Keywords: Base isolation. Seismic isolation systems. Seismic loads. Blast loads. Nuclear power plants (NPP). Performance assessments. Friction pendulum bearings. Lead rubber bearings. Low-damping rubber bearings. Risk assessments. Spectral demands.
Abstract: The study presented in this report assesses the performance of conventional and base-isolated Nuclear Power Plant (NPP) reactor buildings subjected to earthquakes and blast loadings. Three base isolation systems, including Friction Pendulum, lead-rubber and low damping rubber bearings, are studied. This report proposes a new procedure for probabilistic seismic risk assessment of structures built on the methodology presented in the ATC-58 Guidelines and the Zion method. The procedure improves the Zion method by using fragility curves defined in terms of structural response parameters instead of ground motion parameters, providing a more suitable technique for the assessment of damage and failure of NPP components. The seismic performance assessment confirms the ability of base isolation systems to reduce spectral demands on secondary systems. Procedures for reducing the construction cost of secondary systems in isolated reactor buildings are also presented. Response-history analyses of conventional and base isolated reactor buildings to external blast loads are performed. The spectral demands on the secondary systems in the base isolated reactor building due to air blast loadings are greater than for a conventional reactor building, but much smaller than the demands associated with the safe shutdown earthquake loading. The base isolation systems are effective at filtering out high acceleration-high frequency ground shock loading.