Soutenance de thèse de Abdelmounaim Failali

Titre de la thèse:

Molecular Modeling of organic phases relevant for Plutonium extraction

Résumé de la thèse:

Résumé de thèse : The nuclear fuel after its dwell time in reactor still bears a substantial amount of recoverable U and Pu. In France, in order to reduce of nuclear waste, these elements are currently recovered by the PUREX process (Plutonium Uranium Refining by Extraction), in which U and Pu are first selectively extracted and separated thanks to liquid-liquid extraction technics using TBP (Tri-Butyl-Phosphate) as extractant molecule.  As part of the studies carried out on 4th generation systems, separation processes are currently under development in CEA for the multi-recycling of these recoverable materials. For the understanding and improvement of these separation processes, a microscopic description of the molecular organization of the actinides and separation ligands in the organic and aqueous phases is needed. To this end, molecular-level simulations can help gaining insights into the coordination, dynamics and mobility of these elements in the two phases and across the interface.  Regarding the large size of those systems, the numerous species involved and since we are aiming at describing the temporal evolution of the system in a long-time scale, the classical mechanic simulation appears to be the most relevant tool.  However, the reliability of the MD results depends on the quality of the force fields (FF), the analytical description of the intermolecular energy potentials. The first part of my Ph.D. consists in developing a FF model describing, at first, the interaction between Pu, HNO3, counter-ion and solvent molecules. The parameters of the various analytical terms, such as repulsion, polarization, charge transfer, are adjusted to reproduce highly accurate quantum chemical data. The second part will be dedicated to the use of these force fields to explore the dynamical behavior of the Pu(IV) in organic solvent and extracts relevant quantities from the statistical analysis.