On the effect of Al on alumino-borosilicate glass chemical durability

Abstract The chemical durability of borosilicate glass used to confine nuclear wastes non-linearly depends on a slight variation of their composition. Here, we focus on Al, a major oxide of these materials. Both matrix dissolution and long term-rates are investigated through experiments conducted at 90°C and pH 9. We demonstrate that low Al content glasses dissolve initially faster than glasses with higher Al content, but they form a gel that reorganized faster and eventually becomes more passivating. These results can be tied to recent findings at the molecular level showing that Al impacts the activation energy of Si‒O bond breaking. The implications for the geological disposal of high-level waste glass of these findings are discussed.