This project is intended to develop a deeper understanding of how glass chemistry can be used to maximise waste incorporation while minimising volatilisation. Specific aims are to understand the waste incorporation reactions and radionuclide incorporation mechanisms for a variety of representative wastes. These aims will be addressed by undertaking 1) investigations of quenched melts produced at various time intervals; 2) investigations of the final equilibrium glass composition and 3) real time measurements of the off-gas from the melts.
While borosilicate glasses are most commonly used for nuclear waste immobilisation such glasses have limited compatibility with, for example, wastestreams with significant halide, molybdate or actinide contents. Thus the project will look at the different behaviours of conventional borosilicate, aluminosilicate (calcium aluminosilicates have a greater capacity for chloride containing wastes) and titanosilicate (potentially attractive for high soda and molybdate wastes) melts. Incorporation of specific species into a glass is determined both by the final glass structure and the role of specific species within that structure (both of which are related to the melt structure) as well as kinetically favoured species that are formed during the melt process, which if volatile, lead to notable losses from the melt. Thus the intention of this project is to study 1) the final glass using a range of structural analysis techniques including Raman and FTIR spectroscopies (existing facilities) and NMR and XAS (national facilities), chemical analysis techniques including XRF and EDS (existing facilities); 2) the evolved gas species by melting in a controlled environment with a dedicated off-gas line. At the moment these facilities rely on analysis of the species that either plate-out or end up in washing solutions, which may not be identical the actual forms that are evolved from the glass melts. In-situ Raman analysis, requiring a portable Raman system with a specialist cell is required for this element of the project and has been included in the project costs.
Academic Lead: Russell Hand
Researcher: Lucas-Jay Woodbridge
Location: University of Sheffield