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Title: Colloid Formation at Waste Plume Fronts

Abstract

Highly saline and caustic tank waste solutions containing radionuclides and toxic metals have leaked into sediments at U. S. Department of Energy (DOE) facilities such as the Hanford Site (Washington State). Colloid transport is frequently invoked to explain migration of radionuclides and metals in the subsurface. To understand colloid formation during interactions between highly reactive fluids and sediments and its impact on contaminant transport, we simulated tank waste solution (TWS) leakage processes in laboratory columns at ambient and elevated (70 C) temperatures. We found that maximum formation of mobile colloids occurred at the plume fronts (hundreds to thousands times higher than within the plume bodies or during later leaching). Concentrations of suspended solids were as high as 3 mass%, and their particle-sizes ranged from tens of nm to a few {micro}m. Colloid chemical composition and mineralogy depended on temperature. During infiltration of the leaked high Na{sup +} waste solution, rapid and completed Na{sup +} replacement of exchangeable Ca{sup 2+} and Mg{sup 2+} from the sediment caused accumulation of these divalent cations at the moving plume front. Precipitation of supersaturated Ca{sup 2+}/Mg{sup 2+}-bearing minerals caused dramatic pH reduction at the plume front. In turn, the reduced pH caused precipitation of othermore » minerals. This understanding can help predict the behavior of contaminant trace elements carried by the tank waste solutions, and could not have been obtained through conventional batch studies.« less

Authors:
; ; ; ; ;
Publication Date:
Research Org.:
Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
Sponsoring Org.:
USDOE Director. Office of Science. Office of Biological and Environmental Research (US)
OSTI Identifier:
841063
Report Number(s):
LBNL-56059
R&D Project: G42401; TRN: US200513%%282
DOE Contract Number:
AC03-76SF00098
Resource Type:
Journal Article
Resource Relation:
Journal Name: Environmental Science and Technology; Journal Volume: 38; Journal Issue: 22; Other Information: Submitted to Environmental Science and Technology: Volume 38, No.22; Journal Publication Date: 11/15/2004; PBD: 22 May 2004
Country of Publication:
United States
Language:
English
Subject:
58 GEOSCIENCES; CATIONS; CHEMICAL COMPOSITION; COLLOIDS; ELEMENTS; LEACHING; LIQUID WASTES; MINERALOGY; PLUMES; PRECIPITATION; RADIOISOTOPES; SEDIMENTS; TANKS; TRACE AMOUNTS; TRANSPORT; WASTES

Citation Formats

Wan, Jiamin, Tokunaga, Tetsu K., Saiz, Eduardo, Larsen, Joern T., Zheng, Zuoping, and Couture, Rex A.. Colloid Formation at Waste Plume Fronts. United States: N. p., 2004. Web. doi:10.1021/es0492384.
Wan, Jiamin, Tokunaga, Tetsu K., Saiz, Eduardo, Larsen, Joern T., Zheng, Zuoping, & Couture, Rex A.. Colloid Formation at Waste Plume Fronts. United States. doi:10.1021/es0492384.
Wan, Jiamin, Tokunaga, Tetsu K., Saiz, Eduardo, Larsen, Joern T., Zheng, Zuoping, and Couture, Rex A.. Sat . "Colloid Formation at Waste Plume Fronts". United States. doi:10.1021/es0492384. https://www.osti.gov/servlets/purl/841063.
@article{osti_841063,
title = {Colloid Formation at Waste Plume Fronts},
author = {Wan, Jiamin and Tokunaga, Tetsu K. and Saiz, Eduardo and Larsen, Joern T. and Zheng, Zuoping and Couture, Rex A.},
abstractNote = {Highly saline and caustic tank waste solutions containing radionuclides and toxic metals have leaked into sediments at U. S. Department of Energy (DOE) facilities such as the Hanford Site (Washington State). Colloid transport is frequently invoked to explain migration of radionuclides and metals in the subsurface. To understand colloid formation during interactions between highly reactive fluids and sediments and its impact on contaminant transport, we simulated tank waste solution (TWS) leakage processes in laboratory columns at ambient and elevated (70 C) temperatures. We found that maximum formation of mobile colloids occurred at the plume fronts (hundreds to thousands times higher than within the plume bodies or during later leaching). Concentrations of suspended solids were as high as 3 mass%, and their particle-sizes ranged from tens of nm to a few {micro}m. Colloid chemical composition and mineralogy depended on temperature. During infiltration of the leaked high Na{sup +} waste solution, rapid and completed Na{sup +} replacement of exchangeable Ca{sup 2+} and Mg{sup 2+} from the sediment caused accumulation of these divalent cations at the moving plume front. Precipitation of supersaturated Ca{sup 2+}/Mg{sup 2+}-bearing minerals caused dramatic pH reduction at the plume front. In turn, the reduced pH caused precipitation of other minerals. This understanding can help predict the behavior of contaminant trace elements carried by the tank waste solutions, and could not have been obtained through conventional batch studies.},
doi = {10.1021/es0492384},
journal = {Environmental Science and Technology},
number = 22,
volume = 38,
place = {United States},
year = {Sat May 22 00:00:00 EDT 2004},
month = {Sat May 22 00:00:00 EDT 2004}
}
  • Insoluble plutonium- and americium-bearing colloidal particles formed during simulated weathering of a high-level nuclear waste glass. Nearly 100 percent of the total plutonium and americium in test ground water was concentrated in these submicrometer particles. These results indicate that models of actinides in ground water, underestimate the potential for radionuclide release into the environment. A colloid-trapping mechanism may be necessary for a waste repository to meet long-term performance specifications.
  • For a series configurations of high-level waste (HLW) storage in a salt repository, gamma transport and deposition have been calculated together with the heating of the salt around waste containers. These time-dependent data were used to calculate colloid growth due to irradiation using a theory by Jain and Lidiard. The results show that by a proper choice of storage parameters the colloid fraction can be limited to a few percent. Overpacking by a few centimeters of steel will reduce the amount to < 1%. With the methods described a safe and economic design of HLW containers for final disposal willmore » be possible.« less
  • No abstract prepared.
  • No abstract prepared.
  • Solutions of high pH, ionic strength, and aluminum concentration have leaked into the subsurface from underground waste storage tanks at the Hanford Reservation in Washington State. Here, we test the hypothesis that these waste solutions alter and dissolve the native minerals present in the sediments and that colloidal (diameter < 2 m) feldspathoids form. We reacted Hanford sediments with simulated solutions representative of Hanford waste tanks. The solutions consisted of 1.4 or 2.8 mol/kg NaOH, 0.125 or 0.25 mol/kg NaAlO4, and 3.7 mol/kg NaNO3 and were contacted with the sediments for a period of 25 or 40 days at 50more » C. The colloidal size fraction was separated from the sediments and characterized in terms of mineralogy, morphology, chemical composition, and electrophoretic mobility. Upon reaction with tank waste solutions, native minerals released Si and other elements into the solution phase. This Si precipitated with the Al present in the waste solutions to form secondary minerals, identified as the feldspathoids cancrinite and sodalite. The solution phase was modeled with the chemical equilibrium model GMIN for solution speciation and saturation indices with respect to sodalite and cancrinite. The amount of colloidal material in the sediments increased upon reaction with waste solutions. At the natural pH found in Hanford sediments (pH 8) the newly formed minerals are negatively charged, similar to the unreacted colloidal material present in the sediments. The formation of colloidal material in Hanford sediments upon reaction with tank waste solutions is an important aspect to consider in the characterization of Hanford tank leaks and may affect the fate of hazardous radionuclides present in the tank waste.« less