Experience of iodine removal in Tokai reprocessing plant

In the Tokai reprocessing plant about 170 ton of irradiated fuels have been processed since the beginning of hot operations in 1977. There was no effective equipment for iodine removal from the off-gas except for alkaline scrubbers when the plant construction was completed. In order to reduce the iodine discharge to the atmosphere, silver-exchanged zeolite (AgX) filters were installed additionally in 1979 and 1980, and they have been effective. However, those decontamination factors (DFs) were not as high as expected, and increasing the reprocessing amount of spent fuels it became necessary to lower the iodine discharge to the atmosphere. Therefore, other iodine removal equipment is planned to be installed in the plant. Concerning these investigations and development of iodine removal techniques, the iodine concentration of actual off-gases was measured and useful data were obtained