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The Extended Defect as a Mechanism for the Immobilization of HLW Species in Zirconolite, Perovskite and Hollandite

Published online by Cambridge University Press:  28 February 2011

T. J. White
T. J. White*
Affiliation:
School of Science, Griffith University, Nathan, Brisbane, QLD 4111, Australia
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Abstract

High resolution electron microscopy, analytical electron microscopy and selected area electron diffraction are used to establish the crystallochemical mechanisms by which simulated high level waste enters Synroc. It is shown that waste species are incorporated largely as a non-continuous solid solution. In other words, simple isomorphic substitution of waste elements in place of matrix cations, i.e. the classical continuous solid solution, does not operate (or is only significant at very low waste levels of radwaste). Usually, substitution is accompanied by the appearance of coherent extended defects which can take the form of antiphase boundaries, unit cell twinning (both mimetic and polysynthetic), or cation ordering. In this manner, a numb~er of closely related phases appear in response to variations in waste composition and loading. It is believed that the mechanism of structural modification will endow Synroc with considerable flexibility to respond to chemical changes in the wastestream. Other ceramic materials currently being evaluated as possible wasteforms (viz. sphene glass-ceramics and APO4 phosphates), are also likely to possess this capacity.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 50: Symposium STOCKHOLM – Scientific Basis for Nuclear Waste Management IX , 1985 , 283
Copyright
Copyright © Materials Research Society 1985

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