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Static dissolution tests of α-doped UO2 under repository relevant conditions: Influence of Boom Clay and α-activity on fuel dissolution rates

Published online by Cambridge University Press:  21 March 2011

Sonia Salah ,
Christelle Cachoir ,
Karel Lemmens  and
Norbert Maes
Sonia Salah
Affiliation:
Radioactive Waste and Restoration Division, SCK•CEN, Boeretang 200, B-2400 Mol, Belgium
Christelle Cachoir
Affiliation:
Radioactive Waste and Restoration Division, SCK•CEN, Boeretang 200, B-2400 Mol, Belgium
Karel Lemmens
Affiliation:
Radioactive Waste and Restoration Division, SCK•CEN, Boeretang 200, B-2400 Mol, Belgium
Norbert Maes
Affiliation:
Radioactive Waste and Restoration Division, SCK•CEN, Boeretang 200, B-2400 Mol, Belgium
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Abstract

Since reprocessing is no longer the reference policy in Belgium, studies on the direct disposal of spent fuel in a clay formation have gained increased interest in the last years. In order to determine to what extent the clay properties and the α-activity influence the dissolution kinetics of spent fuel for the long term disposal, static dissolution tests have been performed on 5 different types of α-doped UO2, representing a PWR fuel with a burn-up of 45 or 55 GWd · tHM−1 and fuel ages ranging between 150 and 90,000 years, in different Boom Clay (BC) media at room temperature and in an anoxic atmosphere for 90 to 720 days. The uranium activity in the clay fraction over time was found to be much higher than the U-activity in the leachates, which has been mainly ascribed to the high retention capacity of the BC. The average dissolution rate between 0 and 90 days obtained for the 5 types of α-doped UO2 were all found to be high and quite similar at ~263 µg · m−2 · d−1and a “longer-term” rate (181 to 720 days) ranging between zero and 15 µg · m−2· d−1. These results suggest that the activity of the fuels does not seem to have an effect on the UO2 dissolution rates under the considered test conditions. In order to study the partition/redistribution of U during UO2dissolution, sequential extraction experiments were performed. Results of the latter have provided a better mechanistic understanding of BC/spent fuel interaction processes as well as information on the role of the different minerals controlling the U-retention/immobilization.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 932: Symposium – Scientific Basis for Nuclear Waste Management XXIX , 2006 , 85.1
Copyright
Copyright © Materials Research Society 2006

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