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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.
Sato, Rina; Sanada, Yukihisa; Yoshimura, Kazuya; Nakayama, Mariko*
JAEA-Review 2022-055, 42 Pages, 2023/01
JAEA-Review-2022-055.pdf:1.31MB
The evacuation order zones established after the accident at the Tokyo Electric Power Company's Fukushima Daiichi Nuclear Power Station have been reorganized according to the decrease in ambient dose equivalent rates and the decontamination progress. It has been decided to decontaminate the difficult-to-return zones and lift the evacuation order depending on the evacuee's intention of returning to the areas over the course of the 2020s. In order to consider the future of individual exposure dose assessment for residents for lifting of the evacuation orders, the methods and characteristics of the assessment that have been conducted after the accident using personal dosimeter measurements and simulations were systematically reviewed. This report summarized the results of the review.
Hiraoka, Hirokazu; Komatsuzaki, Joji*; Hanaka, Norihiko*; Okamoto, Akiko; Saito, Yoshihiko*; Munakata, Masahiro; Togawa, Orihiko
JAEA-Technology 2022-003, 70 Pages, 2022/07
JAEA-Technology-2022-003.pdf:2.53MB
In contamination inspections for public in nuclear emergency, it is assumed that a large number of motor vehicles and evacuees will be inspected. At present, first measurement points of vehicles are tires and around a wiper, and they are basically inspected by persons using portable radiation surface contamination meters such as GM survey meters. However, in order to efficiently inspect contamination of vehicles, utilization of portable radiation portal monitors is being considered for the inspection. In this study, examination of performance of the portal monitor was conducted in order to obtain basic data. In this examinations, sealed radiation sources, 
Ba, were substituted for the contamination of Operational Intervention Level 4 (OIL4), the evaluation criteria to conduct simple decontamination in the contamination inspection. The radiation source was attached practically to a tire and around the wipers of a vehicle, and the counting rate of 
-rays from the radiation sources was measured using the portal monitor. Three examinations were conducted: static examination with a vehicle stationary, moving examination to mock the actual inspection, and high back ground examination to investigate performance of the equipment in high back ground environment. The vehicle mainly used in the experiments was a sedan, which is generally used as standard vehicles. And, a van whose front body is like that of a bus was used at this experiment. In addition, the "Gamma Pole" manufactured by the Chiyoda Technol Corporation was used as the portal monitor. As the result, it was estimated that the case of contamination equivalent to 40,000 cpm, the default value of the OIL4, deposited on the tread on a vehicle tire, when the vehicle passes through the portal monitor at 10 km/h or less, the contamination would be detected with a probability of 99% or more. Similarly, when the contamination deposited on around the wipers and the vehicle speed is 5 km/h or less,
Shimada, Kazumasa; Iijima, Masashi*; Watanabe, Masatoshi*; Takahara, Shogo
Proceedings of Asian Symposium on Risk Assessment and Management 2021 (ASRAM 2021) (Internet), 17 Pages, 2021/10
The radiation doses received by the off-site responders in the Fukushima Daiichi Nuclear Power Station accident were assessed. Atmospheric dispersion simulation was conducted with the source term of the previous research to calculate the atmospheric concentration and ground surface deposition in the municipalities where off-site responders actives. The external exposure dose from cloudshine and groundshine, the internal exposure dose due to inhalation of radioactive plume and resuspended radio nuclei, and the temporal and spatial distribution within each municipality were assessed. As a result of comparing the assessed values of the external exposure dose with the measured values of the personal dosimeter, the measured values were within the assessed range. As a result of our assessment with internal dose exposure, if the exposures occurred without protective measures, the potential daily effective dose in the period between 12 and 31 March 2011 were several tens mSv per day or more in the relatively high dose area. Therefore, to keep the doses received by the responders below the reference level of 20 mSv recommended by the ICRP, it is necessary to ensure that the protective measures for internal exposures such as masks are taken, and to manage the time spent for their activity at least daily.
