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3D modelling of thermal and fluid transfers around a natural fission reactor (Oklo, Gabon)

Benoit Gerard, Jean-Jacques Royer, Christian Le Carlier de Veslud and Maurice Pagel
Modelisation 3D des transferts thermiques et fluides autour d'un reacteur naturel de fission (Oklo, Gabon)
Bulletin de la Societe Geologique de France (May 1998) 169 (3): 459-466

Abstract

Numerical modelling is used to quantify heat and mass transfers around the Oklo site. A 3D model of a reactor, at decametric scale, built with the GOCAD software shows that the functioning of the reactor acts as a powerful but local thermal perturbation. This perturbation increases the temperature within a range of 50 to 250 degrees C, according to assumed heat production, with a spatial extent less than 50 m. The steady state regime is reached very rapidly, in less than 100 years. The heat dissipation is essentially conductive, the reactor inducing only weak fluid movements. A forced convection model has been also investigated, where fluids come from basin scale circulations. It shows that, in the range of the studied filtration velocities, temperatures are not significantly affected by these circulations. Nevertheless, they induce an asymmetry between upstream and downstream parts of the flow. Assuming low permeability, the high temperature increase could have caused local fluid overpressures, which could lead to the development of a radial hydraulic fracturation near the reactor, as has been observed around the reactor 10.


ISSN: 0037-9409
EISSN: 1777-5817
Serial Title: Bulletin de la Societe Geologique de France
Serial Volume: 169
Serial Issue: 3
Title: Modelisation 3D des transferts thermiques et fluides autour d'un reacteur naturel de fission (Oklo, Gabon)
Translated Title: 3D modelling of thermal and fluid transfers around a natural fission reactor (Oklo, Gabon)
Affiliation: Centre de Recherches Petrographiques et Geochimiques, Vandoeuvre-les-Nancy, France
Pages: 459-466
Published: 199805
Text Language: French
Summary Language: English
Publisher: Societe Geologique de France, Paris, France
References: 27
Accession Number: 1999-014826
Categories: General geochemistry
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 2 tables, geol. sketch maps
Secondary Affiliation: Universite Paris XI, FRA, France
Country of Publication: France
Secondary Affiliation: GeoRef, Copyright 2022, American Geosciences Institute.
Update Code: 199906
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