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Yamano, Hidemasa; Sakai, Takaaki; Kurisaka, Kenichi
Proceedings of 9th International Topical Meeting on Nuclear Thermal-Hydraulics, Operation and Safety (NUTHOS-9) (CD-ROM), 16 Pages, 2012/09
This study is aimed to develop a methodology of failure probability evaluation for the passive safety features. In this paper, the first step of this development is reported for both the passive shutdown and the decay heat removal systems, namely identification of failure causes on the passive safety features as well as identification of important uncertainty parameters for sensitivity analyses that will be performed in the subsequent step of this study. This paper describes the failure causes, ranking table, and identified important uncertain parameters.
Takeda, Takeshi; Watanabe, Tadashi; Nakamura, Hideo
Proceedings of 9th International Topical Meeting on Nuclear Thermal-Hydraulics, Operation and Safety (NUTHOS-9) (CD-ROM), 12 Pages, 2012/09
Kimura, Nobuyuki; Onojima, Takamitsu; Kamide, Hideki
Proceedings of 9th International Topical Meeting on Nuclear Thermal-Hydraulics, Operation and Safety (NUTHOS-9) (CD-ROM), 12 Pages, 2012/09
In the Japan Sodium-cooled Fast Reactor, thermal stratification phenomena occur in the reactor vessel during scram transient. In the study, the characteristics of stratification interface were investigated under the natural circulation operation during the scram transient using the 1/11th scale upper plenum model. The experimental results showed that the temperature gradient under the natural circulation operation was reduced to 1/2.6-1/6.2 in comparison with that under the forced circulation operation.
Doda, Norihiro; Kamide, Hideki; Ohshima, Hiroyuki; Watanabe, Osamu*
Proceedings of 9th International Topical Meeting on Nuclear Thermal-Hydraulics, Operation and Safety (NUTHOS-9) (CD-ROM), 11 Pages, 2012/09
In the design study for Japan Sodium Cooled Fast Reactor (JSFR), fully natural circulation system is adopted as the decay heat removal system. We have been developing a new evaluation method of core hot spot in transition from rated operation to natural circulation decay heat removal conditions. Since the method is currently based on conservative assumptions and data, there is room for further rationalization of the safety margin which can be achieved by conducting best estimate analyses with confidence and with quantified uncertainty of results. This paper describes a development of PIRT (Phenomena Identification and Ranking Table) and the global sensitivity analyses of the uncertainties in the event of loss of external power as the first step to improve the evaluation method.