Abstraction of Seepage into Drifts
A total-system performance assessment (TSPA) for a potential nuclear-waste repository requires an estimate of the amount of water that might contact waste. This paper describes the model used for part of that estimation in a recent TSPA for the Yucca Mountain site. The discussion is limited to estimation of how much water might enter emplacement drifts; additional considerations related to flow within the drifts, and how much water might actually contact waste, are not addressed here. The unsaturated zone at Yucca Mountain is being considered for the potential repository, and a drift opening in unsaturated rock tends to act as a capillary barrier and divert much of the percolating water around it. For TSPA, the important questions regarding seepage are how many waste packages might be subjected to water flow and how much flow those packages might see. Because of heterogeneity of the rock and uncertainty about the future (how the climate will evolve, etc.), it is not possible to predict seepage amounts or locations with certainty. Thus, seepage is treated as a stochastic quantity in TSPA simulations, with the magnitude and spatial distribution of seepage sampled from uncertainty distributions. The distillation of the essential components of process modeling into a form suitable for use in TSPA simulations is referred to as abstraction. In the following sections, seepage process models and abstractions will be summarized and then some illustrative results are presented.
- Research Organization:
- Yucca Mountain Project, Las Vegas, Nevada
- Sponsoring Organization:
- USDOE
- OSTI ID:
- 840697
- Report Number(s):
- NA; MOL.20010103.0155, DC#26818
- Country of Publication:
- United States
- Language:
- English
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Abstraction of Seepage into Drifts
Numerical experiments on the probability of seepage intounderground openings in heterogeneous fractured rock