In the event of an accident occurring in a nuclear reactor in service, the radioactive iodine released would account for a major part of the short-term exposure of the population affected. The radioactive iodine inhaled when the plume passes would quickly enter the blood stream and would be concentrated mainly in the thyroid gland. This would result in an increase in cases of thyroid cancer, especially in children. An increase of this type was noted in children severely contaminated in Ukraine and Belarus by radioactive iodine released into the atmosphere during the Chernobyl accident.
To avoid this type of effect, action plans provide for the possibility of stable iodine tablets being taken orally by people located within a 10 km radius of a nuclear accident site. This figure is based on current best estimates of foreseeable releases in the event of core meltdown in a water reactor. These estimates are, however, subject to important uncertainties, especially regarding the formation of organic iodines which are particularly volatile.
This is why IRSN is conducting a programme aimed at acquiring experimental data to improve and validate models describing the chemical and physical phenomena governing how volatile iodine forms and what happens to it in a containment, as well as the kinetics of the formation and destruction of organic iodine in representative conditions.
In order to carry out these tests, IRSN developped an irradiation facility (EPICUR), on the Cadarache site, producing a dose rate of 10 kGy/h which is representative of accident conditions in a containment.
In parallel with the tests regarding iodine, a study of the chemistry of ruthenium (another radiotoxic product) in the reactor containment in an accident situation will be conducted in the EPICUR facility.