• Nuclear Engineering and Technology
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• 제46권2호
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• pp.207-216
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• 2014

This paper revisits the Fukushima accident to draw lessons in the aspect of nuclear safety considering the fact that the Fukushima accident resulted in core damage for three nuclear power plants simultaneously and that there is a high possibility of a failure of the integrity of reactor vessel and primary containment vessel. A brief review on the accident progression at Fukushima nuclear power plants is discussed to highlight the nature and characteristic of the event. As the severe accident management measures at the Fukushima Daiich nuclear power plants seem to be not fully effective, limitations of current severe accident management strategy are discussed to identify the areas for the potential improvements including core cooling strategy, containment venting, hydrogen control, depressurization of primary system, and proper indication of event progression. The gap between the Fukushima accident event progression and current understanding of severe accident phenomenology including the core damage, reactor vessel failure, containment failure, and hydrogen explosion are discussed. Adequacy of current safety goals are also discussed in view of the socio-economic impact of the Fukushima accident. As a conclusion, it is suggested that an investigation on a coherent integrated safety principle for the severe accident and development of innovative mitigation features is necessary for robust and resilient nuclear power system.

• Asian Journal for Public Opinion Research
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• 제5권1호
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• pp.1-14
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• 2017

The Fukushima nuclear accident caused by an earthquake and a subsequent tsunami on March 11, 2011 has seriously impacted the environment surrounding the Fukushima Daiichi nuclear power plant. While all the residents near the plant were evacuated from the area deemed uninhabitable after the accident, residents of the neighboring area outside of the evacuation zone still seem to live in fear of invisible radiation. To understand Fukushima residents' thinking about the environmental risks that accompany a nuclear disaster, we utilize a poll of the residents of Fukushima conducted in 2013. Based on the survey data, we reveal factors that seem to strongly affect their knowledge and concerns about nuclear power plants. The results of the multivariate analysis show the importance of the following two factors: (1) confidence in mass media, and (2) trust in institutions in charge of administering the accident, especially the central government, the Nuclear and Industrial Safety Agency, and Tokyo Electric Power Company. We conclude that the more people trust mass media and particular institutions, the more likely it is that they are have an elevated sense of anxiety and fear of the presence of nuclear plants.

• 방사성폐기물학회지
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• 제21권1호
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• pp.95-114
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• 2023

During the decades after the Fukushima Daiichi Nuclear Power Station (FDNPS) accident, ambient dose rates have markedly decreased when compared to those at the early state of the accident. Government projects have been continuously conducted by surveying the ambient dose rate and radiocesium distributions. Airborne surveys using crewed helicopters and unmanned aerial vehicles (UAVs) are the best methods for obtaining an overall picture of the distribution. However, ground-based surveys are required for accurate measurements near the population. The differences between these methods include the knowledge of the post depositional behavior of radionuclides in land use. The survey results form the basis for policy decisions such as lifting evacuation zones, decontamination, and other countermeasures. These surveys contain crucial findings regarding post-accident responses. This paper reviews the survey methods of government projects and current situation around the FDNPS. The visualization methods and databases of ambient dose rates are also reviewed to provide information to the population.

• Nuclear Engineering and Technology
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• 제50권8호
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• pp.1199-1209
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• 2018

After the Fukushima-Daiichi accident in 2011, the multi-unit risk, i.e., the risk due to several nuclear power plants (NPPs) in a site has become an important issue in several countries such as Korea, Canada, and China. However, the multi-unit risk has been discussed for a long time in the nuclear community before the Fukushima-Daiichi nuclear accident occurred. The regulatory authorities around the world and the international organizations had proposed requirements or guidelines to reduce the multi-unit risk. The concerns regarding the multi-unit risk can be summarized in the following three questions: How much the accident of an NPP in a site affects the safety of other NPPs in the same site? What is the total risk of a site with many NPPs? Will the risk of the simultaneous accidents at several NPPs in a site such as the Fukushima Daiichi accident be low enough? The multi-unit risk assessment (MURA) in an integrated framework is a practical approach to obtain the answers for the above questions. Even though there were few studies to assess the multi-unit risk before the Fukushima-Daiichi nuclear accident, there are still several issues to be resolved to perform the complete MURA. This article aims to provide an overview of the multi-unit risk issues and its assessment. We discuss the several critical issues in the current MURA to get useful insights regarding the multi-unit risk with the current state art of probabilistic safety assessment (PSA) technologies. Also, the qualitative answers for the above questions are addressed.

