Assessment of positrons for defect studies in CeO2 materials

Abstract

Disposal of spent nuclear fuel poses significant challenges, as the UO2 and fission products are under constant irradiation and must be safely stored for millennia. CeO2 is a non-radioactive analog for UO2 for studying microstructure and its evolution. Many techniques have been applied to uranium and cerium oxides to investigate point defects. Positron annihilation spectroscopies (PAS) are sensitive to neutral and negatively charged vacancy-like point defects and impurity vacancy complexes. PAS has been applied previously to UO2+x to investigate nuclear fuels, but virtually no PAS work exists on CeO2. Here, the basics of positron annihilation spectroscopy is reviewed, and preliminary work on undoped and doped CeO2 is shown and compared to the literature results from UO2. To simulate fission product incorporation in spent nuclear fuels, CeO2 samples were doped at different concentration with yttrium. Select samples were irradiated with heavy ions at different doses. Doping and irradiation are shown to give rise to different defect characteristics.