1993 Technical Reports
Simulation of Unsaturated Flow and Nonreactive Solute Transport in a Heterogeneous Soil at the Field Scale
M.L. Rockhold
Pacific Northwest National Laboratory, Richland, Washington
NUREG/CR-5998, PNL-8496, Pacific Northwest National Laboratory, Richland, Wa., 1993.
Summary
A field-scale, unsaturated flow and solute transport experiment at the Las Cruces trench site in New Mexico was simulated as a part of the "blind" modeling exercise to demonstrate the ablility or inability of uncalibrated models to predict unsaturated flow and solute transport in spatially variable porous media. Simulations were conducted using a recently developed multiphase flow and transport simulator. Uniform and heterogeneous soil models were tested, and data from a previous experiment at the site were used with an inverse procedure to estimate water retention parameters. A spatial moment analysis was used to provide a quantitative basis for comparing the mean observed and simulated flow and transport behavior. The results of this study suggest that defensible predictions of waste migration and fate at low-level-waste sites will ultimately require site-specific data for model calibration.
Preliminary Total-System Analysis of a Potential High-Level Nuclear Waste Repository at Yucca Mountain
P.W. Eslinger, L.A. Doremus, D.W. Engel, T.B. Miley, M.T. Murphy, W.E. Nichols, M.D. White, D.W. Langford, S.J. Ouderkirk
Pacific Northwest National Laboratory, Richland, Washington
PNL-8444 (UC-814), Pacific Northwest National Laboratory, Richland, Wa., 1993.
Summary
The placement of high-level radioactive wastes in mined repositories deep underground is considered a disposal method that would effectively isolate these wastes from the environment for long periods of time. In the United States, the U.S. Department of Energy (DOE) is responsible, and, within certain limitations, has the authority to implement the provisions of the Nuclear Waste Policy Act of 1982, as amended in 1987, that provides the regulatory framework for development of a mined geologic repository. However, before a repository can be used for the disposal of nuclear waste it must meet standards established by the U.S. Nuclear Regulatory Commission, the Environmental Protection Agency (EPA 1985), and must be licensed by the NRC. The Performance Assessment Scientific Support (PASS) program at Pacific Northwest Northwest Laboratory (PNNL) provides modeling capabilities to the DOE to assist in assessing the performance of any potential repositories.