• Nuclear Engineering and Technology
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• 제47권1호
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• pp.11-25
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• 2015

The accident at Japan's Fukushima Daiichi nuclear power plant in March 2011, caused by an earthquake and a subsequent tsunami, resulted in a failure of the power systems that are needed to cool the reactors at the plant. The accident progression in the absence of heat removal systems caused Units 1-3 to undergo fuel melting. Containment pressurization and hydrogen explosions ultimately resulted in the escape of radioactivity from reactor containments into the atmosphere and ocean. Problems in containment venting operation, leakage from primary containment boundary to the reactor building, improper functioning of standby gas treatment system (SGTS), unmitigated hydrogen accumulation in the reactor building were identified as some of the reasons those added-up in the severity of the accident. The Fukushima accident not only initiated worldwide demand for installation of adequate control and mitigation measures to minimize the potential source term to the environment but also advocated assessment of the existing mitigation systems performance behavior under a wide range of postulated accident scenarios. The uncertainty in estimating the released fraction of the radionuclides due to the Fukushima accident also underlined the need for comprehensive understanding of fission product behavior as a function of the thermal hydraulic conditions and the type of gaseous, aqueous, and solid materials available for interaction, e.g., gas components, decontamination paint, aerosols, and water pools. In the light of the Fukushima accident, additional experimental needs identified for hydrogen and fission product issues need to be investigated in an integrated and optimized way. Additionally, as more and more passive safety systems, such as passive autocatalytic recombiners and filtered containment venting systems are being retrofitted in current reactors and also planned for future reactors, identified hydrogen and fission product issues will need to be coupled with the operation of passive safety systems in phenomena oriented and coupled effects experiments. In the present paper, potential hydrogen and fission product issues raised by the Fukushima accident are discussed. The discussion focuses on hydrogen and fission product behavior inside nuclear power plant containments under severe accident conditions. The relevant experimental investigations conducted in the technical scale containment THAI (thermal hydraulics, hydrogen, aerosols, and iodine) test facility (9.2 m high, 3.2 m in diameter, and $60m^3$ volume) are discussed in the light of the Fukushima accident.

• Nuclear Engineering and Technology
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• 제46권1호
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• pp.27-38
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• 2014

The Fukushima Dai-Ichi accident in 2011 has affected various aspects of the nuclear society worldwide. The accident revealed some problems in the conventional approaches used to ensure the safety of nuclear installations. To prevent such disastrous accidents in the future, we have to learn from them and improve the conventional approaches in a more systematic manner. In this paper, we will cover three issues. The first is to identify the key issues that affected the progress of the Fukushima Dai-Ichi accident greatly. We examine the accident from a defense-in-depth point of view to identify such issues. The second is to develop a more systematic approach to enhance the safety of nuclear installations. We reexamine nuclear safety from a risk point of view. We use the concepts of residual and unknown risks in classifying the risk space. All possible accident scenarios types are reviewed to clarify the characteristics of the identified issues. An approach is proposed to improve our conventional approaches used to ensure nuclear safety including the design of safety features and the safety assessments from a risk point of view. Finally, we address some issues to be improved in the conventional risk assessment and management framework and/or practices to enhance nuclear safety.

• 한국언론정보학보
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• 제76권
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• pp.124-150
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• 2016

이 연구는 후쿠시마 원전 사고 이전과 이후를 비교해 우리나라 원전 보도의 일반적 특성과 보도 프레임 차이를 확인하기 위한 것이다. 이를 위해 중앙 일간신문과 원전 소재 지역 일간신문을 선정해 이들 신문이 게재한 원전 관련 기사에 대한 내용 분석을 실시했다. 연구 결과, 후쿠시마 원전 사고 이후 우리나라 원전에 대한 보도는 크게 늘어난 것으로 나타났다. 또한 이전에 주로 경제적 측면이 강조됐던 우리나라 원전 보도는 후쿠시마 원전 사고 이후 사회적 차원이 강조되기 시작했다. 그리고 우리나라 원전 보도 기사가 주요 기사로 다뤄지는 계기가 됐다. 한편 후쿠시마 원전 사고 이후 우리나라 원전 보도의 프레임 역시 크게 변화했다. 당연하게도 환경 안전 프레임이 크게 증가한 것으로 나타났다. 이는 후쿠시마 원전 사고를 계기로 우리나라 원전의 안정성과 관련된 보도가 대폭 늘어났기 때문으로 보인다. 특히 원전 소재 지역의 일간신문에서 환경 안전 프레임은 후쿠시마 원전 사고 이전에도 다른 프레임과 비교해 가장 많은 29.3%였는데, 그 이후에는 77.6%로까지 증가한 것으로 확인됐다.

