Carbon Isotopic Data from Test Hole USW UZ-1, Yucca Mountain, Nevada

by In C. Yang, U.S. Geological Survey, Denver, United States,
C. A. Peters, U.S. Geological Survey, Denver, United States,
D. C. Thorstenson, U.S. Geological Survey, Denver, United States,

Document Type: Proceeding Paper

Part of: High Level Radioactive Waste Management 1993


Rock-CO2-gas analyses in test hole USW UZ-1 at Yucca Mountain indicate that gas movement in the unsaturated zone is likely through a dry-fracture system with little porewater or caliche-calcite interaction. This is because near-surface δ13C values are of biogenic origin and have changed little throughout the total depth. Post-bomb 14C activity is observed to the depth of about 12 m. An abrupt change in plotted 14C/depth slope is seen at 61 m. The less steep upper segment corresponds to the zone with greater porosity and moisture content, and consequently more tortuosity, with an estimated traveltime of 1.27 cm/yr; the steeper sloped zone corresponding to the lower segment has smaller porosity and moisture content but larger fracture density for gas transport, with an estimated traveltime of 3.26 cm/yr.

Subject Headings: Porosity | Radioactive wastes | Slopes | Water content | Carbon fibers | Data analysis | Field tests | Pore water | United States | North America | Georgia | Nevada | Oregon

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