Neutron moisture meter calibration in large diameter boreholes

Conference · · Soil Science Society of America Journal; (USA)

OSTI ID:5436532

Tyler, S W ^[1]

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1. Desert Research Institute, Reno, NV (USA)

In studies of soil moisture flux in the arid, alluvial basins of Nevada, drilling technologies have been developed to easily and economically install 15-cm diam, steel casing to depths of up to 100 m. Laboratory and field calibration of a low source strength (3.7 {times} 10{sup 8} Bq or 10 mCi) neutron moisture meter was carried out to determine the impact of such large casing on tool performance. Both laboratory and field tests showed that a quadratic calibration equation relating returned thermal neutron counts (N) to the volumetric water content ({theta}) of the form N = b{sub 0} + b{sub 1} {theta} + b{sub 2} {theta}{sup 2} was acceptable to determine soil profile water content. The density of thermal neutrons returned to the detector was considerably reduced when compared to reported fluxes in traditional small diameter aluminum access pipe. This reduction is attributed to the increased air gap between the tool and the soil, and neutron capture by the steel casing.

• OSTI ID: 5436532
• Report Number(s): CONF-881108--
• Conference Information: Journal Name: Soil Science Society of America Journal; (USA) Journal Volume: 52:3
• Country of Publication: United States
• Language: English

Related Subjects

54 ENVIRONMENTAL SCIENCES
540211* -- Environment
Terrestrial-- Basic Studies-- Radiometric Techniques-- (1990-)
ARID LANDS
BARYON REACTIONS
CALIBRATION
CAPTURE
EQUATIONS
FEDERAL REGION IX
HADRON REACTIONS
MEASURING INSTRUMENTS
MOISTURE
MOISTURE GAGES
NEUTRON REACTIONS
NEVADA
NORTH AMERICA
NUCLEAR REACTIONS
NUCLEON REACTIONS
SOILS
USA