Keywords: light water reactors, severe accidents, iodine chemical forms, thyroid doses, low radiation, nuclear accidents, nuclear reactors, removal mechanisms, dose rates, radioactive iodine, nuclear power plants
Effect of iodine chemical form on thyroid doses during a severe accident
In most of the accidents that may occur in nuclear reactors, the short-term radiological consequences are expected to be dominated by isotopes of iodine. The assessment of doses resulting from iodine release during a severe reactor accident requires knowledge of the iodine chemical forms and removal mechanisms prior to the release to the environment. In this paper, the arguments concerning iodine chemical form in severe accidents are stated. Removal mechanisms prior to release to the environment are summarised. Various assumptions of iodine chemical form during a severe accident were used to assess the radiation doses to thyroid at site boundaries and at the low population zone of a pressurised water reactor. Doses were calculated for an adult and a ten-year-old child. It was concluded that if the spray system was used prior to the release, with proper additives to raise the pH of the sump, the doses are generally reduced. The main contributor to dose in this case is organic iodine.