Drift-Scale THC Seepage Model

The purpose of this report is to document the thermal-hydrologic-chemical (THC) seepage model and model simulations. The simulations predict the composition of fracture water that could potentially seep into repository emplacement drifts and the composition of the associated gas phase. The THC seepage model is not used to feed the total system performance assessment (TSPA) for the license application (LA). However, results of this model are intended to provide confidence in the results of simpler models discussed in Engineered Barrier System: Physical and Chemical Environment (SNL 2007 [DIRS 177412]), which directly feed TSPA LA. Specifically, simulation results from the THC seepage model are used for validation of the near field chemistry model component of the physical and chemical environment model (SNL 2007 [DIRS 177412], Section 7.1.3). The THC seepage model is also intended for use in the bases of screening discussions on features, events, and processes (FEPs) regarding drift-scale coupled THC processes (as described in Section 6.1).
This report has been developed in accordance with SCI-PRO-006, Models, and with Technical Work Plan for: Revision of Model Reports for Near-Field and In-Drift Water Chemistry (SNL 2007 [DIRS 179287]). The technical work plan (TWP) describes planning information pertaining to the technical scope, content, and management of this report. The plan for validation of the models documented in this report is given in Section 2.2.1 of the TWP (SNL 2007 [DIRS 179287]). Section 3.2 of the TWP (SNL 2007 [DIRS 179287]) identifies Acceptance Criteria 1 to 5 for “Quantity and Chemistry of Water Contacting Engineered Barriers and Waste Forms” (NRC 2003 [DIRS 163274]) as being applicable to this report, and the criteria are addressed in Section 4.2.