HR: 0800h
AN: H51F-0848    [Abstracts]
TI: Validating Thermohydrologic Models Using the Drift Scale Test of the Proposed Repository at Yucca Mountain: Impact of Capillary-Pressure Cap
AU: Sun, Y
EM: sun4@llnl.gov
AF: Lawrence Livermore National Laboratory, PO Box 808, Livermore, CA 94551, United States
AU: Lee, K
EM: lee23@llnl.gov
AF: Lawrence Livermore National Laboratory, PO Box 808, Livermore, CA 94551, United States
AU: * Buscheck, T A
EM: buscheck1@llnl.gov
AF: Lawrence Livermore National Laboratory, PO Box 808, Livermore, CA 94551, United States
AU: James, S C
EM: scjames@sandia.gov
AF: Sandia National Laboratories, Thermal/Fluid Science & Engineering, PO Box 969, Livermore, CA 94551-0969, United States
AU: Hao, Y
EM: HAO1@LLNL.GOV
AF: Lawrence Livermore National Laboratory, PO Box 808, Livermore, CA 94551, United States
AB: The MultiScale ThermoHydrologic Model (MSTHM) supports the total system performance assessment (TSPA) for the proposed nuclear-waste repository at Yucca Mountain. The MSTHM uses the Nonisothermal Unsaturated Flow and Transport (NUFT) code to represent thermal-hydrologic (TH) processes occurring at scales from a few tens of centimeters around individual waste packages and emplacement drifts (tunnels) all the way to the kilometer scale for heat flow through the mountain. The TH model involves two-phase (liquid and gas) nonisothermal flow and transport in an unsaturated fractured rock system, using a dual-permeability model of overlapping fracture and matrix continua. The TH model depends on calibrated system parameters, including the van~Genuchten α and m parameters for the capillary pressure versus saturation relationship. Waste- package heat generation can drive liquid saturation to below residual saturation. Extending the van Genuchten capillary-pressure function to below residual saturation involves establishing a physically reasonable capillary- pressure cap. Various extension methods are considered for the van Genuchten capillary-pressure function as applied to a 3-D nested-mesh TH model of the Drift Scale Test (DST), as well as a corresponding 2-D drift-scale TH submodel, which supports the MSTHM. Simulated temperatures and liquid saturations are compared with field measurements from the DST. Compared to past DST model-validation studies, agreement between the simulated results and field measurements is improved, partially due to implementing a capillary-pressure cap. Because the same hydrologic properties and capillary-pressure cap are applied in the TH submodels supporting the MSTHM, this model-validation study builds confidence in the MSTHM as it is applied to Yucca Mountain TSPA. This work was performed under the auspices of the U.S. Department of Energy by University of California Lawrence Livermore National Laboratory under contract No. W-7405-Eng-48. Sandia is a multi-program laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.
DE: 1829 Groundwater hydrology
DE: 1846 Model calibration (3333)
DE: 1847 Modeling
SC: Hydrology [H]
MN: 2007 Fall Meeting