Accurately predicting the long-term corrosion of glasses has been a long-standing problem that has generated multiple opinions on the controlling process. It is largely agreed that radionuclide release from glass is due to is the combined contributions of mechanisms that can be placed into two general categories: reaction control (impacted by solution affinity, local solution changes due to secondary phase precipitation, and kinetic limitations) and transport control (impacted by ion exchange, pore tortuosity in alteration layers, and diffusion of rate-limiting ions).Isotopic substitution provides a mechanism for tracing the progress of ions through mature alteration layers while not changing the system chemistry. An experiment simultaneously targeting glass formers (Si, B), an alkali modifier (Li), an alkaline earth modifier (Ca), and several transition metals (Fe, Zr, and Mo) has shown that several previous assumptions regarding ion transport in corroding glass systems are incomplete. Substantial and rapid participation of several monitored ions in solution with the innermost alteration layers was observed. Lithium exhibited diffusion far into the glass in remarkably short time-scales. Based on these results and other recent results in the literature, a new model of the dominant mechanism controlling glass corrosion is proposed. This model proposes that the glass quickly alters to form a dense material that then provides the interface between the dissolving solution and the glass that controls the dissolution reaction. The composition of this interface material, however, can and does change with environmental and solution conditions. The insertion of this non-static interface can account for the dynamic behaviors seen in the study of glass corrosion. This talk will explore many of these behaviors and will show how they can be modeled in this fashion.

Variable Affinity: A modification of the TST-based rate law for glasses

247th National Meeting (2014)

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