High temperature properties of an iron phosphate melt containing high chrome nuclear waste

Iron phosphate glasses are of interest for immobilizing high level nuclear waste (HLW). The high temperature viscosity and AC electrical conductivity of an iron phosphate melt containing 2.8 mass% chrome oxide were investigated in this work. The viscosity of this melt varied from 10 to 50 poise from 1350 to 1150 °C, respectively, while the activation energy for viscous flow was 82 and 126 kJ/mol during heating and cooling the melt, respectively. The viscosity of the melt at 1250 °C increased with time due to the reduction of Fe3+ to Fe2+. The AC electrical conductivity of the melt varied from 45 to 65 S/m at 1050 and 1350 °C, respectively. The activation energy for AC electrical conductivity was 28 and 18 kJ/mol during heating and cooling, respectively. The weight loss rate of the melt at 1250 °C after 20 h was only 5 × 10−4 g/cm2/h.