Thyroid equivalent doses for evacuees and radiological impact from the Fukushima nuclear accident

The present paper summarizes the scientific activities of the authors which have been focused on environmental monitoring and estimating thyroid dose for evacuees of the Fukushima Nuclear Power Plant accident. The radionuclide components of the absorbed dose rates in air obtained by a gamma-ray spectrometer depend on the radioactive plume behavior. Furthermore, continuous measurements by a car-borne survey are important to know the radioactive plume behavior. A few thyroid dose estimations have been obtained by different techniques. Direct measurements by the authors were in agreement with these published estimations. However, the dose from 132I was not taken into account in the previously published thyroid dose estimation due to the lack of information. After a nuclear accident, prompt thyroid measurements are required, and a standard technique for the measurement of activity in thyroid should be established.