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Journal Articles

Ten years since the Fukushima Daiichi NPP disaster; What's important when protecting the population from a multifaceted technological disaster

Callen-Kovtunova, J.*; Homma, Toshimitsu

International Journal of Disaster Risk Reduction (Internet), 70, p.102746_1 - 102746_10, 2022/02

 Times Cited Count:2 Percentile:45.94(Geosciences, Multidisciplinary)

This paper presents key lessons on protecting the public during an emergency at a nuclear power plant (NPP) that have been identified from the accident at the Fukushima Daiichi NPP. The paper describes what emergency arrangements were in place prior to the accident, what occurred during the emergency and then the ascertained lesson. The paper highlights the failings of dose project models, emphasizes several lessons identified from past emergencies, such as the importance of predetermined criteria and emergency zones for determining protective actions. It also presents an essential lesson previously overlooked: the need for arrangements to ensure the safe evacuation of patients from hospitals and care homes.

Journal Articles

Decision making in protection against radiation from nuclear disaster; Risk trade-off and stakeholder involvement

Kanda, Reiko*; Homma, Toshimitsu*; Takahara, Shogo; Tsubokura, Masaharu*; Osako, Masahiro*; Kawaguchi, Isao*; Kato, Takaaki*

Risukugaku Kenkyu, 30(3), p.133 - 139, 2021/04

Almost ten years have passed since Fukushima nuclear accident. Our experience should be used to improve current emergency protective measures and preparedness. A review of the protective measures implemented in the aftermath of Fukushima nuclear accident has revealed problems such as paternalistic intervention for inhabitants and increased health risks due to the evacuation of vulnerable groups. The risk trade-offs in environmental recovery actions are more complex and ongoing; the stakeholders are the next generation and residents outside of the prefecture. Since one of the characteristics of nuclear disasters is the distance and time dependency of the risk, countless individual cases need to be addressed. While generalization of protective measures is essential, the appropriate deployment of personnel in a variety of roles may require to really address individual cases. To improve nuclear emergency preparedness in the future, it is necessary to incorporate both a top-down approach and a bottom-up approach in a well-balanced manner.

Journal Articles

Lessons learned in protection of the public for the accident at the Fukushima Daiichi Nuclear Power Plant

Callen, J.*; Homma, Toshimitsu

Health Physics, 112(6), p.550 - 559, 2017/06

 Times Cited Count:5 Percentile:46.25(Environmental Sciences)

What insights can the accident at the Fukushima Daiichi Nuclear Power Plant provide in the reality of decision making on actions to protect the public during a severe reactor and spent fuel pool emergency? In order to answer this question, and with the goal of limiting the consequences of any future emergencies at a nuclear power plant due to severe conditions, this article presents the main actions taken in response to the emergency in the form of a timeline. The focus of this paper are those insights concerning the progression of an accident due to severe conditions at a light water reactor nuclear power plant that must be understood in order to protect the public.

JAEA Reports

Survey on evacuation facilities in case of nuclear emergency in Shimane prefecture (Contract research)

Takahara, Shogo; Watanabe, Masatoshi; Oguri, Tomomi; Kimura, Masanori; Hirouchi, Jun; Munakata, Masahiro; Homma, Toshimitsu

JAEA-Data/Code 2016-016, 65 Pages, 2017/02


We surveyed on structural and material data on 22 facilities which are listed in local disaster management plan in Matsue city. These facilities can be divided into educational facilities, communal facilities and gymnastic hall. Height and floor-area of rooms, as well as window-area were collected as the structural data. We also collected information on constructional materials, and density of those. In addition, mass-thicknesses of the constructional materials were evaluated based on our surveys, and compared to the previous studies which were made in Japan, U.S., and European countries. Consequently, it was found that there is no significant difference of mass-thickness of constructional materials between the results of our surveys and the previous studies. However, for gymnastic hall, since thin metal plates are used for roofs, we can point out that the mass-thickness of roofs are much lower than those for other concrete facilities and clay tile roofing wooden houses.

Journal Articles

JAEA Reports

Actions to protect the public in an emergency due to severe conditions at a light water reactor (Translated document)

Homma, Toshimitsu; Takahara, Shogo; Iijima, Masashi; Sato, Sohei; Kimura, Masanori; Shimada, Kazumasa

JAEA-Review 2016-013, 162 Pages, 2016/07


This is a Japanese translation of "Actions to Protect the Public in an Emergency due to Severe Conditions at a Light Water Reactor", which is published by the International Atomic Energy Agency in May 2013. The original IAEA Publication is available on the IAEA Website (

Journal Articles

Changes in risk perceptions before and after nuclear accidents; Evidence from Japan

Nishikawa, Masashi*; Kato, Takaaki*; Homma, Toshimitsu; Takahara, Shogo

Environmental Science & Policy, 55(Part 1), p.11 - 19, 2016/01

 Times Cited Count:12 Percentile:37.81(Environmental Sciences)

Journal Articles

Investigating the gap between actual and perceived distance from a nuclear power plant; A Case study in Japan

