Characterization of monazite glass–ceramics as wasteform for simulated α-HLLW

Two monazite glass–ceramic wasteforms were sintered by mixing the lanthanum metaphosphate glass powder with the oxide powder of the components in simulated α-HLWs. The co-existence of components Al and Mo in an iron phosphate melt separated the melt into two immiscible glass melts, namely aluminum iron phosphate glass (Gb) and molybdenum iron phosphate glass (Gg). 24 wt% of ZrO2, together with P2O5 and proper amounts of Fe and Mo formed a zirconium pyrophosphate glass (Gg1), which was immiscible with the phase Gg. The iron ions in the wasteforms were all in Fe3+, 1/3 of which was in 4-fold coordination. The O/P and O/(P + 1/3Fe3+) ratios for the glass phases were Gg1 3.70, Gb 3.89–3.98, Gg 4.23–4.25, and Gg1 3.58, Gb 3.47–3.42, Gg 3.74–3.69, respectively. The dissolution rates of two wasteforms were 0.3008 and 0.2598 g/m2d, respectively.