PNNL

Abstract

Appendix L of the ASME Section XI code sets standards for augmented inspections of piping components that have experienced high levels of fatigue usage, and provides a basis for continued operation of components beyond their original design life. This paper describes probabilistic fracture mechanics calculations that estimate the reductions in piping failure probabilities associated with the Appendix L inspections. The improvements in piping reliability are a function of the frequency of the inspections and the quality of the ultrasonic examination methods (probability of flaw detection). Both preexisting fabrication flaws and flaws initiated by fatigue cycling are included in the probabilistic calculations. The calculations show that a program of Appendix L inspections can maintain piping failure rates during a period of extended operation at levels that are at or below the failure frequencies that are estimated for the original period of the design life.