Evaluation of the Limit State of a Six-Inch Carbon Steel Pipe Elbow in Base-Isolated Nuclear Power Plants

Sung-Wan Kim, Da-Woon Yun, Bub-Gyu Jeon, Dae-Gi Hahm and Min-Kyu Kim
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Sung-Wan Kim: Seismic Research and Test Center, Pusan National University, 49 Busandaehak-ro, Yangsan 50612, Korea
Da-Woon Yun: Seismic Research and Test Center, Pusan National University, 49 Busandaehak-ro, Yangsan 50612, Korea
Bub-Gyu Jeon: Seismic Research and Test Center, Pusan National University, 49 Busandaehak-ro, Yangsan 50612, Korea
Dae-Gi Hahm: Smart Structural Safety & Prognosis Division, Korea Atomic Energy Research Institute, 111 Daedeok-daero, 989 beon-gil, Yusung-gu, Daejon 34057, Korea
Min-Kyu Kim: Smart Structural Safety & Prognosis Division, Korea Atomic Energy Research Institute, 111 Daedeok-daero, 989 beon-gil, Yusung-gu, Daejon 34057, Korea

Energies, 2021, vol. 14, issue 24, 1-15

Abstract: The installation of base isolation systems in nuclear power plants can improve their safety from seismic loads. However, nuclear power plants with base isolation systems experience greater displacement as they handle seismic loads. The increase in relative displacement is caused by the installed base isolation systems, which increase the seismic risk of the interface piping system. It was found that the failure mode of the interface piping system was low-cycle fatigue failure accompanied by ratcheting, and the fittings (elbows and tees) failed due to the concentration of nonlinear behavior. Therefore, in this study, the limit state was defined as leakage, and an in-plane cyclic loading test was conducted in order to quantitatively express the failure criteria for the SCH40 6-inch carbon steel pipe elbow due to low-cycle fatigue failure. The leakage line and low-cycle fatigue curves of the SCH40 6-inch carbon steel pipe elbow were presented based on the test results. In addition, the limit state was quantitatively expressed using the damage index, based on the combination of ductility and energy dissipation. The average values of the damage index for the 6-inch pipe elbow calculated using the force−displacement (P–D) and moment−relative deformation angle (M–R) relationships were found to be 10.91 and 11.27, respectively.

Keywords: nuclear power plant; interface piping system; low-cycle fatigue; carbon steel pipe elbow; limit state (search for similar items in EconPapers)
JEL-codes: Q Q0 Q4 Q40 Q41 Q42 Q43 Q47 Q48 Q49 (search for similar items in EconPapers)
Date: 2021
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