DEPLOYING TECHNOLOGY ADVANCEMENTS FOR CHARACTERIZING THE VADOSE ZONE IN SINGLE-SHELL TANK WASTE MANAGEMENT AREAS
As much as one million gallons of waste is believed to have leaked from tanks, pipelines or other equipment in the single-shell tank farm waste management areas (WMAs) within the 200 East and West areas of the U.S. Department of Energy's Hanford Site near Richland, Washington. Although some contamination has reached groundwater, most contamination still resides in the vadose zone. The magnitude ofthis problem requires new approaches for soil characterization if we are to understand the nature and extent of the contamination and take action to protect the enviromnent. Because of the complexity and expense of drilling traditional boreholes in contaminated soil, direct push characterization using a hydraulic hammer has been extensively employed. Direct push probe holes <3-inch diameter have been pushed to a maximum depth of 240 feet below ground surface in 200 East area. Previously gross gamma and moisture logging of these narrow probe holes was perfonned to identify the location of cesium-137 ({sup 137}Cs) (which has limited mobility in Hanford soil) and moisture peaks. Recently a bismuth germinate detector has been deployed for detecting and quantifying the spectrum of cobalt-60 ({sup 60}Co) (a more mobile contaminant), which provides additional information. The direct push system is configured to allow the collection ofmultiple soil core samples throughout the depth ofthe probe hole. The direct push unit has been used to place individual electrodes at a variety of depths as the probe hole is being decommissioned. These deep electrodes enable the use of soil resistivity measurement methods between surface and deep electrodes as-well-as between sets of deep electrodes. Initial testing of surface-to-deep electrode resistivity measurements in WMA C demonstrated significant improvement in defining the three dimensional extent of a contamination plume. A multiple-electrode string is presently being developed to further enhance the resolution of resistivity data. The combined use of direct push logging/sampling and soil resistivity measurement allows more extensive characterization of the large tank farm WMAs with less cost and time commitment than required by traditional methods. An additional tool is in the laboratory testing stage to support these investigations. A beta detection tool is being evaluated to determine if it might be deployed with the direct push unit to identify technetium-99 ({sup 99}Tc) contamination. {sup 99}Tc is a mobile, long-lived contaminant that is the major risk driver from tank waste contamination. A screening tool to locate {sup 99}Tc contamination is anticipated to further increase the cost-effectiveness ofvadose zone characterization efforts.
- Research Organization:
- Hanford Site (HNF), Richland, WA (United States)
- Sponsoring Organization:
- USDOE Assistant Secretary for Environmental Management (EM)
- DOE Contract Number:
- DE-AC27-08RV14800
- OSTI ID:
- 970553
- Report Number(s):
- WRPS-44388-FP Rev 0; TRN: US201002%%1277
- Resource Relation:
- Conference: WM2010 CONFERENCE WASTE MANAGEMENT SYMPOSIA 03/07/2010 THRU 03/11/2010 PHOENIX AZ
- Country of Publication:
- United States
- Language:
- English
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