Austenitic steel piping testing exercises in PISC

Abstract

In this paper capability and reliability studies of NDT procedures for the inspection of wrought and cast stainless steel piping used in nuclear power plants will be presented. The capability study was designed to identify procedures that have the potential to detect and size defects and to discriminate between flawed and unflawed material. The reliability study was undertaken to quantify on real and realistic flaws in-service inspection performance (detection and false call capability) under realistic field conditions. Furthermore parametric studes were performed to complement the capability and reliability studies by evaluating the effect of important material and flaw variables. The specimens used in these studies were cast-to-cast, cast-to-wrought, and wrought-to-wrought pipework welds. The evaluation methods used to quantify the inspection performance were selected to be as comparable as possible to the PISC II methods. These were adapted to allow also the evaluation of the effect of false calls. During the PISC II screening exercise for the cast-to-cast stainless steel round robin test and other piping round robin studies, it was indeed found that false call probabilities were large and could not be ignored in the evaluation of the inspection performance. The matrix of samples has also been designed to allow the implementation of specific statistical analysis procedures for the evaluation of results such as for example the relative operative characteristics analysis.