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The Use of μCT and ESEM in the Study of the Osmosis-Induced Water Uptake by Eurobitum Bituminized Radioactive Waste

Published online by Cambridge University Press:  09 October 2012

An Mariën ,
Elie Valcke ,
Nele Bleyen ,
Maarten Van Geet  and
Martine Wevers
An Mariën*
Affiliation:
Waste and Disposal Expert Group, The Belgian Nuclear Research Centre (SCK•CEN), Boeretang 200, 2400 Mol, Belgium
Elie Valcke
Affiliation:
Waste and Disposal Expert Group, The Belgian Nuclear Research Centre (SCK•CEN), Boeretang 200, 2400 Mol, Belgium
Nele Bleyen
Affiliation:
Waste and Disposal Expert Group, The Belgian Nuclear Research Centre (SCK•CEN), Boeretang 200, 2400 Mol, Belgium
Maarten Van Geet
Affiliation:
The Belgian Agency for Radioactive Waste and Enriched Fissile Materials (ONDRAF/NIRAS), Kunstlaan 14, 1210 Brussel, Belgium
Martine Wevers
Affiliation:
Department of Metallurgy and Materials Engineering, Katholieke Universiteit Leuven, Kasteelpark Arenberg 44, 3001 Leuven, Belgium
*
*Corresponding author. E-mail: amarien@sckcen.be
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Abstract

Laboratory water uptake tests are performed at the Belgian Nuclear Research Centre SCK•CEN to obtain insight into the hydromechanical behavior of Eurobitum bituminized radioactive waste under geological disposal conditions. Small nonradioactive and radioactive Eurobitum samples are hydrated in restricted swelling conditions (i.e., nearly constant volume conditions and constant stress conditions). Microfocus X-ray computer tomography (μCT) proves to be a very suitable technique to follow up the ingress of water in the samples. μCT analyses demonstrate that, under the studied hydration conditions, the water uptake by Eurobitum samples is a diffusion controlled process. A characterization of the partially leached samples with environmental scanning electron microscopy (ESEM) shows that the hydration of salt crystals and the subsequent dilution of the salt solution result in an increase in pore size that is limited to a few tens of μm in restricted swelling conditions. The μCT and ESEM analyses allow improvement in the understanding of water uptake by Eurobitum in restricted swelling conditions. In this article we discuss the μCT and ESEM analyses of nonradioactive Eurobitum samples that were hydrated for 2 to 4 years at a constant stress of 1, 22, 33, and 44 bar or in nearly constant volume conditions.

Keywords

Eurobitum bituminized radioactive wasteosmosisNaNO3water uptakemicrofocus X-ray computer tomography (μCT)environmental scanning electron microscopy (ESEM)
Type
Materials Applications
Information
Microscopy and Microanalysis , Volume 18 , Issue 5 , October 2012 , pp. 1163 - 1180
Copyright
Copyright © Microscopy Society of America 2012

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