Radiation dose distribution for workers in South Korean nuclear power plants

A total of 33 680 nuclear power plants (NPPs) workers were monitored and recorded from 1990 to 2007. According to the record, the average individual radiation dose has been decreasing continually from 3.20 mSv man(-1) in 1990 to 1.12 mSv man(-1) at the end of 2007. After the International Commission on Radiological Protection 60 recommendation was generalised in South Korea, no NPP workers received > 20 mSv radiation, and the numbers of relatively highly exposed workers have been decreasing continuously. The age distribution of radiation workers in NPPs was composed mainly of 20-30 y olds (83 %) for 1990-1994 and 30-40 y olds (75 %) for 2003-2007. The difference in individual average dose by age was not significant. Most (77 %) of the NPP radiation exposures from 1990 to 2007 occurred mostly during the refueling period. With regard to exposure type, the majority of exposures was external exposures, representing 95 % of the total exposures, whereas internal exposures represented only 5 %. External effective dose was affected mainly by gamma radiation exposure, with an insignificant amount of neutron exposure. As for internal effective dose, tritium in the pressurised heavy water reactor was the biggest cause of exposure.