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Jang, S.*; Yamaguchi, Akira*; Takata, Takashi
Proceedings of 13th Probabilistic Safety Assessment and Management Conference (PSAM-13) (USB Flash Drive), 11 Pages, 2016/10
The current approach to Level 2 probabilistic risk assessment (PRA) using the conventional event-tree (ET)/fault-tree (FT) methodology requires pre-specifications of event order occurrence and component failure probabilities which may vary significantly in the presence of uncertainties. In the present study, a new methodology is proposed to quantify the level 2 PRA in which the accident progression scenarios are dynamic and interactive with the instantaneous plant state and related phenomena. The accident progression is treated as a continuous Markov process and the transition probabilities are evaluated based on the computation of plant system thermal-hydraulic dynamics. A Monte Carlo method is used to obtain the resultant probability of the radioactive material release scenarios. The methodology is applied to the protected loss of heat sink accident scenario of the level 2 PRA of a generation IV fast reactor.
Tamaki, Hitoshi
no journal, ,
no abstracts in English
Zheng, X.; Tamaki, Hitoshi; Maruyama, Yu; Takada, Tsuyoshi; Narukawa, Takafumi*; Takata, Takashi*
no journal, ,
The dynamic probabilistic risk assessment (dynamic PRA) methodology explicitly treats the dynamics of event progression, enabling risk assessment that does not require predefined scenarios or success criteria. Based on these characteristics, from the perspective of risk triplet, we investigated the concept and measures of risk importance in dynamic PRA. Furthermore, the importance measures were applied to a dynamic PRA to evaluate their effectiveness. In this presentation, the authors provide a review on the application status of traditional risk importance measures in nuclear regulatory activities, and by using quantities such as release amount (consequence) of time-dependent source term to the environment and associated containment failure frequency (CFF), they confirm the applicability of the proposed risk importance measure to dynamic Level 2 PRA.