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 rep-resentative 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 simula-tion 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 de-sign (trench versus a concrete-lined vault). In contrast, corrosion of the steel pour canister sur-rounding 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.
Revised: March 2, 2004 |
Published: February 21, 2001