ics. The purpose of the model is to define the geochemical stability o f the spent fuel matrix and its resistance to internal and external di sturbances. The model has been built in basis the reductive capacity ( RDC) of the spent fuel/water system. A sensitivity analysis has been p erformed in order to identify the main parameters that affect the RDC of the system, the oxidant consumption and the radionuclide release. T he number of surface co-ordination sites, the surface area to volume r atio, the kinetics of oxidants generation by radiolysis and the kineti cs of oxidative dissolution of UO2, have been found to be the main par ameters that can affect the reductive capacity of the spent fuel matri x, The model has been checked against some selected UO2 and spent fuel dissolution data, pet-formed under oxidizing conditions. The results are quite encouraging.