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Technetium and Neptunium Reactions in Basalt/Groundwater Systems

Published online by Cambridge University Press:  26 February 2011

R. E. Meyer
Affiliation:
Oak Ridge National Laboratory, Oak Ridge, TN 37831
W. D. Arnold
Affiliation:
Oak Ridge National Laboratory, Oak Ridge, TN 37831
A. D. Kelmers
Affiliation:
Oak Ridge National Laboratory, Oak Ridge, TN 37831
J. H. Kessler
Affiliation:
Oak Ridge National Laboratory, Oak Ridge, TN 37831
R. J. Clark
Affiliation:
Oak Ridge National Laboratory, Oak Ridge, TN 37831
J. S. Johnson Jr
Affiliation:
Oak Ridge National Laboratory, Oak Ridge, TN 37831
G. C. Young
Affiliation:
Oak Ridge National Laboratory, Oak Ridge, TN 37831
F. I. Case
Affiliation:
Oak Ridge National Laboratory, Oak Ridge, TN 37831
C. G. Westmoreland
Affiliation:
Oak Ridge National Laboratory, Oak Ridge, TN 37831
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Abstract

Sorption isotherms and apparent concentration limits for Tc(VII) and Np(V) for a variety of groundwater/basalt systems were determined using Grande Ronde basalt samples representative of the Hanford Site candidate high-level waste repository. Under oxic redox conditions (air present), little or no sorption of technetium was observed; neptunium exhibited low to moderate sorption ratios. Under anoxic redox conditions (oxygen-free), low to moderate sorption of technetium was often observed, but the extent of sorption was highly dependent upon the groundwater composition and the method of pretreatment (if any) of the basalt. Sorption isotherms for technetium under reducing redox conditions (hydrazine added) indicate an apparent concentration limit of approximately 10−6 mol/L Tc. No apparent concentration limit was found for neptunium for concentrations in groundwater up to.∼10−6 mol/L and 8 × 10−7 mol/L under oxic and reducing (hydrazine added) redox conditions, respectively.

Valence control and valence analysis experiments suggest that the sorption or precipitation of Tc and Np from groundwater in the presence of basalt may result from a heterogeneous reaction occurring on the surface of the basalt. One of the critical factors of this reduction reaction appears to be the accessibility of the reactive ferrous iron component of the basalt. The laboratory simulation of groundwater redox conditions representative of the repository environment through the use of solution phase redox reagents is of questionable validity, and information obtained by such experimental methods may not be defensible for site performance assessment calculations. Anoxic experiments conducted in an argon-filled glove box appear better suited for the laboratory simulation of in situ redox conditions.

Type
Research Article
Copyright
Copyright © Materials Research Society 1985

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References

1. Palmer, D. A. and Meyer, R. E., J. Inorg. Nucl. Chem. 43, 2979 (1981).Google Scholar
2. Salter, P. F., Ames, L. L., McGarrah, J. E., The Sorption Behavior of Selected Radionuclides on Columbia River Basalts, RHO-BWI-LD-48 (1981).Google Scholar
3. Meyer, R. E., Arnold, W. D., Case, F., Shiao, S. Y., and Palmer, D. A., Valence Effects on Adsorption - A Preliminary Assessment of the Effects of Valence State Control on Sorption Measurements, NUREG/CR-2863- ORNL–5978 (1983).Google Scholar
4. Barney, G. S., Radionuclide Reactions with Groundwater and Basalts from Columbia River Basalt Formations, RHO-SA-217 (1981).Google Scholar
5. Bondietti, E. A. and Francis, C. W., Science 203, 1337 (1979).Google Scholar
6. Salter, P. F. and Jacobs, G. K., “Evaluation of Radionuclide Transport: Effect of Radionuclide Sorption and Solubility,” in Scientific Basis for Radioactive Waste Management – Lutze, V, Werner, Ed., pp. 801810 (1982).Google Scholar
7. Early, T. O., Drewes, D. R., Jacobs, G. K., and Routson, R. C., Geochemical Controls on Radionuclide Releases from a Nuclear Waste Repository in Basalt: Estimated Solubilities for Selected Elements, RHO-BW-ST-39P (1982).Google Scholar
8. Meyer, R. E., Arnold, W. D., Case, F. I., Valence Effects on the Sorption of Nuclides on Rocks and Minerals, NUREG/CR-3389- ORNL-5978 (1984).Google Scholar
9. Kelmers, A. D., Clark, R. J., Cutshall, N. H., Jacobs, G. K., Johnson, J. S., Kessler, J. H., and Meyer, R. E., Evaluation of Radionuclide Geochemical Information Developed by DOE High-Level Nuclear Waste Repository Site Projects, NUREG/CR-3730- ORNL/TM-9109 (1984).Google Scholar
10. Kelmers, A. D., Kessler, J. H., Arnold, W. D., Meyer, R. E., Cutshall, N. H., and Jacobs, G. K., Progress in Evaluation of Radionuclide Geochemical Information Developed by DOE High-Level Nuclear Waste Repository Site Projects: Report for October-December 1983, NUREG/CR-3851, Vol.1- ORNL/TM-9191/VI (1984).Google Scholar
11. Kelmers, A. D., Kessler, J. H., Arnold, W. D., Meyer, R. E., Cutshall, N. H., Jacobs, G. K., Lee, S. Y., and Clark, R. J., Progress in Evaluation of Radionuclide Geochemical Information Developed by DOE High-Level Nuclear Waste Repository Site Projects: Report for January-March 1984, NUREG/CR-3851, Vol.2- ORNL/TM-9191/V2 (1984).Google Scholar
12. Salter, P. F., Personal Communication, Rockwell Hanford Operations, Richland, Washington, January, 1984.Google Scholar
13. Serne, R. J., WISAP Task 4 Contractor Information Meeting Proceedings, PNL-SA-6957 (1980).Google Scholar
14. Barney, G. S., FY 1981 Annual Report Radionuclide Sorption on Basalt Interbed Materials, RHO-BW-ST-35P (1982).Google Scholar
15. Allard, B., “Actinide and Technetium Solubility Limitations in Groundwater of Crystalline Rocks,” in Scientific Basis for Nuclear Waste Management - VII, McVay, G. L., Ed., pp. 219226 (1984).Google Scholar