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Hashimoto, Makoto; Kinase, Sakae; Munakata, Masahiro; Murayama, Takashi; Takahashi, Masa; Takada, Chie; Okamoto, Akiko; Hayakawa, Tsuyoshi; Sukegawa, Masato; Kume, Nobuhide*; et al.
JAEA-Review 2020-071, 53 Pages, 2021/03
JAEA-Review-2020-071.pdf:2.72MB
In the case of a nuclear accident or a radiological emergency, the Japan Atomic Energy Agency (JAEA), as a designated public corporation assigned in the Disaster Countermeasures Basic Act and the Armed Attack Situation Response Law, undertakes technical supports to the national government and local governments. The JAEA is requested to support to evaluate radiation doses to residents in a nuclear emergency, which is specified in the Basic Disaster Management Plan and the Nuclear Emergency Response Manual. For the dose evaluation, however, its strategy, target, method, structure and so on have not been determined either specifically or in detail. This report describes the results of investigation and consideration discussed in the "Working Group for Radiation Dose Evaluation at a Nuclear Emergency" established within the Nuclear Emergency Assistance and Training Center to discuss technical supports for radiation dose evaluation to residents in the case of a nuclear emergency, and aims at contributing to specific and detailed discussion and activities in the future for the national government and local governments, also within the JAEA.
Kimura, Masanori; Oguri, Tomomi*; Ishikawa, Jun; Munakata, Masahiro
Journal of Nuclear Science and Technology, 58(3), p.278 - 291, 2021/03
Times Cited Count：0 Percentile：0.01(Nuclear Science & Technology)The authors developed an evaluation method for planning urgent protection strategies in a nuclear emergency by using a Level 3 Probabilistic Risk Assessment (PRA) code, OSCAAR. For a given accident scenario, the OSCAAR can calculate received doses in the early phase of a nuclear accident and the dose reduction effect of implementing urgent protective actions such as evacuation, sheltering, and iodine thyroid blocking. The authors considered the combination of these urgent protective actions within a precautionary action zone (PAZ) and an urgent protective action planning zone (UPZ) for an accident scenario and then calculated received doses after implementing these protective actions using the OSCAAR. After that, the authors performed sensitivity analysis for protective action models of the OSCAAR and then optimized the protection strategy by reducing doses to below generic criteria of the International Atomic Energy Agency (IAEA). Consequently, the effective urgent protection strategy for the accident scenario could be designed, such as precautionary evacuation within the PAZ, and the combination of evacuation after sheltering, sheltering in concrete building, or in normal housing and thyroid blocking within the UPZ. The developed evaluation method will be very useful in developing effective urgent protection strategies for an accident scenario.
Takai, Shizuka; Kimura, Hideo*; Uchikoshi, Emiko*; Munakata, Masahiro; Takeda, Seiji
JAEA-Data/Code 2020-007, 174 Pages, 2020/09
JAEA-Data-Code-2020-007.pdf:4.23MB
The MIG2DF computer code is a computer program that simulates groundwater flow and radionuclide transport in porous media for the safety assessment of radioactive waste disposal. The original version of MIG2DF was released in 1992. The original code employs a two-dimensional (vertical or horizontal cross-section, or an axisymmetric configuration) finite-element method to approximate the governing equations for density-dependent saturated-unsaturated groundwater flow and radionuclide transport. Meanwhile, for geological disposal of radioactive wastes, landscape evolution such as uplift and erosion needs to be assessed as a long-term geological and climate events, considering site conditions. In coastal areas, the impact to groundwater flow by change of salinity distribution to sea level change also needs to be considered. To deal with these events in the assessment, we have revised the original version of MIG2DF and developed the external program which enables MIG2DF to consider unsteady landscape evolution. In these developments, this report describes an upgrade of MIG2DF (Version 2) and presents the configuration, equations, methods, and verification. This reports also give the explanation external programs of MIG2DF: PASS-TRAC (the particle tracking code), PASS-PRE (the code for dataset preparation), and PASS-POST (the post-processing visualization system).
