Peach Bottom Atomic Power Station Structural Response Analysis

A seismic probabilistic risk assessment (SPRA) was performed for Exelon’s Peach Bottom Atomic Power Station, a dual-unit plant in Pennsylvania, to gain a better understanding of the impact of updated site seismic hazard estimates on plant earthquake safety.  SC Solutions’ primary role on the project team was to build detailed finite element models of critical plant structures and perform soil-structure interaction (SSI) analyses using SASSI software to generate in-structure response spectra (ISRS) used as demands for component fragility evaluations.  Structures analyzed include the reactor building (RB), radwaste / main control room (RW/MCR), turbine building (TB), diesel generator building (DGB), intake pumping structure (PS), and the emergency cooling tower (ECT).

Due to the nature of the updated seismic hazard for the site, estimating realistic (versus conservative or bounding) structural response was paramount to support the SPRA objectives.  Therefore, SSI analyses included consideration for ground motion incoherency, variability in both soil and structure properties, randomness in ground motion records, and location-specific response quantities.  Additionally, several buildings sharing a common foundation (2xRB, 2xTB, and RW/MCR) were combined to form a single Reactor Building Complex to address structure-soil-structure interaction (SSSI) as well as to capture the full beneficial effects of ground motion incoherency.  The dual-unit Reactor Building Complex SSSI model is one of the largest SASSI models to date, made possible through use of the High Performance Computing (HPC) capabilities of the SC-SASSI software version developed by SC Solutions.

SC Solutions’ unique expertise in advanced computational techniques applied to frequency-domain SSI analysis, coupled with innovative approaches to efficiently address variability in modeling and seismic analysis of the soil-structure system, provided Exelon with detailed demand information suitable for subsequent fragility evaluations while effectively minimizing unwarranted conservatism.  The approach and techniques applied by SC Solutions ensured such detail and realism could be successfully provided cost-effectively and expediently within a challenging regulatory environment and project constraints.