Short-term corrosion of HLW glass in aqueous solutions enriched with various metal cations

Static short-term corrosion tests were performed with the simulated HLW glass GP WAK1 at 80 deg. C and constant pH in deionized water, in water enriched with a single element (Si, Al, Nd and Mg) and enriched with two elements (Si + Al, Si + Nd, Si + Mg). The objective of the experiments was to study the effect of Si and other dissolved species on the initial high and on the low final rate under Si-saturated conditions. In pure water and Si-enriched water the release rates of B (Li) are nearly identical despite the different Si concentration in the solution. Close to saturation, the dissolution rates decrease sharply due to condensation reactions of the silanol groups forming a highly protective surface layer. In solutions enriched with Al or Nd, the initial B release rate is similar to pure water, but the release of Si is much lower. Therefore, Si saturation and the low final rate are attained after longer times. In the solutions enriched with Si and an additional element, the initial high B release rate drops down already after few hours to the low final rate as saturation conditions are attained much earlier. In all solutions studied, the dissolution rate slows down after Si saturation to the same low constant rate depending on the solution pH. The impact of the results on the corrosion mechanism and long-term behaviour of HLW glasses is discussed