Effect of a low-permeability layer on calculated gas flow at Yucca Mountain
- Disposal Safety Inc., Washington, DC (United States)
Seasonal flows of air with velocities as high as 3.5 m/s have been observed in deep boreholes at Yucca Mountain. These flows are attributed to convective circulation arising from topographic relief, seasonal temperature variation, and density differences resulting from variation in gas composition. If a repository were built there, heat from the emplaced waste would also contribute to gas flow. Large-scale air flows may be significant to repository performance because they control the movement of carbon dioxide within the mountain and also result in a net flux of water vapor to the surrounding atmosphere. An understanding of the velocity, trajectories, and mixing of the gas in Yucca Mountain, is necessary both as input for a model of the carbon-14 movement in the unsaturated zone and evaluation of the net vapor flux. Amter and Ross developed a model called TGIF (TopoGraphic Induced Flow) to simulate gas flow under Yucca Mountain. This paper describes a systematic sensitivity study that was designed to test several aspects of the TGIF model when used to simulate gas flow under Yucca Mountain. Values of three important inputs to the model were systematically varied to form a matrix of 80 runs. The matrix consisted of five values of permeability contrast between a bedded tuff layer and surrounding welded units (in all cases, bulk permeabilities were used to represent the combined effect of both fractures and matrix permeability), four temperature profiles representing different stages of repository cooldown, and four finite-difference grids.
- Research Organization:
- American Nuclear Society, La Grange Park, IL (United States); American Society of Civil Engineers, New York, NY (United States)
- DOE Contract Number:
- AC04-76DP00789
- OSTI ID:
- 145457
- Report Number(s):
- CONF-910435--Vol.1
- Country of Publication:
- United States
- Language:
- English
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