The occupation mechanism and service stability of Ca2.5Ce0.5Zr2Fe3O12 type garnet ceramics for the immobilization of tetravalent actinides

Garnet is a promising candidate for the long-term immobilization of radionuclides. However, the irradiation stability and occupation mechanism of Ce-doped garnet remains to be further explored. Herein, a single-phase garnet Ca2.5Ce0.5Zr2Fe3O12 was prepared by microwave sintering at 1300 °C for the immobilization of actinide (Ce substitutes), and its phase transition, occupation mechanism, chemical stability and irradiation stability were systematically investigated by the first principle thinking and synchrotron radiation. The results suggested that Ce occupied Ca-site in garnet. The thermal expansion test showed that the thermal expansion stability of Ca2.5Ce0.5Zr2Fe3O12 (7.30 × 10−5 °C−1) was considerably lower than Ca3Zr2Fe3O12. For accelerated irradiation experiments, irradiated by 2 MeV α-particles could lead to an amorphous effect of crystal structure after dose. Furthermore, the leach rate of Ce in Ca2.5Ce0.5Zr2Fe3O12 was approximately 10−5 g m−2 d−1 after irradiation remained. This work provides data support and theoretical basis for the immobilization of actinides in garnet.