Long-term modeling of alteration-transport coupling: Application to a fractured Roman glass

Nuclear Energy Advanced Modeling and Simulation (NEAMS) Waste Integrated Performance and Safety Codes (IPSC) : FY10 development and integration.

“…The rates of glass degradation observed from ancient glass artifacts are much slower than those observed in laboratory tests (Verney-Carron et al 2010), similar to the slower degradation rates observed in nature for mineral degradation (White and Brantley 2003;Ganor et al 2005;Hellmann and Tisserand 2006;Bryan et al 2009). Studies of natural and synthetic glass dissolution rates show far-from equilibrium behavior can be compositionally dependent on Si content (Wolf-Boenisch et al 2004) and Al content (Hamilton et al 2001) of the glass.…”

“…The slower degradation glass rates observed in the natural system result from a number of differences between those systems and glass studies in the laboratory including (a) dissolution mechanisms (Hamilton et al 2001) and (b) glass reactive surface area (Wolf-Boenisch et al 2004). Each of these aspects of the degradation are affected by coupled feedback processes resulting during glass degradation due to formation of diffusion pathways through intermediate phases (e.g., gel layer), which may also develop to isolate fresh glass surfaces from contact with the bulk fluid (Cailleteau et al 2008;Verney-Carron 2010).…”

“…The GLAMOR project (Van Iseghem et al 2006;Van Iseghem et al 2007) was a concerted effort to evaluate the primary evolving processes of glass degradation and to compare the capabilities of two specific models to represent those multiple processes using a selected set of experimental data from the literature. A number of more recent studies have extended glass degradation modeling from the end point of the GLAMOR project using the GRAAL model applied to SON68 nuclear glass (Frugier et al 2008;Frugier et al 2009) and explicitly evaluating coupled processes in the alteration of Roman glass (Verney-Carron et al 2010). In these cases, the details of choosing parameter values for input to the model of these coupled processes emphasizes the facility of an integrated framework for evaluating experiments and analogs.…”

“…Coupled diffusion and alteration processes in the PRI play a role in moderating the degradation rate of the glass (Frugier et al 2009). At the field scale, understanding the feedback of the coupled processes that result in formation of the gel, and especially precipitation of secondary stable phases (e.g., clays) is central to elucidating the longtime slower rates observed for glass in nature (Verney-Carron et al 2010) and will be central to application within PA models.…”

“…Definition of the equilibrium phase for glass dissolution and correlations among glass rate parameters. Because glass is a thermodynamically unstable phase, choosing the appropriate representative composition for defining the equilibrium condition for use in a chemical affinity approach to the dissolution rate has been handled in various empirical ways in the literature (e.g., Verney-Carron et al 2010). This introduces a variability based on conceptual uncertainty into these approaches that may lead to disparate results that are not related directly to the use of chemical affinity to describe the rate, but simply due to the variability of the reference point assumed for the equilibrium condition.…”