Ishizaki, Azusa; Nakanishi, Chika*; Takubo, Kazuya*; Munakata, Masahiro
Proceedings of 27th International Conference on Nuclear Engineering (ICONE-27) (Internet), 9 Pages, 2019/05
Ishizaki, Azusa; Futemma, Akira; Takubo, Kazuya*; Nakanishi, Chika*; Munakata, Masahiro
JAEA-Data/Code 2018-022, 20 Pages, 2019/03
JAEA-Data-Code-2018-022.pdf:2.05MB
If a nuclear disaster occurs, we may evacuate indoor escape facilities and buildings such as houses as avoid extra exposure doses. In order to evaluate exposure doses, it is necessary to estimate shielding capabilities of the building materials constituting the sheltering facility. Therefore, photon irradiation tests with three kinds of photon energy were carried out for Japanese familiar building materials in Japan, and photon transmittance of each building material is acquired and summarized. As a result, it was found that the shielding capabilities of composite walls and roofs which are widely used in a tree structure and a steel structure were relatively low. And, difference of materials used for composite walls and roofs resulted in a difference in shielding capabilities. For example, in the case of composite walls, compared with the photon transmittance of wall with ceramic-based siding materials, those of wall with lightweight concrete were lower. Furthermore, photon transmittance was also measured for building materials with relatively low shielding performance added shielding materials as additional measures to enhance shielding capabilities.
Shimada, Kazumasa; Sasaki, Toshihisa*; Iijima, Masashi*; Munakata, Masahiro
JAEA-Research 2018-012, 68 Pages, 2019/02
JAEA-Research-2018-012.pdf:4.15MB
The external exposure dose of off-site emergency responders at Fukushima Dai-ichi Nuclear Power Station accident were evaluated in order to consider a radiation protection of emergency responders. The maximum value of individual daily dose of emergency responders whose activities details were recorded from 12th to 31th March 2011 was 650 
Sv engaged in evacuation support in Futaba Town on 12th. Next, atmospheric concentrations and deposition of radionuclides were calculated from the source terms estimated by previous studies using atmospheric diffusion and deposit calculation codes, and air dose rates at off-site were estimated. Then, the external exposure dose was calculated for 6 emergency responders whose daily activities and personal doses were continuously recorded. Furthermore, the maximum value and the average value of the calculation external dose of emergency responders in the activity area were compared with the measurement value of the personal dosimeter of them. These results showed that the calculated value of the external exposure dose of emergency responders calculated from the maximum value of the dose rate in the active area roughly includes the measured value.
Kihara, Shinji; Amazawa, Hiroya; Sakai, Akihiro; Nakata, Hisakazu; Kugo, Teruhiko; Matsuda, Norihiro; Oizumi, Akito; Sasamoto, Hiroshi; Mitsui, Seiichiro; Miyahara, Kaname
JAEA-Research 2013-033, 320 Pages, 2014/07
JAEA-Research-2013-033.pdf:119.17MB
JAEA performed decontamination experiments at two test sites that combined a range of buildings and different types of land use, located in Date and Minami Soma municipalities as field pilot projects in order to accumulate knowledge and data for full-scale decontamination activities performed by local governments. In the pilot projects, we established its plan using practical decontamination methods that can be easily implemented, according to decontamination targets (e.g., forests, agricultural land, residential house and roads) at each site. As a result of the decontamination, the average air dose rates were reduced to approximately one half of the values before decontamination.
Watanabe, Masahisa; Tagawa, Akihiro
JAEA-Review 2013-053, 84 Pages, 2014/03
JAEA-Review-2013-053.pdf:48.63MB
To discover technologies that can be utilized for decontamination work and verify their effects, economic feasibility, safety, and other factors, the Cabinet Office, Government of Japan launched the FY2011 Decontamination Technology Demonstrations Project to publicly solicit decontamination technologies that would be verified in demonstration tests and adopted 25 candidates. JAEA was commissioned by the Cabinet Office, Government of Japan to provide technical assistance related to these demonstrations. JAEA carried out a demonstration test and evaluation of 25 technologies (e.g., decontamination technology of soil classifiers, ultra-high pressure water jets and volume reduction of organic materials) to perform decontamination of the environment
Sanada, Yukihisa; Nishizawa, Yukiyasu; Yamada, Tsutomu; Ikeda, Kazutaka*; Matsui, Masashi*; Tsuchida, Kiyofumi; Sato, Yoshiharu; Hirayama, Hirokatsu; Takamura, Yoshihide; Nishihara, Katsuya; et al.
JAEA-Research 2013-049, 129 Pages, 2014/03
JAEA-Research-2013-049.pdf:15.5MB
By the nuclear disaster of Fukushima Daiichi Nuclear Power Plant (NPP), Tokyo Electric Power Company (TEPCO), caused by the East Japan earthquake and the following tsunami occurred on March 11, 2011, a large amount of radioactive materials was released from the NPP. In recent years, technologies for autonomous unmanned helicopters (AUHs) have been developed and applied to natural disasters. In expectation of the application of the AUHs to aerial radiation monitoring, we had developed a remote radiation monitoring system. Then, we measured the radiation level by using unmanned helicopter in soil contaminated areas by radioactive cesium emitted from the NPP to evaluate ambient dose-rate distribution around the areas and to investigate the decontamination effect by the measurements before and after decontamination treatment. Here, we reports on the measurement technique and the result.