• Nuclear Engineering and Technology
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• 제51권3호
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• pp.837-842
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• 2019

A large amount of radioactive material was released from the Fukushima Daiichi Nuclear Power Plant (FDNPP) in 2011 and dispersed into the environment. Though seven years have passed since the Fukushima Daiichi Nuclear Power Plant accident, some parts of Japan are still under the influence of radionuclide contamination, especially Fukushima Prefecture and prefectures neighboring Fukushima Prefecture. The long-term effective doses and the contributions of each exposure pathway (5 exposure pathways) and radionuclide ($^{131}I$, $^{134}Cs$, and $^{137}Cs$) were evaluated for people living in the regions of Fukushima and neighboring prefectures in Japan using a developed dose assessment code system with Japanese specific input data. The results estimated in this study were compared with data from previously published reports. Groundshine and ingestion were predicted to contribute most significantly to the total long-term dose for all regions. The contributions of each exposure pathway and radionuclide show different patterns for certain regions of Japan.

• 한국환경보건학회지
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• 제37권3호
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• pp.226-233
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• 2011

Exactly 25 years after the Chernobyl nuclear disaster, 11th of March 2011 the Fukushima nuclear accident occurred in Japan and was ranked at level 7 same to the Chernobyl. A Korean and Japanese joint civil survey was conducted around Fukushima on April 13-17. The radiation survey data clearly shows a large hotspot area between 20 km and 50 km radius north and west direction from the accident reactors, with the highest radiation recorded being 55.64 ${\mu}Sv/hr$ in the air, 99.89 ${\mu}Sv/hr$ in the surface air, and 36.16 ${\mu}Sv/hr$ in a car, respectively. 3.65 ${\mu}Sv/hr$ in the air and 6.89 ${\mu}Sv/hr$ in the surface air were detected at the playground of an elementary school in Fukushima City. Spring came with full cherry blossoms in Fukushima, but it was silent spring of radiation contamination. Interviews with Fukushima nuclear refugees reveal serious problems about Japanese nuclear safety systems, such as there was no practical evacuation drill within 1-10 km and no plan at all for 10-30 km areas. Several reforms items for Korean nuclear safety system can be suggested: minimization of accident damage, clear separation of regulatory and safety bureaus with a new and independent administrating agency, community participation and agreement regarding the safety system and levels, which is the major concern of 80% Korean. To tackle threats of nuclear disaster in neighboring nations like China, a new position entitled 'Ambassador for nuclear safety diplomacy' is highly necessary. The nuclear safety of Korea should no longer be the monopoly of those nuclear engineers and limited technocrats criticized as a 'nuclear mafia'.

• Journal of Contemporary Eastern Asia
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• 제12권2호
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• pp.19-34
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• 2013

Previous research assessed media reporting on nuclear accidents and risks, whilst studies about the Fukushima accident focused on the impact of the Internet on coverage of the incident. However, little research has addressed news framing or comparisons of the perceptions of journalists in relation to reporting nuclear accidents. The aim of this study is to apply framing analysis to news content in The New York Times, the Los Angeles Times, and USA Today about the Fukushima accident. It explores the question of how journalists view reporting on complex events. Content analysis of these three newspapers shows that conflict, responsibility, and economic consequences were the most frequently used frames. According to the journalists interviewed, the biggest problem was the inability to assess information due to contrary positions held by experts. It is argued that the Fukushima accident was framed as a conflict of experts and officials' opinions, utility and government officials' responsibility, and economic consequences for the United States. Adherence to professional norms of objectivity and impartiality was signified as the best approaches to risk reporting.