Abdelmounaim Failali PhD defense

Thesis title:

Molecular Modelling of organic phases after Plutonium extraction

Summary of the thesis:

The nuclear fuel after its dwellings in reactor still bears a substantial amount of recoverable U and Pu. PUREX process (Plutonium Uranium Refining by Extraction), in which the results of the process are summarized in the following table: -Butyl-Phosphate) as an extractant molecule. As part of the studies carried out on fourth generation systems, these 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 these systems, the number of species involved in the long-term evolution of the system of long-time scales, the classical mechanics simulation is most relevant. 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 of developing a 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 forces to explore the dynamics of Pu (IV) in organic solvents and extracts from the statistical analysis.