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Aqueous Dissolution of Pyrochlore and Zirconolite in F--bearing Solutions

Published online by Cambridge University Press:  17 March 2011

Zhaoming Zhang ,
Huijun Li ,
Eric R. Vance ,
Terry McLeod  and
Nicholas Scales
Zhaoming Zhang
Affiliation:
Australian Nuclear Science and Technology Organisation, Lucas Heights, NSW 2234, Australia, zzx@ansto.gov.au
Huijun Li
Affiliation:
Australian Nuclear Science and Technology Organisation, Lucas Heights, NSW 2234, Australia, zzx@ansto.gov.au
Eric R. Vance
Affiliation:
Australian Nuclear Science and Technology Organisation, Lucas Heights, NSW 2234, Australia, zzx@ansto.gov.au
Terry McLeod
Affiliation:
Australian Nuclear Science and Technology Organisation, Lucas Heights, NSW 2234, Australia, zzx@ansto.gov.au
Nicholas Scales
Affiliation:
Australian Nuclear Science and Technology Organisation, Lucas Heights, NSW 2234, Australia, zzx@ansto.gov.au
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Abstract

We have studied the aqueous durability of pyrochlore-structured yttrium-titanate (Y2Ti2O7) and Nd/Al-bearing zirconolite [(Ca0.8Nd0.2)Zr(Ti1.8Al0.2)O7] in both neutral and acidic solutions, with and without the presence of 0.001 M of NaF. Scanning Electron Microscopy (SEM), X-ray Diffraction (XRD), X-ray Photoelectron Spectroscopy (XPS) and Atomic Force Microscopy (AFM) were used to characterize the composition, structure and morphology of the pyrochlore (Y2Ti2O7) and zirconolite surfaces, both before and after static dissolution testing at 90 and 150°C for four weeks. The leachates were also analyzed using Inductively Coupled Plasma Mass Spectrometry (ICP-MS) to estimate the individual elemental releases. The results show that the presence of F- ions only has a significant effect in acidic media on the dissolution behavior of pyrochlore and zirconolite. This detrimental effect is more pronounced for pyrochlore than zirconolite; the Y2Ti2O7 surface was replaced completely by alteration products after dissolution testing at 150°C for 4 weeks in acidic media with 0.001 M fluoride ions.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 824: Symposium CC – Scientific Basis for Nuclear Waste Management XXVIII , 2004 , CC8.22
Copyright
Copyright © Materials Research Society 2004

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