Assessment of unsaturated zone radionuclide contamination in the 200 areas of the Hanford site, Washington

摘要

The 200 East and 200 West Areas at the Department of Energy's Hanford site in southeastern Washington, contain chemical and nuclear fuel processing facilities that disposed of large volumes of chemical and radionuclide effluents to the ground via various structures such as ponds, cribs and ditches. A geophysical logging investigation was implemented in 1992 to assess the nature and extent of contamination beneath select liquid disposal sites in the 200 Areas. The borehole geophysical logging was accomplished with a recently developed spectral gamma-ray logging system called the Radionuclide Logging System (RLS). This system has a high-resolution, intrinsic germanium detector mounted in a downhole probe and is calibrated and operated specifically for use in a borehole environment. It provides a means to develop in-situ, gamma-emitting radioelement concentration profiles. Approximately 50 boreholes were logged in this study. The RLS log data provided information about the migration and deposition patterns of specific radionuclides in the unsaturated zone and their impacts on the groundwater. Approximately 10 radionuclide species were detected and quantified. Results of the field investigation are being used to refine site specific conceptual models, support Hanford Site remediation decisions and focus future characterization activities.