Kato, Takaaki*; Takahara, Shogo; Homma, Toshimitsu

Journal of Disaster Research, 10(4), p.627 - 634, 2015/08

Journal Articles

Study for shielding efficiency of evacuation facilities in nuclear emergency

Oguri, Tomomi*; Takahara, Shogo; Kimura, Masanori; Homma, Toshimitsu

Progress in Nuclear Science and Technology (Internet), 4, p.767 - 770, 2014/04

Sheltering is one of the protective actions in a nuclear emergency. To introduce the actions with effect, preparedness is needed from a point of efficiency of reduction of radiation exposure and also capacity and location. In this study, we surveyed building materials and construction of real facilities listed in prefectural regional emergency prevention plans and then evaluated the shielding efficiency of these facilities for external exposure. As the results, we obtained knowledge of distribution of shielding factor for actual evacuation facilities by cloudshine and groundshine. Moreover, based on the sensitivity analyses, basic data was obtained that easily evaluate the shielding efficiency of facilities with different structures and materials from basic building models.

Journal Articles

Probabilistic assessment of doses to the public living in areas contaminated by the Fukushima Daiichi Nuclear Power Plant accident

Takahara, Shogo; Iijima, Masashi; Shimada, Kazumasa; Kimura, Masanori; Homma, Toshimitsu

Radiation Monitoring and Dose Estimation of the Fukushima Nuclear Accident, p.197 - 214, 2014/02


The aim of this study is to provide the scientifically-based quantitative information about a range of received doses to the evacuees from the evacuation areas and the deliberate evacuation areas. To achieve the aim, we adopted a probabilistic approach. The dose assessments were performed based on the measurement data of the surface activity concentrations of $$^{137}$$Cs and the results of actual survey on behavioral patterns of the population groups living in Fukushima Prefecture. As the result of assessments, the 95th percentile of the annual effective doses received by the inhabitants evacuated from the evacuation areas were mainly in the 1-10 mSv dose band in the first year after the contamination. However, the 95th percentile of the doses received by some outdoor workers, inhabitants evacuated from the deliberate evacuation areas and highly contaminated areas were in the 10-50 mSv dose band.

Journal Articles

Monetary values of unit collective dose in optimization of radiation protection

Takahara, Shogo; Kato, Takaaki*; Homma, Toshimitsu

Hoken Butsuri, 48(4), p.180 - 192, 2013/12

The monetary value of the person-sievert is a key element in implementing the optimization principle of the radiation protection. The objective of this paper are to evaluate the country-specific monetary value of the person-sievert reflecting the economic and population characteristics in Japan. When we calculated the monetary values of the person-sievert in Japan using human capital method and willingness to pay approach, the values were around several million yen/person-Sv and 20 million yen/person-Sv, respectively. In addition, we reviewed the cost of radiological protective measures per person-sievert avoided. As the results of comparing the cost and benefit, the costs of radiological protective measures to reduce the concentration of radon in homes and to protect workers in nuclear facilities were balanced with the benefit. On the other hand, the costs of radionuclide emission control measures at industrial facilities tend to be higher than the benefit of those measures.

Journal Articles

A Case study of economic incentives and local citizens' attitudes towards hosting a nuclear power plant in Japan; Impacts of the Fukushima accident

Kato, Takaaki*; Takahara, Shogo; Nishikawa, Masashi*; Homma, Toshimitsu

Energy Policy, 59, p.808 - 818, 2013/08


 Times Cited Count:26 Percentile:78.87(Economics)

This case study of the areas that host Kashiwazaki Kariwa NPP compares local citizens' attitude towards the benefits and the drawbacks of hosting the NPP. In December 2011, our survey respondents became more negative about hosting the NPP after the Fukushima accident in March 2011 compared to the survey in January 2010. Another comparison between the November 2005 and the December 2011 surveys provided a different look. The magnitude of the negative shift in Kariwa Village, which saw a large expansion of social welfare programs, was modest in the sense that its 2011 results were similar to its 2005 results. Local tax revenues, subsidies from the national government and the donation from a utility contributed to this budget expansion in Kariwa. The negative shifts from 2005 to 2011 were clear in the other two municipalities which did not see such a large expansion of economic benefits during this period.

Journal Articles

Evaluation of the precautionary action zone using a probabilistic consequence analysis

Kimura, Masanori; Takahara, Shogo; Homma, Toshimitsu

Journal of Nuclear Science and Technology, 50(3), p.296 - 303, 2013/03

 Times Cited Count:2 Percentile:18.91(Nuclear Science & Technology)

JAEA Reports

Development of evaluation method for the effect of reducing equivalent doses to the thyroid by implementing iodine thyroid blocking

Kimura, Masanori; Takahara, Shogo; Homma, Toshimitsu

JAEA-Research 2012-039, 24 Pages, 2013/02


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 such actions using a Level 3 Probabilistic Safety Assessment (PSA) code, the OSCAAR, developed by the JAEA. Iodine thyroid blocking is an effective urgent protective action to reduce the equivalent doses to the thyroid due to inhalation of radioactive iodine. However, the timing of the administration of stable iodine 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 introduced a metabolic model of iodine into the OSCAAR for evaluating the effect of the administration of stable iodine for reducing equivalent doses to the thyroid depending on the its timing. Then, examined the effectiveness of iodine thyroid blocking combined with sheltering or evacuation in the containment bypass scenario with large radioactive release to the environment.

