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Influence of Carbonate on Uranium Solubility in the WIPP

Published online by Cambridge University Press:  24 May 2012

Jean-Francois Lucchini
Affiliation:
Los Alamos National Laboratory, Earth and Environmental Sciences Division, 115 N. Main, Carlsbad, NM 88220, U.S.A
Sally Ballard
Affiliation:
Carlsbad Environmental Monitoring and Research Center, New Mexico State University, 1400 University Drive, Carlsbad, NM 88220, U.S.A.
Hnin Khaing
Affiliation:
URS, Washington Safety Management Solutions, 1400 University Drive, Carlsbad, NM 88220, U.S.A.
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Abstract

In the performance assessment (PA) for the Waste Isolation Pilot Plant (WIPP), the solubility of uranium (VI) was conservatively set at 10-3 M for all expected WIPP conditions, including the potential and likely effects of carbonate complexation [1]. Under WIPP-relevant conditions, long-term experiments were performed to establish the uranium (VI) solubility limits in WIPP-simulated brine over a broad range of pCH+ values [7.5-12.5] and to evaluate the contribution of carbonate complexation and hydrolysis to uranium (VI) speciation. Data obtained in carbonate-free ERDA-6 brine, a simulated WIPP brine, were reported earlier [2]. In the absence of carbonate, uranium solubility approached 10-7 M at the expected pCH+ in the WIPP (~ 9.5). In the presence of a significant amount of carbonate (millimole levels), recent experimental results showed that uranium (VI) concentrations will not exceed 10-4M. This measured solubility limit is an order of magnitude lower than the uranium solubility value currently used in the WIPP PA [3]. A small effect of borate complexation was found in the pCH+ range [7.5-10]. At pCH+ ≥ 10, hydrolysis overwhelmed carbonate effects, and no amphoteric effect was observed.

Type
Articles
Copyright
Copyright © Materials Research Society 2012

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References

REFERENCES

1. U.S. Environmental Protection Agency (EPA). Teleconference with U.S. Department of Energy (DOE), Sandia National Laboratories (SNL), and Los Alamos National Laboratory (LANL) re: Change in U(VI) Solubility Assumption to a Concentration to 1 mM. 2 March 2005.Google Scholar
2. Lucchini, J.F., Khaing, H., Reed, D.T. Uranium (VI) Solubility in Carbonate-free ERDA-6 Brine. Scientific Basis for Nuclear Waste Management XXXIV, edited by Smith, K.L., Kroeker, S., Uberuaga, B., Whittle, K.R.. Material Research Society Symposium Proceedings, Volume 1265, 21 (2010) – LAUR-10–1817.Google Scholar
3. U.S. Department of Energy (DOE). 2009. Title 40 CFR Part 191 Subparts B and C Compliance Recertification Application for the Waste Isolation Pilot Plant. Appendix SOTERM-2009. DOE/WIPP 2009-3424. Carlsbad, NM: Carlsbad Field Office.Google Scholar
4. Neck, V. and Kim, J.I., Radiochim. Acta 89, 1 (2001).Google Scholar
5. Lucchini, J.F., Borkowski, M., Richmann, M.K., Ballard, S. and Reed, D.T., Journal of Alloys and Compounds 444/445, 506 (2007).Google Scholar
6. Lucchini, J.F., Khaing, H., Borkowski, M., Richmann, M.K. and Reed, D.T., Report LA-UR-10–00497, 2010.Google Scholar
7. Rai, D., Felmy, A.R., Juracich, S.P. and Rao, L.F., Report SAND94–1949, 1995.Google Scholar
8. Borkowski, M., Lucchini, J.F., Richmann, M.K. and Reed, D.T., Report LA-14360, 2009.Google Scholar
9. Lucchini, J.F., Richmann, M.K., Borkowski, M., Uranium (VI) Solubility in Carbonate-free WIPP Brine, to be submitted to Radiochimica Acta.Google Scholar