Kimura, Masanori; Munakata, Masahiro; Hato, Shinji*; Kanno, Mitsuhiro*
JAEA-Data/Code 2020-002, 38 Pages, 2020/03
JAEA-Data-Code-2020-002.pdf:3.23MB
To consider the method of implementing urgent protective actions in a nuclear accident appropriately, the authors have been assessing the effects of reducing doses by taking urgent protective actions using a Level 3 Probabilistic Risk Assessment (PRA) code, the OSCAAR, developed by the JAEA. Iodine thyroid blocking is an effective urgent protective action to reduce equivalent doses to the thyroid due to inhalation of radioactive iodine. However, the timing of the administration of stable iodine (SI) is important to maximize the effectiveness for thyroidal blocking. Therefore, the careful consideration should be given to the most effective way of iodine thyroid blocking when preparing off-site emergency plans. In the present study, the authors developed a new metabolic model for thyroid by combining the respiratory tract model (Publ.66) and gastrointestinal tract model (Publ.30) of the ICRP with a metabolic model for thyroid (Johnson's model) in order to calculate the behavior of radioiodine and stable iodine in the body more realistically. The model is useful to evaluate the effect of the administration of SI for reducing equivalent doses to the thyroid depending on the its timing. We also calculated the reduction factor for equivalent doses to the thyroid in order to the thyroid by using the model, and then developed the its database for the OSCAAR. Consequently, the OSCAAR can evaluate the effectiveness for thyroidal blocking realistically and promptly.
Mori, Airi; Takahara, Shogo; Yoshida, Hiroko*; Sanada, Yukihisa; Munakata, Masahiro
Health Physics, 117(6), p.606 - 617, 2019/12
Times Cited Count：0 Percentile：0.01(Environmental Sciences)Hirouchi, Jun; Takahara, Shogo; Komagamine, Hiroshi*; Munakata, Masahiro
Proceedings of Asian Symposium on Risk Assessment and Management 2019 (ASRAM 2019) (USB Flash Drive), 7 Pages, 2019/09
no abstracts in English
Hiraoka, Hirokazu; Hokama, Tomonori; Munakata, Masahiro
Proceedings of 27th International Conference on Nuclear Engineering (ICONE-27) (Internet), 5 Pages, 2019/05
Neighboring inhabitants of nuclear facilities must evacuate according to an ambient dose rate at a nuclear accident. The evacuation is judged by the measured value by monitoring posts (MPs). However, if the measured value increase by artificial radionuclide deposited to MP, it is considered that the dose rate of the surrounding environment is overestimated. The purpose of this research is to evaluate exactly the dose rate even if the radionuclide deposit to the MP, in order to adequately evacuate inhabitants. Just a MP and horizontal ground was simulated. To calculate ambient dose rates from the roof surface of MP and ground surface, Monte Carlo calculation was done. And, it was obtained that the ratio which the dose rate from the roof account for sum of two these dose rates. According to the result, the ratio was 42%. It suggested that the radionuclide could increase the measured value. However, because simulated system was simple, it is considered that the ratio was overestimated.
Ishizaki, Azusa; Nakanishi, Chika*; Takubo, Kazuya*; Munakata, Masahiro
Proceedings of 27th International Conference on Nuclear Engineering (ICONE-27) (Internet), 9 Pages, 2019/05
Kimura, Masanori; Ishikawa, Jun; Oguri, Tomomi*; Munakata, Masahiro
Proceedings of 27th International Conference on Nuclear Engineering (ICONE-27) (Internet), 5 Pages, 2019/05
An integrated system between the THALES2 and the OSCAAR was developed in order to assist in preparing the input file of the OSCAAR. For the result of a state-of-the-art source term analysis with the THALES2, the authors implemented a preliminary analysis using the OSCAAR in order to evaluate the difference in setting of release fraction rates for the radionuclide groups. The effective dose was calculated for some cases by changing of release fraction rates divided into 1h (case 1), 3h (case 2), 5h (case 3), none (case 4) and arbitrary hours (case 5). After that, the ratio of the effective dose for these cases was compared. The result indicates that it was better to set short duration of release stages while the release fraction rates increased sharply. It seems that the case 5 is a better method in order to adapt to various accident scenarios. The method shows that it is useful for reducing the uncertainty in a Level 3 PRA analysis.
Mori, Airi; Ishizaki, Azusa; Futemma, Akira; Tanabe, Tsutomu; Wada, Takao; Kato, Mitsugu; Munakata, Masahiro
Hoken Butsuri (Internet), 54(1), p.45 - 54, 2019/04
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.
