Effect of Am addition on oxygen potential in (U0.55Pu0.3Am0.15)O2−x

• The oxygen potential of (U 0.55 Pu 0.3 Am 0.15 )O 2-x has been studied. • The measured oxygen potentials were analyzed by the defect chemistry method. • The oxygen potential of (U 0.55 Pu 0.3 Am 0.15 )O 2-x was represented as a function of O/M ratio and temperature. • The cation valence is estimated to be (U 4+ 0.4 U 5+ 0.15 Pu 4+ 0.3 Am 3+ 0.15 )O 2.00 in the stoichiometric composition. Oxygen potential measurement was conducted at 1273 K, 1473 K, 1573 K, and 1623 K for (U 0.55 Pu 0.3 Am 0.15 )O 2−x using a thermogravimeter and oxygen sensors. Adding 15% Am instead of U increased the oxygen potential of (U 0.7 Pu 0.3 )O 2−x by 100 – 150 kJ/mol. The measured oxygen potentials were analyzed by the defect chemistry method. This analysis showed that the oxygen potential of (U 0.55 Pu 0.3 Am 0.15 )O 2−x was formulated as a function of O/M ratio and temperature, and that the calculated results were consistent with the measured data. The cation valence is estimated to be (U 4+ 0.4 U 5+ 0.15 Pu 4+ 0.3 Am 3+ 0.15 )O 2.00 in the stoichiometric composition.