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Title: Two-phase unsaturated flow at Yucca Mountain, Nevada - A Report on Current Understanding

Technical Report ·
DOI:https://doi.org/10.2172/6514· OSTI ID:6514

The U.S. civilian nuclear waste program is unique in its focus on disposal of high-level wastes in the unsaturated zone (UZ), above the water table. The potential repository site currently under investigation is located in a semi-arid region of the southwestern U.S. at Yucca Mountain, Nevada. The geology of the site consists of layered sequences of faulted, fractured, and bedded tuffs. The groundwater table is approximately 600 m beneath the land surface, while the proposed repository horizon is at a nominal depth of approximately 375 m. In this kind of environment, two-phase flow is not just a localized perturbation to natural conditions, as in the saturated zone, but is the predominant mode of water and gas flow. The purpose of this report is to review the current understanding of gas and water flow, and mass transport, in the unique hydrogeologic environment of Yucca Mountain. Characteristics of the Yucca Mountain site are examined, and concepts and mathematical modeling approaches are described for variably saturated flow in thick unsaturated zones of fractured rock. The paper includes a brief summary of the disposal concept and repository design, as developed by a team of engineering contractors to the U.S. Department of Energy (DOE), with strong participation from the DOE National Laboratories.

Research Organization:
Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
Sponsoring Organization:
Office of Civilian Radioactive Waste Management (US)
DOE Contract Number:
AC03-76SF00098
OSTI ID:
6514
Report Number(s):
LBNL-42075; TRN: US200305%%750
Resource Relation:
Other Information: Supercedes report DE00006514; PBD: 1 Aug 1998; PBD: 1 Aug 1998
Country of Publication:
United States
Language:
English