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Theses in progress

Aging mechanism of uranium in lacustrine sedimentary deposits: spectroscopic approaches and geochemical modeling

Host laboratory: Research Laboratory on the Future of the Radioactive Sites Pollution (LELI)​

Beginning of the thesis: October 2018

Student name: Pierre LEFEBVRE

Subject description

Uranium is a toxic radionuclide whose dispersion in the environment must be limited. As such, understanding the mechanisms by which uranium is immobilized in reducing environments is an essential step in the remediation of contaminated sites. In addition, the reactivity of the chemical forms of uranium recently identified in current sediments raises questions about the conditions for using this element as a paleo-redox marker.

The objective of this thesis work is to strengthen our knowledge on the evolution of uranium speciation in anoxic natural environments based on the study of sedimentary records dating back several hundreds to thousands of years. This will be achieved by coupling a spectroscopic approach using synchrotron radiation and an isotopic approach on dated cores.

This work will provide new results on the long-term evolution of uranium's behaviour in a reducing environment, information that is essential to better assess the safety of low-level nuclear waste storage sites. At the same time, the work will place strong constraints on the acquisition and conservation of the isotopic signal recorded by uranium during sediment diagenesis.


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