Effect of coupled electronic and nuclear energy deposition on strain and stress levels in UO2

UO2 polycrystals were irradiated in the nuclear energy-loss regime, Sn (900 keV I and 2 Mev Au ions) and also with an additional electronic energy deposition, Se (900 keV I and 36 MeV W ions simultaneously, i.e. Sn&Se). The strain/stress state exhibited by the irradiated pellets was determined by x-ray diffraction measurements. Results show that both measured strain and estimated stress are lower in the dual-beam irradiated samples, indicating that there is an ionization-induced change in the ballistically-generated-defect spectrum. Furthermore, it is shown that the thin irradiated layers maintain the lattice parameter of the pristine material in the basal plane.