A bioassay experience and lessons learned on the internal contamination of 131I during a maintenance period in a Korean nuclear power plant

During a maintenance period at a Korean nuclear power plant, internal exposure of radiation workers occurred by the inhalation of 131I that was released into the reactor building from a primary system opening due to defective fuels. The internal activity in radiation workers contaminated by 131I was immediately measured using a whole body counter (WBC). A whole body counting was performed again a few days later, considering the factors of equilibrium in the body. The intake and the committed effective dose were estimated based on the WBC results. The intake was also calculated by hand, based on both the entrance records to the reactor building, and the counted results of the air concentration for 131I were compared with the whole body counting results. (authors)