EXPERIENCES OF POPULATION MONITORING USING WHOLE-BODY COUNTERS IN RESPONSE TO THE FUKUSHIMA NUCLEAR ACCIDENT

Whole-body counter (WBC) measurements of residents of Fukushima prefecture have been extensively performed after the Fukushima Dai-ichi Nuclear Power Plant accident in March, 2011. These measurements have demonstrated that the levels of internal contamination with radioactive cesium (134Cs and 137Cs) in the residents are very low. This article provides an overview of and lessons learned from these WBC measurements with emphasis on the technical problems encountered, and discusses the effective use of WBCs for assessing the internal thyroid doses of individuals when direct measurements of 131I in the thyroid are difficult or impossible to be implemented for the total affected population in a short time after a nuclear reactor accident. The application of this dose reconstruction method requires determining the intake ratio of 131I to Cs isotopes at appropriate times, and considers the short biological half-lives of Cs isotopes in particular for children