Impact of Cs Loading on Pollucite Formation in Glass–Ceramics for IONSIV Immobilization

A glass–ceramic composite comprising pollucite, rutile, srilankite, and glass is considered for the immobilization of Cs-loaded IONSIV^®, a secondary waste from the treatment of contaminated water systems. The more chemically durable pollucite is targeted for immobilization of Cs-137, although it may also be incorporated in glass. The current work successfully determined the Cs content required in the bulk composition to ensure pollucite formation by investigating the phase formation, microstructural features, and elemental composition of a series of glass–ceramics with varying Cs contents (1–10 wt%). A consistent phase assemblage of srilankite, doped rutile, and glass was produced with near identical elemental compositions for Cs contents ≤ 5 wt% and with Cs incorporated in glass. Higher Cs loadings (10 wt%) resulted in pollucite where Cs was preferentially partitioned. Wasteform performance criteria may necessitate pollucite inclusion in the glass–ceramic in which case non-radioactive Cs may be added to the bulk formulation.