Determination if UO2(s) dissolution rates in a hydrogen peroxide medium as a function of pressure and temperature

A continuously stirred flow-through tank reactor has been developed and successfully used to determine rates of dissolution of powdered samples of uranium dioxide at pressure and temperature conditions above the ambient values. The experiments have been performed in a temperature range from 20 to 50 degrees C and a total hydraulic pressure ranging from 1 to 32 bar. Experiments have been performed in a test solution containing 10(-4) mol/L of H2O2, 3 x 10(-3) mol/L of NaHCO3 and, finally, NaClO4 to get a constant ionic strength of 0.1 mol/L. An empirical equation has been obtained that describes the results in the experimental range studied and gives a good concordance with values obtained at ambient conditions in other works. On the other hand, scanning electron microscopy (SEM) has shown that the solid surface has homogeneously reacted, and, in addition, no secondary solid phase has been formed on the UO2 surface. (C) 2008 Elsevier B.V. All rights reserved.