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Sanada, Yukihisa; Tokiyoshi, Masanori*; Nishiyama, Kyohei*; Sato, Rina; Yoshimura, Kazuya; Funaki, Hironori; Abe, Tomohisa; Ishida, Mutsushi*; Nagamine, Haruo*; Fujisaka, Motoyuki*
Nihon Genshiryoku Gakkai Wabun Rombunshi (Internet), 22(2), p.87 - 96, 2023/04
Since the accident at the Fukushima Daiichi Nuclear Power Plant, many decontamination works have been carried out, but it is difficult to say that much data on workers' exposure has necessarily been analyzed in detail. In this paper, based on the GPS location information carried by the workers together with their personal dosimeters, the air dose rate in the work area and the characteristics of each type of work were analyzed. The results showed that more than 50% of the measured actual doses were more than twice the median planned dose calculated from the air dose rate and actual working hours. Furthermore, as a result of the analysis by work type, it was found that the exposure doses of demolition workers tended to be high, and that this was due to the fact that most of the work was carried out before the work was carried out to reduce the dose at the work site. In addition, when the conversion from air dose to effective dose was taken into account, there were many cases of underestimation where the planned values were lower than the measured values, and it is considered important for management to set appropriate working factor.
Sanada, Yukihisa; Yoshimura, Kazuya; Sato, Rina; Nakayama, Mariko*; Tsubokura, Masaharu*
Journal of Radiation Research (Internet), 64(1), p.2 - 10, 2023/01
Times Cited Count：0 Percentile：0.06(Biology)The evacuation orderareas established due to the accident at the Tokyo Electric Power Company Holdings' (TEPCO) Fukushima Daiichi Nuclear Power Plant (FDNPP) have been reorganized according to the decrease in ambient dose rates and the decontamination progress. The Japanese government decided to decontaminate the difficult-to-return areas and lift the evacuation order by 2030. This radiation protection strategy can be optimized by examining emergency exposure situations to date and the existing exposure after the accident. This article reviews the methods that can determine the individual radiation doses of residents who should return to their homes when the evacuation order is lifted in the specific reconstruction reproduction base area and the difficult-to-return areas outside this base area and summarizes the points to be considered when implementing these methods. In Part 1 of this article, we review the efforts made by the Japanese government and research institutes to assess radiation doses to residents after the FDNPP accident.
Mori, Airi; Tanabe, Tsutomu; Wada, Takao; Kato, Mitsugu
JAEA-Technology 2017-006, 38 Pages, 2017/03
JAEA-Technology-2017-006.pdf:2.98MB
Large quantities of radioactive materials were released into the environment as a result of the Fukushima Daiichi Nuclear Power Station accident. Residential areas and forest areas near the power station were contaminated with the radioactive materials. Outside of the houses, schools and the other buildings are being decontaminated by national authority and local government. On the other hand, the materials (such as walls, floors, or windows) which constitute the houses are not decontaminated officially. In order to prepare decontamination methods that can be applied easily, we conducted examinations of decontamination for various materials in houses. Fibrous materials, woods, glasses, concretes, plastics, vinyl chloride materials, metals and synthetic leathers were used in our examinations. These materials were collected from houses in difficult-to-return zone, and were contaminated by radioactive materials released by the accident. Dry methods (suction, wiping, adsorption and peelable coating), wet methods (wiping, brushing, polishing and washing) and physical method (peeling of materials) were used for decontamination. As a result of our examinations, materials with low water permeability, such as glasses, concretes, vinyl chloride materials and metals, were able to be decontaminated efficiently (about 90% reduction) by using wet methods. Materials with high water permeability like woods were relatively well decontaminated by peelable coating (about 60%-70% reduction). In addition to the examination described above, the difference of contamination reduction effect between chemical properties of detergents and the effect of rubbing of peelable coating were also examined. Finally, the most effective method was summarized based on these examinations.
Sanada, Yukihisa
no journal, ,
Ten years after the accident at the Tokyo Electric Power Company Holdings's Fukushima Daiichi Nuclear Power Station, a policy to lift the remaining evacuation zones is under way. For the lifting of the evacuation, a technical package is being applied, which includes environmental radiation monitoring such as air dose rates and dust sampling, and a set of exposure assessments based on the data. Those technologies are built and operated as simple applications for risk communication with the population. This presentation will summarise the experiences and remaining challenges in the development of these technologies.
Abe, Tomohisa; Sanada, Yukihisa; Tokiyoshi, Masanori*; Nishiyama, Kyohei*; Sato, Rina*; Yoshimura, Kazuya; Funaki, Hironori; Ishida, Mutsushi*; Nagamine, Haruo*; Fujisaka, Motoyuki*
no journal, ,
We attempted to analyze in detail the actual external exposure doses of workers involved in decontamination work, which had been difficult to analyze in detail until now, by recording location information and exposure doses using GPS. As a result, it was found that more than 50% of the planned exposure dose calculated from the air dose rate and the number of actual working hours were more than twice the median the measured exposure doses. Furthermore, analysis by work type showed that the exposure doses of demolition workers tended to be higher. This information on the external exposure dose of workers linked to location information is useful for detailed analysis of external exposure factors and will contribute to the optimization of future radiation protection programs for workers.
Sanada, Yukihisa
no journal, ,
After the Fukushima Nuclear Power Plant accident, radiation monitoring technology using unmanned aircraft was developed and deployed in the field. This technology has provided decision makers with base data for the release of specific reconstruction and rehabilitation sites. On the other hand, efforts are underway to apply this technology to nuclear disaster prevention in the future. In this presentation, examples of the application of the radiation measurement technique developed in Fukushima as a disaster prevention technology will be introduced.
Sanada, Yukihisa
no journal, ,
no abstracts in English
