Multi-objective-based seismic fragility relocation for a Korean nuclear power plant
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Multi‑objective‑based seismic fragility relocation for a Korean nuclear power plant Shinyoung Kwag1 · Daegi Hahm2 Received: 4 June 2018 / Accepted: 2 July 2020 © Springer Nature B.V. 2020
Abstract An optimal risk-informed seismic fragility relocation is proposed for structures, systems, and components (SSCs) of nuclear power plants (NPPs) that mitigates the core damage risk of the NPP and raises the cost performance. The proposed approach employs a seismic probabilistic safety assessment technique to effectively distribute seismic fragilities of SSCs from the perspective of overall plant risk. The main objectives of the optimal seismic fragility relocation are to mitigate the core damage risk and minimize the total cost for the SSCs of the NPP. To deal with such conflicting purposes, a genetic algorithm-based multiobjective optimization scheme is adopted. This approach systematically obtains a set of Pareto optimal solutions that are neither inferior nor superior to each other. The process for choosing the most appropriate seismic fragility distribution plan from the optimal front of Pareto solutions is also discussed with an emphasis on the study of the uncertainty quantification on such optimal Pareto solutions. As an example for such an optimal fragility relocation study, this study considers a typical type of Korean NPP. The numerical results confirm that the proposed approach provides diverse optimal seismic fragility relocation plans which can effectively reduce the core damage risk as well as the cost compared to the current fragility distribution of this example NPP. Finally, the best optimal alternatives for the fragility relocation are selected based on the Pareto optimal solution’s robustness of performances against their perturbations. Keywords Seismic fragility · Seismic probabilistic risk assessment · Multi-objective optimization · Optimal fragility relocation · Nuclear power plants
1 Introduction To ensure safety against earthquakes in nuclear power plants (NPPs), a probable design basis earthquake that can deterministically or probabilistically occur over a specific period at the installation site is defined as a design response spectrum shape (USNRC 1997, * Shinyoung Kwag [email protected]; [email protected] 1
Hanbat National University, 125 Dongseo‑daero, Yuseong‑gu, Daejeon 34158, Republic of Korea
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Korea Atomic Energy Research Institute, 111 Daedeok‑daero, Yuseong‑gu, Daejeon 34057, Republic of Korea
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2007a, b,2014), and various structures, systems, and components (SSCs) constituting the nuclear plant are designed based on such spectrum loading. Unlike general building structural systems, NPPs are composed of numerous important SSCs around nuclear reactions. Therefore, the design response spectrum defined in the ground is transformed into the floor response spectrum (FRS) at the place where each SSC is located (USNRC 1978), and the detailed seismic design of corresponding SSCs is conducted based on such FRS (IAEA 2003). When making the seismic
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