Hirouchi, Jun; Nishizawa, Yukiyasu*; Urabe, Yoshimi*; Shimada, Kazumasa; Sanada, Yukihisa; Munakata, Masahiro
Applied Radiation and Isotopes, 141, p.122 - 129, 2018/11
Times Cited Count：1 Percentile：18.37(Chemistry, Inorganic & Nuclear)Hirouchi, Jun; Takahara, Shogo; Komagamine, Hiroshi*; Munakata, Masahiro
Proceedings of Asian Symposium on Risk Assessment and Management 2018 (ASRAM 2018) (USB Flash Drive), 8 Pages, 2018/10
no abstracts in English
Pratama, M. A.; Takahara, Shogo; Munakata, Masahiro; Yoneda, Minoru*
Environment International, 115, p.196 - 204, 2018/06
Times Cited Count：1 Percentile：7.07(Environmental Sciences)Ishizaki, Azusa; Sanada, Yukihisa; Nishizawa, Yukiyasu*; Futemma, Akira; Munakata, Masahiro
JAEA-Research 2017-012, 58 Pages, 2018/03
JAEA-Research-2017-012.pdf:9.36MB
At the accident of nuclear facilities, a prediction of behavior of released radioactive plume is indispensable for the decision of the refuge plan of inhabitants. Currently, prediction system which is based on atmospheric dispersion simulation has been implemented for as a tool of the atomic energy disaster prevention. However, direct measurement method of radioactive plume has not existed. In this study, some component technologies were developed for establishment of direct measurement methods of radioactive plume using unmanned aerial vehicle whose technological innovation is remarkable. In addition, algorism of making flight plan was developed based on prediction model of radioactive plume. This report summarized the outcome of the first year with plan of three years.
Takahara, Shogo; Watanabe, Masatoshi*; Hirouchi, Jun; Iijima, Masashi*; Munakata, Masahiro
Health Physics, 114(1), p.64 - 72, 2018/01
Times Cited Count：1 Percentile：18.37(Environmental Sciences)Ishizaki, Azusa; Sanada, Yukihisa; Ishida, Mutsushi; Munakata, Masahiro
Journal of Environmental Radioactivity, 180, p.82 - 89, 2017/12
Times Cited Count：6 Percentile：32.08(Environmental Sciences)After the Fukushima Daiichi Nuclear Power Station (FDNPS) accident in 2011, aerial radiation monitoring (ARM) using a manned helicopter was conducted to rapidly measure air dose rates and the deposition of radioactive nuclides over a large area. Typically, the air dose rate is obtained by conversion from the count rate using the conventional flat source model (FSM). The converted dose rate via aerial monitoring poorly matches the results of ground measurement in the mountain and forest areas because the FSM does not consider topographical effects. To improve the conversion accuracy, we developed new methods to analyze aerial monitoring data using the topographical source model (TSM) based on the analytical calculation of the 
-ray flux. The ARM results converted using both the FSM as well as TSM were compared with ground measurement data obtained after the FDNPS accident. By using TSM, the conversion accuracy was improved.
Hirouchi, Jun; Takahara, Shogo; Komagamine, Hiroshi*; Watanabe, Masatoshi*; Munakata, Masahiro
Proceedings of Asian Symposium on Risk Assessment and Management 2017 (ASRAM 2017) (USB Flash Drive), 11 Pages, 2017/11
no abstracts in English
Kimura, Masanori; Hato, Shinji*; Matsubara, Takeshi*; Kanno, Mitsuhiro*; Munakata, Masahiro
Proceedings of Asian Symposium on Risk Assessment and Management 2017 (ASRAM 2017) (USB Flash Drive), 9 Pages, 2017/11
The authors developed a new metabolic model for iodine by combining the respiratory tract model (Publ.66), the gastrointestinal tract model (Publ.30) of the ICRP and the metabolic model for iodine (Johnson's model) in order to evaluate the behavior of radioiodine and stable iodine in the body more realistically. The developed metabolic model indicated that a reduction factor (RF) depends on dosage of stable iodine, timing of the administration of stable iodine, different iodine isotopes (
I - 
I), and age groups. Therefore, the RF was calculated by changing these parameters and then a database of the RF was constructed for the application to the OSCAAR code.
