Standardization of Geophysical Logging Data at the Hanford Site - 16208
Gamma activity has been measured in boreholes at the US DOE Hanford Site in southeastern Washington State since the 1940's. Over the years, detectors and data recording methods have changed, but the accumulated data provide a record of subsurface gamma activity spanning the period from active operations into interim stabilization. A basic problem is comparability of data between different detectors over a wide range of gamma activity. Many logs are simply presented in terms of raw count rate, and it is difficult to compare count rates between two different detectors, particularly when they have very different response characteristics. The Hanford Gamma Unit (HGU) is proposed as an empirical unit of gamma activity. The HGU is defined in terms of gamma activity at a specified location at the Hanford Borehole Model Facility, and its magnitude is defined such that 1 HGU is approximately equal to typical background gamma activity in uncontaminated soil. The HGU provides a means to convey information about the basic level of subsurface contamination without any implications as to the specific source of the gamma activity. (authors)