Kristopher Kuhlman and Anke Schneider are collaborating to improve basin-scale groundwater flow and solute transport models near salt repositories. Their efforts include reimplementing and extending an existing 1996 groundwater model of the WIPP basin to include density dependent flow and improved mesh elements. They have implemented solute concentration-dependent fluid density in the PFLOTRAN model and conducted initial model comparisons. This work will lead to an updated regional groundwater flow and chemistry model for the WIPP area and improved understanding of issues in past and future regional models surrounding salt repositories.

1. Basin-scale Density-dependent Groundwater Flow
near a Salt Repository
Kristopher L. Kuhlman, Sandia National Laboratories (SNL)
Anke Schneider, Gesellschaft für Anlagen- und Reaktorsicherheit (GRS)
7th US/German Workshop on
Salt Repository Research, Design and Operation
Washington, DC
September 7-9, 2016
ABSTRACT
Basin-scale groundwater flow and solute transport modeling in the geological units surrounding
a salt repository are typically important parts of the safety case for radioactive waste disposal in
salt. Because salt is highly soluble, aquifers surrounding the repository present a significant
potential failure mechanism in salt. The dissolution of bedded salt could occur by laterally
migrating dissolution fronts by inter-salt-bed sedimentary aquifers or by vertically circulating
groundwater.
Ongoing collaboration between GRS (d3f) and Sandia (PFLOTRAN) compares and extends our
existing numerical groundwater flow and solute transport models to improve conceptualization
and numerical implementation of regional groundwater flow simulations near repositories. Our
effforts include reimplementation and extension of the WIPP basin-scale groundwater model,
from 1996. The collaboration began by identifying key features missing from existing models
(density dependent flow and mesh element types). Several features have since been
implemented, most notably solute concentration-dependent fluid density in PFLOTRAN.
Initial model comparison has been conducted, and issues and complications have been identified.
The modeling comparison and collaboration continues. This work will lead to an updated
regional groundwater flow and chemistry model for the WIPP area, and improved understanding
of the issued in previous and future regional groundwater models for either bedded or domal salt
surrounding a repository.
Sandia National Laboratories is a multi-mission laboratory operated by Sandia Corporation, a wholly owned
subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security
Administration under contract DEAC04-94AL85000. SAND2016-9236 A.