Management of iodine-129 from reprocessing plants

The technological and radiological aspects of the management of 129I arising in fuel reprocessing plants (FRPs) are reviewed and discussed. The dissolver off-gases of FRPs can be made to contain about 99% of the 129I throughput, and efficient techniques are available for trapping iodine from this stream. This iodine could be discharged as a liquid effluent (e.g. to coastal waters) if local circumstances permit; otherwise it would have to be immobilized and disposed of as a solid. All management modes for 129I (except transmutation or extraterrestrial disposal, neither of which is a real option at present) will ultimately lead to its dispersal throughout the natural global iodine reservoirs, particularly in the long term the deep oceans and sediments. A revised global-circulation model for iodine is presented, together with new results for the radiological impact of 129I discharged as an airborne or liquid effluent, or trapped and disposed of as a solid to the deep ocean bed or to two kinds of deep geologic repository. The long-term radiological impacts of different management modes for 129I are very similar owing to the common factor of global circulation; but there are considerable differences in the shorter term. Atmospheric discharges of 129I from large FRPs would need to be abated, to control doses to the local critical group; none of the other management modes considered appears to be precluded on radiological grounds. (Auth.)