Treatment of spent ion exchange resins: Comparison between hydrothermal and acid leaching processes

Ion exchange resins (IERs) are used to treat radioactive liquid effluents from nuclear industry. Today, the management of spent IERs as nuclear waste is an issue. We propose here the use of hydrothermal and leaching treatments to transfer radioactivity from organic solid phase to aqueous phase, in order to connect to existing outlet systems. Co, Cs, Sr and Eu were chosen as α and βγ radionuclide surrogates. The efficiency of the treatment was assessed in terms of extraction yields and contaminant concentrations in wastewaters. The highest extraction efficiencies of 90–100 % were obtained in supercritical water in batch and semi-dynamic mode in the presence of oxidant. In subcritical conditions, yields adequate are lower but suitable with the disposal criteria for the residual solid waste. Complete extraction was also achieved by leaching with ethylenediaminetetraacetic acid solutions. The optimal choice between all these processes is therefore discussed with regards to the requirements of effluent treatment plant including post-treatment steps such as coprecipitation and advanced oxidation.