Preliminary evaluation of waste package releases using drift-scale thermo-hydrologic analyses

In a 1993 performance assessment, the uncertainty associated with using panel-scale thermo-hydrologic analyses to define the near-field environment in the vicinity of the waste packages was identified as one of the major factors impacting the predicted performance. This was because of the impact of the thermo-hydrologic regime on the initiation of aqueous corrosion as well as the rate of corrosion, rate of waste form dissolution (due to the uncertainty in the percent of the waste form surface covered by water film), solubility limits, and the effective diffusion through the waste package and engineered barrier. This document presents an initial attempt to incorporate, in a more representative fashion, the anticipated thermo-hydrologic response in the vicinity of in-drift emplaced waste packages into the post-closure performance assessment. It illustrates some of the issues which must be resolved prior to justifying the inclusion of these representations into the assessment