1. Formulation of ceramics for waste conditioning

In the 1970s, researchers at the University of Pennsylvania (USA) developed ceramic matrices for conditioning fission product solutions, based on crystalline silicate, phosphate and molybdate phases whose main feature was that they had natural analogues reputed to be durable. These ceramics, synthesized in air at 1,100°C, had high waste incorporation rates (of the order of 70% by mass).

The main constituent crystalline phases of this assemblage were pollucite (CsAlSiO ₄ ), powellite (CaMoO ₄ ), apatites and monazites containing rare earth ions