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On the Oxidation of Uraninite From Natural Reactor Cores

Published online by Cambridge University Press:  10 February 2011

Daqing Cui ,
Trygve Eriksen  and
Ulla-Britt Eklund
Daqing Cui
Affiliation:
Department of Chemistry, Nuclear Chemistry, Royal Institute of Technology, S-100 44 Stockholm, Sweden
Trygve Eriksen
Affiliation:
Department of Chemistry, Nuclear Chemistry, Royal Institute of Technology, S-100 44 Stockholm, Sweden
Ulla-Britt Eklund
Affiliation:
Studvik Nuclear AB, S-611 82 Nykölping, Sweden
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Abstract

Natural nuclear reactors provide unique evidence in helping to understand the processes that might occur over long timescales in radioactive waste disposal sites. In the presented work, the extent and kinetics of oxidation of core material from the Oklo-Bangombé natural reactors are investigated. The X-ray powder diffraction analysis shows that the uraninites core samples from the Bangombé Reactor and Oklo Reactor 2. and Oklo Reactor 13 have the same unit-cell parameters as synthetic UO2.25. A significant amount of fourmarierite, Pb(UO2)4O3(OH)4 4H2O, was identified in the core samples from two shallow reactors Bangombé and Oklo 2, but not in the deeper reactor Oklo 13. The results of U(IV)/U(IV) measurements indicate that the extent of oxidative weathering of shallow reactors (Bangombé and Oklo 2) is greater than for the deeper reactor Oklo 13. Evaporable organic compounds found in the uraninite inclusion containing “bitumen” at the edge of Okelobondo Reactor (400 °C) and in the black shale immediately above the Bangombé Reactor (260 °C) may work as a reducing buffer or/and a hydrophobic water shield to depress the oxidative dissolution of the uraninite cores.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 556: Symposium QQ – Scientific Basis for Nuclear Waste Management XXII , 1999 , 817
Copyright
Copyright © Materials Research Society 1999

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References

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