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Carbonaceous substances in Oklo reactors; analogue for permanent deep geologic disposal of anthropogenic nuclear waste

David J. Mossman, Francois Gauthier-Lafaye, Adriana Dutkiewicz and Ralf Bruening
Carbonaceous substances in Oklo reactors; analogue for permanent deep geologic disposal of anthropogenic nuclear waste (in Deep geologic repositories, Norbert T. Rempe (editor))
Reviews in Engineering Geology (2008) 19: 1-13

Abstract

Seventeen known natural nuclear fission reactors sustained criticality in hydro-thermally altered low-grade metasedimentary rocks of the Proterozoic Franceville Series ca. 1968+ or -50 Ma. About half of these reactors contain only traces of carbonaceous substances, and in these, fission products including strontium, cesium, rubidium, and boron migrated away from the reactors and were nearly completely lost. The others are rich in carbonaceous substances, particularly solid, partly graphitized bitumen and kerogen, as well as liquid oil in fluid inclusions. In these carbonaceous substance-rich reactors,uranium and fissiogenic isotopes are held in uraninite, which became enclosed in liquid bitumen during criticality and was subsequently fixed when the bitumen solidified. The preservation of liquid oil in fluid inclusions for over two billion years suggests that time is not a parameter that controls petroleum degradation. This is viewed as a potentially important aspect in engineered nuclear waste containment projects. Likewise, because of the hydrophobic qualities of solid bitumen, its inducible plasticity, and its capability of conversion to nonflammability, it deserves serious consideration for use in permanent deep geologic disposal sites. Indications are that at Oklo, Gabon, carbonaceous substances have combined to restrain the migration of radionuclides and limit the extent to which migration occurs. The strength of the Oklo analogue lies in the fact that it represents more extreme conditions than those likely to be met in a deep geologic repository. The carbonaceous substance-rich reactors of Oklo stand as time-tested analogues for anthropogenic nuclear waste containment strategies.


ISSN: 0080-2018
EISSN: 2169-799X
Coden: GAEGA4
Serial Title: Reviews in Engineering Geology
Serial Volume: 19
Title: Carbonaceous substances in Oklo reactors; analogue for permanent deep geologic disposal of anthropogenic nuclear waste
Title: Deep geologic repositories
Affiliation: Mount Allison University, Department of Geography, Sackville, NB, Canada
Affiliation: 1403 North Country Club Circle, Carlsbad, NM, United States
Pages: 1-13
Published: 2008
Text Language: English
Publisher: Geological Society of America (GSA), Boulder, CO, United States
ISBN: 978-0-8137-4119-2
References: 80
Accession Number: 2009-010021
Categories: Engineering geologyIgneous and metamorphic petrology
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. geol. sketch map, 2 plates, sect.
S04°00'00" - N02°30'00", E08°30'00" - E14°30'00"
Secondary Affiliation: CNRS. Centre de Geochimie de la Surface, FRA, FranceUniversity of Sydney, AUS, Australia
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute.
Update Code: 200906
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