Groundwater contamination associated with a potential nuclear waste repository at Yucca Mountain, USA

Abstract

The groundwater contamination originating from a potential nuclear waste repository at Yucca Mountain, USA, is evaluated in a three-dimensional flow transport simulation. The model has 833,079 elements and includes both the saturated and unsaturated zone. Vertical grid spacing is 20 m in the saturated zone and 40 m in the unsaturated zone. Spacing in the x and y directions is 250 m in both the saturated and unsaturated zone. The simulation period is 1,000,000 years. Three scenarios with different saturation values (0.056, 0.1 and 0.18) for Dirichlet conditions at the top of the model and different permeabilities for the total model are calculated. The results differ from previous calculations conducted with a combination of one-dimensional models for the saturated zone and uncoupled models for the unsaturated zone. Since one-dimensional models produce averaged values for the three-dimensional space, they necessarily produce a relatively low radioactive dose. In contrast, the peak dose for the 250 x 250 x 20-m cells in the three-dimensional space is relatively high but closer to the risk an individual is exposed to within a reasonably small area.