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Evaluation of thermally converted silicotitanate waste forms

Published online by Cambridge University Press:  10 February 2011

Y. SU ,
M. L. Balmer ,
L. Wang ,
B. C. Bunker ,
M. Nyman ,
T. Nenoff  and
A. Navrotsky
Y. SU
Affiliation:
Pacific Northwest National Laboratory, P. 0. Box 999, Richland, WA 99352, ya.su@pnl.gov
M. L. Balmer
Affiliation:
Pacific Northwest National Laboratory, P. 0. Box 999, Richland, WA 99352, ya.su@pnl.gov
L. Wang
Affiliation:
Pacific Northwest National Laboratory, P. 0. Box 999, Richland, WA 99352, ya.su@pnl.gov
B. C. Bunker
Affiliation:
Sandia National Labs, P.O. Box 5800, Albuquerque, NM 87185
M. Nyman
Affiliation:
Sandia National Labs, P.O. Box 5800, Albuquerque, NM 87185
T. Nenoff
Affiliation:
Sandia National Labs, P.O. Box 5800, Albuquerque, NM 87185
A. Navrotsky
Affiliation:
Dept. of Chemical Engineering and Material Science, University of California, Davis, CA 95616
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Abstract

Crystalline silicotitanate ion exchangers are highly selective for separating Cs from Narich waste streams. However, use of these ion exchangers for removal of Cs from radioactive tank waste will result in large volumes of secondary wastes. Thermal conversion of silicotitanates produces a durable waste form with reduced volumes up to 40%. Leach tests (MCC-l and PCT) have shown that Cs leach rates of IE-91 1-Na (heat treated at 900°C for an hour) are extremely low, ranging from 0.1 to lwt% Cs loss in Cs fraction release, or 10-1 to 10-8g/m2day in normalized Cs mass loss. These are several orders of magnitude lower than that of borosilicate glass. In order to understand the interplay between the structure and high Cs durability, X-ray diffraction, 133Cs NMR, and thermogravimetric analysis have been used to identify phase(s) responsible for trapping Cs in these silicotitanates. Results indicate that Cs is likely to be contained in a crystalline silicate phase.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 556: Symposium QQ – Scientific Basis for Nuclear Waste Management XXII , 1999 , 77
Copyright
Copyright © Materials Research Society 1999

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References

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