A gas sampling system for withdrawing humid gases from deep boreholes

Conference · Sat Dec 31 04:00:00 EST 1994

OSTI ID:60949

Rousseau, J P; Thordarson, W ^[1]; Kurzmack, M A ^[2]

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1. Geological Survey, Denver, CO (United States)
2. 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 Using this sampling system, nearly vapor-saturated formation rock-gases can be withdrawn from deep boreholes without condensing water vapor in the sampling tubes, and fractionating heavy isotopes of oxygen, hydrogen, and carbon.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, New York, NY (United States); American Nuclear Society, La Grange Park, IL (United States)
• DOE Contract Number: AI08-92NV10874
• OSTI ID: 60949
• Report Number(s): CONF-940553--Vol.4
• Country of Publication: United States
• Language: English

Related Subjects

05 NUCLEAR FUELS
44 INSTRUMENTATION
INCLUDING NUCLEAR AND PARTICLE DETECTORS
54 ENVIRONMENTAL SCIENCES
BOREHOLES
FEASIBILITY STUDIES
HIGH-LEVEL RADIOACTIVE WASTES
MONITORING
PSYCHROMETRY
RADIOACTIVE WASTE DISPOSAL
RADIOACTIVE WASTE MANAGEMENT
SAMPLING
SITE CHARACTERIZATION
WATER VAPOR
YUCCA MOUNTAIN
Yucca Mountain Project