Morphologies of CaMoO4 crystals in simulated nuclear waste disposal glass

Diffusion of fission products through nuclear waste disposal glass may eventually lead to crystallisation, causing stresses to develop which can lead to fracture and exposure of an increased surface area to environmental attack. Several kinds of crystals, including CaMoO4, have been identified in the glass after heat treatment. The morphologies of CaMoO4 crystals in simulated nuclear waste disposal glass consisting of Na2O, B2O3, SiO2 and other oxides heat-treated between 850 and 1120 K are presented. Two kinds of morphology were identified. One kind of morphology is rather special. It is elongated in one direction, and the cross-section normal to the longer direction is a cross with two perpendicular arms of the same length. Crystals having this special morphology only appear in glass heat-treated between 870 and 1050 K. 4 refs.