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Mori, Airi; Takahara, Shogo; Ishizaki, Azusa; Iijima, Masashi; Sanada, Yukihisa; Munakata, Masahiro
Journal of Environmental Radioactivity, 166(Part 1), p.74 - 82, 2017/01
Times Cited Count：8 Percentile：26.82(Environmental Sciences)Large quantities of radioactive materials were released into the environment as a result of the Fukushima Daiichi Nuclear Power Station accident. Many inhabitants residing in the affected areas are now exposed to radiation in their daily lives. In an attempt to manage this radiation dose, an additional radiation dose of 1 mSv/y was adopted as a long-term dosimetric target. An activity level reading of 0.23 
Sv/h was then determined as a guidance value to achieve the target by implementing decontamination measures. The objectives of this study are to assess the effects of decontamination based on this guidance value and to predict any possible future problems with the decontamination strategy. Using a probabilistic approach, we assessed the annual effective dose of indoor workers, outdoor workers, and pensioners in the Fukushima Prefecture. Our probabilistic model considers the variabilities in behavioral patterns and Cs-137 surface-activity levels. Five years after the initial contamination, the 95th percentiles of indoor workers and pensioners in 53 of the 59 municipalities were found to receive annual effective doses of below 1 mSv/y (0.026-0.73 mSv/y). However, for outdoor workers in 25 municipalities, the annual doses were over 1 mSv/y (1.0-35 mSv/y). Therefore, the guidance value is effective for indoor workers and pensioners; to determine whether additional countermeasures for outdoor workers should be implemented, a detailed assessment that uses more realistic assumptions is required.
Ota, Masakazu; Nagai, Haruyasu
Radioprotection, 46(6), p.S417 - S422, 2011/12
Times Cited Count：1 Percentile：10.73(Environmental Sciences)A simulation study was carried out, to evaluate formation of organically-bound tritium (OBT) after wet deposition of atmospheric HTO onto soil, a process which would be important for an accidental HTO release. To evaluate tritium transfers in atmosphere-vegetation-soil system, we adopted a sophisticated numerical-model SOLVEG-II which calculates diffusion of HTO in atmosphere, diffusion and advection of HTO in soil, and, tritium exchange and OBT assimilation in leaves, in conjunction with transport of heat and water, and CO
exchange. Evaporation and condensation between atmospheric HTO and rainwater are newly modeled, to calculate wet deposition of atmospheric HTO. Then a simulation was carried out, assuming an acute release of atmospheric HTO in nighttime at which a rainfall event exists. Successive TFWT variation and OBT formation were calculated, and, importance of wet deposition and re-emission of HTO for the OBT formation was discussed.
Matsubara, Takeshi*; Homma, Toshimitsu
Proceedings of International Conference on Environmental Radioactivity (Internet), 5 Pages, 2010/00
no abstracts in English
Yankovich, T. L.*; Koarashi, Jun; Kim, S. B.*; Davis, P. A.*
Applied Radiation and Isotopes, 66(11), p.1726 - 1729, 2008/11
Times Cited Count：9 Percentile：52.81(Chemistry, Inorganic & Nuclear)The IAEA's model evaluation program EMRAS (Environment Modelling for Radiation Safety) includes a Tritium and C-14 Working Group (TCWG), the goal of which is to test the performance of environmental tritium and C-14 models. The TCWG has undertaken nine scenarios in which model predictions were compared with experimental data. Two of these scenarios are discussed here, one involving the prediction of time-dependent tritium concentrations in freshwater mussels subject to an abrupt change in ambient tritium levels, and the second involving the prediction of C-14 concentrations in rice grown in the vicinity of continuous atmospheric C-14 sources.
I releases from ChernobylKrajewski, P.*; Ammann, M.*; Bartuskov
, M.*; Duffa, C.*; Filistovic, V.*; Homma, Toshimitsu; Kanyr, B.*; Maltov, I.*; Nedveckaite, T.*; Simon, S.*; et al.
Applied Radiation and Isotopes, 66(11), p.1730 - 1735, 2008/11
Times Cited Count：6 Percentile：40.09(Chemistry, Inorganic & Nuclear)Bartuskov, M.*; Maltov, I.*; Berkovskyy, V.*; Krajewski, P.*; Ammann, M.*; Filistovic, V.*; Homma, Toshimitsu; Horyna, J.*; Kanyr, B.*; Nedveckaite, T.*; et al.
no journal, ,
Kawachi, Naoki; Yin, Y.-G.; Suzui, Nobuo; Ishii, Satomi; Yoshihara, Toshihiro*; Watabe, Hiroshi*; Yamamoto, Seiichi*; Fujimaki, Shu
no journal, ,
Yoshihara, Toshihiro*; Hashida, Shinnosuke*; Kawachi, Naoki; Nagao, Yuto; Yamaguchi, Mitsutaka; Suzui, Nobuo; Yin, Y.-G.; Fujimaki, Shu
no journal, ,
Iijima, Kazuki; Funaki, Hironori; Oyama, Takuya; Niizato, Tadafumi; Sato, Haruo*; Yui, Mikazu
no journal, ,
Goal of the project is to develop mechanistic models to predict transport behavior of radioelements strongly adsorbed on soil particles from forests to sea through river systems, evaluate evolution of dose, and propose methods to constrain the transport. This study overviewed the behavior of radioactive caesium through one of the river systems in the coastal area of Fukushima. Concequently, caesium is considered to be strongly adsorbed on the soil particles in the transport through the river water system since more than 90% of caesium has still remained within 5 cm from the surface of topsoil in the forest, and the concentration of caesium in the lake water was extremely low. The difference of concentrations of caesium in the sediments in the river water system can be explained by the effect of particle size on the adsorption site density of caesium.
