Piping seismic adequacy criteria recommendations based on performance during earthquakes

Abstract

Design and analysis of piping in a typical nuclear power plant has been estimated to cost as much as $80 million, at least 60% of which is associated with the implementation of current seismic design criteria. These current design criteria require seismic qualification of nuclear plant piping based on rigorous and expensive mathematical analysis and testing. Past earthquake experience has shown that piping within power facilities which have undergone little or no seismic qualification have performed very well with only a limited number of resulting cases in which the pressure boundary has been breached. The purpose of this paper is to document the performance of piping in past earthquakes and to explore the possibilities of using the results of this earthquake experience data to guide the development of a more reasonable criteria for assessing the seismic adequacy of power piping. Experience data has shown that the three critical areas to be considered for a seismic adequacy assessment of a welded steel piping system are: (1) seismic anchor movement, (2) corrosion, and (3) system interaction. The data presented within this study implies that excessive emphasis in both time and money are currently being expended to demonstrate the adequacy of piping for inertia effects.