Evidence for Neptunium Incorporation into Uranium (VI) Phases

Abstract

This paper examines the ability of electron energy-loss spectroscopy (EELS) combined with transmission electron microscopy (TEM) to detect both low concentrations of Np in a U matrix and to provide evidence for incorporation of Np in U(VI) phases. The case for U(VI) secondary minerals acting as solubility-controlling phases for Np in repository performance assessment models has not been fully established. Direct evidence for incorporation, rather than sorption, continues to be difficult to obtain. Detection of Np with TEM-EELS is hampered by the occurrence of a plural (multiple) scattering event from the more abundant U atoms (U-M5 + U-(O4,5), that results in severe overlap on the Np-M5 edge at ~3665 eV. By examining the energy 'gap' between the Np-M5 and Np-M4 edges (184 eV), a method for observing Np independently of the plural scattering event has been established. Clear evidence of Np incorporation into synthetic studtite {(UO2)(O2)(H2O)2](H2O)2} and uranophane {Ca(UO2)2(SiO3OH)2(H2O)5} has been found with TEM-EELS. The EELS technique continues to remain an important tool for examining the potential for transuranic behavior in nuclear waste materials.

This is a preview of subscription content, access via your institution.

References

  1. 1.

    E. C. Buck, R. J. Finch, P. A. Finn and J. K. Bates, Mater. Res. Soc. Symp. Proc. 506 87–94 (1998).

    CAS  Article  Google Scholar 

  2. 2.

    F. Chen, P. C. Burns and R. C. Ewing, J. Nucl. Mater. 278 225–232 (2000).

    CAS  Article  Google Scholar 

  3. 3.

    F. Chen, P. C. Burns and R. C. Ewing, J. Nucl.Mater. 275 81–94 (1999).

    CAS  Article  Google Scholar 

  4. 4.

    C. W. Kim, D. J. Wronkiewicz, R. J. Finch and E. C. Buck, Mater. Res. Soc. Symp. Proc. 713 663–670 (2002).

    CAS  Google Scholar 

  5. 5.

    M. Douglas, S. B. Clark, S. Utsunomiya, R. C. Ewing, E. C. Buck and B. D. Hanson, Migration’03, Gyeongju (Kyongju), Korea, September 21-26, 2003.

  6. 6.

    P. C. Burns, K. M. Deely and S. Skanthakumar, Radiochimica Acta 92 151–154 (2004).

    CAS  Article  Google Scholar 

  7. 7.

    J. A. Fortner, R. J. Finch, J. A. Kropf and J. C. Cunnane, Nucl. Tech. (in press)

  8. 8.

    P. C. Burns, M. L. Miller and R. C. Ewing. J. Nucl. Mater. 245 1–9 (1997).

    CAS  Article  Google Scholar 

  9. 9.

    R. F. Egerton, private communication, 2002.

  10. 10.

    R. J. Finch and T. Murakami, Rev. Mineral. 38 91–180 (1999).

    CAS  Google Scholar 

  11. 11.

    D. J. Wronkiewicz, J. K. Bates, S. F. Wolf and E. C. Buck, J. Nucl. Mater. 238 78–95 (1996).

    CAS  Article  Google Scholar 

  12. 12.

    R. J. Finch, E. C. Buck, P. A. Finn and J. K. Bates, Mater. Res. Soc. Symp. Proc. 556 431–438 (1999).

    CAS  Article  Google Scholar 

  13. 13.

    K-A. Hughes Kubatko, K. B. Helean, A. Navrotsky and P. C. Burns, Science 302 1191–1193 (2003).

    CAS  Article  Google Scholar 

  14. 14.

    B. K. McNamara, E. C. Buck and B. D. Hanson, Mater. Res. Soc. Symp. Proc. 757 401–408 (2003).

    CAS  Google Scholar 

  15. 15.

    S. Skanthakumar, D. Gorman-Lewis, A. Locock, M. H. Chiang, M. P. Jensen, P. C. Burns, J. Fein, C. D. Jonah, K. Attenkofer and L. Soderholm, Mater. Res. Soc. Symp. Proc. 802 (2004) (in press)

Download references

Acknowledgments

The transmission electron microscopy work was performed at the Environmental Molecular Sciences Laboratory, a national scientific user facility sponsored by DOE's Office of Biological and Environmental Research and located at Pacific Northwest National Laboratory, operated for DOE by Battelle under Contract DE-AC06-76RL01830. We thank Drs. Jonathan Icenhower (PNNL and Jeffrey Fortner (ANL) for their insightful reviews.

Author information

Affiliations

Authors

Corresponding author

Correspondence to Edgar C. Buck.

Rights and permissions

Reprints and Permissions

About this article

Cite this article

Buck, E.C., Hanson, B.D., Friese, J.I. et al. Evidence for Neptunium Incorporation into Uranium (VI) Phases. MRS Online Proceedings Library 824, 538–543 (2004). https://doi.org/10.1557/PROC-824-CC9.3

Download citation