MoO3 Solubility and Chemical Durability of V2O5-Bearing Borosilicate Glass

Abstract

In the vitrification of high-level radioactive liquid waste (HLW), the separation of sodium-molybdate melts is a problem because it reduces the chemical durability of the vitrified waste. A glass with both high MoO3 solubility and chemical durability is required for the safe disposal of radioactive waste. In this study, we investigate the effects of vanadium oxide on the phase separation of the molybdenum-rich phase and the water resistance of the resulting glass by phase equilibrium experiments and chemical durability test. Phase equilibrium experiments were performed on SiO2-B2O3-Al2O3-ZnO-CaO-Na2O-LiO2-MoO3 system glasses and on glasses with V2O5 added. The results showed that MoO3 solubility increased when V2O5 was added. The increase in MoO3 solubility in borosilicate melts may be associated with the viscosity-lowering effect of V2O5. Chemical durability tests were performed on borosilicate glass compositions obtained from phase equilibrium experiments. The normalized leaching rates of V2O5-bearing glasses were higher than those of other glasses. This is due to the higher network modifier/network former ratio of the glass tested. The normalized elemental mass loss of glass containing waste components increases with increasing leaching duration. This suggests that the waste component prevents the formation of a gel layer at the reaction front.