Abstract: This invention relates to a process for the treatment of organic wastes, resulting from the extraction of metal elements by a solvent of the phosphoric acid ester type in the presence or not of an organic diluent.These organic wastes result in particular from the extraction of metals in radiochemical separation plants, especially in plants for the reprocessing of irradiated nuclear fuels.The process according to this invention comprises the following three main steps:A. separation of the phosphoric acid ester from its organic diluent in such a way that the phosphate phase contains the degradation products and also the elements to be finally insolubilized;B. de-esterification of the phosphate, i.e. conversion of it into phosphoric acids on one side and organic compounds mainly consisting of hydrocarbons on the other side;C. solidification of the liquid radioactive phosphoric acids in the form of inorganic phosphates, which can eventually be incorporated into a suitable matrix material.