Behaviour of (U,Am)O$_2$ in oxidizing conditions: a high-temperature XRD study

Abstract

International audienceUranium–americium oxides U$_{1−y}$Am$_y$O$_{2±x}$ are currently investigated as possible transmutation targets for next generation nuclear reactors. In the context of a comprehensive investigation of the thermodynamic and thermal properties of these materials, their behaviour in oxidizing conditions is here investigated for the first time. The results of high-temperature X-ray diffraction measurements in air are here presented. A wide composition domain of the solid solution has been investigated, measuring U$_{1−y}$Am$_y$O$_{2±x}$ oxides with Am/(Am + U) ratios ranging from 0.10 to 0.67. This allowed determining the effect of the americium content on the oxidation kinetics in air. Specifically, it will be shown that americium hinders the formation of the M$_4$O$_9$ and M$_3$O$_8$ phases