Approaches to estimate pipe failure rates for risk-informed in-service applications at nuclear power plants

Piping failure frequencies are needed e.g. for quantifying initiating event frequencies in probabilistic safety assessments (PSA), and for the application of quantitative risk-informed in-service inspection methodology. The paper summaries different approaches to estimate failure frequencies of piping at nuclear power plants (NPPs). These approaches are the use of structural reliability models, statistical estimation from operating experience data and the use of expert judgement for probability statements based on e.g. deterministic analyses. We illustrate the use of these approaches with a simple example. Further we discuss what kind of input data is needed and evaluate their availability.