Radiogenic iodine is one of the more difficult fission products to capture and immobilize during the reprocessing of spent nuclear fuel.

However, for metallic fuels reprocessed by electrometallurgical treatment, it is believed that the majority of fission-product iodine is retained during the various processing steps. Spent fuel from the Experimental Breeder Reactor II (EBR-II) at the Idaho National Laboratory (INL) is being treated by a combination of electrochemical and pyrometallurgical methods to deactivate the bond sodium of the fuel, recover uranium, and immobilize fission products for disposal. This paper discusses the progress of various strategies and experiments to confirm the expected retention of iodine during the electrometallurgical treatment of EBR-II spent fuel. This includes surveys of previous observations and measurements, and the direct measurement of iodine from various process samples. Current measurements are aimed at iodine determination in the bond sodium and plenum regions of the fuel, refined iodine measurements in electrorefiner salt, and the retention of iodine during waste form production.