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Geochemical behaviour of host phases for actinides and fission products in crystalline ceramic nuclear waste forms

By
Gregory R. Lumpkin
Gregory R. Lumpkin
Cambridge Centre for Ceramic Immobilisation, Department of Earth Sciences, University of Cambridge, Downing Street, Cambridge CB2 3EQ, UKAustralian Nuclear Science and Technology Organisation, PMB 1, Menai, NSW 2234, Australia
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Katherine L. Smith
Katherine L. Smith
Australian Nuclear Science and Technology Organisation, PMB 1, Menai, NSW 2234, Australia
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Reto Gieré
Reto Gieré
Department of Earth and Atmospheric Sciences, Purdue University, West Lafayette, IN 47907-1397, USA Institut für Mineralogie, Petrologie und Geochemie, Universität Freiburg, Albertstrasse 23B, D-79104 Freiburg, Germany gregl@esc.cam.ac.uk
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C. Terry Williams
C. Terry Williams
Department of Mineralogy, The Natural History Museum, Cromwell Road, London SW7 5BD, UK
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Published:
January 01, 2004

Abstract

A number of polyphase or single-phase ceramic waste forms have been considered as options for the disposal of nuclear waste in geological repositories. Of critical concern in the scientific evaluation of these materials is their performance in natural systems over long periods of time (e.g., 103 to 106 years). This paper gives an overview of the aqueous durability of the major titanate host phases for actinides (e.g., Th, U, Np, Pu, Cm) and important fission products (e.g., Sr and Cs) in alternative crystalline ceramic waste forms. These host phases are compared with reference to some basic acceptance criteria, including the long-term behaviour determined from studies of natural samples. The available data indicate that zirconolite and pyrochlore are excellent candidate host phases for actinides. These structures exhibit excellent aqueous durability, crystal chemical flexibility, high waste loadings, and well-known processing conditions. Although both pyrochlore and zirconolite become amorphous due to alpha-decay processes, the total volume swelling is only 5–6% and there is no significant effect of radiation damage on aqueous durability. Hollandite also appears to be an excellent candidate host phase for radioactive Cs isotopes. Brannerite and perovskite, on the other hand, are more prone to alteration in aqueous fluids and have a lower degree of chemical flexibility. With the exception of hollandite, many of the properties of these potential host phases have been confirmed through studies of natural samples.

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Contents

Geological Society, London, Special Publications

Energy, Waste and the Environment: a Geochemical Perspective

R. Gieré
R. Gieré
Universität Freiburg, Germany
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P. Stille
P. Stille
ULP-École et Observatoire des Sciences de la Terre-CNRS, Strasbourg, France
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Geological Society of London
Volume
236
ISBN electronic:
9781862394841
Publication date:
January 01, 2004

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