Takahara, Shogo; Iijima, Masashi; Kushida, Teruo; Shiratori, Yoshitake
JAEA-Research 2013-029, 36 Pages, 2013/12
JAEA-Research-2013-029.pdf:2.7MB
In the areas contaminated by the Fukushima Daiichi Nuclear Power Plant accident, to clarify the influences of the lifestyle habits to radiation exposures for inhabitants, we performed surveys on their behavioral patterns and measurements of their individual doses due to external exposures. In addition, an assessment model was developed and the assessments of the doses were performed based on the results of the surveys and the measurements of ambient dose equivalent rates. The assessed individual doses were compared with those measured in order to confirm the validity of the model. Clear differences were found in time spent outdoors of the inhabitants of various occupations. Significant differences in individual doses were also observed between those of indoor workers and outdoor workers. In order to assess more precisely the doses of inhabitants who continue to live in the affected areas, assessments should be performed taking into account the population-specific behavioral patterns.
Iijima, Kazuki; Funaki, Hironori; Tokizawa, Takayuki; Nakayama, Shinichi
Proceedings of 15th International Conference on Environmental Remediation and Radioactive Waste Management (ICEM 2013) (CD-ROM), 6 Pages, 2013/09
In decontamination pilot projects conducted by Japan Atomic Energy Agency (JAEA), many different techniques were tested to determine their applicability to remediate areas evacuated after the Fukushima Daiichi nuclear accident. The projects evaluated the radioactive contamination of trees and the effectiveness of decontaminating a highly contaminated evergreen forest. As the first step, three Japanese cedar trees and three fir trees were cut down and the distributions of radioactive cesium (Cs) were measured in each. The total concentrations of 
Cs and 
Cs in the leaves and branches were about 1 MBq/kg for both cedar and fir trees, and were appreciably higher than in the bark for cedar. The concentrations in the outer part of the trunks (under the bark) were lower, on the order of 10 kBq/kg, and those in the core of the trunks were lower than 1 kBq/kg for both kinds of trees. The observation that the Cs concentrations are higher in the outer part of trees, is compatible with the assumption that radio-Cs was mostly adsorbed on the surface of trees and partly penetrated into the trunks through the bark. Evolution of air dose rates in a 100
60 m pasture adjacent to the forest was monitored during decontamination of the forest and of the pasture itself. The dose rates in the pasture decreased drastically after stripping contaminated topsoil from the pasture and decreased slightly more after stripping contaminated topsoil of the forest floor and pruning the trees. Cutting down and removing 84 trees in the outermost area (10-m width) of the forest also slightly decreased these dose rates. After decontamination, the residual dose rates around the highly contaminated forest were mostly attributed to radioactive Cs existing in or on trees and topsoil in the untouched forest beyond the decontaminated area.
Sanada, Yukihisa; Torii, Tatsuo
Hozengaku, 12(2), p.10 - 15, 2013/07
no abstracts in English
Saegusa, Hiromitsu; Funaki, Hironori; Kurikami, Hiroshi; Sakamoto, Yoshiaki; Tokizawa, Takayuki
Nihon Genshiryoku Gakkai Wabun Rombunshi, 12(1), p.1 - 12, 2013/03
Since the Fukushima Daiichi Nuclear Power Plant accident caused by the Tohoku Region Pacific Coast Earthquake, decontamination work has been conducted. Decontamination wastes including removed soil, grass and trees are to be stored safely at temporary storage facilities for up to three years, after which they will be transferred to a planned interim storage facility. The decontamination pilot project was carried out in both the restricted and planned evacuation areas in order to assess decontamination methods and demonstrate measures for radiation protection of workers. Temporary storage facilities of different technical specifications were designed and constructed under various topographic conditions and land-use. In order to support designing, constructing and monitoring of temporary storage facilities for decontamination wastes during the full-scale decontamination, technical know-how obtained during the decontamination pilot project has been identified and summarized in this paper.
Satoh, Daiki
Isotope News, (696), p.14 - 19, 2012/04
Due to the accident at the Fukushima Daiichi Nuclear Power Plant, a large amount of radionuclides had been discharged to the environment. A computer software, named CDE (Calculation system for Decontamination Effect), has been developed to support making remediation strategy for the contaminated environment. In this issue, the overview of CDE, calculation method, validation, and trends in use are introduced.