Journal Articles

Assessment of radiation doses to the public in areas contaminated by the Fukushima Daiichi Nuclear Power Station accident

Takahara, Shogo; Iijima, Masashi; Shimada, Kazumasa; Kimura, Masanori; Homma, Toshimitsu

Proceedings of International Symposium on Environmental monitoring and dose estimation of residents after accident of TEPCO's Fukushima Daiichi Nuclear Power Station, p.212 - 220, 2012/12

In the areas contaminated by radioactive materials due to the Fukushima Daiichi Nuclear Power Station accident, many residents are exposed to radiation through various exposure pathways. To assess the doses realistically and comprehensively, a probabilistic approach was adopted using data that reflected realistic environmental trends and lifestyle habits in Fukushima Prefecture. In the first year after the contamination, the 95th percentile of the annual effective dose received by the inhabitants evacuated from the evacuation areas and the deliberate evacuation areas was mainly in the 1-10 mSv dose band. However, the 95th percentile of the dose received by some outdoor workers and inhabitants evacuated from highly contaminated areas was in the 10-50 mSv dose band. The doses due to external exposure to deposited radionuclides were the dominant exposure pathway, and their contributions were about 90% under prevailing contamination conditions in Fukushima Prefecture. In addition, 20%-30% of the lifetime effective dose was delivered during the first year after the contamination.

Journal Articles

A Preliminary dose assessment for the population in an area outside the 30 km zone after the Fukushima Daiichi Nuclear Power Plant accident

Kimura, Masanori; Kinase, Sakae; Takahara, Shogo; Homma, Toshimitsu

Progress in Nuclear Science and Technology (Internet), 3, p.19 - 24, 2012/10

The dose received by the public was assessed for one month since the Fukushima Daiichi Nuclear Power Plant accident onset to reconstruct and predict external and internal doses to the public at an area using the radiation monitoring data provided by regulatory authorities. The cumulative doses were estimated by fitting the exponential model, with the decay of nuclides ($$^{131}$$I, $$^{134}$$Cs + $$^{137}$$Cs) considered, to the measurement data. The external doses were evaluated by supplementing the measurement data with the estimates. In addition, the internal doses by inhalation and ingestion of radioiodine $$^{131}$$I were evaluated using the concentration of airborne effluents and the tap water. Consequently, the total dose for the public was found to be less than 20 mSv. The averted dose by restrictions on the ingestion of the tap water was also discussed.

Journal Articles

Using ICRP/ICRU voxel models to evaluate specific absorbed fractions

Kinase, Sakae; Kimura, Masanori; Takahara, Shogo; Homma, Toshimitsu

Progress in Nuclear Science and Technology (Internet), 3, p.69 - 71, 2012/10

Journal Articles

Assessment of doses from external exposure in contaminated areas resulting from the Fukushima Daiichi Nuclear Power Plant accident

Takahara, Shogo; Kimura, Masanori; Kinase, Sakae; Ishikawa, Jun; Suyama, Kenya; Hosoyamada, Ryuji; Homma, Toshimitsu

Progress in Nuclear Science and Technology (Internet), 3, p.25 - 29, 2012/10

Dose assessment is one of the important issues to make decisions in contaminated areas resulting from the Fukushima Daiichi Nuclear Power Plant accident. The doses to inhabitants of contaminated areas should be assessed prospectively and retrospectively taking into account the impact from various exposure pathways. The external exposure from deposited radioactive materials of short-lived and long-lived is one of the most important pathways. In the present study, the radionuclide compositions have been evaluated by source term analysis taking into account 54 radionuclides. This analysis consists in evaluating the inventory and the fraction of the radionuclides that were released into the atmosphere. On the assumption that dose rate may be decreased due to the radioactive decay as well as weathering effects, we have assessed the dose for future and past at the contaminated areas. The assessed values are almost consistent with the measured ones during the first month.

Journal Articles

Sensitivity analysis of a passive decay heat removal system under a post-loss of coolant accident condition

Liu, Q.; Homma, Toshimitsu

Journal of Nuclear Science and Technology, 49(9), p.897 - 909, 2012/09

 Times Cited Count:4 Percentile:32.44(Nuclear Science & Technology)

Passive safety features are now of interest to the design of future generation reactors. Though passive safety systems are considered to be more reliable, the large uncertainty associated with the system response can not be ignored. It is necessary to identify the uncertain inputs that have the important impact on the uncertainty of the system performance. In this study, two global sensitivity measures, the first-order sensitivity index and the total-order sensitivity index, are applied to a passive decay heat removal system of a gas-cooled fast reactor for identifying the key uncertainty inputs. It is found that the uncertainty in the system pressure contributes the most to the uncertainty in the system outputs. In addition, the cooler wall temperature, the Nusselt number and the friction factor in the mixed convectional flow regime also have small impact on the uncertainty of the system outputs.

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