Modeling Resumption of Glass Alteration Due to Zeolites Precipitation

Under hyper-alkaline pH or relatively high temperatures, a resumption of glass alteration can occur. This sudden acceleration of the glass corrosion rate is almost always associated with zeolites precipitation. Zeolites precipitation consumes silica and aluminum, key elements of the glass surface layer controlling its dissolution. A better understanding and quantification of this mechanism is crucial for predicting glass long-term behavior. Geochemical modeling applied to experimental data is a useful tool to reach that goal. However, it has never been applied successfully so far for modeling the kinetics of that reaction. Within the framework of the GRAAL glass dissolution model, and with simple zeolite precipitation kinetic assumptions, a simulation of glass resumption of alteration is attempted. Concentrations in solution and element mass balance between amorphous and crystallized phases are reproduced. Key parameters are revealed. Better understanding is now achievable through sensitivity studies on minerals stoichiometry and on the respective weight of dissolution and precipitation kinetics in the control of the whole reaction rate.