1A draft Safety Guide on seismic hazards in site evaluation for nuclear installations is in preparation, to supersede Ref. [4].

2The development and use of guidelines on the seismic safety evaluation of existing nuclear installations started in the United States of America, where such guidelines were developed and their application to all existing nuclear power plants was required.

3The term ‘selected SSCs’ is used in this Safety Guide to mean those SSCs that have been selected for evaluation of their seismic capacity using criteria consistent with the regulatory requirements and ultimate objectives of the seismic safety evaluation programme. This is consistent with the terminology used in Ref. [6]. In IAEA technical guidance developed in the 1990s for the seismic safety evaluation of specific nuclear power plants, the term ‘safe shutdown equipment list (SSEL)’ was also used, as borrowed from earlier usage in the United States of America. However, as the SSCs cover more than ‘equipment’ and the goals of the programme may exceed ‘safe shutdown’, the term ‘selected SSCs’ is preferred.

4In some Member States, a small loss of coolant accident is defined as the cumulative equivalent break size of a 25 mm diameter pipe.

5HCLPF capacity is the earthquake motion level at which there is a high confidence of a low probability of failure. HCLPF capacity is a measure of seismic margin. In seismic PSA, this is defined as the level of earthquake ground motion at which there is a high (95%) confidence of a low (at most 5%) probability of failure. Using the log-normal fragility model, the HCLPF capacity is expressed as Am e^{[–1.65βr+βu)]}. When the logarithmic standard deviation of composite variability βc is used, the HCLPF capacity can be approximated by the ground motion level at which the composite probability of failure is at most 1%. In this case, the HCLPF capacity is expressed as Am e^{[-2.33 βc]}. In deterministic SMAs, the HCLPF is calculated using the conservative deterministic failure margin method.

6See footnote 3 on p. 25.

1In the CDPM method, the seismic margin of an SSC is calculated by using a set of deterministic rules that are more realistic than design procedures.