Local and Electronic Structure of Americium-Bearing PuO2

X-ray Diffraction and X-ray Absorption Spectroscopy have shown that a material composed of two (Pu,Am)O2-x substoichiometric fluorite-type structures is obtained by sintering in moisturized Ar-H2. The Pu oxidation state is, surprisingly, strictly (+IV) while Am exhibits a (+III/+IV) mixed valence. Thus, the Am-O system and particularly the Am oxidation state play a major role in the sintering behavior of the Pu-Am-O system. The heating of this compound in air leads to the formation of a fluorite Pu0.80Am0.20O1.98 solid solution. The transition from one phase to two phase structure takes place in a temperature inferior to 800°C. The results were compared with previous studies on Am bearing UO2 and ThO2 which have evidenced different behaviors.JRC.E.4-Nuclear fuel