INER developed the Seismic Equipment Lists (SELs) identifying components to be included in SPRA. SGH performed seismic walkdowns of the items on the SELs for each plant following EPRI NP-6041-SL guidelines.
The plants were previously analyzed by deterministic seismic margin method for beyond design basis earthquake ground motion defined by a median NUREG/CR-0098 ground spectral shape anchored to 1.67 times the peak ground accelerations for the Safe Shutdown Earthquakes. The in-structure response spectra (ISRS) for the SPRAs were developed by scaling the deterministic ISRS to the preliminary uniform hazard spectra from recently updated probabilistic seismic hazard analyses.
We are currently performing seismic fragility evaluations for selected structures, systems, and components (SSCs) for each plant following methods recommended by EPRI TR-103959 and EPRI 1019200. The selected SSCs include those we judged to have potential seismic vulnerabilities by our seismic walkdowns, and those identified as being potentially risk-significant by systems reviews conducted by INER.