Prediction of oxygen potential in americium thorium oxides phase of a cermet fuel

Prediction of the oxygen potential variation during burnup for ThO2-based Am-containing cermet fuel, which consists of (Am, Th)O2−x host phase and molybdenum inert matrix, in a fast reactor was carried out by the chemical thermodynamic method. The oxygen potentials of (Eu, U)O2−x and (Pu, Th)O2−x were analyzed and related thermodynamic data were obtained. These data, together with those in the literature for the components in the burnup fuel, were used for oxygen potential prediction during burnup considering the oxygen and metal balances. It was revealed that the addition of a small amount of depleted-U to the host phase of the fuel effectively lowered the high oxygen potential observed at the initial stage of the burnup.