HR: 0800h
AN: H11D-1292    [Abstracts]
TI: Assessment of Uncertainty of Radionuclide Transport in the Yucca Mountain Unsaturated Zone: Parametric and Parameter Estimation Uncertainty
AU: Pan, F
EM: Feng.Pan@dri.edu
AF: Division of Hydrologic Sciences, Desert Research Institute, 755 E. Flamingo Road, Las Vegas, NV 89119 United States
AU: * Ye, M
EM: Ming.Ye@dri.edu
AF: Division of Hydrologic Sciences, Desert Research Institute, 755 E. Flamingo Road, Las Vegas, NV 89119 United States
AU: Wu, Y
EM: yswu@lbl.gov
AF: Hydrogeology Department Lawrence Berkeley National Laboratory, Berkely, Berkely, CA 94720 United States
AU: Hu, B
EM: hu@quartz.gly.fsu.edu
AF: Department of Geologic Sciences, Florida State University, Tallahassee, Tallahassee, FL 32306 United States
AU: Shirley, C
EM: Craig.Shirley@dri.edu
AF: Division of Hydrologic Sciences, Desert Research Institute, 755 E. Flamingo Road, Las Vegas, NV 89119 United States
AU: Yu, Z
EM: Zhongbo.unlv.nevada.edu
AF: Department of Geosciences, University of Nevada, Las Vegas, Las Vegas, Las Vegas, NV 89119 United States
AB: This study is to assess uncertainty of radionuclide transport in the unsaturated zone at Yucca Mountain. The uncertainty is attributed to parametric uncertainty due to parameter spatial variability and parameter estimation uncertainty when fitting van Genuchten parameters alpha and n based on water retention measurements. The uncertainty assessment is conducted using Monte Carlo simulation and the three-dimensional flow and transport numerical code, TOUGH2, is employed to simulate unsaturated flow and radionuclide transport in the unsaturated zone. Matrix porosity, saturated hydraulic conductivity, sorption coefficient, and van Genuchten alpha and n parameters are treated as statistically homogeneous random variables. Distributions of the first three random parameters are determined based on site measurements. Seven transformations including three transforms from the Johnson system are applied to the measurements and Lilliefors test is used to identify the best transform that renders the transformed data closest to normal distribution. The fitted matrix van Genuchten alpha and n parameters are assumed to follow normal distributions and parameter estimation uncertainty is measured by the covariance matrix obtained from least square analysis. For each model layer, Latin Hypercube Sampling (LHS) method is used to generate 200 realizations random fields, among which matrix porosity is correlated with saturated hydraulic conductivity and van Genuchten alpha and n are correlated also. The correlation between the former two is measured by Spearman rank correlations estimated from site measurements. The Spearman rank correlation of the latter two is calculated from a large number of generated values using MINTAB software based on their estimated means, variances and covariance. 200 Monte Carlo simulations are conducted using the TOUGH2 and convergence of the Monte Carlo results is thoroughly examined. Mean, variances, 5% and 95% percentiles of saturation, capillary pressure, and fluxes are estimated. The 5% and 95% percentiles of saturation and capillary pressure bracket a large portion of site measurements, indicating the success of the uncertainty analysis. Uncertainty of the reactive and conservative tracer transport in the vadose zone is also assessed in similar manner.
DE: 1832 Groundwater transport
DE: 1838 Infiltration
DE: 1869 Stochastic hydrology
DE: 1873 Uncertainty assessment (3275)
SC: Hydrology [H]
MN: Fall Meeting 2005