Measurements of matric and water potentials in unsaturated tuff at Yucca Mountain, Nevada [electronic resource]
Two types of instruments were installed in a borehole in order to monitor matric and water potentials of various hydrogeologic units consisting of tuff. The borehole was drilled as part of a study to provide information to the US Department of Energy for their use in evaluating Yucca Mountain, Nevad...
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| Corporate Author: | |
| Format: | Government Document Electronic eBook |
| Language: | English |
| Published: |
Las Vegas. Nev. : Oak Ridge, Tenn. :
United States. Dept. of Energy. Nevada Operations Office ; distributed by the Office of Scientific and Technical Information, U.S. Dept. of Energy,
1985.
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| Summary: | Two types of instruments were installed in a borehole in order to monitor matric and water potentials of various hydrogeologic units consisting of tuff. The borehole was drilled as part of a study to provide information to the US Department of Energy for their use in evaluating Yucca Mountain, Nevada, for a repository for high-level radioactive waste. Heat-dissipation probes were used to monitor matric potentials and thermocouple psychrometers were used to monitor water potentials. Two major concerns regarding the use of these instruments in deep boreholes are: (1) the effect of length of the lead wires, and (2) the inability to recalibrate the instruments after installation. The length of the lead wire contributes to the source resistance and lead capacitance, which affects the signal settling time. Both instruments tested proved to be insensitive to lead-wire length, except when connected to smaller input-impedance data loggers. Thermocouple wires were more sensitive than heat-dissipation probe wires because of their greater resistance and quality of voltmeters used. Two thermocouple psychrometers were installed at every instrument station for backup and verification of data, because the instruments could not be recalibrated in situ. Multiple scanning rather than single-point scanning of the evaporation curve of a thermocouple psychrometer could give more reliable data, especially in differentiating between very wet and very dry environments. An isolated power supply needs to be used for each heat dissipation probe rather than a single power supply for a group of probes to avoid losing data from all probes when one probe malfunctions. This type of system is particularly desirable if the site is unattended by an operator for as long as a month. 20 refs., 13 figs., 2 tabs. |
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| Item Description: | Published through the Information Bridge: DOE Scientific and Technical Information. 12/31/1985. "conf-8511172--7" "DE86008848" Conference on characterization and monitoring of the vadose zone, Denver, CO (United States), 19-21 Nov 1985. Thamir, F.; McBride, C.M. Goodson and Associates, Inc., Denver, CO (United States) Western State Coll. of Colorado, Gunnison, CO (United States) |
| Physical Description: | 15 p. : digital, PDF file. |