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Dissolution Mechanisms of the Perovskite and Hollandite Phases in the Synroc Assemblage

Published online by Cambridge University Press:  21 February 2011

S. Nyhra ,
D.K. Pham ,
R.St.C. Smart  and
P.S. Turner
S. Nyhra
Affiliation:
Division of Science and Technology, Griffith University, Nathan, Qid. 4111, Australia
D.K. Pham
Affiliation:
Division of Science and Technology, Griffith University, Nathan, Qid. 4111, Australia
R.St.C. Smart
Affiliation:
School of Chemical Technology, South Australian Institute of Technology Ingle Farm, S.A. 5098, Australia
P.S. Turner
Affiliation:
Division of Science and Technology, Griffith University, Nathan, Qid. 4111, Australia
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Abstract

Perovskite (CaTiO3 )and hollandite ([BaxCsy,][(Ti,Al) 3+ Ti4 + ]016) 2x+y 8-2x-y are two of the three major phases of the Synroc titanate mineral assemblage. The chemical durabilities of these two phases have been investigated by solution analysis, surface analysis and electron microscopy. While a detailed model of the durability of perovskite has evolved from previous work, much less is known about the mechanisms which affect the durability of hollandite. The present investigations show that, for single-phase hollandite, selective extraction by ion exchange of Cs+ and Ba 2+ does not play a significant role. On the other hand, total dissolution of the network does seem to occur as a result of base-catalysed hydrolysis. Also, complexation and precipitation of Al and TI species in solution has the effect of driving the system to low pH. These results can be correlated with the more complete model for dissolution of perovskite in order to infer the overall effects of aqueous attack on the Synroc HLW solid.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 176: Symposium U – Scientific Basis for Nuclear Waste Management XIII , 1989 , 249
Copyright
Copyright © Materials Research Society 1990

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References

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