Design of novel zirconolite glass-ceramics for actinide immobilisation

Zirconolite is a candidate material (wasteform) for the immobilisation of actinide (U/Pu/Th) wastes and a component of ANSTO’s Synroc (Synthetic Rock) technology, which is under development at ANSTO. Zirconolite is a geochemically stable titanate mineral with demonstrated ability to immobilise uranium in the geological environment for billions of years. This collaborative project between ANSTO and UNSW investigated the addition of glass to the wasteform design to form glass-ceramics with the aim of improving flexibility to accommodate heterogeneous wastes and to simplify the processing requirements. A range of glass-ceramics with varying glass contents and compositions were prepared and the phase assemblage, phase composition, speciation and partitioning determined.

The analytical results showed that the effectually designed glass-ceramics added flexibility to the wasteform design. Further, the addition of glass was demonstrated to significantly enhance the potential to simplify processing requirements by lowering the temperature required to fabricate phase-pure zirconolite glass-ceramics and minimise undesirable phase formation. These advancements have significant potential in nuclear waste treatment and will continue to be investigated for the implementation of actinide waste immobilisation.