Multi-scale X-ray diffraction study of strains induced by He implantation in UO2 polycrystals

Mechanical behaviour of 60 keV He implanted UO2 polycrystals has been analysed at a macroscopic scale using X-ray diffraction techniques (conventional θ/θ mode and sin2ψ method). The free swelling in the implanted layer has been determined at low damage levels (below 1 dpa) i.e. in a strain regime where the UO2 crystal structure deforms elastically. The obtained results are in excellent agreement with previous measurements performed at the micrometre (grain) scale using Laue X-ray diffraction. Finally it is shown that evolutions of free swelling with damage level in implanted polycrystals and in self-irradiated (U, 238Pu)O2 pellets are similar.