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Traçage de la mobilité des radionucléides naturels en milieu sédimentaire profond à l'aide des déséquilibres radioactifs (234U/238U): Application aux formations mésozoïques de l'Est du Bassin de Paris

Abstract : This thesis forms part of the geological investigations undertaken by the French agency for nuclear waste management, ANDRA, around the Meuse/Haute-Marne Underground Research Laboratory (URL) located in the Eastern part of the Paris Basin in order to evaluate the feasibility of high-level radioactive waste repository in deep argilite formations. The aim of the study is to examine the radionuclide migration in the deep Callovo-Oxfordian target argilite layer and its surrounding low- permeability Bathonian and Oxfordian limestone formations in order to assess the long term confining capacities of the sedimentary series. This study is based on measurement of radioactive disequilibria within U-series by Multiple-Collector Inductively Coupled Plasma Mass Spectrometry (MC-ICP-MS). The high precision and accuracy achieved allowed to demonstrate the 234U/238U radioactive equilibrium in the Callovo-Oxfordian argilites. This result shows the uranium immobility in the target formation and provides a strong evidence for the current chemical stability and closure of the system for uranium and most probably for the other actinides. This is a fundamental result with respect to the problematic of disposal of high level radioactive waste in deep geological formation since it provides a in situ indication of the confining capacities of the clayey target formation in the current settings. Conversely, (234U/238U) disequilibria are systematically observed within zones, located in the surrounding carbonate formations, that are characterized by pressure dissolution structures (stylolites or dissolution seams). These disequilibria provide evidence for a discrete uranium relocation during the last two million years in the vicinity of stylolitic structures. This is a surprising result since it is generally supposed that these deep, low permeability, compact formations behave as closed system at the time scale of the U-series.
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https://tel.archives-ouvertes.fr/tel-00004257
Contributor : Pierre Deschamps <>
Submitted on : Wednesday, January 21, 2004 - 12:35:24 AM
Last modification on : Wednesday, October 14, 2020 - 3:59:08 AM
Long-term archiving on: : Friday, April 2, 2010 - 8:02:20 PM

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  • HAL Id : tel-00004257, version 1

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Pierre Deschamps. Traçage de la mobilité des radionucléides naturels en milieu sédimentaire profond à l'aide des déséquilibres radioactifs (234U/238U): Application aux formations mésozoïques de l'Est du Bassin de Paris. Géochimie. Université Paris Sud - Paris XI, 2003. Français. ⟨tel-00004257⟩

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