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Iodine Waste Forms: Calcium Aluminate Hydrate Analogues

Published online by Cambridge University Press:  26 February 2011

Dale R. Brown  and
Michael W. Grutzeck
Dale R. Brown
Affiliation:
Materials Research Laboratory, The Pennsylvania State University, University Park, PA 16802
Michael W. Grutzeck
Affiliation:
Materials Research Laboratory, The Pennsylvania State University, University Park, PA 16802
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Abstract

Phase relations in the system 3CaO·AI2O3-CaSO4-CaI2-H2O in equilibrium with excess water were established by means of room temperature bottle hydration of various bulk chemistries in the system. Starting with end members ettringite (3CaO·Al2O3·3CaSO4·32H2O) and tetracalcium aluminate monosulfate-12-hydrate (3CaO·Al2O3-CaSO4-12H2O), iodine-substituted analogue phases were synthesized which containe increasingly greater percentages of iodine. The iodine-substituted ettringite was found to be unstable whereas the iodine-substituted monosulfate formed readily. SEM, wet chemistry, IR, and x-ray diffraction characterization of the latter phase suggest that its formula is 3CaO·Al2O3·Ca(IO3)2·2H2O. Cement pellets containing this “Afm” iodine-substituted phase were subjected to a modified MCC-1 static leach test. Although the normalized iodine leach rate was relatively high when compared with AgI encapsulated in portland Type III cement, this same leach rate was approximately equal to the rates that have been reported for Ba(IO3)2, Ca(IO3)2, and Hg(IO3)2 in portland cement. The normalized iodine leach rate obtained also was found to be roughly comparable to that given for I-sodalite in cement. Diffusion is indicated as the primary leach mechanism, becoming dominant after the first three days of leaching.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 44: Symposium N – Scientific Basis for Nuclear Waste Management VIII , 1984 , 911
Copyright
Copyright © Materials Research Society 1985

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References

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