Coupled effects of electronic and nuclear energy deposition in UO2 crystals: A high-resolution XRD study carried out at the MARS beamline of the SOLEIL synchrotron facility

For the first time at the SOLEIL synchrotron facility’s MARS beamline, UO₂ single-crystal-like samples underwent characterization, and strain depth profiles were established. Single crystals oriented along (1 1 0) and (1 1 1) were submitted to ion irradiation in the nuclear energy-loss regime (S_n) using 900 keV I²⁺ ions, and also with concomitant electronic energy deposition (S_e) using 27 MeV Fe⁹⁺ ions. X-ray diffraction measurements were conducted at the MARS beamline, specialized for radioactive material analysis. High-angular-resolution reciprocal space maps around asymmetrical reflections and conventional symmetrical θ/2θ scans were recorded. Analysis with the RaDMaX software allowed retrieving the strain depth profiles. Results reveal that the S_n-irradiated surface layer exhibits tensile strain along its normal with no in-plane strain, that this normal strain is partially relaxed by S_e. Both crystal orientations display similar behavior, but not with the same magnitude. Comparison with polycrystals indicates a more pronounced strain relaxation in the latter case.