An in situ TEM study of the evolution of Xe bubble populations in UO2

Transmission electron microscopy (TEM) experiments were carried out on the JANNUS platform (Joint Accelerators for Nano-science and NUclear Simulation) at CSNSM (Center of Nuclear Spectrometry and Mass Spectrometry) laboratory in Orsay. The experiment was devoted to the study of the evolution of the xenon aggregate population with increasing implantation fluence. A thin UO2 foil was implanted at fluences ranging from 3 × 1012 to 7 × 1014 at cm−2 with 390 keV Xe3+ ions at an irradiation temperature of 873 K. The TEM results indicate the presence of nanometer size bubbles above a fluence of 6 × 1012 Xe cm−2 and an increase in the bubble number density was observed between 6 × 1012 Xe cm−2 and 2 × 1014 Xe cm−2. Above 2 × 1014 Xe cm−2, the number density levels off at 4 × 1023 ± 0.5 × 1023 m−3.