Confining caesium in expanded natural Perlite

We present the potential use of expanded perlite, a metastable amorphous hydrated aluminum silicate, as a permanent medium for the long-term confinement of caesium. A simple loading by mixing an aqueous caesium nitrate solution and expanded perlite at 300 K followed by thermal annealing leads to 96% sintering. The formation of pollucite, CsAlSi2O6, a naturally occurring mineral phase, appears as the crystalline phase embedded in a glassy phase. Leaching tests on the resulting glass-ceramics reveal a very low Cs departure of 0.5 mg m−2 day−1. This simple method seems to be a good way to permanently confine caesium issued from recycled nuclear waste.