Crystallization behavior, quantitation of Ce3+/Ce4+ and chemical stability analysis of multiple alkaline earths borosilicate glasses for immobilizing simulated tetravalent actinides

A series borosilicate glasses containing three alkaline earth metals (Ca, Mg, Ba) and immobilized with ceria from low content (3 wt%) to exceed the solubility limit (20 wt%) were prepared by the solid-state melt method. The results of phase separation revealed by SEM, XRD and EDX show that simulated waste CeO2 loading was below 13 wt%, and the excess part was tightly connected with glass. The controlled heat treatment of the quenched blocks and the green pellets was conducted to explore the effect of ceria content of the system on the crystalline state. The solidified waste forms with a ratio of Ce3+/Ce4+ close to 1 have the lower leaching rate after 28 d (LRSi=9.84 × 10−4 g m−2 d−1, LRCa=6.68 × 10−4 g m−2 d−1) and LRCe of all samples is always maintained in the order of magnitude of 10−5 g m−2 d−1, suggesting that cerium doped multiple alkaline earths borosilicate glasses have higher chemical stability.