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Characterization of Th Carbonate Solutions Using XAS and Implications for Thermodynamic Modeling

Published online by Cambridge University Press:  03 September 2012

N. J. Hess ,
A. R. Felmy ,
D. Rai  and
S. D. Conradson
N. J. Hess
Affiliation:
Pacific Northwest National Laboratory, Richland WA 99352
A. R. Felmy
Affiliation:
Pacific Northwest National Laboratory, Richland WA 99352
D. Rai
Affiliation:
Pacific Northwest National Laboratory, Richland WA 99352
S. D. Conradson
Affiliation:
Los Alamos National Laboratory, Los Alamos NM 89545
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Abstract

The chemical behavior of actinide elements in tank solutions, in soil, and in groundwater is dependent upon the chemical species that form when aqueous solutions come in contact with the actinide compounds. In particular the chemical speciation of the reduced actinide oxidation states (III and IV) are important, for example, to DOE waste tank processing and, more generally, to nuclear waste disposal issues. Predicting the solubility of the actinides in these solutions requires identification of the strong aqueous complexes, such as carbonates and organic chelating agents, that can form in aqueous solution.

Previous speciation work has often relied on indirect techniques such as potentiometric titrations or solubility measurements. Recent XAS experiments determine directly the speciation of the Th carbonato species of seven solutions under a range of carbonate concentrations and pH conditions. The presence of the pentacarbonato complex is confirmed and the complex's stability at low carbonate concentrations is determined. These experimental results support a proposed thermodynamic model that describes the solubility of Th(IV) hydrous oxide in the aqueous Na+-HCO3--CO32--OH--ClO4--H2O system extending to high concentrations at 25°C. This model is relatively simple in that only two aqueous species are included Th(OH)3CO3- and Th(CO3)56-.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 465: Symposium II – Scienfific Basis for Nuclear Waste Management XX , 1996 , 729
Copyright
Copyright © Materials Research Society 1997

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References

REFERENCES

1. Rai, D., Felmy, A.R., Moore, D.A., and Mason, M.J., Mat. Res. Soc. Symp. Proc. 353, p. 1143 (1995).Google Scholar
2. Clark, D.L., Conradson, S.D., Ekberg, S.A., Hess, N.J., Janeky, D.R., Neu, M.P., Palmer, P.D., and Tait, C.D., New Journal of Chemistry, 20, p. 211 (1996).Google Scholar
3. Joao, A., Bigot, S., and Fromage, F., Bull. Soc. Chim. France 1, p. 42 (1987).Google Scholar
4. Osthols, E., Bruno, J., and Grenthe, I., Geochim Cosmochim Acta 58, p. 613 (1994).10.1016/0016-7037(94)90492-8Google Scholar
5. McMaster, W.H., Kerr del Grande, N., Mallett, J.H., and Hubbell, J.H., Calculation of X-Ray Cross Sections, Univ of Calif, Livermore, 1969, 350p.Google Scholar
6. Voliotis, S. and Rimsky, A., Acta Cryst. B31, p. 2612 (1975).10.1107/S0567740875008308Google Scholar
7. Rehr, J.J., Zabinsky, S.I., and Albers, R.C., Phys. Rev. Let. 69, p. 3397 (1992).10.1103/PhysRevLett.69.3397Google Scholar
8. Zabinsky, S.I., Rehr, J.J., Ankudinov, A., Albers, R.C., and Eller, M.J., Phys. Rev. B. 52, p. 2995 (1995).10.1103/PhysRevB.52.2995Google Scholar
9. Clark, D.L., Hobart, D.E., and Neu, M.P., Chemical Reviews 95, p. 25 (1995).Google Scholar
10. Pratopo, M.I., Moriyama, H., and Higahi, K., Radiochim. Acta. 51, p. 27 (1990).Google Scholar
11. Yamaguchi, T., Sakamoto, Y., Ohnuki, T., In Migration 'P5; Charleston SC, (1993).Google Scholar