[en] This invention concerns a process for decontaminating very radioactive liquid effluents from the dissolving of magnesium alloy fuel element claddings in a nitric medium. This process enables the treated effluents to be discharged into the sea and, at the same time, to concentrate into a solid phase the very radioactive elements and, among them, the actinides and the fission products. This concerns the precipitation of the bodies contained in the cladding digesting solutions. These are produced, one after the other, with decanting of the precipitates until a liquid phase suitable for removal to the sea is achieved