Numerical Analyses to Evaluate Backfilling Repository Drifts in Unsaturated Tuff

摘要

Preliminary numerical analyses were performed to determine if the choice of drift backfill could influence water flow past waste packages adjacent to a repository drift in unsaturated volcanic tuff. These numerical analyses for a prospective nuclear-waste repository in Yucca Mountain located on and adjacent to the Nevada Test Site consisted of unsaturated flow modeling using the computer code TRUST. An idealized configuration of a repository drift with vertical emplacement of waste packages was evaluated, considering both fine and coarse materials as backfill in the drift. In the numerical simulations, coarse-grained material drained more completely than fine-grained material and formed a more effective capillary barrier to water flow in the unsaturated medium of the repository horizon. Although the magnitude of flow in the modeled regions is small, backfill material was shown to influence flow inside a repository drift. However, the numerical analyses demonstrate that selection of backfill does not significantly influence water flow past vertically emplaced waste packages for the conditions simulated. 17 references, 11 figures, 2 tables. (ERA citation 10:020020)