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 He-3 at a nominal fluence of 5 x 10(16) He-3 cm(-2) using a Van de Graaff accelerator. The He-3(d,alpha)H-1 nuclear reaction analysis method was used to determine the helium depth profile in the UO2 disks. Partial flaking was observed after annealing at 500 degreesC for local He concentration of 1 at.%. After annealing at 600 degreesC flaking has affected the whole surface. The formation of helium bubbles is discussed. (C) 2003 Elsevier B.V. All rights reserved.