RADIATION DEFECTS IN THE OXYGEN SUBLATTICE OF UO2 SINGLE-CRYSTALS

Measuring radiation damage processes occurring in the oxygen sublattice in such a heavy matrix like UO2 is difficult. The ion backscattering/channeling technique of high energy He-4 ions has been successfully applied for this purpose. Use was made of the broad resonance of O-16(alpha, alpha)O-16 scattering occurring at 7.6 MeV. It was possible to detect oxygen in UO2 at practically the same counting Tate as uranium. UO2 single crystals were implanted with 200 keV Kr and 300 keV Xe ions with doses ranging from 3 X 10(14) to 8 x 10(15) at./cm2 and subsequently annealed in the temperature range of 200-400-degrees-C. The damage in the O sublattice increased sharply with dose up to approximately 2 x 10(15) ions/cm2 and reached saturation for higher doses. For the lower implantation doses, channeling analysis revealed an important increase of the damage peak for the O sublattice due to annealing at 300-degrees-C. The damage peak decreased during subsequent annealing at higher temperatures. This effect was dose dependent and disappeared for implantation doses exceeding 2 x 10(15) at./cm2.