Oxygen potentials of plutonium and uranium mixed oxide

The oxygen potentials of (Pu0.3U0.7)O2−x in the near stoichiometric region were measured by a thermogravimetric technique which was used to establish the equilibrium between the oxide phases and H2/H2O system gas. The experimental results of (Pu0.3U0.7)O2−x show a consistent variation in PO2 with O/M and temperature and are in agreement with other works. The relationship between the partial oxygen pressure and x in MO2−x was evaluated by the lattice defect theory. The relationship in the hypo-stoichiometric region was x∝PO2-1/2 near the stoichiometric composition, and became x∝PO2-1/3 with a decrease in O/M.