Assessment of effectiveness of Geologic Isolation Systems. The development and application of a geologic simulation model

The Geologic Simulation Model (GSM) developed under the Assessment of Effectiveness of Geologic Isolation Systems (AEGIS) project at the Pacific Northwest Laboratory for the Department of Energy is a quasi-deterministic process-response model which simulates the development of the geologic and hydrologic systems of a ground-water basin for a million years into the future. Effects of natural processes on the ground-water hydrologic system are modeled principally by rate equations. The combined effects and synergistic interactions of different processes are approximated by linear superposition of their effects during discrete time intervals in a stepwise-integration approach. The completed AEGIS GSM was used to generate 500 Monte Carlo simulations of the behavior of the geologic/hydrologic system affecting a hypothetical repository in the Pasco Basin over the next million years. These simulations used data which were not subjected to a review adequate to the needs of a real site performance assessment. However, the general care used in generating the data, and the overall behavior of the GSM suggest that the results are plausible at this time