[en] Before considering a future use of ionic liquids at ambient temperature with actinides, a previous study confirming their stability at strong irradiation doses is required. The ionic liquid used in this study is the methyl-tributyl-ammonium bis-triflimide, composed of the MeBu₃N⁺ cation and of the (CF₃SO₂)₂N^- anion. The radiolysis resistance of this ionic liquid has been studied under two different atmospheres (argon and air) with different water quantities (dry, contacted with water and half-water). For obtaining absorbed doses between 0 and 2 MGy, these samples have been bombarded with a cesium 137 source in the Marcel irradiator. The study of the degradation compounds has been made by electro-spray ionization mass spectrometry. NMR has been used too in this study. The obtained results are explained here. (O.M.)