Risk-Informed Inservice Inspection (RI-ISI) allows the use of risk assessment plus an understanding of component-specific degradation mechanisms to establish a cost-effective inspection program as an alternative to current ASME Code Section XI requirements. Section XI has issued several Code Cases that provide risk-informed alternatives to current requirements. Code Cases N-560 for Class 1 piping and N-578 for general scope application both use the EPRI RI-ISI methodology. The EPRI-RI-ISI methodology has been approved by the NRC and proven on numerous pilot plant studies and follow-on plant applications. SI played a key role in the development of the EPRI RI-ISI methodology and ASME Code Cases N-560 and N-578.
SI has performed Code Case N-560 and N-578 evaluations for twenty-seven PWR units and ten BWR units. In all cases, the EPRI methodology has been proven to significantly reduce the number of piping inspections with negligible impact on plant risk. Recently issued Code Case N-716 (risk-informed safety-based, or RIS_B) pre-defines high safety significant (HSS) piping components based upon industry experience, thereby eliminating the need for a consequence evaluation. This approach is expected to result in significant cost savings over traditional RI-ISI, and SI is deeply involved in the N-716 pilot plant studies. In addition, SI has experience in risk-informed applications of Break Exclusion Region (BER) program piping, as well as performing RI-ISI Living Program Updates.
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