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Okano, Yasushi; Yamano, Hidemasa
Dai-8-Kai Kozobutsu No Anzensei, Shinraisei Ni Kansuru Kokunai Shimpojiumu (JCOSSAR 2015) Koen Rombunshu (CD-ROM), p.86 - 91, 2015/10
A sodium-cooled fast reactor uses ambient air as an ultimate heat sink under accident conditions. Risk assessment of external hazards such as a forest fire that affect air cooling system is therefore important for safety. This paper describes analyses of forest fire related phenomena and influential factors, and associated potential risks on air cooling system in order to apply to a methodology development of an event progress as a part of a probabilistic risk assessment. A simplified assessment method for fragility of relevant structure and component to maintain decay heat removal function are proposed.
Nishida, Akemi; Igarashi, Sayaka*; Sakamoto, Shigehiro*; Muramatsu, Ken; Takada, Tsuyoshi*
Dai-8-Kai Kozobutsu No Anzensei, Shinraisei Ni Kansuru Kokunai Shimpojiumu (JCOSSAR 2015) Koen Rombunshu (CD-ROM), p.108 - 113, 2015/10
Research and development on next-generation seismic probabilistic risk assessment by using 3D vibration simulators is ongoing to evaluate the seismic safety performance of nuclear plants with high reliability. Most structural PRA uses probabilistic schemes such as the scheme that uses probabilistic seismic hazard and fragility curves. Even when earthquake ground motions are required in Monte Carlo Simulations (MCS), they are generated to fit the specified response spectra, such as uniform hazard spectra at a specified exceedance probability. However, these ground motions are not directly linked with their corresponding seismic source characteristics. In this context, the authors propose a methodology based on MCS to reproduce a set of input ground motions to develop an advanced PRA scheme. This paper describes the methodology to reproduce a set of input ground motions briefly and the analytical results of a nuclear plant building and equipment using the set of input ground motions.
Igarashi, Sayaka*; Sakamoto, Shigehiro*; Nishida, Akemi; Muramatsu, Ken; Takada, Tsuyoshi*
Dai-8-Kai Kozobutsu No Anzensei, Shinraisei Ni Kansuru Kokunai Shimpojiumu (JCOSSAR 2015) Koen Rombunshu (CD-ROM), p.535 - 541, 2015/10
In this study, building function loss induced by hazard-consistent ground motions (HCGMs), which are consistent with seismic hazard of the reference site and are associated with seismic source characteristics, was evaluated in order to confirm the influence by the variance and/or inter-period correlation of response spectra of ground motions on the resulted damage probabilities of equipment system. Firstly, the statistics values of the response spectra of HCGMs were evaluated, and 3 cases of simulated ground-motions sets are generated so that they fit to the median response spectra of HCGMs. The authors conducted structural response analysis with these ground motions set, and calculated annual damage frequency of equipment system. As a result, it was found that the variance of response spectra was more important factor on damage probability evaluation of systems than inter-period correlation.
Masumoto, Kiyoshi*; Onoe, Hironori; Kohashi, Akio; Yamamoto, Shinya*
no journal, ,
no abstracts in English
Yamamoto, Shinya*; Honda, Makoto*; Sakurai, Hideyuki*; Onoe, Hironori; Masumoto, Kiyoshi*
no journal, ,
no abstracts in English
Onoe, Hironori; Yamamoto, Shinya*; Masumoto, Kiyoshi*; Kohashi, Akio; Saegusa, Hiromitsu
no journal, ,
no abstracts in English
Yamano, Hidemasa; Nishino, Hiroyuki; Okano, Yasushi; Kurisaka, Kenichi; Sakai, Takaaki; Yamamoto, Takahiro*; Ishizuka, Yoshihiro*; Furukawa, Ryuta*; Geshi, Nobuo*; Nanayama, Futoshi*; et al.
no journal, ,
A four-year research project since 2012 is being performed to develop risk assessment methodologies that include probabilistic risk assessment (PRA) and margin assessment methodologies against external hazards mainly for a sodium-cooled fast reactor. The present paper describes briefly the project overview and then mainly the development of PRA and margin assessment methodologies against strong wind. In this project, by 2014, PRA methodologies against snow, tornado, rain and strong wind were developed as well as their hazard evaluation methodologies. For a volcanic eruption hazard, tephra fallout simulations were carried out to contribute to the hazard evaluation methodology development. In developing the strong wind PRA methodology, hazard curves were estimated using the Gumbel distributions based on weather data recorded in Japan. Next, failure probabilities for components related to the decay heat removal function were calculated as a product of two probabilities: a probability for the missiles to enter the intake/outtake in the decay heat removal system, and fragility caused by the missile impacts. After developing event trees, a core damage frequency was estimated about 6
10
/year by multiplying discrete hazard frequencies and conditional decay heat removal failure probabilities. The present study also developed the wind margin assessment methodology that the margin was regarded as wind speed leading to the decay heat removal failure.