Critical excitation method for calculating earthquake effects on nuclear plant structures: an assessment study. Technical report

The critical excitation method provides a new, alternative approach to methods presently used for seismic analysis of nuclear power plant structures. The critical excitation method offers the advantages that: (1) it side-steps the assumptions regarding the probability distribution of ground motions, and (2) it does not require an artificial, and to some extent arbitrarily generated, time history of ground motion, both features to which structural integrity analyses are sensitive. Potential utility of the critical excitation method is studied from the user's viewpoint. The method is reviewed and compared with the response spectrum method used in current practice, utilizing the reactor buildings of a PWR and a BWR plant in case studies. Two types of constraints on critical excitation were considered in the study. In one case, only an intensity limit was used. In the other case, imposition of an intensity limit together with limits on the maximum acceleration and/or velocity for the critical excitation is considered.