Oxygen potential of (Pu0.91Am0.09)O2−x

Oxygen potentials of (Pu0.91Am0.09)O2−x were measured by thermogravimetric analysis with H2O/H2 gas equilibrium and dilute O2 gas at 1123 K, 1273 K and 1423 K. The oxygen potentials were extremely high from stoichiometry to O/M = 1.99 and were somewhat lower than those of AmO2−x near stoichiometry. On the other hand, those below O/M = 1.96 were much lower than those of AmO2−x. Valence state changes of Am and Pu in the oxide were assumed, and experimentally determined data were examined using the slope of the plot of oxygen partial pressure versus deviation from stoichiometry, the oxygen potential as a function of mean valence state of metal, activity coefficient of AmO2−x and the partial molar enthalpy and entropy of oxygen. It was concluded through these examinations that aspects of the oxygen potential of (Pu0.91Am0.09)O2−x could be interpreted by the present assumption and that several interactions between Am and Pu could exist.