ANSI/ANS-58.21-2007;W2009 (W=Withdrawn): External Events in PRA Methodology
Historical Standard, This standard was superseded by ASME/ANS RA-Sa-2009
The scope of a PRA covered by this standard is limited to analyzing accident sequences initiated by external events that might occur while a nuclear power plant is at nominal full power. It is further limited to requirements for (a) a Level 1 analysis of the core damage frequency (CDF) and (b) a limited Level 2 analysis sufficient to evaluate the large early release frequency (LERF). The scope of a seismic margin assessment (SMA) covered by this standard is limited to analyzing nuclear power plant seismic capacities according to either the so-called Electric Power Research Institute (EPRI) method ("EPRI Method") or the so-called U.S. Nuclear Regulatory Commission (NRC) method ("NRC Method").
Although both seismic PRA and SMA are intended to support risk-informed applications, the distinction between them regarding their applicability to develop risk insights needs to be clearly understood. The SMA is a deterministic methodology, and in this context, a well-executed SMA can provide qualitative, and limited, risk insights that could be used to support an intended application. However, for situations where detailed quantitative risk insights are necessary, a seismic PRA is needed.