Studies on Ca substituted CePO4 as waste form matrix for the immobilization of simulated high level radioactive waste

The monazite phase, Ce0.9Ca0.1PO4, was prepared and explored as a matrix for the nuclear waste immobilization. Ce0.9Ca0.1PO4 and 20 wt.% simulated waste loaded Ce0.9Ca0.1PO4 were prepared using solution chemistry route and sintered at 1200 °C. Various characterizations such as XRD, Raman, SEM, TGA, UV–Vis and FTIR analysis were carried out. XRD analysis on bare monazite confirms the formation of single phase materials and simulated waste loaded monazite reveals the formation of cubic structured Pd and ZrP2O7 as minor phases present in the system. XPS results on Ce0.9Ca0.1PO4 revealed shift in Ce-3d peak position compared to the reported CePO4 confirming the influence of Ca2+. The UV–Vis result shows the charge compensation existing in the materials which is essential for the accommodation of higher valence cations. FTIR and Raman results of waste loaded Ce0.9Ca0.1PO4 showed peak shift and broadening due to the incorporation of various elements in the crystal lattice. Chemical durability studies on 20 wt.% simulated waste loaded Ce0.9Ca0.1PO4 showed Mo leaching which could be avoided by preparing monazite—IPG glass–ceramic composite. The results suggest that, Ce0.9Ca0.1PO4—IPG glass–ceramic composite can be a versatile matrix for the immobilization of high level radioactive waste.