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JAEA Reports

Examinations of performance for utilization of radiation portal monitors in contamination inspection for motor vehicles in nuclear emergency (Contract research)

Hiraoka, Hirokazu; Komatsuzaki, Joji*; Hanaka, Norihiko*; Okamoto, Akiko; Saito, Yoshihiko*; Munakata, Masahiro; Togawa, Orihiko

JAEA-Technology 2022-003, 70 Pages, 2022/07


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, $$^{133}$$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 $$gamma$$-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,

JAEA Reports

Investigation and consideration on evaluation of radiation doses to residents in the case of a nuclear emergency

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


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.

Journal Articles

Development of an evaluation method for planning of urgent protection strategies in a nuclear emergency using a level 3 probabilistic risk assessment

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.

JAEA Reports

Development of MIG2DF Version 2

Takai, Shizuka; Kimura, Hideo*; Uchikoshi, Emiko*; Munakata, Masahiro; Takeda, Seiji

JAEA-Data/Code 2020-007, 174 Pages, 2020/09


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).

JAEA Reports

Development of database of dose reduction factor for reducing equivalent doses to the thyroid by implementing iodine thyroid blocking (Contract research)

Kimura, Masanori; Munakata, Masahiro; Hato, Shinji*; Kanno, Mitsuhiro*

JAEA-Data/Code 2020-002, 38 Pages, 2020/03


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.

Journal Articles

Development of an external radiation dose estimation model for children returning to their homes in areas affected by the Fukushima Nuclear Accident

Mori, Airi; Takahara, Shogo; Yoshida, Hiroko*; Sanada, Yukihisa; Munakata, Masahiro

Health Physics, 117(6), p.606 - 617, 2019/12

 Times Cited Count:1 Percentile:12.54(Environmental Sciences)

Journal Articles

Investigation on the influence of additional protective measures on sheltering effectiveness for internal exposure

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

Journal Articles

Influence of artificial radionuclide deposited on a monitoring post on measured value of ambient dose rate

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.

Journal Articles

Evaluation of the radiation protection capability in shelter facilities with positive pressure ventilation

Ishizaki, Azusa; Nakanishi, Chika*; Takubo, Kazuya*; Munakata, Masahiro

Proceedings of 27th International Conference on Nuclear Engineering (ICONE-27) (Internet), 9 Pages, 2019/05

Journal Articles

Development of integrated system for accident consequence evaluation using Level 2 and Level 3 PRA codes

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.

Journal Articles

Investigation of removal factors of various materials inside houses after Nuclear Power Station Accident

Mori, Airi; Ishizaki, Azusa; Futemma, Akira; Tanabe, Tsutomu; Wada, Takao; Kato, Mitsugu; Munakata, Masahiro

Hoken Butsuri (Internet), 54(1), p.45 - 54, 2019/04

JAEA Reports

Photon transmittance data collection of building materials for evaluating radiation protection capability of buildings (Contract research)

Ishizaki, Azusa; Futemma, Akira; Takubo, Kazuya*; Nakanishi, Chika*; Munakata, Masahiro

JAEA-Data/Code 2018-022, 20 Pages, 2019/03


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.

JAEA Reports

External dose evaluation of emergency responder in off-site at the time of Fukushima-Dai-ichi Nuclear Power Station Accident (Contract research)

Shimada, Kazumasa; Sasaki, Toshihisa*; Iijima, Masashi*; Munakata, Masahiro

JAEA-Research 2018-012, 68 Pages, 2019/02


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 $$mu$$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.

Journal Articles

Development and application of a method for discriminating the influence of radon progenies in air from aerial radiation monitoring data

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:12.37(Chemistry, Inorganic & Nuclear)

Journal Articles

Investigation of reduction factor of internal exposure for sheltering in Japan

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

Journal Articles

Estimation of radiocesium dietary intake from time series data of radiocesium concentrations in sewer sludge

Pratama, M. A.; Takahara, Shogo; Munakata, Masahiro; Yoneda, Minoru*

Environment International, 115, p.196 - 204, 2018/06

 Times Cited Count:2 Percentile:7.91(Environmental Sciences)

JAEA Reports

Development of measurement system of radioactive plume using unmanned airplane in the fiscal year 2016 (Contract research)

Ishizaki, Azusa; Sanada, Yukihisa; Nishizawa, Yukiyasu*; Futemma, Akira; Munakata, Masahiro

JAEA-Research 2017-012, 58 Pages, 2018/03


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.

Journal Articles

Dose-reduction effects of vehicles against gamma radiation in the case of a nuclear accident

Takahara, Shogo; Watanabe, Masatoshi*; Hirouchi, Jun; Iijima, Masashi*; Munakata, Masahiro

Health Physics, 114(1), p.64 - 72, 2018/01


 Times Cited Count:2 Percentile:22.77(Environmental Sciences)

Journal Articles

Application of topographical source model for air dose rates conversions in aerial radiation monitoring

Ishizaki, Azusa; Sanada, Yukihisa; Ishida, Mutsushi; Munakata, Masahiro

Journal of Environmental Radioactivity, 180, p.82 - 89, 2017/12

 Times Cited Count:6 Percentile:22.03(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 $$gamma$$-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.

Journal Articles

Factors affecting the effectiveness of sheltering in reducing internal exposure

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

134 (Records 1-20 displayed on this page)