Determination of the Probability of Failure (POF) in a Sensitivity Study Based on a Probabilistic FAD-Approach and POD-Curves Using PAUT

The application of the software PVrisk is discussed which was compiled in 2008 to solve probabilistic fracture mechanical problems in case of pressure vessels and pipes by utilizing approaches based on the Failure Assessment Diagram (FAD). The probabilistic feature is embedded due to Monte Carlo simulation (MCS). Compared to other tools available the advantage of PVrisk is to take the combination of fracture mechanics and NDT results based on Probability of Detection (POD) data into account. This data can be the result of an experimental POD trial or the result of computed POD-curves due to numerical modeling of the inspection process. This paper uses POD curves by evaluating experimental data obtained in a project in the German nuclear safety research program. The NDT task was the inspection of welds in austenitic stainless steel plates by using ultrasonic testing (UT) and the application of phased array transducers (PAUT - Phased Array UT) as inspection technique. Taking into account a realistic statistical population of half-elliptical, axial oriented, subsurface and surface breaking cracks in a larger diameter austenitic pipe as well as the material properties such as elastic limit Rp0.2, tensile strength Rm, and fracture toughness KIC numerical statistical modeling is used to calculate the probability of failure (POF). The advantage of using NDT with optimized POD is documented.