An approach to the quantification of seismic margins in nuclear power plants: The importance of BWR plant systems and functions to seismic margins

The objective is to discuss progress to date in studying the issue of quantification of seismic margins in nuclear power plants. In particular, it deals with progress towards the establishment of review guidelines that would be useful in studying how much seismic margin exists. The work presented in this report is the result of a detailed study of seismic Probabilistic Risk Assessments, historical earthquake performance of the nuclear and non-nuclear facilities, and test date, augmented by the individual experience and expertise of the Panel members. The major development discussed in this report is the HCLPF concept, which demonstrates margin by showing that there is a High Confidence of a Low Probability of Failure for a given earthquake size. 38 figs., 62 tabs.