Seismic qualification of structures, systems and components in a Canadian nuclear power plant

The seismic qualification of a Nuclear Power Plant (NPP) is a complex subject where the structural response to the ground motion leads to the floor vibrations transferred to a system (pipe lines or electrical cabinets mounted on the floor) which in turn propagates its own shaking to its components (a valve or a electric switch). Such components and their parent systems are classified in different categories depending on their required functionality or integrity (or both) during and/or after a seismic event. Canadian nuclear standards mandate the process of seismic qualification, incorporating the requirements of the American standards, guidelines and reports from organizations such as Nuclear Regulatory Commission (NRC), Electric Power Research Institute (EPRI), Seismic Qualification Utility Group (SQUG) etc. providing enormous amount of information on the seismic input, experience database and test reports from various sources recognized by the regulator. Some of the NPPs in Canada were constructed to the seismic demand known as Design Basis Earthquake (DBE) based on the west coast (near the Pacific Ocean) earthquake records whereas some relatively older NPPs, designed with limited seismic requirements, have been assessed in the recent past for an event known as Review Level Earthquake (RLE) based on the east coast records (closer to the Atlantic Ocean in comparison to Pacific). The entire process of seismic qualification becomes challenging with references to a plethora of documents, catering to different categories subject to varieties of seismic input. This paper presents a road map to navigate a seismic engineer through the seismic qualification process of NPPs in Canada and investigates the areas for improvement in the existing standards.