Defect evolution under intense electronic energy deposition in uranium dioxide

Abstract

The coupled effects of nuclear and electronic energy losses were investigated in uranium dioxide (UO2). Single and sequential ion irradiations were carried out with 92 MeV Xe ions and 0.9 MeV I ions. Raman spectroscopy and X-ray diffraction analyses were combined with the inelastic thermal spike (iTS) model to investigate the effect of electronic ionizations on the ballistic damage. It appears that the high-energy ions induce a significant change in the defect distribution with an amplitude that depends on the level of pre-existing disorder. This modification essentially results in an acceleration of the transformation from the dislocation loops to the dislocation lines, a process that is accompanied by a stress relaxation. Surprisingly, with the fluence increase of 92 MeV Xe ions, the stress starts to increase again, highlighting a possible synergetic effect between the pre-existing defects and those generated by the 92 MeV Xe ions irradiation.