[en] The room temperature ionic liquids are potentially interesting for the treatment of nuclear fuel. But the knowledge of the behaviour of actinides in the ionic liquids is fragmented because these solvents are new, young and many. In a first time, the ionic liquids [BuMeIm][Tf₂N] and [MeBu₃N][Tf₂N] have been studied in α and γ irradiation with different atmosphere (argon and air) and concentrations of water. ESIMS, NMR and liquid chromatography coupled ESI-MS analysis demonstrate a multitude of degradation products but in very small quantities. This good radiolytic stability makes it a major advantage for the studies of actinides. In a second time, the interaction between an anionic complex of uranium (UCl₆^2-) and the cation of the ionic liquid and too the study of the hydrolysis of An⁴⁺ (An uranium, neptunium, plutonium) were conducted in different ionic liquids ([MeBu₃N][Tf₂N], [BuMe₂Im][Tf₂N] and [BuMeIm][Tf₂N]). The experimental results showed that the intensity of these interactions between UCl₆^2- anion and the ionic liquid cation depends on the latter and follows the order: MeBu₃N⁺ ∼ BuMe₂Im⁺ ≤BuMeIm⁺. In addition, the results obtained by UV/Vis spectroscopy showed that the reaction of hydrolysis in the ionic liquids is slow, secondary compared to the oxidation or the disproportionation and that the amount of water in ionic liquid must be relatively large compared to the concentration of actinide. The results from the coupling of different analytical techniques (NMR, mass spectrometry, UV-Visible, Infra-red, Electrochemistry..) have allowed a first approach in the understanding of the actinides in the room temperature ionic liquids. (author)