Book Description

This report describes the 1991 yearly calibration of a gross gamma-ray geophysical pulse logging system owned by the US Department of Energy (DOE) and operated by the Pacific Northwest Laboratory. The calibration was conducted to permit the continued use of this system for geologic and hydrologic studies associated with remedial investigations at the Hanford Site. Primary calibrations to equivalent uranium units were conducted in DOE borehole model standards that reside on the Hanford Site. The calibrations were performed in borehole models SBL/SBH and SBA/SBB, which contain low-equivalent uranium concentrations. Correlations were established based on two similar approaches for relating observed count rate in before- and after-logging field calibrations to equivalent uranium concentrations. A new field source (Ra-20S-82) was fabricated to replace the old source (Ra-20S-204), whose activity led to variable field calibration results previously caused by a nonfixed geometry. A cross-calibration study was performed to compare the operation of the new source relative to the old source. A digitally based collection/recording system was recently acquired, so that many of the procedures were performed with the old analog system and the new digital system to compare the performance of the digital system. 7 refs., 2 figs., 9 tabs.