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Mobility of Chelated Radionuclides in Engineered Concrete Barriers

Published online by Cambridge University Press:  01 January 1992

Craig A. Dicke  and
Robert W. Smith
Craig A. Dicke
Affiliation:
Idaho National Engineering Laboratory, P.O. Box 1625, Idaho Falls, ID 83415-2110
Robert W. Smith
Affiliation:
Idaho National Engineering Laboratory, P.O. Box 1625, Idaho Falls, ID 83415-2110
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Abstract

Concrete is a major component in many low-level radioactive waste (LLW) disposal facilities. The use of concrete is widespread because of its physical and structural properties and because it provides geochemical control on metal and radionuclide releases. Organic compounds are often disposed with radionuclides in LLW disposal facilities. Interactions between radionuclides and chelating agents must be evaluated to estimate mobility of radionuclides in concrete vaults. This paper quantifies the effects of two common organic components [citric acid and ethylenediaminetetraacetic acid (EDTA)] on radionuclide mobility in concrete barriers by using equilibrium geochemical calculations.

Equilibrium speciation calculations indicate that some radionuclides are chelated in groundwater (pH 7) but are destabilized in the highly alkaline (pH 13) concrete pore fluids. Radionuclides complexed by EDTA and citrate are replaced by calcium in the concrete pore fluids. In addition, the citrate nuclide complex reacts to form uncomplexed citrate in concrete pore fluids. The chemical performance of concrete LLW disposal facilities should not be compromised by small amounts of chelating agents disposed with some radionuclides. However, EDTA may form significant nickel and cobalt complexes above the pH important in the long-term service life of concrete barriers.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 294: Symposium V – Scientific Basis for Nuclear Waste Management XVI , 1992 , 279
Copyright
Copyright © Materials Research Society 1993

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References

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