Fabrication of rare earth calcium phosphate glass waste forms for the immobilization of rare earth phosphates generated from pyrochemical process

The pyrochemical process for the recycling of used nuclear fuels generates LiCl and LiCl-KCl waste salt during a series of processes. In particular, for the reduction of LiCl-KCl waste volume, radioactive rare earth nuclides in the LiCl-KCl waste salt are separated by a phosphorylation precipitation reaction, generating rare earth phosphate waste in a powder form. In this study, for the immobilization of rare earth phosphate wastes, rare earth calcium phosphate (RCP) glass waste forms have been fabricated using a CaO-P2O5 glass system under a moderate vitrification temperature of below 1200 °C. Vitrification properties of NdPO4, which is a representative rare earth phosphate material have been investigated through XRD, SEM, EDX, DSC, IR, and density measurements. The RCP glass waste form fabricated from the 4CaO-6P2O5 system showed an immobilization capacity of about 32 wt.% NdPO4 waste loading. Also, chemical durabilities of RCP glass waste forms are investigated by PCT-A test.