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Book Chapter

The geochemical behaviour of Tc, Np and Pu in spent nuclear fuel in an oxidizing environment

By
Edgar C. Buck
Edgar C. Buck
Pacific Northwest National Laboratory, Richland, Washington, 99352, USA edgar.buck@pnl.gov
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Brady D. Hanson
Brady D. Hanson
Pacific Northwest National Laboratory, Richland, Washington, 99352, USA edgar.buck@pnl.gov
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Bruce K. McNamara
Bruce K. McNamara
Pacific Northwest National Laboratory, Richland, Washington, 99352, USA edgar.buck@pnl.gov
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Published:
January 01, 2004

Abstract

Spent fuel from commercial nuclear reactors consists mainly of uranium oxide. However, the changes that occur during reactor operations have a profound effect on chemical and physical properties of this material. Heat build-up in the fuel pellet during reactor operations can cause redistribution of fission products. The fission products may aggregate in one of three types of precipitates; gaseous, metallic, or oxide, depending on the burn-up and in-core treatment. Radiation damage and variations in fission and neutron capture yields across the fuel pellets lead to Pu enrichment and increased porosity with increasing burn-up. A more porous surface may make the fuel more susceptible to oxidative dissolution. As the level of actinides and fission products increases, the fuel may become more resistant to oxidation. These changes may limit the usefulness of natural uraninite (UO2) analogues for predicting the geological behaviour of spent fuel disposed in a high-level waste (HLW) repository. In this Chapter, an overview of spent fuel microstructure, radiolytic effects, and alteration processes is presented. Evidence for Np incorporation into U6+ phases, the nature of Pu surface precipitates on spent fuel, and evidence for the preferential removal of 4d-metals from ε-particles in corroded spent fuel is discussed. Understanding the potential mechanisms of radionuclide attenuation through sorption and/or incorporation requires techniques with both high spatial resolution and excellent elemental sensitivity.

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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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