Subject:
Environmental Safety Research Based on the Results of the Fukushima Dai-ichi NPP Accident:
Development of Rapid and Sophisticated Application of Environmental Monitoring Data to Analyze Radioactive Release
During the Fukushima Dai-ichi NPP accident in March 2011, partially caused by extensive damage to regional power supply and traffic due to the big earthquake and subsequent huge tsunami, insufficient observations of local meteorology and environmental radiation and radioactivity had been obtained with monitoring activities. What could we do for more effective monitoring at that time? Study on the emergency response and countermeasures against the situation at that time is needed for our understandings and solutions to the lessons from the accident.
Determination Method of Environmental Radionuclides from Gamma-ray Energy Spectrum Measured by Monitoring Stations
Now many and many monitoring stations that always measure environmental gamma-ray dose rates are installed in Japan. The most popular type for the dose rate monitoring is NaI(Tl) scintillation detector. By using this type detector, one can obtain not only real-time dose rate but also gamma-ray energy spectrum (pulse height distribution), even remotely available on-line. The energy resolution of this type detector is, however, low and its precision for detection and determination of radionuclides is much lower than that with a germanium semiconductor detector. Thus, widespread installation of the germanium detectors for monitoring is desirable, but its expensiveness and hardness to handling make difficulty in their installation. We have studied rapid methods to measure precisely radioactivity concentrations in air and on the ground from monitoring data with NaI(Tl) scintillation detectors which have already widely installed. This method is expected to be applicable to rapid decision making whether effective countermeasures, such as evacuation of the public and limitation of shipping of crops, are required or not.
Fig. 1 A monitoring station that measures environmental radiation and radioactivity in Shizuoka Pref.
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