Hirouchi, Jun; Nishizawa, Yukiyasu*; Urabe, Yoshimi*; Shimada, Kazumasa; Sanada, Yukihisa; Munakata, Masahiro
no journal, ,
After the Fukushima Dai-ichi Nuclear Power Station (NPS) accident, a series of aerial radiation monitoring (ARM) was conducted as a national project to map the ground surface distribution of radiocesium. The influence of 
-rays from natural nuclides, especially the radon progenies (Pb-214 and Bi-214) should be excluded from the ARM measurement data to accurately estimate deposition of artificial radionuclides. Therefore, the aim of this study is to develop a method for discriminating the influence of the radon progenies in air from the measurement data. The discrimination method was applied to the ARM data around Sendai NPS and we compared the dose rate at a height of 1 m above the ground measured by NaI survey meter with the ARM data. The coefficient of determination (R2) and normalized mean square error (NMSE) were improved by applying the method, showing that the validity of the method was confirmed.
Terada, Hiroaki; Nagai, Haruyasu
no journal, ,
For the assessment of the radiological doses to the public due to the atmospheric discharge of radioactive materials during the Fukushima Daiichi Nuclear Power Station accident, the spatiotemporal distribution of radioactive materials in the environment are reconstructed by atmospheric dispersion simulation with the improved WSPEEDI. In this study, the influence of chemical form of I (particle, inorganic and organic gas) in source term on the simulated results was analyzed to assess the uncertainty of the simulation. From the sensitivity test with the chemical form composition, surface deposition distribution of I was influenced according to the property of the chemical forms to deposition processes, whereas time-integrated air concentration was less influenced. From the comparison with the measurement, the surface deposition simulated with the source term in Katata et al. (2015) had a good reproducibility compared with those with extreme gas to particle ratios.
Mori, Airi; Takahara, Shogo; Sanada, Yukihisa; Munakata, Masahiro
no journal, ,
Inhabitants residing in part of Fukushima Prefecture are now exposed to radiation due to radioactive materials released by the Fukushima Daiichi Nuclear Power Station accident. To mitigate the radiation doses, an additional dose of 1 mSv/y was adopted as a long-term dosimetric target, and some municipalities were designated as the evacuation area. The evacuation area has been narrowing along with the decreasing of air dose rate. It was decided that evacuation orders in parts of 5 municipalities are lifted in 2016-2017. Radiation dose will be an important information for the inhabitants to make a decision on whether to return or not. Many inhabitants are concerned about radiation doses, particularly doses to their children. In this study, we developed the dose assessment model for children to estimate radiation doses to children that returned to their hometown. As a result of our calculation, it was revealed that the doses will not cause any health effect but continual efforts to achieve the dosimetric target of 1 mSv/y are necessary.
Pratama, M. A.; Takahara, Shogo; Munakata, Masahiro; Homma, Toshimitsu; Yoneda, Minoru*
no journal, ,
Kobayashi, Takuya; Kawamura, Hideyuki; Fujii, Katsuji*; Kamidaira, Yuki
no journal, ,
The Fukushima Dai-ichi Nuclear Power Station (FNPS1) accident in Japan in March 2011 led to the release of large amounts of radionuclides into the atmosphere as well as direct discharges into the ocean. Various environmental assessments have been performed by many research groups using marine dispersion simulations after the FNPS1 accident. It was recognized from these woks that the risk of radionuclide release from nuclear facilities to the environment was very high and the establishment of emergency ocean dispersion forecasting systems was necessary. Then, the Japan Atomic Energy Agency (JAEA) has developed the Short-Term Emergency Assessment system of Marine Environmental Radioactivity (STEAMER) to immediately predict the radionuclide migration for a nuclear accident in ocean around Japan, by integrating previous study results. In this study, structure, performance test results, and utilization of the system are described.
Pratama, M. A.; Takahara, Shogo; Munakata, Masahiro; Yoneda, Minoru*
no journal, ,
Ishizaki, Azusa; Mori, Airi; Kawase, Keiichi; Kato, Mitsugu; Watanabe, Masanori; Aoki, Isao; Munakata, Masahiro
no journal, ,
Kinase, Sakae; Honda, Fumiya*
no journal, ,
Cs/
Cs isotope ratio near the Fukushima Daiichi Nuclear Power StationShimada, Asako; Tsukahara, Takehiko*; Nomura, Masao*; Shimada, Taro; Takeda, Seiji
no journal, ,
no abstracts in English
Yoshimura, Kazuya; Watanabe, Takayoshi; Kurikami, Hiroshi
no journal, ,
Nihei, Naoto*; Yoshimura, Kazuya; Nakanishi, Tomoko*
no journal, ,
