Structural investigation of self-irradiation damaged AmO2

•The structure of highly self-irradiated AmO2 (36 dpa) was studied by XAS and TEM.•XRD, EXAFS and TEM confirm the high stability of the fluorite structure.•XRD and EXAFS show an increase of 0.3% of the structural distances.•XANES shows that Am is tetravalent as well as the Np recoil nucleus.•The presence of He bubbles was evidenced by TEM.

Studying self-irradiated materials is an ideal means to investigate the effect of the damage on material structure and to better understand the behavior of irradiated nuclear fuels. In this context, X-ray diffraction, X-ray absorption spectroscopy and transmission electron microscopy have been used to investigate self-irradiation damaged AmO2. Combining these techniques allows studying the microstructure and the variation of the fluorite structure at both short-range and long-range order. Thus, the increase of both interatomic distances and lattice parameter was shown, as well as the presence of nanometer sized He bubbles and dislocation loops. As confirmed by the observed high-level of crystallinity, the fluorite structure exhibits a high radiation tolerance, which is confirmed by the low increase of the lattice parameter. This could be explained by a self-annealing mechanism of the created defects at room temperature.

Graphical abstractThe structure of damaged AmO2 (36 dpa) has been studied by XRD, XAS and TEM. Thus, the effects of the self-irradiation on the oxidation state, the lattice distances, the structural disorder, the radiation stability and the microstructure have been discussed. Figure optionsDownload full-size imageDownload as PowerPoint slide