Alteration of basalt glasses: implications for modelling the long-term stability of nuclear waste glasses

Abstract

The long-term stability of nuclear waste form borosilicate glasses must be predicted from extrapolations of short-term laboratory data and then verified, which is only possible by comparing the glasses with their natural analogues of geological age. Here, we suggest that basalt glasses are useful analogues for predicting the long-term behaviour of nuclear waste form borosilicate glasses. Previous workers1–11 have considered the possibility of using natural glasses as analogues, but our study is a direct comparison of the experimentally studied corrosion products of basalt glasses, their natural long-term corrosion products and those of borosilicate glasses. Observations on the alteration processes for natural basalt glasses are combined with the experimental data on the alteration of basalt glasses and borosilicate glasses and are used to generate radioactivity release curves for nuclear waste form borosilicate glasses using the QTERM computer code12–15. Our data on natural glasses place significant constraints on the anticipated fraction of activity released; major differences between our two release curves do not occur until after 1,000 years.