Radioiodine releases in nuclear emergency scenarios.

This document provides a comprehensive overview study on the physico-chemical speciation of radioiodine observed in the atmosphere after various emissions related to nuclear activities: nuclear weapon tests, accident and incident releases, and routine discharges. The study covers different types of nuclear facilities including medical isotope production facilities (MIPFs), reprocessing plants (RPs), and nuclear power plants (NPPs). Most attention is paid to 131I which has a major human health impact in the early stages of a nuclear emergency situation with regard to inhalation. Iodine-131 combines a high yield by neutron-induced nuclear fission of 235U (2.87%) or 239Pu (3.8%), high dose coefficients, and a radioactive half-life long enough to allow for spreading at global scales and entering the food chain but sufficiently short to produce a significant dose commitment when inhaled or ingested. Reliable dose assessment requires both detailed and valid information on the physico-chemical composition of 131I present in the air. Apart from reactor explosions and fires, which produce large amounts of particles and may therefore favor the presence of iodine in particulate form at short distance, other nuclear accident scenarios will lead fairly rapidly to a dominant gaseous radioiodine proportion in the atmosphere