The evolution of vacancy defects as a function of temperature was studied by positron annihilation spectroscopy in 1MeV He-implanted sintered disks. A slow positron beam, coupled with a Doppler broadening spectrometer, was used to measure the low and high momentum annihilation fractions, S and W respectively, as a function of positron energy in disks 3He-implanted to a fluence of 1016/cm2; before and after annealing. The S and W behaviors changed during annealing at 160 to 1300C, thus indicating that the vacancy-defect distribution evolved. The positron trapping rate at vacancy defects decreased with increasing annealing temperature, with stages at around 250C and 800C.

Thermal Evolution of the Vacancy Defects Distribution in 1MeV Helium Implanted Sintered UO2. H.Labrim, M.F.Barthe, P.Desgardin, T.Sauvage, C.Corbel, G.Blondiaux, J.P.Piron: Nuclear Instruments and Methods in Physics Research Section B, 2007, 261[1-2], 883-7