Accelerated weathering of waste glass at 90°C with the pressurized unsaturated flow (PUF) apparatus: Implications for predicting glass corrosion with a reactive transport model

The interest in the long-term durability of waste glass stems from the need to predict radionuclide release rates from the corroding waste form over geologic time-scales. Several long-term test methods have been developed to accelerate the glass-water reaction [drip test, vapor hydration test, product consistency test-B, and pressurized unsaturated flow (PUF)]. Currently, the PUF test is the only method that can mimic the unsaturated hydraulic properties expected in a subsurface disposal facility and simultaneously monitor the glass-water reaction. PUF tests are being conducted to accelerate the weathering of glass and validate the model parameters being used to predict long-term glass behavior. The model parameters are obtained by conducting a series of single-pass flow-through experiments and are used to parameterize the chemical affinity rate equation to predict the effect of rate influencing variables on glass dissolution. A one-dimensional reactive chemical transport simulations of glass dissolution and secondary phase formation during a 1.5-year long PUF experiment was conducted with the subsurface transport over reactive multi-phases (STORM) code. Results show that parameterization of the computer model by combining direct laboratory measurements and thermodynamic data provides an integrated approach to predicting glass behavior over geologic-time scales. The results from these bench-scale experiments will be extended to a set of field lysimeter experiments (i.e., experiments on buried glass at the Hanford Site) that have been in progress for 6 years on several glass specimens.