Effect of CeO2 and Nd2O3 on phases, microstructure and aqueous chemical durability of borosilicate glass-ceramics for nuclear waste immobilization

Abstract

The borosilicate glass-ceramics containing zirconolite phase were prepared successfully and the effect of cerium and neodymium on their phases, microstructure and aqueous chemical durability has been investigated in detail. The results show that zirconolite is the main crystalline phase in borosilicate glass-ceramics. With increasing the contents of CeO2 and Nd2O3 to 15 wt%, the transformation from zirconolite-2M to zirconolite-4M occurs, which leads to accommodating larger amounts of rare-earth ions compared with those without the phase transformation. Oxyapatite phase appears in the glass-ceramics while increasing the contents of CeO2 and Nd2O3 to 40 wt%, which insignificantly influences the chemical durability of final glass-ceramics. After 28 leaching days, normalized leaching rates of Ca, Si and Nd are in order of 10−3, 10−3, 10−4 g m−2 d−1 from MCC-1 test respectively, which shows the good chemical durability of glass-ceramics. The obtained conclusions suggest that the glass-ceramic containing zirconolite as main crystalline phase is a potential candidate for immobilizing high-level nuclear wastes, which are rich in lanthanides and actinides.