Evaluating the temperature dependence of Magnox waste glass dissolution

Before vitrified waste can be safely disposed of, a comprehensive understanding of the effects of temperature on wasteform aqueous durability must be acquired. In the experiments herein, a Magnox waste glass of 25 wt% simulant waste loading was leached in static batch experiments at 40, 70, 80 and 90 °C to investigate the Arrhenius dependence of dissolution. Results from ICP-OES/MS, EDX, SEM and XRD analyses are discussed in terms of the roles of the glass species within Magnox waste glasses. Here we show that changing the dissolution temperature changed the rate of hydrolysis relative to interdiffusion. At higher temperatures, the initial release of sodium deviated from Arrhenius-type behaviour and instead displayed an almost flat Arrhenius plot; demonstrating changes in temperature affect sodium differently to other glass species. Whilst the activation energies of the lithium and boron releases were in the range of a mixed reaction, the higher activation energy of sodium at lower temperatures combined with its non-Arrhenius behaviour suggested the dissolution processes of lithium and sodium differed. These observations were attributed to the preference of sodium to charge compensate the boron network.