Microstructure effects on He diffusion in sintered UO2 by μNRA

A two-dimensional analysis of helium in UO2 sintered disks has been achieved on a micrometric scale by using the NRA technique and upgrading the detection arrangement. The transmission mode detection procedures, localization of the region scanned and normalization of the helium lateral distributions are now well established. For sintered UO2 pellets implanted at a dose of 2 × 10163He/cm2, the results show that the lateral helium distribution is correlated to the sample microstructure after annealing for 1 h at 1300 °C. The enhanced desorption of helium in the vicinity of grain boundaries points to them playing an essential part in helium diffusion in UO2.