Year
1995
Abstract
Solubility of minor components (Cl, F, P2O5, SO3, and Cr2O3) in low-level waste (LLW) glasses were determined. The dependency of solubility on glass processing temperature was negligible, but significant on the glass composition. In laboratory scale studies, the effects of minor components on volatility, molten salt segregation, crystallization, and glass melt viscosity were studied. Volatility of molten glass with additions of Cl, F, and SO3 was significant when the minor components were in excess of their solubility limits, which was in the order: Cl, > SO3 > F. Higher BA content in glass further enhanced volatilization. Two types of phase segregation were observed among these minor components. For glasses over-saturated with Cl or SO3, phase segregation initiated in the melt and then accumulated on the melt surface, which occurred at the glass processing temperature. For glasses over-saturated with F, P2O5 and Cr2O3, no phase segregation was observed on the melt surface, and crystallization occurred only in the melt. Chlorine and phosphate were found to increase glass melt viscosity, while fluorine had an opposite effect. The melt viscosity data suggested that SO3 and Cr2O3 played a dual role in glass, depending on glass composition. In a glass with low BA (5 wt%) and high CaO (4 wt%), addition of either increased the melt viscosity, but decreased the melt viscosity in a glass with high boron (9 wt%) and no CaO.