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 (110) and (111) were submitted to ion irradiation in the nuclear energy-loss regime (Sn) using 900 keV I2+ ions, and also with concomitant electronic energy deposition (Se) 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 Sn-irradiated surface layer exhibits tensile strain along its normal with no in-plane strain, that this normal strain is partially relaxed by Se. 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.