Thoria, a quasi-inert matrix for actinides dispositions

Thoria is a promising matrix for the immobilisation of plutonium in either a burning or a conditioning strategy. The aim of this work is twofold: to study the impact of the addition of plutonium, simulated with cerium, on the physico-mechanical properties of thoria and to investigate the possibility of synthesising ceramics employing simple fabrication routes. Th1−xCexO2 powders with ceria concentrations from 0 to 75% were synthesised by the co-precipitation method. The properties of the powders, such as thermal and crystallisation behaviour, were determined as a function of ceria content and calcination temperature. (Th, Ce)O2 pellets containing up to 20% ceria were compacted from non-ground 675 K calcined powder using a double repressing method. The pellets have densities of up to 0.98 TD and a homogeneous surface with well-distributed pores. The main mechanical properties, such as microhardness and fracture toughness, were also investigated as a function of ceria content.