Modelling The Alteration of Son-68 Glass with Nearfield Materials

Abstract

ABSTRACTThe model tested in this paper couples glass dissolution rate and geochemistry in the surrounding environment, thus leading to the comprehensive description of the interactions between the glass and the minerals and their transformations. Leaching of glass is simulated at 90°C and S/V=80 cm-1 in pure water or with iron from the canister and overpack or with argillite. The glass dissolution is described with an affinity law with respect to a nontronite-like phase, which saturation state depends on Si, Al, Fe, Na and Ca activities. The simulations results allow to reproduce both the decrease of the initial alteration rate and the so-called residual regime while the composition of the alteration layers are explained in terms of precipitated phases. In presence of metallic iron, the corrosion does not affect much glass dissolution rate if silica sorption is neglected. On the contrary, in presence of argillite, the alteration is enhanced by the dissolution of primary clay minerals and the precipitation of feldspar, K-zeolite and clay minerals.