Identifying the sources of subsurface contamination at the Hanford site in Washington using high-precision uranium isotopic measurements
In the mid-1990s, a groundwater plume of uranium (U) was detected in monitoring wells in the B-BX-BY Waste Management Area (WMA) at the Hanford Site in Washington. This area has been used since the late 1940s to store high-level radioactive waste and other products of U fuel-rod processing. Using multiple collector ICP source magnetic sector mass spectrometry (MC ICPMS) high precision uranium isotopic analyses were conducted of samples of vadose zone contamination and of groundwater. The ratios {sup 236}U/{sup 238}U, {sup 234}U/{sup 238}U and {sup 238}U/{sup 235}U are used to distinguish contaminant sources. Based on the isotopic data, the source of the groundwater contamination appears to be related to a 1951 overflow event at tank BX-102 that spilled high level U waste into the vadose zone. The U isotopic variation of the groundwater plume is a result of mixing between contaminant U from this spill and natural background U. Vadose zone U contamination at tank B-110 likely predates the recorded tank leak and can be ruled out as a source of groundwater contamination, based on the U isotopic composition. The locus of vadose zone contamination is displaced from the initial locus of groundwater contamination, indicating that lateral migration in the vadose zone was at least 8 times greater than vertical migration. The time evolution of the groundwater plume suggests an average U migration rate of {approx}0.7-0.8 m/day showing slight retardation relative to a ground water flow of {approx}1 m/day.
- Research Organization:
- Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
- Sponsoring Organization:
- USDOE. Assistant Secretary for Environmental Management. Office of Science and Technology. Environmental Management Science Program. Contracts DE-AC03-76SF00098 and DE-AC06-76RL01830, USDOE Director. Office of Science. Office of Basic Energy Sciences. Chemical Sciences Geosciences and Biosciences Division. Contract DE-AC03-76SF00098 (US)
- DOE Contract Number:
- AC03-76SF00098
- OSTI ID:
- 835428
- Report Number(s):
- LBNL-54979; R&D Project: 468202; TRN: US0500060
- Journal Information:
- Environmental Science and Technology, Vol. 38, Issue 12; Other Information: Submitted to Environmental Science and Technology, Volume 38, No.12; Journal Publication Date: June 15, 2004; PBD: 30 Mar 2004
- Country of Publication:
- United States
- Language:
- English
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