A Regulatory Perspective on Canadian Practices on the Use of Indirect Methods in Seismic Qualification and Their Evolution

Abstract of the technical paper/presentation presented at:
26th International Conference on Structural Mechanics in Reactor Technology (SMiRT)
July 10-15, 2022

Prepared by:
Seyun Eom, George Stoyanov, Thambiayah Nitheanandan of the Canadian Nuclear Safety Commission and Khalid Chaudhry 

Abstract

Seismic qualification (SQ) is a process of verifying the performance capability of a structure, system, or component (SSC) through testing, analysis, or other methods for ensuring that its design-intended performance is maintained during and/or following the design basis earthquake (DBE) and that sufficient margin exists beyond the design basis. Canadian Standards Association (CSA) standard N289.1, titled “General requirements for seismic design and qualification of CANDU nuclear power plants,” provides SQ guidance for both direct methods (i.e., by test, by analysis, or combination of thereof) and indirect methods (e.g., generic implementation procedure (GIP), experience-based method).

Indirect methods were originally developed to verify the seismic adequacy of installed mechanical and electrical equipment in the A-46 plants, which have limited or no original seismic design. The term A-46 refers to US Unresolved Safety Issue number concerning the seismic adequacy of mechanical and electrical equipment in older nuclear power plants. Currently, there are 19 nuclear power plants (NPPs) operating in Canada. As per the CSA N289.1, both direct methods and indirect methods have been used to demonstrate the seismic adequacy of a replaced SSC for the fitness for service (FFS) and refurbishments in Canadian NPPs. The purpose of this paper is to summarize Canadian SQ practices and discuss important elements that should be considered in SQ and establishing seismic adequacy when using indirect methods.

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