Résumé
Understanding the structure of actinide ions in organic solution is of particular inter-est in the development of effective solvent extraction separations for waste remedia-tion in advanced nuclear fuel cycles. In complex organic phases, actinide-ligand bonds are diverse and versatile. Several complexes coexist and structural infor-mations frequently lack because the few experimental data are available are difficult to understand. Quantum chemistry and Classic Molecular Dynamic methods, may be associated with these experimental data, to improve the data analysis and more particularly help in the Extended X-ray Absortion Fine Structure (EXAFS) signal in-terpretation.This work shows some example of EXAFS and theoretical calculations combinations applied to understand polydispersity in organic solutions. In one scenario, plu-tonium EXAFS spectra were measured as a function of the chemical conditions while the equivalent ab initio EXAFS spectra were computed from quantum chemis-try calculations (both structural parameters and Debye-Waller factors derived from this calculation). It was then applied to elucidate the structures of plutonium(IV) with a series of N,N-dialkyl amide and carbamide ligands [1, 2, 3], as well as co-extracted uranium/technetium [4]. The second study focus on molecular dynamics and EXAFS to support uranyl speciation in organic solution. [5, 6] Finally, this work aim to promote the fruitful collaboration between actinides X-ray spectroscopies and theoretical models to structurally describe actinides ions in com-plex systems.