In this study, we investigated the microstructure of such doped fuels as well as a reference standard UO2 by positron annihilation spectroscopy (PAS). Although this technique is particularly sensitive to lattice point defects in materials, a wider application in the UO2 research is still missing. | Positron annihilation spectroscopy study of lattice defects in non-irradiated doped and un-doped fuels EPJ Nuclear Sci. Technol. 3 3 2017 Nuclear Sciences M. Chollet et al. published by EDP Sciences 2017 amp Technologies DOI epjn 2016040 Available online at http REGULAR ARTICLE Positron annihilation spectroscopy study of lattice defects in non-irradiated doped and un-doped fuels Mélanie Chollet Vladimir Krsjak Cédric Cozzo and Johannes Bertsch Nuclear Energy and Safety Department Paul Scherrer Institut 5232 Villigen PSI Switzerland Received 23 September 2015 Received in final form 17 June 2016 Accepted 5 December 2016 Abstract. Fission gas behavior within the fuel structure plays a major role for the safety of nuclear fuels during operation in the nuclear power plant. Fission gas distribution and retention is determined by both micro- and lattice-structure of the fuel matrix. The ADOPT Advanced Doped Pellet Technology fuel containing chromium and aluminum additives shows larger grain sizes than standard undoped UO2 fuel enhancing the fission gas retention properties of the matrix. However the additions of such trivalent cations shall also induce defects in the lattice. In this study we investigated the microstructure of such doped fuels as well as a reference standard UO2 by positron annihilation spectroscopy PAS . Although this technique is particularly sensitive to lattice point defects in materials a wider application in the UO2 research is still missing. The PAS-lifetime components were measured in the hotlab facility of PSI using a 22Na source sandwiched between two 500-mm- thin sample discs. The values of lifetime at the center and the rim of both samples examined to check at the radial homogeneity of the pellets are not significantly different. The mean lifetimes were found to be longer in the ADOPT material 220 ps than in standard UO2 190 ps which indicates a larger presence of additional defects presumably generated by the dopants. .
