Cerium(III, IV) in cement: Implications for actinide (III, IV) immobilisation

Cementitious materials show potential for the immobilisation of radionuclides, including actinides. The mechanism by which such elements interact with the immobilisation matrix is of fundamental importance to an assessment of future performance. Ce(III, IV) were used as actinide (III, IV) simulants to study the reactions of aqueous solutions of cerium with cement components and characterise the likely solubility-limiting phases in cement–actinide systems. Two newly identified phases are reported, namely CeSiO4 and Ca2Ce8(SiO4)6O2. The many examples of naturally occurring minerals with these structure types suggest the potential for long-term immobilisation of actinide (III, IV) elements in cement.