ATHLET-CD/COCOSYS Analyses of Severe Accidents in Fukushima Daiichi Units 2 and 3: German Contribution to the OECD/NEA BSAF Project, Phase 1

2016 ◽  
Vol 196 (2) ◽  
pp. 211-222 ◽  
Author(s):  
M. Sonnenkalb ◽  
S. Band
Keyword(s):  
Phase 1 ◽  
Severe Accidents ◽  
Fukushima Daiichi ◽  
German Contribution

scholarly journals EVALUATION METRICS APPLIED TO ACCIDENT TOLERANT FUEL CLADDING CONCEPTS FOR VVER REACTORS

2016 ◽  
Vol 4 ◽  
pp. 89 ◽  
Author(s):  
Martin Sevecek ◽  
Mojmir Valach
Keyword(s):  
Severe Accident ◽  
Evaluation Metrics ◽  
Development Phase ◽  
Fuel System ◽  
Fuel Cladding ◽  
High Interest ◽  
Severe Accidents ◽  
Time Period ◽  
Fukushima Daiichi ◽  
Reactor Types

Enhancing the accident tolerance of LWRs became a topic of high interest in many countries after the accidents at Fukushima-Daiichi. Fuel systems that can tolerate a severe accident for a longer time period are referred as Accident Tolerant Fuels (ATF). Development of a new ATF fuel system requires evaluation, characterization and prioritization since many concepts have been investigated during the first development phase. For that reason, evaluation metrics have to be defined, constraints and attributes of each ATF concept have to be studied and finally rating of concepts presented. This paper summarizes evaluation metrics for ATF cladding with a focus on VVER reactor types. Fundamental attributes and evaluation baseline was defined together with illustrative scenarios of severe accidents for modeling purposes and differences between PWR design and VVER design.

Post-Fukushima Research and Development Strategies and Priorities for Water Cooled Reactor Technology Development

2016 ◽  
Author(s):  
Katsumi Yamada ◽  
Abdallah Amri ◽  
Lyndon Bevington ◽  
Pal Vincze
Keyword(s):  
Research And Development ◽  
International Organizations ◽  
Nuclear Power ◽  
Power Plants ◽  
Development Strategies ◽  
Lessons Learned ◽  
Member States ◽  
North East ◽  
Severe Accidents ◽  
Fukushima Daiichi

The Great East Japan Earthquake and the subsequent tsunami on 11 March 2011 initiated accident conditions at several nuclear power plants (NPPs) on the north-east coast of Japan and developed into a severe accident at the Fukushima Daiichi NPP, which highlighted a number of nuclear safety issues. After the Fukushima Daiichi accident, new research and development (R&D) activities have been undertaken by many countries and international organizations relating to severe accidents at NPPs. The IAEA held, in cooperation with the OECD/NEA, the International Experts’ Meeting (IEM) on “Strengthening Research and Development Effectiveness in the Light of the Accident at the Fukushima Daiichi Nuclear Power Plant” at IAEA Headquarters in Vienna, Austria, 16–20 February 2015. The objective of the IEM was to facilitate the exchange of information on these R&D activities and to further strengthen international collaboration among Member States and international organizations. One of the main conclusions of the IEM was that the Fukushima Daiichi accident had not identified completely new phenomena to be addressed, but that the existing strategies and priorities for R&D should be reconsidered. Significant R&D activities had been already performed regarding severe accidents of water cooled reactors (WCRs) before the accident, and the information was very useful for predicting and understanding the accident progression. However, the Fukushima Daiichi accident highlighted several challenges that should be addressed by reconsidering R&D strategies and priorities. Following this IEM, the IAEA invited several consultants to IAEA Headquarters, Vienna, Austria, 12–14 May 2015, and held a meeting in order to discuss proposals on possible IAEA activities to facilitate international R&D collaboration in relation to severe accidents and how to effectively disseminate the information obtained at the IEM. The IAEA also held Technical Meeting (TM) on “Post-Fukushima Research and Development Strategies and Priorities” at IAEA Headquarters, Vienna, Austria, 15–18 December 2015. The objective of this meeting was to provide a platform for experts from Member States and international organizations to exchange perspectives and information on strategies and priorities for R&D regarding the Fukushima Daiichi accident and severe accidents in general. The experts discussed R&D topic areas that need further attention and the benefits of possible international cooperation. This paper discusses lessons learned from the Fukushima Daiichi accident based on the presentations and discussions at the meetings mentioned above, and identifies the needs for further R&D activities to develop WCR technologies to cope with Fukushima Daiichi-type accidents.

