Nuclear plant severe accidents: challenges and prevention (original) (raw)
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The Fukushima Nuclear Accident: Insights on the Safety Aspects
The Fukushima nuclear accident has generated doubts and questions which need to be properly understood and addressed. This scientific attitude became necessary to allow the use of the nuclear technology for electricity generation around the world. The nuclear stakeholders are working to obtain these technical answers for the Fukushima questions. We believe that, such challenges will be, certainly, implemented in the next reactor generation, following the technological evolution. The purpose of this work is to perform a critical analysis of the Fukushima nuclear accident, focusing at the common cause failures produced by tsunami, as well as an analysis of the main redundant systems. This work also assesses the mitigative procedures and the subsequent consequences of such actions, which gave results below expectations to avoid the progression of the accident, discussing the concept of sharing of structures, systems and components at multi-unit nuclear power plants, and its eventual inappropriate use in safety-related devices which can compromise the nuclear safety, as well as its consequent impact on the Fukushima accident scenario. The lessons from Fukushima must be better learned, aiming the development of new procedures and new safety systems. Thus, the nuclear technology could reach a higher evolution level in its safety requirements. This knowledge will establish a conceptual milestone in the safety system design, becoming necessary the review of the current acceptance criteria of safety-related systems.
Compare and Contrast Major Nuclear Power Plant Disasters: Lessons Learned from the Past
10th Annual Conference of the International Institute for Infrastructure Renewal and Reconstruction, 2014
The construction of nuclear power plants is a major step towards reducing greenhouse gas emissions compared to the conventional coal-fired or oil-fired power plants. However, some of the major nuclear accidents in the past have raised questions about the safety and reliability of nuclear power plants. This paper compares and contrasts the major nuclear accidents of the past for example, the Chernobyl disaster (USSR), the Fukushima Daiichi disaster (Japan), and the Three Mile Island incident (USA). Although each of the accidents was unique, a thorough comparison found some common issues, such as faulty design of reactors and safety systems, safety rules violations, and lack of trained operators. The primary impacts mostly involved radiation hazards such as exposure to varying doses of radiation, uninhabitable neighborhoods and health problems; the levels of impact varied mostly due to different intensities of warnings and precautionary measures taken by the local governments. The research findings would serve as an important resource for the nuclear professionals to plan proper precautionary measures in order to avoid the major issues that initiated or resulted from the accidents in the past.
Reflections on the Fukushima Daiichi Nuclear Accident
Reflections on the Fukushima Daiichi Nuclear Accident, 2015
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Fukushima Daiichi accident study : status as of April 2012
2012
In response to the accident at the Fukushima Daiichi nuclear power station in Japan, the U.S. Nuclear Regulatory Commission (NRC) and Department of Energy agreed to jointly sponsor an accident reconstruction study as a means of assessing severe accident modeling capability of the MELCOR code. MELCOR is the state-of-the-art system-level severe accident analysis code used by the NRC to provide information for its decision-making process in this area. The objectives of the project were: (1) collect, verify, and document data on the accidents by developing an information portal system; (2) reconstruct the accident progressions using computer models and accident data; and (3) validate the MELCOR code and the Fukushima models, and suggest potential future data needs. Idaho National Laboratory (INL) developed an information portal for the Fukushima Daiichi accident information. Sandia National Laboratories (SNL) developed MELCOR 2.1 models of the Fukushima Daiichi Units 1, 2, and 3 reactors and the Unit 4 spent fuel pool. Oak Ridge National Laboratory (ORNL) developed a MELCOR 1.8.5 model of the Unit 3 reactor and a TRACE model of the Unit 4 spent fuel pool. The good correlation of the results from the SNL models with the data from the plants and with the ORNL model results provides additional confidence in the MELCOR code. The modeling effort has also provided insights into future data needs for both model development and validation.
Consequences of post-Fukushima safety examinations
2013
The Swiss Authority decreed several provisions after the Fukushima event. Due to these provisions many examinations and safety increasing measures had to be done in a very short time. The result is the use of safety systems to show the control of Fukushima like events which were originally designed for other special events like aircraft crashes or explosion pressure waves. At the end of such ad-hoc measure the safety systems and the events controlled by using these functions are mixed up. Another effect of these ad-hoc measures is the prohibition of larger safety improvements with a concept that fits to the existing safety concept of the power plant. INTRODUCTION TO THE POWER PLANT
Nuclear Science and Engineering, 2012
The Three Mile Island Unit 2 (TMI-2) accident, which occurred on March 28, 1979, led industry and regulators to enhance strategies to protect against severe accidents in commercial nuclear power plants. Investigations in the years after the accident concluded that at least 45% of the core had melted and that nearly 19 tonnes of the core material had relocated to the lower head. Postaccident examinations indicate that about half of that material formed a solid layer near the lower head and above it was a layer of fragmented rubble. As discussed in this paper, numerous insights related to pressurized water reactor accident progression were gained from postaccident evaluations of debris, reactor pressure vessel (RPV) specimens, and nozzles taken from the RPV. In addition, information gleaned from TMI-2 specimen evaluations and available data from plant instrumentation were used to improve severe accident simulation models that form the technical basis for reactor safety evaluations. Finally, the TMI-2 accident led the nuclear community to dedicate considerable effort toward understanding severe accident phenomenology as well as the potential for containment failure. Because available data suggest that significant amounts of fuel heated to temperatures near melting, the events at Fukushima Daiichi Units 1, 2, and 3 offer an unexpected opportunity to gain similar understanding about boiling water reactor accident progression. To increase the international benefit from such an endeavor, we recommend that an international effort be initiated to (a) prioritize data needs; (b) identify techniques, samples, and sample evaluations needed to address each information need; and (c) help finance acquisition of the required data and conduct of the analyses.
Open Journal of Applied Sciences, 2015
Concerning the increasing global energy demand, the current paper considers nuclear energy as a solution. Within this context, the 2011 disaster in Fukushima Nuclear Power Plant and, particularly, the technical disorders in boiling water reactors are explained. The deficiency of safety technique in boiling water reactors is explained. The deficiencies in safety procedure of this type of reactors manifested during 2011 earthquake and subsequent tsunami are explained. To complete the discussion, the newer technologies of reactors enabling them to act more safely during natural disasters are introduced. These investigations indicate that despite improvement in the fission reactor technologies, the danger embedded in them still remains. Therefore, the nuclear fusion using Deuterium-Tritium reaction is the best way forward for energy production in the future, and the best candidate of this type of reactors is Tokamak.
EPJ Nuclear Sciences & Technologies, 2020
The Fukushima-Daiichi accidents in 2011 underlined the importance of severe accident management (SAM), including external events, in nuclear power plants (NPP) and the need of implementing efficient mitigation strategies. To this end, the Euratom work programmes for 2012 and 2013 was focused on nuclear safety, in particular on the management of a possible severe accident at the European level. Relying upon the outcomes of the successful Euratom SARNET and SARNET2 projects, new projects were launched addressing the highest priority issues, aimed at reducing the uncertainties still affecting the main phenomena. Among them, PASSAM and IVMR project led by IRSN, ALISA and SAFEST projects led by KIT, CESAM led by GRS and sCO2-HeRO lead by the University of Duisburg-Essen. The aim of the present paper is to give an overview on the main outcomes of these projects.