Shock Fragility Spectra for Equipment Survivability under Aircraft Impact

Abstract

Nuclear Energy Institute guidelines present a standard for assessing shock effects due to aircraft impact on nuclear power plants. The guidelines provide the capacity of equipment to survive shock-induced loading from aircraft impact through median-based fragility limits for six equipment categories. However, the basis of these limits is not well defined, the limits are scalar values, and the provided safe distances are safeguards information not available to the public. This paper presents efforts to extend the guideline’s fragility limits to frequency-dependent fragility spectra, which can be used in median-based equipment fragility assessments or in developing site-specific safe distances. Acceleration time histories from aircraft impact analyses are spectrally matched to equal or exceed assumed equipment fragility capacity spectra. The matched time histories are used as demands in finite-element analyses of three representative pieces of equipment (battery rack, fan, and tank). The analysis results indicate the equipment can maintain functionality after the application of the spectrally matched shock demands, giving confidence that the assumed equipment fragility capacities are reasonably representative for the corresponding equipment.