Utilization of a mixed-bed column for the removal of iodine from radioactive process waste solutions

Safety and appropriate management of nuclear waste are of major importance in radioisotope production. Radioiodine has been identified as one of the most dangerous radioelements in terms of radiological effects in case of accidental release; accordingly substantial efforts are made to optimize the iodine capture in liquid effluents to avoid any possible iodine gas release from liquid waste during storage. The IRE (National Institute for Radioelements) produces radioelements such as Mo-99 for nuclear medicine. Its production process results in highly acidic and oxidizing effluents containing iodine which might thus be present in various oxidation states and species. This needs to be taken into account for the development of a decontamination process for these effluents. CL Resin (TrisKem International) is an extraction chromatographic resin showing high selectivity for noble metals over a large number of other elements. The CL Resin retains silver over a wide pH range including high acid concentrations. It was further shown, after being loaded with silver, to strongly retain iodine species forming insoluble complexes with silver making it well suited for use in the given context; XAD-4 Resin (Sigma-Aldrich) on the other hand is known to retain elemental iodine. A mixed bed column based on silver loaded CL Resin and XAD-4 resin was developed and optimized for iodine removal from IRE's process effluents. Prepared mixed bed columns were evaluated by treating multi-curies production process solutions at the IRE. These columns showed high iodine removal from elevated effluent volumes (>10 L) even at flow-rates up to >180 mL min-1. (author)