Characterisation and behaviour under irradiation of rare-earth doped powellite phases - Application to the long term behaviour of nuclear waste matrices

This work deals with the behaviour under irradiation of a glass-ceramic made after heat treatment of a molybdenum rich R7/T7 type glass. Rare earth elements (Eu3+ and Nd3+) are used as surrogates of minor actinides and fission products as well as structural luminescent probes. We will focus on the behaviour of the crystalline phase which is a powellite type calcium molybdate that incorporated other elements including rare earth elements. In order to determine the crystalline-chemical properties of the powellite structure, Raman spectroscopy and photoluminescence analyses are led on natural powellite samples and synthetic ceramics with compositions from pure CaMoO4 to Ca0.76Sr0.1Na0.07Eu0.01La0.02Nd0.02Pr0.02MoO4, a model composition of the crystalline phase of the glass-ceramic. The analyses of synthetic samples irradiated with He, Ar and Pb ions compared to the behaviour of a natural powellite sample that contains uranium indicate that powellite resist strongly to irradiation and never reach the amorphous state. (author)