A gas sampling system for withdrawing humid gases from deep boreholes
- Geological Survey, Denver, CO (United States)
- Foothill Engineering Consultants, Golden, CO (United States)
A gas sampling system, designed to withdraw nearly vapor-saturated gases (93 to 100% relative humidity) from deep, unsaturated zone boreholes, was developed by the U.S. Geological Survey for use in the unsaturated zone borehole instrumentation and monitoring program at Yucca Mountain, Nye County, Nevada. This gas sampling system will be used to: (1) sample formation rock gases in support of the unsaturated zone hydrochemical characterization program; and (2) verify downhole, thermocouple psychrometer measurements of water potential in support of the unsaturated zone borehole instrumentation and monitoring program. Using this sampling system, nearly vapor-saturated formation rock-gases can be withdrawn from deep boreholes without condensing water vapor in the sampling tubes, and fractionating heavy isotopes of oxygen, hydrogen, and carbon. The sampling system described in this paper uses a dry carrier-gas (nitrogen) to lower the dew point temperature of the formation rock-gas at its source. Mixing of the dry carrier gas with the source gas takes place inside a specially designed downhole instrument station apparatus (DISA). Nitrogen inflow is regulated in a manner that lowers the dew point temperature of the source gas to a temperature that is colder than the coldest temperature that the mixed gas will experience in moving from warmer, deeper depths, to colder, shallower depths near the land surface. A test of this gas sampling system was conducted in December, 1992, in a 12.2 meter deep borehole that was instrumented in October, 1991. The water potential calculated using this system reproduced in-situ measurements of water potential to within five percent of the average value, as recorded by two thermocouple psychrometers that had been in operation for over 12 months.
- Research Organization:
- American Society of Civil Engineers (ASCE), New York, NY (United States); American Nuclear Society (ANS), La Grange Park, IL (United States)
- DOE Contract Number:
- AI08-92NV10874
- OSTI ID:
- 60949
- Report Number(s):
- CONF-940553-Vol.4; TRN: 94:010821-0043
- Resource Relation:
- Conference: International high-level radioactive waste management conference, Las Vegas, NV (United States), 22-26 May 1994; Other Information: PBD: 1994; Related Information: Is Part Of High Level Radioactive Waste Management: Proceedings of the fifth annual international conference. Volume 4; PB: 1048 p.
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
54 ENVIRONMENTAL SCIENCES
44 INSTRUMENTATION
INCLUDING NUCLEAR AND PARTICLE DETECTORS
BOREHOLES
MONITORING
YUCCA MOUNTAIN
SITE CHARACTERIZATION
PSYCHROMETRY
HIGH-LEVEL RADIOACTIVE WASTES
RADIOACTIVE WASTE DISPOSAL
RADIOACTIVE WASTE MANAGEMENT
SAMPLING
WATER VAPOR
FEASIBILITY STUDIES
Yucca Mountain Project