Structural Thermodynamic Model for the Durability and Viscosity of Nuclear Waste Glasses

Abstract

AbstractA model based upon structural thermodynamic considerations has been proposed for both chemical durability and viscosity of nuclear waste glasses. This model assumes the bond strength between atoms in the glass to be the predominant factor in controlling the composition dependence of physical properties such as viscosity and chemical properties like durability. These characteristic bond strengths in the glass are obtained from known heats of formation of the constituent oxides with a few simple structural rules deduced by distinguishing the structural roles of the various oxides, i.e., separating those components that are clearly “network-formers” (e.g. SiO2, Al2O3, ZrO2) from those that are clearly “network-breakers” (e.g. alkali oxides). This model has been successfully applied to the correlation of glass composition with modified MCC-3 leach test results on nuclear waste glasses measured at various laboratories on one hand and with the viscosities of numerous glasses over a temperature range of 850°C to 1600°C with remarkable accuracy on the other hand.