文摘
Uranium鈥揳mericium mixed oxides could be used as transmutation targets to lower Am inventory in spent nuclear fuels. Due to 241Am activity, these materials are subjected to 伪-self-irradiation which provokes crystallographic disorder. Previous studies on U鈥揂m mixed oxides gave first insight into 伪-radiation tolerance of these compounds, but have never been carried out for more than a year, whereas these compounds might be stored up to a few years between fabrication and irradiation. In this work, we study effects of self-irradiation on the structure of U1鈥?i>xAmxO2卤未 solid solutions (x = 0.15 and 0.20) aged 3 to 4 years. Especially, X-ray diffraction and X-ray absorption spectroscopy are combined to observe these effects from both long-range and local perspectives. Results show that the fluorite-type structure of U鈥揂m mixed oxides withstands 241Am 伪-irradiation without major damage. Despite the increase of interatomic distances and crystallographic disorder observed during the first months of storage, the present results show that a steady state is then reached. Thus, no detrimental factors have been identified in this study in terms of structural damage for several-year storage of U1鈥?i>xAmxO2卤未 pellets before irradiation. Furthermore, comparison between long-range and local evolution suggests that 伪-self-irradiation-induced defects are mainly located in low-ordered domains. Based on literature data and present results, the steady state appears related to the equilibrium between radioinduced defect formation and material self-healing.