Abstract
A significant lack of experimental data concerning the thermophysical properties of U1-yPuyO2-x for high Pu contents (y > 0.45) is observed. To bridge this gap, dense, monophasic, stoichiometric and homogenous oxides U1-yPuyO2.00 samples (with y = 0.60–0.70) were initially manufactured and characterized. To study the impact of the Oxygen/Metal ratio on thermal properties, hypo-stoichiometric samples were obtained from the previous batches. The strategy was to optimize annealing to reach O/M = 1.98 and perform multi-scale characterizations (optical microscopy, X-ray diffraction, Raman spectroscopy, electron probe microanalysis and X-ray Absorption Near Edge Structure). These revealed monophasic and hypo-stoichiometric samples with a homogeneous chemical distribution of cations and oxygen and a complex redox cations speciation: U(IV)/U(V), Pu(III)/Pu(IV) and Am(III). The results demonstrate the potential of these samples for measuring thermophysical properties, and enable the extension of the Pu content validation range of some empirical laws from y = 0.45–0.69.