Secondary impacts on SSCs in nuclear power plants caused by gantry crane damage modes following seismic events: A preliminary assessment using fragility analysis

Damage to gantry cranes in nuclear power plants (NPPs) during earthquakes can lead to secondary impacts on adjacent safety-related structures, systems, and components (SSCs). Previous studies primarily focused on evaluating the seismic capacity of the crane itself, whereas quantitative assessments of how crane damage affects SSCs have been limited. To address this gap, this study uses numerical analysis to estimate the seismic response of a gantry crane installed in an NPP and quantify the potential for secondary impacts on SSCs through fragility assessments of key crane damage modes. Post-derailment travel behavior is considered to develop damage scenarios at the safe shutdown earthquake (SSE) level, and the probability of each scenario is estimated. The results indicate that, at the SSE level (PGA=0.3 g), the overall probability of secondary impacts on SSCs due to gantry crane damage is very low. By performing a quantitative case analysis of crane–SSC interaction in an NPP, this study provides baseline information for future seismic safety evaluations of NPP structures and associated risk-informed decision-making.