Both 22Na-based positron lifetime spectroscopy and slow positron beam Doppler annihilation broadening spectrometry were used to characterize the bulk and the first micron below the surface, respectively, of sintered disks that had been polished and annealed (1700C, 24h, ArH2). The results revealed the presence of negative ions that were tentatively identified as being negatively-charged O atoms located at interstitial sites. The positron annihilation characteristics of the lattice were SL = 0.371, WL = 0.078 and τL = 169ps. Such disks were irradiated with electrons and α-particles to various fluences at room temperature. The positron measurements revealed the formation of U-related vacancy defects after 2.5MeV electron irradiation, whereas no defects were detected after irradiation at 1MeV.

Positron Annihilation Characteristics in UO2 - for Lattice and Vacancy Defects Induced by Electron Irradiation. M.F.Barthe, H.Labrim, A.Gentils, P.Desgardin, C.Corbel, S.Esnouf, J.P.Piron: Physica Status Solidi C, 2007, 4[10], 3627-32