Modeling seepage into heated waste emplacement tunnels in unsaturated fractured rock
Predicting the amount of water that may seep into waste emplacement tunnels (drifts) is important for assessing the performance of the proposed geologic repository for high-level radioactive waste at Yucca Mountain, Nevada. The repository will be located in thick, partially saturated fractured tuff that-for the first several hundred years after emplacement-will be heated to above-boiling temperatures as a result of heat generation from the decay of radioactive waste. Heating of rock water to above-boiling conditions induces water saturation changes and perturbs water fluxes that affect the potential for water seepage into drifts. In this paper, we describe numerical analyses of the coupled thermal-hydrological (TH) processes in the vicinity of waste emplacement drifts, evaluate the potential of seepage during the heating phase of the repository, and discuss the implications for the performance of the site. In addition to the capillary barrier at the rock-drift interface-independent of the thermal conditions-a second barrier exists to downward percolation at above-boiling conditions. This barrier is caused by vaporization of water in the fractured rock overlying the repository. A TOUGH2 dual-permeability simulation model was developed to analyze the combined effect of these two barriers; it accounts for all relevant TH processes in response to heating, while incorporating the capillary barrier condition at the drift wall. Model results are presented for a variety of simulation cases that cover the expected variability and uncertainty of relevant rock properties and boundary conditions.
- Research Organization:
- Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
- Sponsoring Organization:
- USDOE Office of Civilian Radioactive Waste Management. Yucca Mountain Site Characterization Office. Office of Licensing and Regulatory Compliance (US)
- DOE Contract Number:
- AC03-76SF00098
- OSTI ID:
- 836672
- Report Number(s):
- LBNL-53894; R&D Project: 81BC7H; TRN: US0500775
- Journal Information:
- Vadose Zone Journal, Vol. 3; Other Information: Submitted to Vadose Zone Journal: Volume 3; Journal Publication Date: 2004; PBD: 1 Oct 2003
- Country of Publication:
- United States
- Language:
- English
Similar Records
DRIFT-SCALE COUPLED PROCESSES (DST AND TH SEEPAGE) MODELS
Drift-Scale Coupled Processes (DST and TH Seepage) Models
Related Subjects
54 ENVIRONMENTAL SCIENCES
58 GEOSCIENCES
BOUNDARY CONDITIONS
DECAY
EVAPORATION
HEATING
HIGH-LEVEL RADIOACTIVE WASTES
PERFORMANCE
POSITIONING
RADIOACTIVE WASTES
SIMULATION
TUFF
WASTES
WATER
WATER SATURATION
YUCCA MOUNTAIN
FRACTURED ROCK BOILING THERMAL-HYDROLOGICAL PROCESSES