Options for the Treatment of Uncertainty in Seismic Safety Assessment of Nuclear Power Plants

Abstract

This paper proposes options for improving seismic safety analysis for nuclear power plants. Cumulative absolute velocity (CAV) has been considered and analyzed for describing different load-cycle-dependent phenomena, e.g., fatigue failure and soil liquefaction. Fatigue damage estimation is based on load-cycle counting, which can be performed by counting zero or level crossings if power spectral density (PSD) of load time history is known. Correlation between CAV and moments of PSD of load time history is derived in this paper. A fatigue failure criterion is developed in terms of CAV. P-box theory is proposed for improving uncertainty modeling of probabilistic seismic safety assessment. P-boxes are represent upper and lower bounds of the distribution function specified by left side and right side distribution functions. The utilization of the p-box method has an advantage if the conditional probability of a particular failure mode of a component is known approximately only, and the sample size of damage histories is small or inconsistent or modeling of component failure is uncertain.