Kobayashi, Naoki*; Naoi, Yosuke; Wakabayashi, Shuji; Tazaki, Makiko; Senzaki, Masao
JAEA-Review 2009-035, 88 Pages, 2010/03
JAEA-Review-2009-035.pdf:10.85MB
In order to facilitate the international discussion of the assurance of supply (AOS) system, authors have been conducted studies of AOS. We focused and based our study on Japanese proposal "IAEA Standby Arrangement System (INFCIRC/683)". In this paper, we have been able to show the feasibility of AOS system more specifically by supposing additional costs and the required period necessary for the AOS and present a system we made that we hope as a practical system. And we studied the issues surrounding AOS and presented our proposal of their solutions. The issues we are tackling here are the definitions of AOS; issues on consumer states, supplier states, IAEA and the nuclear industries. The proposals we present here are the broadening the cause of AOS, the declaration of the supplier states on AOS, the advisory committee on the initiation of AOS of IAEA and setting up a IAEA fund for AOS.
Kanamori, Masashi; Hashimoto, Kazuichiro; Terunuma, Hiroshi; Ikeda, Takeshi; Omura, Akiko; Terakado, Naoya; Nagakura, Tomohiro; Fukumoto, Masahiro; Watanabe, Fumitaka; Yamamoto, Kazuya; et al.
JAEA-Review 2009-023, 61 Pages, 2009/09
JAEA-Review-2009-023.pdf:8.49MB
When a nuclear emergency occurs in Japan, the Japan Atomic Energy Agency (JAEA) provides technical support to the National government, local governments, police, fire station and license holder etc. They are Designated Public Organizations conforming to the Basic Law on Emergency Preparedness and the Basic Plan for Disaster Countermeasures. The Nuclear Emergency Assistance and Training Center (NEAT) of JAEA provides a comprehensive range of technical support activities to an Off-Site Center in case of a nuclear emergency. Specifically, NEAT gives technical advice and information, provides for the dispatch of specialist as required, supplies emergency equipments and materials to the Joint Council of Nuclear Disaster Countermeasures, which meets at the Off-Site Center. NEAT provide various lectures and training course concerning nuclear disaster prevention for those personnel taking an active part in emergency response organizations at normal time. And NEAT researches on nuclear disaster prevention and also cooperate with international organizations. This annual report summarized the activities of JAEA/NEAT in the fiscal year 2008.
Naoi, Yosuke; Kobayashi, Naoki; Tazaki, Makiko
Proceedings of 2008 INMM/ESARDA Tokyo Workshop "Meeting Safeguards Challenges in an Expanding Nuclear World" (CD-ROM), 19 Pages, 2008/10
This paper proposes basic principles and mechanisms of the International Atomic Energy Agency (IAEA)-centered AOS mechanism as a whole, delineating detailed structure of both virtual fuel reserve and physical fuel bank. Since the proposal encompasses further implementation of the Japanese proposal (INFCIRC/683), the supply to be assured are not only limited to low enriched uranium (LEU) and enrichment service, but also enhanced to LEU and important services of the front end of nuclear fuel cycle, namely uranium ore supply, uranium storage, conversion, enrichment and fuel fabrication. The proposal, consequently, rearranges and redefines three levels described in "Possible framework" of IAEA Director Generals' report in June 2007 under a new name of "three phases". Several new ideas for the AOS, such as preliminary declaration by supplier states and creation of the advisory committee on the AOS are incorporated in the proposal.
Saito, Shinzo*; Tanaka, Ryuichi*; Kume, Tamikazu; Inoue, Tomio*; Takahashi, Shoji*
Genshiryoku eye, 54(5), p.34 - 41, 2008/05
no abstracts in English
Yanagisawa, Kazuaki; Inoue, Tomio*; Hayakawa, Kazushige*; Shiotari, Harutaka*; Nakamura, Yoshihide*; Matsuyama, Kazuya*; Nagasawa, Kiyoshi*
no journal, ,
Our economic study performed in 1997 revealed that the use of radiological technology in medicine was tended to spread. A reimbursement of medicine was about 10 billion dollars corresponding to about 4% of the national health expenditures (240 billion dollars) or to an average expenditure of 1,900 dollars a year for the Japanese. In 2005 it was about 13 billion dollars. An increasing rate was 17%. One of main cause of this increase is a significant advancement of medical devices represented by digital-X ray, multi-slice CT, PET and PET-CT.
