In the context of risk-informed applications, this paper addresses the progress with piping reliability analysis methods and techniques and their role in supporting development of risk-informed structural integrity programs for small modular reactors (SMRs). The structural integrity of a pressure boundary is determined by multiple and interrelated reliability attributes and influence factors. Depending on the conjoint requirements for damage and degradation, certain combinations of material, operating environment, loading conditions together with applicable design codes and standards, certain passive components are substantially more resistant to damage and degradation than others. As an example, for stabilized austenitic stainless steel pressure boundary components, there are no recorded events involving active, through-wall leakage. By contrast, for unstabilized austenitic stainless steel, multiple events involving through-wall leakage have been recorded, albeit with relative minor leak rates.
The field experience with safety- and non-safety related piping in commercial GenI through GenIII nuclear power reactors is quite extensive. Equally extensive is the experience gained from the implementation of different degradation mechanism mitigation strategies. By applying advanced piping reliability models, this body engineering data and integrity management insights can be used to assess the projected structural integrity of new piping system designs, including those of SMRs. The paper presents an overview of recent methodological advances and insights from the application of statistical piping reliability models to advanced reactor designs. Examples are provided on how piping reliability parameter estimates are affected by different integrity management strategies as well as by advanced, degradation mechanism (DM) resistant materials. The technical basis for the work that is presented in this paper has evolved over a period of 20+ years of focused and sustained R&D in the area of statistical models of piping reliability.