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Interpreting Uranyl Mineral Diffraction Patterns

Published online by Cambridge University Press:  02 July 2020

Edgar C. Buck
Edgar C. Buck*
Affiliation:
Argonne National Laboratory, 9700 South Cass Avenue, Argonne, IL, 60439
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Extract

Secondary phases that form during the corrosion of nuclear waste forms may influence both the rate of waste form dissolution and the release of radionuclides [1]. The identification of these phases is critical in developing models for the corrosion behavior of nuclear waste forms. In particular, the secondary uranyl (VI) minerals that form during waste form alteration may control uranium solubility and release of radionuclides incorporated into these phases [2].

The U6+ cation in uranyl minerals is almost always present as a linear (UO2)2+ ion [3]. This uranyl (Ur) ion is coordinated by four, five, or six anions (ϕ) in the equatorial plane resulting in the formation of square (Urϕ4), pentagonal (Urϕ5), and hexagonal (Urϕ6) bipyramids, respectively [3]. These bipyramid polyhedra may polymerize to form complex infinite sheet structures. The linking of Urϕ5 is observed in a number of uranyl minerals formed during waste glass and spent fuel corrosion [2,4], such as weeksite [Na,K(UO2)2(Si205)3*4H2O] and β-uranophane [Ca[(UO2)(SiO3OH)]2*5H2O].

Type
Microscopy of Ceramics and Minerals
Information
Microscopy and Microanalysis , Volume 4 , Issue S2: Proceedings: Microscopy & Microanalysis '98, Microscopy Society of America 56th Annual Meeting, Microbeam Analysis Society 32nd Annual Meeting, Atlanta, Georgia July 12-16, 1998 , July 1998 , pp. 560 - 561
Copyright
Copyright © Microscopy Society of America

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References

References:

[1]Radioactive Waste Forms for the Future, ed. Lutze, W. and Ewing, R. C. (North Holland, Amsterdam, 1988) 778 pages.Google Scholar
[2]Buck, E. C. et al., Scientific Basis for Nuclear Waste Management XXI, Davos, Switzerland, Sept 29-Oct 4 (1997).Google Scholar
[3]Burns, P. C. et al., Can. Mineral., 34 (1996) 845.Google Scholar
[4]Buck, E. C. et al., J. Nucl. Mater. 249 (1997) 70.CrossRefGoogle Scholar
[5]Finch, R. J., Eos, 78 (1997) p. S328.Google Scholar
[6]Walenta, K., Am. Miner. 59 (1974) 166.Google Scholar
[7] Work supported by the Environmental Management Science Program, US Department of Energy under contract W-31-109-ENG-38.Google Scholar