1992 Yearly calibration of Pacific Northwest Laboratory's gross gamma-ray borehole geophysical logging system

This report describes the 1992 yearly calibration of a gross gamma-ray geophysical pulse logging system owned by the US Department of Energy (DOE) and operated by Pacific Northwest Laboratory. The calibration was conducted to permit the continued use of this system for geologic and hydrologic studies associated with remedial investigation at the Hanford Site. The calibration is limited to the probe identified as CG27A-97. 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. A previous correlation for relating observed count rate in before- and after-logging field calibrations to equivalent-uranium concentrations was confirmed for field source Ra-20S-82. A computer-based digital collection/recording system was used simultaneously on many of the procedures with the original analog system so that the performance of the two collection systems could be correlated and compared at some future date