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.
Highlights
Study areaThe candidate repository for nuclear waste at Yucca Mountain, USA (Fig. 1), is conceived for waste storage above the water table
Modelling potential groundwater contamination is a challenging task if the contaminant source is located above the water table
Groundwater contamination associated with a potential nuclear waste repository at Yucca Mountain, USA
Summary
The candidate repository for nuclear waste at Yucca Mountain, USA (Fig. 1), is conceived for waste storage above the water table. Modelling potential groundwater contamination is a challenging task if the contaminant source is located above the water table. The models published to date consist of a combination of a three-dimensional (3D) transport model for the unsaturated zone and an uncoupled one-dimensional (1D) model for the saturated zone (DOE 2009). This combination has the disadvantage of relying on a large number of assumptions that are difficult to verify. Integrating the saturated and unsaturated zone in a single 3D model drastically reduces the number of assumptions required. The 1057.5-km model (Fig. 2) is located in an area where explosive magmatism dominated the geologic history during the Miocene (Table 1; DOE 2007a). The southwest corner of the model is located 1 km northeast of the Nevada-California state boundary
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