Changes in voids induced by ion irradiations in UO2: In situ TEM studies

Abstract

Transmission electron microscopy experiments coupled with 4 MeV Au and 390 keV Xe implantations were conducted on polycrystalline UO2 thin foils in order to study the void change with damage, temperature (ranging from −180 to 1100 °C) and exogenous xenon atoms incorporation. Void size is weakly dependent on the ion dose in the range of [0.01–10] × 1014 i/cm2, whereas void density increases strongly at the early beginning of irradiation and then saturates after 3–4 × 1013 i/cm2. Change in void size and density are shown as weak functions of temperature and xenon atoms incorporation in these experimental conditions. These results indicate a heterogeneous void nucleation and a change monitored by ballistic effects. Studying voids is very tricky. This work also highlights the strong dependence of the measured void size on the TEM settings and capabilities. Thus, it is important to discuss only data obtained in the same conditions to derive influence parameters.