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Microstructure and Composition of Synroc Samples Crystallized From a CaCeTi2O7 Chemical System: HRTEM/EELS Investigation

Published online by Cambridge University Press:  10 February 2011

Huifang Xu ,
Yifeng Wang ,
Robert L. Putnam ,
Jose Gutierriez  and
Alexandra Navrosky
Huifang Xu
Affiliation:
Transmission Electron Microscopy Laboratory, Department of Earth and Planetary Sciences, The University of New Mexico, Albuquerque, New Mexico 87131. E-mail: [email protected]
Yifeng Wang
Affiliation:
Sandia National Laboratories, 115 North Main Street, Carlsbad, New Mexico 88220 E-mail: [email protected]
Robert L. Putnam
Affiliation:
Los Alamos National Laboratory, Los Alamos, New Mexico 87545
Jose Gutierriez
Affiliation:
Dept. of Chemical Engineering and Materials Science, University of California at Davis, One Shields Avenue, Davis, CA 95616-8779
Alexandra Navrosky
Affiliation:
Dept. of Chemical Engineering and Materials Science, University of California at Davis, One Shields Avenue, Davis, CA 95616-8779
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Abstract

Ce-pyrochlore, CaCeTi2O7 is a chemical analogue for CaPuTi2O7, which is a proposed ceramic endmember waste form for the disposition of excess weapon-usable plutonium in geological repositories. Ce-pyrochlore was synthesized by firing and annealing in air a mixture of CeO2, TiO2, and CaCO3 with a stoichiometry of CaCeTi2O7. The annealed products contain Cepyrochlore, Ce-bearing perovskite, CeO2, and minor CaO. The mixture annealed at a temperature of 1140 °C contains more pyrochlore phase than that annealed at a higher temperature (1300 °C), indicating that a low temperature condition favors the formation of the Ce-pyrochlore. The Ca/Ce ratio of the pyrochlore is slightly lower than the ideal ratio (one). Electron energy-loss spectroscopy results show that there is a small fraction of Ce3+ present in the pyrochlore. Ce present in perovskite is dominated by Ce3. High-resolution TEM images show that the boundary between pyrochlore and perovskite is semi-coherent. No glassy phases were observed at the grain boundary between pyrochlore and perovskite, nor between CeO2and pyrochlore. It is postulated, based on the presence of trivalent Ce in the Ce-pyrochlore, that neutron poisons such as trivalent cation Gd would be incorporated into the CaPuTi2O7 phase

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 608: Symposium QQ – Scientific Basis for Nuclear Waste Management XXIII , 1999 , 461
Copyright
Copyright © Materials Research Society 2000

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References

REFERENCES

[1] Dosch, R. G., Headley, T. J., Northrup, C. J., and Hlava, P. F., Sandia National Laboratories Report, Sandia 82-2980, 84pp (1982).Google Scholar
[2] Ringwood, A. E., Kesson, S. E., Reeve, K. D., Levins, D. M., and Ramm, E. J., Synroc. In Lutze, W. and Ewing, R. C. eds., “Radioactive Waste Forms for the Future.” North-Holland, Amsterdam, p. 233 (1988).Google Scholar
[3] Jostsons, A., Vance, E. R., Mercer, D. J., Oversby, V. M., In Murakami, T. and Ewing, R. C. eds. “Scientific Basis for Nuclear Waste Management XVIII.” MRS, Pittsburgh, p. 775 (1995).Google Scholar
[4] Ewing, R.C., Weber, W. J., and Lutze, W., In Merz, E. R. and Walter, C. E. eds., “Disposal of Excess Weapons Plutonium as Waste.” NATO ASI Series, Kluwer Academic Publishers, Dordrecht, p. 65 (1996).Google Scholar
[5] Weber, W. J., Ewing, R. C., and Lutze, W., In Murphy, W. M. and Knecht, D. A. eds., “Scientific Basis for Nuclear Waste Management XIX.” Materials Research Society, Pittsburgh, p. 25(1996).Google Scholar
[6] Bakel, A. J., Buck, E. C., and Ebbinghaus, B., In “Plutonium Future - The Science.” Los Alamos National Laboratories, p. 135 (1997).Google Scholar
[7] Begg, B. D., and Vance, E. R., In Gray, W. J. and Triay, I. R. eds. “Scientific Basis for Nuclear Waste Management XX.” MRS, Pittsburgh, p. 333 (1997).Google Scholar
[8] Begg, B. D., Vance, E. R., Day, R. A., Hambley, M., and Conradson, S. D. In Gray, W. J. and Triay, I. R. eds. “Scientific Basis for Nuclear Waste Management XX.” MRS, Pittsburgh, p. 325 (1997).Google Scholar
[9] Buck, E. C., Ebbinghaus, B., Bakel, A. J., and Bates, J. K., Characterization of a plutonium-bearing zirconolite-rich Synroc. In Gray, W. J. and Triay, I. R. eds. “Scientific Basis for Nuclear Waste Management XX.” MRS, Pittsburgh, p. 1259 (1997).Google Scholar
[10] Vance, E. R., MRS Bulletin, vol. XIX, 28 (1994).Google Scholar
[11] Vance, E. R., Jostsons, A., Stewart, M. W. A., Day, R. A., Begg, B. D., Hambley, M. J., Hart, K. P., and Ebbinghaus, B. B., In “Plutonium Future - The Science.” Los Alamos National Laboratories, p. 19 (1997).Google Scholar
[12] Vance, E. R., Hart, K. P., Day, R. A., Carter, M. L., Hambley, M., Blackford, M. G., and Begg, B. D., In Gray, W. J. and Triay, I. R. eds., “Scientific Basis for Nuclear Waste Management XX.” MRS, Pittsburgh, p. 341 (1997).Google Scholar
[13] Putnam, R. L., Navrotsky, A., Woodfield, B. F., Boerio-Goates, J., and Shapiro, J. L., J. Chem. Thermochem., 31, 229–243 (1999).Google Scholar
[14] Woodfield, B. F., Boerio-Goates, J., Shapiro, J. L., Putnam, R. L., and Navrotsky, A., J. Chem. Thermochem., 31, 245 (1999).Google Scholar
[15] Putnam, R. L., Navrotsky, A., Woodfield, B. F., Shapiro, J. L., Steven, R. and Boerio-Goates, J., Scientific Basis for Nuclear Waste Management XXII. MRS, Pittsburgh. p. 11(1999).Google Scholar
[16] Xu, H., and Wang, Y., Scientific Basis for Nuclear Waste Management XXII. MRS, Pittsburgh. p. 47 (1999).Google Scholar
[17] Xu, H., and Wang, Y., Journal of Nuclear Materials, 275, 216 (1999).Google Scholar
[18] Wang, Y., and Xu, H., Scientific Basis for Nuclear Waste Management XXIII. MRS (Same as this volume, (2000), Pittsburgh.Google Scholar