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Neptunium Substitution into the Structure of Alpha-U3O8

Published online by Cambridge University Press:  11 February 2011

Robert J. Finch  and
A. Jeremy Kropf
Robert J. Finch
Affiliation:
Chemical Technology Division, Argonne National Laboratory, Argonne, IL 60439. finch@cmt.anl.gov
A. Jeremy Kropf
Affiliation:
Chemical Technology Division, Argonne National Laboratory, Argonne, IL 60439. finch@cmt.anl.gov
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Abstract

We synthesized powder samples of NpxU3-xO8 with x between 0 and 0.33. Analyses of solids by x-ray absorption spectroscopy indicate that Np occupies U sites and is predominantly tetravalent. Lattice parameters vary smoothly as a function of Np concentration. The a and b parameters (parallel to structural sheets in U3O8) depend strongly on Np concentration below x = 0.3; however, extrapolation of a least-squares fit up to x = 1 (the maximum value of x if Np is tetravalent) suggests little expected change in a or b for values of x greater than approximately 0.5. The c cell parameter (perpendicular to the plane of the sheets) shows relatively small dependence on Np concentration for all values of x. The a and b cell parameters vary in a complementary fashion, such that the a-b plane and unit-cell volumes remain nearly constant for small x (below ∼0.2). The projected volume increase at higher x may be accommodated by expansion along c; the maximum volume expansion for NpxU3-xO8 is projected to be less than 0.2% up to x = 1. Our results demonstrate that NpxU3-xO8 forms a homogeneous solid solution up to (at least) x = 0.33, and that a complete solid solution may exist between α-U3O8 and NpU2O8; however, the structure of NpU2O8 may resemble that of β-U3O8.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 757: Symposium II – Scientific Basis for Nuclear Waste Management XXVI , 2002 , II3.3
Copyright
Copyright © Materials Research Society 2003

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References

REFERENCES

1. U.S. Department of Energy, Office of Civilian Radioactive Waste Management: Total System Performance Assessment for a Repository at Yucca Mountain. (December 1998) (available at www.ymp.gov).Google Scholar
2. Efurd, D.W., Runde, W., Banar, J.C., Janecky, D.R., Kaszuba, J.P., Palmer, P.D., Roensch, F.R., and Tait, D., Environ. Sci. Technol. 32, 3893 (1998).Google Scholar
3. Wronkiewicz, D.J. and Buck, E.C., in Uranium: Mineralogy, Geochemistry and the Environment, edited by Burns, P.C. and Finch, R.J.. (Reviews in Mineralogy 38, Mineralogical Society of America, Washington, D.C., 1999) p. 475.Google Scholar
4. Loopstra, B.O., J. Appl. Crystallogr. B 26, 94 (1970).Google Scholar
5. Kropf, A.J., Finch, R.J., Conner, C.J., Karanfil, C., Chapman, L.D., Segre, C., Terry, J., Advanced Photon Source Activity Report, 2000 (ANL-01/03) www.aps.anl.gov/apsar2000/kropfaj4.pdf Google Scholar
6. Zhong, Z., Chapman, D., Bunker, B., Bunker, G., Fischetti, R., and Segre, C., J. Synchrotron Rad. 6, 212 (1999).Google Scholar
7. Loopstra, B.O., Acta Crystallogr. 17, 651 (1964).Google Scholar
8. Ankudinov, A.L. and Rehr, J.J., Phys. Rev. B 62, 2437 (2000).Google Scholar
9. Newville, M., Ravel, B., Haskel, D., Rehr, J. J., Stern, E. A., and Yacoby, Y., Physica B 208&209, 154 (1995).Google Scholar
10. Burns, P.C., Ewing, R.C. and Hawthorne, F.C., Can. Mineral. 35, 1551 (1997).Google Scholar
11. Loopstra, B.O., Acta Crystallogr. B 26, 656 (1970).Google Scholar