A set of reactive chemical transport calculations was conducted with the Subsurface Trans-port Over Reactive Multiphases (STORM) code to evaluate the long-term performance of a representative low-activity waste glass in a shallow subsurface disposal system located on the Hanford Site. 1-D simulations were conducted out to times in excess of 20,000 y. A 2-D simulation was run to 2,000 y. The maximum normalized, decay-corrected Tc release rate from a trench type conceptual design under a constant recharge rate of 4.2 mm/y is 0.76 ppm/y. Factors that were found to significantly impact the predicted release rate were water recharge rate, chemical affinity control of glass dissolution rate, diffusion coefficient, and disposal system design (trench versus a concrete-lined vault). In contrast, corrosion of the steel pour canister surrounding the glass waste, and incorporation of chemical conditioning layer of silica sand at the top of the trench had little impact on Tc release rate.
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