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Retrograde Solubilities of Source Term Phases

Published online by Cambridge University Press:  03 September 2012

William M. Murphy
William M. Murphy*
Affiliation:
Center for Nuclear Waste Regulatory Analyses, Southwest Research Institute, 6220 Culebra Road, San Antonio, TX 78228–0510 USA
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Abstract

Natural analog, experimental, and thermodynamic studies indicate that theproperties of secondary uranyl minerals are likely to control the sourceterm for U and other radioéléments incorporated in these phases in theproposed Yucca Mountain repository. Thermodynamic calculations using datafrom the 1992 NEA data base indicate an increase in the equilibrium constantfor schoepite dissolution from 103.1 to 104.8 withdecreasing temperature from 100° to 25°C, i.e., retrograde solubility.Enthalpies for mineral transformation reactions that consume protons andrelease cations are typically negative, suggesting that solubilities ofother uranyl phases such as uranophane increase more than that of schoepitewith decreasing temperature. Solubilities of mineral phases associated withspent nuclear fuel will be initially relatively low under the elevatedrepository temperature regime. As the temperature of the repositorydecreases due to radioactive decay and heat dissipation, source term mineralsolubilities increase. The rate of release of U and other species iscontrolled by a series of processes: transport of oxidants and flux ofwater; oxidative dissolution of spent fuel; uranyl mineral precipitation;uranyl mineral dissolution or transformation; and radionuclide transport.Decreasing diffusion and reaction rates and increasing uranyl mineralsolubilities with decreasing temperature may lead to a change with time fromsolubility to transport or reaction rate as a source term controllingmechanism. Preservation of large quantities of uranyl minerals formed byoxidation of uraninite and radiometrie ages of secondary uranophane at thenatural analog site at Peña Blanca indicate that oxidative alteration ofuraninite was fast relative to transport of U away from the deposit. Thesuccessive formation of schoepite and uranophane in natural settings whereuraninite has been oxidized may represent a paragenesis reflectingincreasing temperature or increasing incorporation of environmentalcomponents. In contrast, diminishing temperature conditions in a repositorysource area could lead to the reverse sequence of mineral formation.

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Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 465: Symposium II – Scienfific Basis for Nuclear Waste Management XX , 1996 , 713
Copyright
Copyright © Materials Research Society 1997

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References

REFERENCES

1. Murphy, W.M., and Pearcy, E.C., in Scientific Basis for Nuclear Waste Management XV, edited by Sombret, C.G. (Mater. Res. Soc. Proc. 257, Pittsburgh, PA, 1992) pp. 521–527.Google Scholar
2. Finn, P.A., Hoh, J.C., Wolf, S.F., Slater, S.A., and Bates, J.K., in Scientific Basis for Nuclear Waste Management XIX, edited by Murphy, W.M. and Knecht, D.A. (Mater. Res. Soc. Proc. 412, Pittsburgh, PA, 1996) pp. 75–81; Radiochim. Acta 74 pp. 65–71.Google Scholar
3. Grenthe, I., Fuger, J., Konings, R.J.M., Lemire, R.J., Muller, A.B., Nguyen-Trung, C., and Wanner, H., Chemical Thermodynamics of Uranium, edited by Wanner, H., and Forest, I. (Elsevier Science Publishers B.V., Amsterdam, North-Holland, 1992).Google Scholar
4. Tasker, I.R., O'Hare, P.A.G., Johnson, B.M., Johnson, G.K., Cordfunke, E.H.P., Can. J. Chem. 66 (1988) pp. 620–625.10.1139/v88-106Google Scholar
5. Nguyen, S.N., Silva, R.J., Weed, H.C., and Andrews, J.E. Jr., J. Chem. Thermo. 24 (1992) pp. 259–276.10.1016/S0021-9614(05)80155-7Google Scholar
6. Casas, I., Bruno, J., Cera, E., Finch, R.J., and Ewing, R.C., in Kinetic and Thermodynamic Studies of Uranium Minerals Assessment of the Long-Term Evolution of Spent Nuclear Fuel, (Swedish Nuclear Fuel and Waste Management Company, Technical Report 94–16, Stockholm, Sweden, 1994) p. 73.Google Scholar
7. Moll, H., Geipel, G., Matz, W., Bernhard, G., and Nitsche, H., Radiochim. Acta 74 pp. 3–7 (1996).10.1524/ract.1996.74.special-issue.3Google Scholar
8. Holland, H.D. and Brush, L.H., in Proceedings of the Conference on High-Level Radioactive Solid Waste Forms, edited by Casey, L.A., Nuclear Regulatory Commission, NUREG/CP-005, 1979, p. 597–615.Google Scholar
9. Finch, R.J., Hawthorne, F.C., and Ewing, R.C., in Scientific Basis for Nuclear Waste Management XIX, edited by Murphy, W.M. and Knecht, D.A. (Mater. Res. Soc. Proc. 412, Pittsburgh, PA, 1996) pp. 361–368.Google Scholar
10. Weast, R.C., CRC Handbook of Chemistry and Physics, edited by Astle, M.J., and Beyer, W.H., (CRC Press Inc., Boca Raton, Florida, 1988).Google Scholar
11. Based on the EQ3/6 data base data0.com.R2, Lawrence Livermore National Laboratory (1995).Google Scholar
12. Frondel, C., Systematic Mineralogy of Uranium and Thorium, (U.S. Geological Survey Bulletin 1064. Washington, DC: U.S. Government Printing Office, 1958).Google Scholar
13. Gray, W.J., Leider, H.R., and Steward, S.A., J. Nuc. Mater. 190 (1992) pp. 46–52.10.1016/0022-3115(92)90074-UGoogle Scholar
14. Pearcy, E.C., Prikryl, J.D., Murphy, W.M., and Leslie, B.W., App. Geochem. 9 (1994) pp. 713–732.10.1016/0883-2927(94)90030-2Google Scholar
15. Pickett, D.A., Prikryl, J.D., Murphy, W.M., and Pearcy, E.C., Submitted to App. Geochem. (1996).Google Scholar
16. Broxton, D.E., Bish, D.L., and Warren, R.G., Clay Clay Min. 35 (1987) pp. 89–110.10.1346/CCMN.1987.0350202Google Scholar
17. Einziger, R.E., Thomas, L.E., Buchanan, H.C., and Stout, R.B., J. Nuc. Mater. 190 (1992) pp. 53–60.10.1016/0022-3115(92)90075-VGoogle Scholar
18. Wronkiewicz, D.J., Bates, J.K., Gerding, T.J., Veleckis, E., and Tani, B.S., J. Nuc. Mater. 190 (1992) pp. 107–127.10.1016/0022-3115(92)90081-UGoogle Scholar
19. Wilson, C.N., in Scientific Basis for Nuclear Waste Management XIV, edited by Abrajano, T.A. Jr., (Mater. Res. Soc. Proc 212, Pittsburgh, PA, 1991) pp. 197–204.Google Scholar
20. Cachoir, Ch., Guittet, M.J., Gallien, J.-P., and Trocellier, P., Radiochim. Acta 74 (1996) pp. 59–63.10.1524/ract.1996.74.special-issue.59Google Scholar
21. Taylor, R., Lemire, R.J., and Wood, D.D., inHigh Level Radioactive Waste Management, (Amer. Nuc. Soc., La Grange Park, IL, 1992) pp. 1, 442–1, 448.Google Scholar