Assessment of positrons for defect studies in CeO 2 materials

Disposal of spent nuclear fuel poses significant challenges, as the UO 2 and fission products are under constant irradiation and must be safely stored for millennia. CeO 2 is a non-radioactive analog for UO 2 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 UO 2+ x to investigate nuclear fuels, but virtually no PAS work exists on CeO 2 . Here, the basics of positron annihilation spectroscopy is reviewed, and preliminary work on undoped and doped CeO 2 is shown and compared to the literature results from UO 2 . To simulate fission product incorporation in spent nuclear fuels, CeO 2 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.