Aqueous corrosion of natural and nuclear waste glasses I. Comparative rates of hydration in liquid and vapor environments at elevated temperatures

This paper presents the results of aqueous corrosion experiments performed on natural and nuclear waste glasses in liquid and vapor environments. It is shown for all glass compositions considered that the rate of hydration in hydrothermal experiments is higher than the rate of vapor hydration at the same temperature. It is also demonstrated, in the case of the nuclear waste glass SRL 131, that the rate of hydration is a strong function of pH₂O and that a critical pH₂O exists below which hydration rates are negligible. Both phenomena may be explained by the higher surface pH and mobile cation concentrations that develop during glass/vapor interaction relative to glass liquid interaction. High surface pH inhibits ion exchange but enhances network hydrolysis.