How Canadian Nuclear Power Plants Are Protected Against Earthquakes

March 18, 2011

• Could damage occur to Canadian nuclear power plants in the event of an earthquake?
• Is seismic activity taken into account when deciding on where to build nuclear facilities?
• Do Canadian nuclear power plants have established emergency procedures?
• What emergency measures are in place in the event of an earthquake in Canada?
• Are there any seismic licensing requirements from the CNSC for nuclear power plants?

Could damage occur to Canadian nuclear power plants in the event of an earthquake?

The CNSC would like to reassure Canadians that nuclear power plants (NPPs) located in Canada have among the most robust designs in the world and have redundant safety systems to prevent damage in case of an earthquake.

All Canadian NPPs have been designed to withstand potential earthquakes.  Both the actual structures that form containment and the systems important to safety have been seismically qualified. That is, they are designed and built or refurbished to meet seismic standards. CNSC has reviewed and inspected these installations to confirm their robustness with regard to potential earthquakes.

Similarly, waste management facilities are designed to withstand seismic events (as defined under the National Building Code).

The CANDU design uses the concept of defence-in-depth to ensure that there are many barriers (or layers of protection) to prevent undesirable events or in the occurrence of an event such an earthquake or other emergency, to mitigate the consequences.

Types of barriers are: physical (pipes, shielding, buildings built to standards to contain radioactive substances), safety systems (systems that shut down facilities or control equipment, systems that contain radioactivity, emergency core cooling systems) and programmatic (quality management systems, processes and procedures); and operators are trained for routine and abnormal operations, including emergencies.

The CNSC has inspectors at all nuclear power plants; the waste storage facilities are co-located at the plants so staff are available to inspect facilities and confirm that licensees are following their procedures.

Is seismic activity taken into account when deciding on where to build nuclear facilities?

In Canada, reactor sites are geologically screened to ensure they are constructed in a location that is seismically stable.

CANDU nuclear technology is designed to withstand earthquakes of a magnitude greater than the largest known earthquake for the region where it is being built. "Withstand" means that the reactor has the ability to automatically shut down and cool the core without a release of radiation.

As a licensing requirement, nuclear reactors must be qualified to withstand the level of seismic activity that is expected for each individual reactor location. Seismic qualification is a common component of civil and mechanical design, and nuclear reactors do not differ from any other major infrastructure in this respect. The same robustness and defence-in-depth approach that assures safety and security of a nuclear plant plays a major role in its seismic qualification, and often provides a level of conservatism that continues to protect even during very unlikely events.

Source: Geological Survey, Natural Resources Canada

Do Canadian nuclear power plants have established emergency procedures?

All nuclear power plant operators in Canada have well-established and practised emergency procedures in place that include emergency shutdown of the reactors and firefighting. These facilities are inspected regularly by CNSC personnel, and emergency drills are evaluated by CNSC teams.

What emergency measures are in place in the event of an earthquake in Canada?

Public Safety Canada maintains the Federal Emergency Response Plan and works closely with provincial and territorial emergency measures organizations to promote emergency preparedness. Earthquake-prone regions of Canada have earthquake-specific emergency response plans that are exercised on a regular basis. For more information, go to: www.publicsafety.gc.ca

Are there any seismic licensing requirements from the CNSC for nuclear power plants?

All Canadian nuclear power plants have been licensed on the basis of their proven ability to withstand seismic events such as earthquakes. Structures and systems have been designed to safely survive earthquakes to ensure that:

• a loss-of-coolant accident does not occur
• reactors can be shut down and remain shut down
• heat from reactors can be removed
• any required release of radioactivity is minimized
• status of nuclear steam supply system can be monitored
• no radioactive releases above allowable limits result from any damage to systems other than the core reactor
• if one power reactor fails, it will not affect the safety of adjacent systems or structures

Canadian Standards Association standards impose a series of technical specifications for structures and containment of nuclear power plants that must be addressed by Canadian companies in order to obtain a licence to operate by the CNSC. The CNSC ensures that all nuclear power plant licensees comply with regulatory requirements.