Combustion synthesis and characterizations of Sm2O3 doped zirconolite-rich waste forms with CuO as oxidant

Abstract

Zirconolite is one of the most important matrix materials for nuclear waste immobilization. In this study, Sm was employed as the surrogate of trivalent actinides. Sm-doped zirconolite-rich waste forms were readily prepared by combustion synthesis (CS) using CuO as the oxidant. Two different schemes with or without Al2O3 as the charge compensator were carried out simultaneously. The results demonstrate that Al2O3 addition results in complex phase composition. On the other hand, the samples without Al2O3 addition show desirable products of zirconolite and pyrochlore. The EDX analysis shows that Sm is concurrently incorporated into the Ca and Zr sites of zirconolite, which transforms to pyrochlore structure with high Sm2O3 contents. The aqueous durability of representative Sm-doped sample (Sm-0.6) was investigated. The 42 days normalized leaching rate of Sm is as low as 6.41 × 10−7 g/(m2·d), which exhibits high durability of Sm-doped sample.