• Nuclear Engineering and Technology
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• 제50권8호
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• pp.1210-1216
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• 2018

Site or multi-unit (MU) risk assessment has been a major issue in the field of nuclear safety study since the Fukushima accident in 2011. There have been few methods or experiences for MU risk assessment because the Fukushima accident was the first real MU accident and before the accident, there was little expectation of the possibility that an MU accident will occur. In addition to the lack of experience of MU risk assessment, since an MU nuclear power plant site is usually very complex to analyze as a whole, it was considered that a systematic method such as probabilistic safety assessment (PSA) is difficult to apply to MU risk assessment. This paper proposes a new MU risk assessment methodology by using the conventional PSA methodology which is widely used in nuclear power plant risk assessment. The logical failure structure of a site with multiple units is suggested from the definition of site risk, and a decomposition method is applied to identify specific MU failure scenarios.

• Nuclear Engineering and Technology
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• 제44권5호
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• pp.453-458
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• 2012

A major issue for all nuclear stakeholders is to keep the probability of circumstances that could lead to core damage as low as possible. In addition, for NPP, appropriate accident management provisions are to be implemented to limit the consequences associated with an accident. Development and application of L2 PSA is a structured way to demonstrate that such objectives are achieved. The paper presents the efforts recently done in Europe to harmonize some best-practices in that field, from research area to risk assessment. The Fukushima Daiichi accident reiterated the importance of these activities and the need to efficiently reinforce the NPP safety based on risk assessment conclusions. New perspectives in Europe are briefly presented.

• 방사선산업학회지
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• 제8권2호
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• pp.123-132
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• 2014

After the nuclear accident of the Fukushima Dai-ichi Nuclear Power Plants (FDNPPs) on 11 March 2011, a large amount of radioactive materials has been released into the atmosphere and the ocean. A compartment model is used to evaluate the circulation characteristics and the spatiotemporal concentration distributions of radionuclides in the ocean. In the comparison with observed concentrations of $^{137}Cs$ in seawater, calculated concentrations by the compartment model were well agreed with them. On the basis of these results, we performed evaluation of the effective dose and the cancer risk. In the early stage of the accident, the effective doses from ingestion of the seafood near the Fukushima region were much higher than 1 mSv which is the value of the annual effective dose limit to individual recommended by the International Commission on Radiological Protection (ICRP). However, the effective doses by ingestion of the seafood decreased below 1 mSv as distance from the FDNPPs increased and time passed. In addition, it was estimated that the cancer risks by intake of the contaminated marine products were less than natural occurrence probability of cancer. Consequently, it was inferred that the health risk due to the $^{137}Cs$ was low after since mid-term period of the accident.

• 사물인터넷융복합논문지
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• 제6권1호
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• pp.73-81
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• 2020

클라우드 컴퓨팅을 사용하는 사물 인터넷 (IoT)은 원자력 발전소 사고가 안전성 평가를 위해 분석되는 원자력 산업에 적용된다. 후쿠시마 원자력 발전소 사고는 지진으로 인한 플랜트 고장 사고가 클라우드 컴퓨팅 기술 분석에 사용되는 사고 시뮬레이션을 위해 모델링되었습니다. 후쿠시마의 경우 자연 재해에 대한 빠르고 합리적인 치료가 필요했다. 실시간 안전 평가 (RTSA)와 몬테카를로 실시간 평가 (MCRTA)가 구성된다. 이 클라우드 컴퓨팅은 미래의 유사한 사고에 대비할 수있는 실용적인 방법을 제공 할 수 있습니다.

• 한국방사성폐기물학회:학술대회논문집
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• 한국방사성폐기물학회 2018년도 춘계학술논문요약집
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• pp.351-352
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• 2018

• 공학교육연구
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• 제15권1호
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• pp.35-44
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• 2012

This paper analyzes characteristics and discourses related with the risk communication of Fukushima nuclear disaster. I try to pick up and analyze the three strategies of Korean government's and expert system's risk communication, and then understand the relationship between them and the role of expert system in the risk communication and the politics of expertise.

• 농업과학연구
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• 제45권4호
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• pp.889-903
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• 2018

The purposes of this study were to classify consumer types and to analyze purchase behavior depending on food safety attitudes related to the Fukushima nuclear accident. Based on the consumer survey data, factor analysis and cluster analysis were done to classify consumer types. Applying factor analysis, six factors with a total variance of 73.4% were extracted from 22 basic variables. The 6 factors were termed 'anxiety from ingesting agricultural and fishery products after the nuclear accident', 'importance of food safety when purchasing food', 'reduced rate of purchases of agricultural and fishery products after the accident', 'importance of food prices', 'socio-demographic characteristics' and 'family composition'. Using cluster analysis, consumers were classified into 5 types using the factor scores of 6 factors. The main results are as follows. For every consumer type, the anxiety about imported agricultural and fishery products was higher than that for domestic products after the nuclear accident. The food safety attitudes of consumers were mainly formed by the socio-demographic characteristics. Consumer types with high-education and high-income responded flexibly to the food safety concerning the accident; especially, the consumer type with a high-income and kids under 19 responded very reasonably to the accident. However, consumer types with a low-income and aged over 50 or less than 30 years were the least responsive to the accident, mainly due to financial restrictions. Thus, we suggest some food safety strategies and policy implications based on consumer type for food safety after the accident.

