Prototype test of a portable thyroid dose monitoring system using gamma-ray spectrometers

In case of a severe nuclear accident, radioiodine monitoring of the thyroid must be carried out for a large number of residents and emergency workers. In the present study, we developed a portable thyroid dose monitoring system consisting of two independent gamma-ray spectrometers and a radiation shield, which could be used under high background radiation conditions. Two types of prototype thyroid monitors were realized; one utilizing CdZnTe detectors for emergency workers and the other employing LaBr3(Ce) detectors for members of the public. As a result of the performance test, it was confirmed that both monitors effectively assess thyroid equivalent doses of <10 mSv during a 150 s measurement, even under high background radiation conditions.