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Home arrow Environment arrow Radiation Monitoring and Dose Estimation of the Fukushima Nuclear Accident


KURAMA [2] is a γ-ray survey system with Global Positioning System (GPS) and up-to-date network technologies developed for the primary use of carborne surveys. The system outline of KURAMA is shown in Fig. 7.1.

Fig. 7.1 KURAMA system. Monitoring cars and servers are connected over the Internet by cloud technology

An in-vehicle unit of KURAMA consists of a conventional NaI scintillation survey meter with an appropriate energy compensation, an interface box for the analog voltage output of the detector to a USB port of a PC, a GPS unit, a laptop PC, and a mobile Wi-Fi router (Fig. 7.2). Its simple and compact configuration allows users to set up an in-vehicle unit in a common automobile. The software of the invehicle part is developed with LabVIEW. The radiation data, collected every 3 s, are tagged by the respective location data obtained by the GPS and stored in a csv file. The csv files updated by respective monitoring cars are simultaneously shared with remote servers by Dropbox over a 3G network, differing from other typical carborne survey systems in which special telemetry systems or storage media are used for data collection. With this feature, anyone can set up their own “Data Center” anywhere so long as a conventional Internet connection and a PC with Dropbox are available. This kind of flexibility should be required in the disasters such as the present situation because the carborne system owned by Fukushima Prefecture was eventually halted as a result of the shutdown of the data center by the disaster.

Once the radiation data in csv format are shared with remote servers, the data file is processed or analyzed by servers in various ways, including the real-time display on Google Earth in client PCs (Fig. 7.3).

KURAMA has served for monitoring activities in Fukushima and surrounding prefectures employed by the Fukushima prefectural government and the Ministry of Education, Culture, Sports, Science and Technology in Japan (MEXT). The team of Fukushima prefectural government makes precise radiation maps of major cities in Fukushima Prefecture mainly for “Hot Spots” search [3], whereas MEXT performed carborne surveys in eastern Japan [4], including the Tokyo metropolitan area (Fig. 7.4).

Fig. 7.2 The in-vehicle part is compactly composed of mostly commercial components: (1) GPS unit, (2) 3G mobile Wi-Fi router, (3) MAKUNOUCHI, (4) NaI survey meter, (5) PC

Fig. 7.3 Data are simultaneously plotted on Google Earth. The color of each dot represents the air dose rate at the respective point

Fig. 7.4 Air dose rate mapped by KURAMA in December 2011 [4]. MEXT performed the first and second carborne surveys in East Japan by KURAMA in June and December 2011, respectively

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