Helium behavior in UO2 polycrystalline disks

The behavior of helium implanted in sintered uranium dioxide disks has been investigated as a function of annealing temperature. UO2 disks have been implanted with 1 MeV 3He at a nominal fluence of 5 × 1016 3He cm−2 using a Van de Graaff accelerator. The 3He(d,α)1H nuclear reaction analysis method was used to determine the helium depth profile in the UO2 disks. Partial flaking was observed after annealing at 500 °C for local He concentration of 1 at.%. After annealing at 600 °C flaking has affected the whole surface. The formation of helium bubbles is discussed.