CALPHAD optimization of SiO2-B2O3-Al2O3-ZnO-CaO-Na2O-Li2O-MoO3 system and their applications to high-level radioactive waste vitrification

• Phase equilibrium experiments were carried out in the SiO 2 -B 2 O 3 -Al 2 O 3 -ZnO-CaO-Na 2 O-Li 2 O-MoO 3 system at 1200 °C and 1000 °C. • Phase relationship between coexisting silicate melt and molybdate melt was optimized by CALPHAD methodology. • Example application of thermodynamic database was indicated for Japanese high-level waste glass. Element partitioning behavior between immiscible silicate melt and molybdate melt was determined by phase equilibrium experiments in the SiO 2 -B 2 O 3 -Al 2 O 3 -ZnO-CaO-Na 2 O-Li 2 O-MoO 3 system at 1200 °C and 1000 °C. By combining these results and thermodynamic data of silicate melts and molybdenum compounds, CALPHAD analysis was performed to construct a database for thermodynamic calculation of phase equilibria for MoO 3 -bearing alumino-borosilicate melts. The thermodynamic database will be useful for predicting the phase separation of molybdate melt and crystallization of Powellite (CaMoO 4 ) in vitrification process of high-level radioactive waste.