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Title: Identifying the sources of subsurface contamination at the Hanford site in Washington using high-precision uranium isotopic measurements

Abstract

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 themore » 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.« less

Authors:
; ; ; ;
Publication Date:
Research Org.:
Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
Sponsoring Org.:
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)
OSTI Identifier:
835428
Report Number(s):
LBNL-54979
R&D Project: 468202; TRN: US0500060
DOE Contract Number:
AC03-76SF00098
Resource Type:
Journal Article
Resource Relation:
Journal Name: Environmental Science and Technology; Journal Volume: 38; Journal 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
Subject:
12 MANAGEMENT OF RADIOACTIVE WASTES, AND NON-RADIOACTIVE WASTES FROM NUCLEAR FACILITIES; 58 GEOSCIENCES; ACCURACY; CONTAMINATION; GROUND WATER; HIGH-LEVEL RADIOACTIVE WASTES; MASS SPECTROSCOPY; MONITORING; PLUMES; PROCESSING; TANKS; URANIUM; WASHINGTON; WASTE MANAGEMENT; WASTES

Citation Formats

Christensen, John N., Dresel, P. Evan, Conrad, Mark E., Maher, Kate, and DePaolo, Donald J. Identifying the sources of subsurface contamination at the Hanford site in Washington using high-precision uranium isotopic measurements. United States: N. p., 2004. Web. doi:10.1021/es034700q.
Christensen, John N., Dresel, P. Evan, Conrad, Mark E., Maher, Kate, & DePaolo, Donald J. Identifying the sources of subsurface contamination at the Hanford site in Washington using high-precision uranium isotopic measurements. United States. doi:10.1021/es034700q.
Christensen, John N., Dresel, P. Evan, Conrad, Mark E., Maher, Kate, and DePaolo, Donald J. Tue . "Identifying the sources of subsurface contamination at the Hanford site in Washington using high-precision uranium isotopic measurements". United States. doi:10.1021/es034700q. https://www.osti.gov/servlets/purl/835428.
@article{osti_835428,
title = {Identifying the sources of subsurface contamination at the Hanford site in Washington using high-precision uranium isotopic measurements},
author = {Christensen, John N. and Dresel, P. Evan and Conrad, Mark E. and Maher, Kate and DePaolo, Donald J.},
abstractNote = {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.},
doi = {10.1021/es034700q},
journal = {Environmental Science and Technology},
number = 12,
volume = 38,
place = {United States},
year = {Tue Mar 30 00:00:00 EST 2004},
month = {Tue Mar 30 00:00:00 EST 2004}
}
  • In the mid-1990s, a groundwater plume of uranium (U) was detected in monitoring wells in the B-BX-BY Waste Management Area 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, high-precision uranium isotopic analyses were conducted of samples of vadose zone contamination and of groundwater. The isotope ratios 236U/238U, 234U/238U, and 238U/235U are used to distinguish contaminant sources. On the basis of the isotopic data, the source of the groundwater contamination appears to bemore » 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 significant 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 the groundwater plume suggests an average U migration rate of {approx}0.7-0.8 m/day showing slight retardation relative a groundwater flow of {approx}1 m/day.« less
  • This report provides a description of uranium contamination in the subsurface at the Hanford Site's 300 Area. The principal focus is a persistence plume in groundwater, which has not attenuated as predicted by earlier remedial investigations. Included in the report are chapters on current conditions, hydrogeologic framework, groundwater flow modeling, and geochemical considerations. The report is intended to describe what is known or inferred about the uranium contamination for the purpose of making remedial action decisions.
  • The nitrogen and oxygen isotopic compositions of nitrate in pore water extracts from unsaturated zone core samples and groundwater samples indicate at least four potential sources of nitrate plumes in groundwaters at the USDOE Hanford Site in south-central Washington.
  • differences in uranium contributed by contaminated vadose sediments at two locations was investigated. At the BX tank farms, alkaline waste was accidentally released to a thick vadose zone. At the 300 Area, waste of variable acidity was released by unintended infiltration through the base of settling ponds. The waste form at the BX site was devoid of dissolved silica, and reacted with fluids trapped in microfractures to precipitate uranyl silicates. These secondary deposits were isolated physically from the vadose pore space and are not readily leached into pore fluids. At the 300 Area, the aluminum-rich waste precipitated on the surfacesmore » of sediment clasts, forming a microporous reservoir of solid-phase uranium. Interaction of this coating with water in transit through the vadose zone provides a persistent source of dissolved uranium to groundwater.« less