Immobilization of lanthanide oxides waste from pyrochemical process

Lanthanide radioactive wastes are generated during the LiCl-KCl waste salt purification process developed in KAERI. The phosphate-based ceramics were studied for the immobilization of the wastes. The immobilization matrix developed in this study (ZIT ceramic wasteform) composed of zinc titanate (Zn2TiO4), CaHPO4, SiO2 and B2O3. The lanthanide oxides were reacted with CaHPO4 during solid phase sintering. The reaction products of lanthanides phosphate (LnPO4), which has a similar composition to monazite, has been developed as a high-level nuclear waste host. And the physico-chemical properties (XRD, SEM, density and thermal conductivity) and leach resistance of the borosilicate glass and ZIT waste forms were discussed. (author)