Candidate glass–ceramic wasteforms for the immobilisation of Cs-loaded IONSIV^® wastes: A scoping study

In some cases, nuclear wastes can be treated with ion exchange materials to remove specific radionuclides from solution via cationic exchange. A promising inorganic ion exchange material, crystalline silicotitanate (CST) or IONSIV^®, has been previously employed to remove Cs-137 from contaminated aqueous systems with high specificity. Once the radioactive Cs-137 has been incorporated within the IONSIV^® structure, the ion exchange material itself becomes radioactive waste and requires immobilisation within a nuclear wasteform. The current scoping study investigated design and development of advanced glass–ceramic wasteforms for the immobilisation of Cs-loaded IONSIV^®. Two well-established Cs-bearing ceramic phases, hollandite, and pollucite, were considered as the ceramic component of the novel glass–ceramic design. Hollandite appeared to react with the borosilicate glass-component to form celsian and rutile. The pollucite system produced a phase assemblage of pollucite, rutile, srilankite, and glass, as targeted, and is therefore considered a promising wasteform design for Cs-loaded IONSIV^® material.