Positron annihilation spectroscopy study of lattice defects in non-irradiated doped and un-doped fuels Mélanie Chollet, Vladimir Krsjak, Cédric Cozzo and Johannes Bertsch EPJ Nuclear Sci. Technol., 3 (2017) 3 Published online: 30 January 2017 DOI: 10.1051/epjn/2016040