Review on Water Radiolysis in the Fukushima Daiichi Accident: Potential Cause of Hydrogen Generation and Explosion

2014 ◽  
Author(s):  
Genn Saji
Keyword(s):  
Hydrogen Generation ◽  
Hydrogen Gas ◽  
Severe Accident ◽  
Normal Operation ◽  
Water Radiolysis ◽  
Chain Reactions ◽  
Decay Heat ◽  
Severe Accidents ◽  
Heat Curve ◽  
Fukushima Daiichi

Although the water radiolysis, decomposition of water by radiation, is a well-known phenomenon the exact mechanism is not well characterized especially for severe accidents. The author first reviewed the water radiolysis phenomena in LWRs during normal operation to severe accidents (e.g., TMI- and Chernobyl accidents) and performed a scoping estimation of the amount of radiological hydrogen generation, accumulation and release for the Fukushima Daiichi accident. The estimation incorporates the decay heat curve after a reactor trip combined with G-values. As much as 450 cubic meters-STP of accumulated hydrogen gas is estimated to be located inside the PCV just prior to the hydrogen explosion which occurred a day after the reactor trip in Unit 1. When a set of radiological chain reactions are incorporated the resultant reverse reactions substantially reduce the hydrogen generation, even when removal of molecular products (i.e., oxygen and hydrogen) is assumed stripped rapidly from boiling water through bubbles. Even in the most favorable configuration a typical amount of hydrogen gas reduces to only several tens of cubic meters. Finally, the author tested a new mechanism, “radiation-induced electrolysis,” which had been applied to his corrosion studies for last several years. His theory has been verified with the published in-pile test data, although he has never tried to apply this to his severe accident study. The predicted results indicated that the total inventory of hydrogen gas inside RPV may reach as much as 1000 cubic meters in just 3 hours during the SBO due to a high decay heat soon after the reactor trip through this process.

Study on Buckling Strength and Post Buckling Behaviors of Reactor Vessel Lower Heads

2021 ◽  
Author(s):  
Masato Murohara ◽  
Akira Yamazaki ◽  
Takuya Sato ◽  
Naoto Kasahara
Keyword(s):  
Structural Design ◽  
Nuclear Power ◽  
Reactor Vessel ◽  
Lessons Learned ◽  
Buckling Strength ◽  
Severe Accidents ◽  
Design Basis ◽  
Post Buckling ◽  
Fukushima Daiichi ◽  
Very High

Abstract As the lessons learned from the Fukushima Daiichi Nuclear Power Plant accident, the importance of controlling the behavior after a failure and mitigating consequences of a failure was recognized. Conventional reactor structural design has been aimed at preventing the occurrence of failure due to Design Basis Events (DBE). This study aims to improve the resilience of the reactor structure under Beyond Design Basis Events (BDBE), such as very high temperatures and excessive earthquakes during severe accidents, by mitigating the consequences after failure.

scholarly journals Analysis of Severe Accidents in Spent Fuel Pool of Fukushima Daiichi NPP Using MELCOR 1.8.6 Computer Code

2016 ◽  
pp. 13-20
Author(s):  
O. Kotsuba ◽  
Yu. Vorobyov ◽  
O. Zhabin ◽  
D. Gumenyk
Keyword(s):  
Computer Analysis ◽  
Computer Code ◽  
Computer Models ◽  
Reliable Data ◽  
Severe Accident ◽  
Spent Fuel ◽  
Severe Accidents ◽  
Spent Fuel Pool ◽  
Fukushima Daiichi ◽  
To Receive

The paper presents specific approaches to modeling the spent fuel pool (SFP) of Fukushima Daiichi NPP and results of thermohydraulic calculations of severe accidents in SFP using MELCOR 1.8.6 computer code. The dynamics of main processes accompanying severe accident progression in SFP of such a type was defined based on computer analysis. Obtained results may be used to improve available SFP computer models to receive more reliable data on the progression of emergency processes in NPP SFPs.

Rationalization and internalization

2001 ◽  
Vol 60 (4) ◽  
pp. 215-230 ◽  
Author(s):  
Jean-Léon Beauvois
Keyword(s):  
Phase 1 ◽  
Facilitatory Effect ◽  
Phase 2 ◽  
Causal Explanations ◽  
Reduction Effect ◽  
Dissonance Reduction

After having been told they were free to accept or refuse, pupils aged 6–7 and 10–11 (tested individually) were led to agree to taste a soup that looked disgusting (phase 1: initial counter-motivational obligation). Before tasting the soup, they had to state what they thought about it. A week later, they were asked whether they wanted to try out some new needles that had supposedly been invented to make vaccinations less painful. Agreement or refusal to try was noted, along with the size of the needle chosen in case of agreement (phase 2: act generalization). The main findings included (1) a strong dissonance reduction effect in phase 1, especially for the younger children (rationalization), (2) a generalization effect in phase 2 (foot-in-the-door effect), and (3) a facilitatory effect on generalization of internal causal explanations about the initial agreement. The results are discussed in relation to the distinction between rationalization and internalization.

Phase 1: In the Beginning

2004 ◽  
Author(s):  
Carl L. Henderson
Keyword(s):  
Phase 1 ◽  
In The Beginning
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