Self-propagating synthesis and CeO2 immobilization of zirconolite-rich composites using CuO as the oxidant

Synroc is recognized as the second generation waste matrice for HLW immobilization. In this research, one of the most important Synroc component, zirconolite, was rapidly synthesized using self-propagating plus quick pressing technique. As the surrogate of tetravalent actinides, CeO2 was introduced to replace the Zr site of zirconolite with nominal formulation of CaZr1−xCexTi2O7. The fraction of minor perovskite phase increases gradually as the CeO2 addition is elevated. The raw Ce4+ was mostly reduced to Ce3+ after SHS reaction, which leads it preferentially occupies the Ca site of perovskite rather than the Zr site of zirconolite. The Ce-bearing waste form (CC-3) exhibits excellent aqueous durability with 42 d normalized leaching rates of Ca, Cu, Zr and Ce in low values of 0.73, 4.97×10−5, 4.15×10−5 and 2.26×10−6 g m−2 d−1.