Equipment Capacities from Earthquake Experience Data for Use in Fragility Calculations

Electric Power Research Institute (EPRI) has recently researched the development of refined equipment capacities from earthquake experience data for use in fragility calculations, which is a key component of nuclear seismic probabilistic risk assessments (SPRAs). Refined capacities result in more realistic fragilities, ultimately providing more accurate estimates of the risk.

EPRI develops and maintains a large database of earthquake data spanning four decades. A multi-phase project was initiated in 2014 by EPRI to review available data and apply improved statistical methods to update the seismic capacity of selected equipment classes. Phase I (EPRI 3002011627, 2017a) examines two statistical techniques (Frequentist and Bayesian) and develops updated capacities for eight classes: Control Panels, Engine Generators, Fans, Horizontal Pumps, Inverters and Battery Chargers, Motor Control Centers, Motor Operated-Valves, and Medium Voltage Switchgear. Phase II (EPRI 3002013017, 2018a) reviews the capacities of eight additional classes: Air Compressors, Air-operated Valves, Batteries on Racks, Distribution Panels, Instruments on Racks, Low Voltage Switchgear, Transformers, and Vertical Pumps. Updated best-estimate median capacities for these sixteen classes are up to 47% greater than the EPRI NP-6041-SLR1 (1991a) median of 4.8g. A series of sensitivity studies investigate the influence various inputs and demonstrate that updated best-estimate capacities are driven more by data than subjective judgment. This paper summarizes the main findings of the project and provides an example of how these capacities could be used in practice.

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