Water chemistry and dissolution kinetics of waste-form glasses

A simplified water chemistry program was developed for determining the chemical speciation of a solution. This was combined with a linear, first-order kinetic equation to produce a model of the kinetics of dissolution of a nuclear waste glass which includes effects of groundwater flow. Calculations are presented for four waste glasses, giving the rate of glass dissolution in both pure water and a solution intended to simulate basalt groundwater. The calculations are performed for the case of dissolution in a static volume of groundwater and for the case of steady-state dissolution in flowing groundwater. Inclusion of the effects of water chemistry on the solubility of silicon is found to increase the rate of glass dissolution in the case of pure water but to either increase or decrease it in the case of the simulated groundwater, depending upon the glass composition. Implications of the results for prediction of the long-term behavior of a nuclear waste glass are discussed.