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Takeyasu, Masanori; Takeishi, Minoru; Yoda, Tomoyuki; Saegusa, Jun; Koizumi, Jin*; Tanabe, Tsutomu
no journal, ,
The measurement of air dose rate surrounding roads is important for developing plans for reducing radiation exposure with road traffic. The measurements were performed by vehicle-borne or man-borne surveys until now. However, air dose rate resulting from radioactivity on roads in mainly measured for former survey, and much man-power for long time measurement was necessary for the latter. In this study, we focused on the field of view for measurement being different with a difference of the detector setting height above the ground, and carried out the vehicle-borne survey along roads in evacuation zone in Fukushima prefecture with two detectors mounted at different heights. By this measurement, air dose rate surrounding the roads is discriminated. From the results, the radioactivity contamination trend was clarified, and are valuable for developing decontamination plan around the road.
Uezu, Yasuhiro; Ejiri, Akira; Yoda, Tomoyuki
no journal, ,
The Great East Japan Earthquake occurred on 11th March 2011. The Tsunami attacked the Fukushima Daiichi Nuclear Power Station of Tokyo Electric Power Co. As a result, electric power was lost, furthermore electronic power generators were broken. After failing to restore power, there was an explosion and a large amount of radionuclides were released to the atmosphere. Japan Atomic Energy Agency (JAEA) monitored air dose rates, radionuclides in the air and environmental samples. At that time, there were many problems in the environmental radiation monitoring. The dose was beyond the range of the air dose monitor in monitoring car. The Ge detector's iron and lead shields were contaminated by the air. No standard source as "the phantom" could be obtained for children under 4. The JAEA solved these problems by developing new monitoring techniques. In this presentation, these improvements are shown and proposed as a new generation environmental radiation monitoring technique.
Manabe, Kentaro; Matsumoto, Masaki*
no journal, ,
If an insoluble cesium-bearing particle is incorporated into the body, the radioactivity in the particle will move stochastically in the state of a cluster without diffusion to the blood or tissue fluid. A deterministic method is applied to estimate internal doses for generic radioactive aerosols, but the deterministic method cannot be applicable to insoluble cesium-bearing particles. We established a stochastic method to estimate probability density functions of internal doses for intakes of insoluble particles by simulating the stochastic behavior of the particles. In this presentation, we will show the result of the probability density function of doses for particles having a typical size (diameter: 2 
m). In addition, we will describe the parameters that affect probability density functions of doses, and future issues.
Sakoda, Akihiro; Ishimori, Yuu; Murakami, Shoichi*; Horai, Sawako*
no journal, ,
One of major uranium mines in Japan was located in Ningyo-toge, Okayama. Uranium mining and test milling were made here in the past, and then there has been a uranium mill tailings pond in Ningyo-toge Environmental Engineering Center, Japan Atomic Energy Agency. Since spring 2016, we have performed sampling of non-human biota - insects and amphibians (i.e. frog and newt) - as well as water and sediment in the mill tailings and other two locations (for comparison) to better understand the transfer of elements in such ecosystem. Concentrations of radionuclides and stable elements in the samples were measured mostly by ICP-MS and 
-ray spectrometry using a high-purity germanium detector. All samples of sediment, water and organism were found to include more U-238 in the mill tailings pond than those in other two locations. Detailed data will be shown and discussed in terms of the transfer in the environment at the presentation.
Yoshitomi, Hiroshi; Nishino, Sho; Takahashi, Masa; Tanimura, Yoshihiko
no journal, ,
Kowatari, Munehiko; Yoshitomi, Hiroshi; Nishino, Sho; Tanimura, Yoshihiko; Murayama, Takashi; Oishi, Tetsuya; Yoshizawa, Michio
no journal, ,
Tanimura, Yoshihiko; Nishino, Sho; Yoshitomi, Hiroshi; Takahashi, Masa
no journal, ,
A portable thyroid dose monitoring system consisting of spectrometers and a shield has been developed in order to assess the equivalent dose to the thyroid for workers and members of the public in a high dose rate environment at an early stage after a nuclear accident. The LaBr
(Ce), SrI
(Eu) scintillation and CdZnTe semiconductor detectors were selected as the spectrometers of the system in the view point of the energy resolution, sensitive volume, which affects the detection efficiency of the detector, and ease of handling such as non-cooling requirements. The material and thickness of the shield were optimized by the calculation and experiment. In this presentation, the performance test of the spectrometers and the shielding materials will be introduced.