Alpha self-irradiation effect on the local structure of the U0.85Am0.15O2±x solid solution

Uranium–americium mixed oxides are promising fuels for achieving an efficient Am recycling. Previous studies on U0.85Am0.15O2±x materials showed that the high α activity of 241Am induces pellet swelling which is a major issue for cladding materials design. In this context, X-ray Diffraction and X-ray Absorption Spectroscopy measurements were used to study self-irradiation effects on U0.85Am0.15O2±x local structure and to correlate these results with those obtained at the macroscopic scale. For a cumulative α decay dose equal to 0.28 dpa, it was shown that non-defective fluorite solid solutions were achieved and therefore, that the fluorite structure is stable for the studied doses. In addition, both interatomic distance and lattice parameter expansions were observed, which only partially explains the macroscopic swelling. As expected, an increase of the structural disorder with self-irradiation was also observed.

X-ray Diffraction and X-ray Absorption Spectroscopy measurements were performed on U0.85Am0.15O2±x, exhibiting various cumulative α decay doses, in order to study self-irradiation effects on local structure and to correlate these results with those obtained at the macroscopic scale. Thus, it was shown that the fluorite structure is stable for the studied doses. In addition, both interatomic distance and lattice parameter expansions were observed, explaining partially the macroscopic swelling.Figure optionsDownload as PowerPoint slideHighlights
► Non-defective fluorite U0.85Am0.15O2±x solid solutions were achieved.
► The fluorite structure is stable for the studied doses.
► A lattice parameter increase was observed, which partially explains the macroscopic swelling.
► The increase of the structural disorder can be understood from the ballistic effect associated to the Am high alpha activity.