Response of Systems and Components in a Base-Isolated Nuclear Power Plant Building Impacted by a Large Commercial Aircraft

Abstract

Earthquake shaking must be addressed in the design of a nuclear power plant (NPP). The impact of a large commercial airliner on a nuclear power plant building is considered a beyond-design-basis event but assessment is required for new reactors. This paper investigates the effect of beyond-design-basis impact of a large commercial airliner on a base-isolated NPP constructed to resist the effects of design-basis earthquake shaking. A finite element model of the testbed NPP is analyzed for design-basis shaking at a site of high seismic hazard and for aircraft impact. Spectral demands on systems and components inside but not attached to the containment vessel are compared for (1) design-basis shaking of the conventionally constructed testbed; (2) design-basis shaking of the base-isolated testbed; and (3) aircraft impact loading of the base-isolated testbed. The importance of isolation-system parameters, soil-structure-interaction (SSI), and soil modeling on the impact-related spectral demands of the isolated NPP are investigated and reported. Elastic material behavior is assumed for the superstructure and the soil, and nonlinear hysteretic behavior is assumed for the lead-rubber isolation system. For the assumed aircraft impact, the installation of a seismic isolation system increases in-structure spectral demands on structures, systems, and components inside containment with respect to the fixed-base condition. In-structure spectral demands due to aircraft impact in a base-isolated NPP are insensitive to the secant period and/or characteristic strength of the isolation system. The effect of soil-structure interaction on the impact response is significant for the fixed-base NPP but relatively small for the base-isolated NPP.