• Nuclear Engineering and Technology
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• 제56권6호
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• pp.2266-2273
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• 2024

A machine learning platform is proposed for the diagnosis of a severe accident progression in a nuclear power plant. To predict the key parameters for accident management including lost signals, a long short term memory (LSTM) network is proposed, where multiple accident scenarios are used for training. Training and test data were produced by MELCOR simulation of the Fukushima Daiichi Nuclear Power Plant (FDNPP) accident at unit 3. Feature variables were selected among plant parameters, where the importance ranking was determined by a recursive feature elimination technique using RandomForestRegressor. To answer the question of whether a reduced order ML model could predict the complex transient response, we performed a systematic sensitivity study for the choices of target variables, the combination of training and test data, the number of feature variables, and the number of neurons to evaluate the performance of the proposed ML platform. The number of sensitivity cases was chosen to guarantee a 95 % tolerance limit with a 95 % confidence level based on Wilks' formula to quantify the uncertainty of predictions. The results of investigations indicate that the proposed ML platform consistently predicts the target variable. The median and mean predictions were close to the true value.

• Journal of Radiation Protection and Research
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• 제41권1호
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• pp.7-14
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• 2016

연구배경: 본 연구는 일본 후쿠시마 원전사고 이후 원전사고 및 방사능 오염에 대한 우리 국민들의 인식도를 확인하기 위한 목적으로 진행되었다. 재료 및 방법: 설문조사는 수도권에 거주하는 성인 600명을 대상으로 하였다. 결과 및 논의: 연구 결과, 대다수 국민들은 일본 원전사고로 인한 방사능 누출이 우리나라에 영향을 미치고 있다고 우려하였다. 식품, 특히 수산물의 방사능 오염에 대한 우려가 높았고, 선호하는 정보 취득원은 TV(49.8%)와 인터넷 매체(31.3%)였다. 한편 다수의 국민들은 일본 원전사고 및 방사능 오염 정보가 충분히 제공되지 않았고, 원전사고 이후 우리 정부의 대응조치를 잘 모르고 있는 것으로 나타났다. 또한 국민 대다수가 식품 환경 등의 방사능 오염 정도와 안전성에 대한 정보제공 강화가 가장 중요한 것으로 인식하고 있었다. 결론: 본 연구 결과는 향후 방사능에 대한 올바른 인식 확립과 방사능 안전사고 리스크커뮤니케이션을 위한 유용한 자료로 활용될 수 있을 것으로 기대된다.

• Journal of Radiation Protection and Research
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• 제48권3호
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• pp.153-161
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• 2023

Background: Fukushima Medical University (FMU) is located 57 km northwest of the Fukushima Daiichi Nuclear Power Plant. Our laboratory has been conducting environmental radiation measurements continuously before and after the nuclear accident. We aimed to report the observed behavior of radiation originating from the released radioactive materials due to the accident, predict future trends, and disseminate the results to the local residents. Materials and Methods: Measurements of the counting rate by a diameter of 76 mm and a length of 76 mm thallium-doped sodium iodide (NaI[Tl]) scintillation detector (S-1211-T; Teledyne Brown Engineering Environmental Services) in the central part of the laboratory, and the dose rate outward at the window by NaI(Tl) scintillation detector and digital processor (EMF211; EMF Japan Co. Ltd.) were conducted. Results and Discussion: Measurements by Teledyne S-1211-T showed that in the early stages, radiation from radioactive isotopes with short half-lives was dominant, while radiation from radioactive isotopes with longer half-lives became dominant as the measurement period became longer. Through nonlinear least squares regression, both short and long half-lives were successfully determined. It was also possible to predict how the radiation dose would decrease. The environmental radiation trends around FMU were measured by the EMF211. Both measurements were affected by rainfall and snow accumulation. Decontamination work on the FMU campus impacted measurements by the EMF211 especially. Conclusion: The results of two types of measurements, one at the center and the other at the window side of the laboratory, were presented. By applying a simplified model, radiation from radioactive isotopes with short and long half-lives was identified. Based on these results, future trends were predicted, and the information was used for public communication with the local residents.