An assessment of seismic margins in nuclear plant piping

Interim results of an ongoing program to assist the U.S. Nuclear Regulatory Commission (NRC) in developing regulatory positions on the seismic analyses of piping and overall safety margins of piping systems are reported. Results of: (1) reviews of seismic testing of piping components performed as part of the Electric Power Research Institute (EPRI)/NRC Piping and Fitting Dynamic Reliability (PFDR) Program, and (2) assessments of safety margins inherent in the ASME Code, Section III, piping seismic design criteria as revised by the 1994 Addenda are reported. The reviews indicate that the margins inherent in the revised criteria may be less than acceptable and that modifications to these criteria may be required