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Durability of Pu-doped Titanate and Zirconate Ceramics Designed for Pu Immobilisation

Published online by Cambridge University Press:  21 March 2011

Y. Zhang ,
K.P. Hart ,
B.D. Begg ,
E.A. Keegan ,
A.R. Day ,
A. Brownscombe  and
M.W.A. Stewart
Y. Zhang
Affiliation:
Australian Nuclear Science and Technology Organisation, PMB 1, Menai, NSW 2234, Australia
K.P. Hart
Affiliation:
Australian Nuclear Science and Technology Organisation, PMB 1, Menai, NSW 2234, Australia
B.D. Begg
Affiliation:
Australian Nuclear Science and Technology Organisation, PMB 1, Menai, NSW 2234, Australia
E.A. Keegan
Affiliation:
Australian Nuclear Science and Technology Organisation, PMB 1, Menai, NSW 2234, Australia
A.R. Day
Affiliation:
Australian Nuclear Science and Technology Organisation, PMB 1, Menai, NSW 2234, Australia
A. Brownscombe
Affiliation:
Australian Nuclear Science and Technology Organisation, PMB 1, Menai, NSW 2234, Australia
M.W.A. Stewart
Affiliation:
Australian Nuclear Science and Technology Organisation, PMB 1, Menai, NSW 2234, Australia
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Abstract

Ceramics rich in pyrochlore-structured titanate and fluorite-structured zirconate phases designed for surplus Pu immobilisation, with and without process impurities, have been leach tested at 90°C in deionised water. The zirconates consist mainly of a defect-fluorite with secondary impurity-containing phase-powellite/scheelite (when sintered in Ar but not when sintered in air), a spinel or magnetoplumbite type phase, a glass forming silicate and a secondary U-rich phase (when sintered in air with added impurities). The pyrochlore-rich baseline titanate ceramic consists of pyrochlore, brannerite and Hf-rutile. When impurities are added zirconolite and a silicate glass are also present. The pyrochlore-rich titanate with 5 wt% of impurities sintered at 1300°C is highly durable. A well-densified zirconate version without impurities has comparable elemental releases to those of the titanate ceramic but a zirconate with 5 wt% of impurities sintered at 1400°C in air or Ar shows much higher U and Ca releases than the titanate ceramic. Sintering atmospheres, changing from Ar to air, can influence Pu and U release rates up to an order of magnitude. High Ga releases from zirconates with impurities show that the secondary phase containing Ga is not durable. The higher processing temperature and the apparent inability to incorporate many impurity elements suggest that zirconates are not as flexible as titanates in respect of processing conditions and aqueous durability.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 713: Symposium JJ – Scientific Basis for Nuclear Waste Management XXV , 2002 , JJ6.1
Copyright
Copyright © Materials Research Society 2002

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References

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