in depthNuclear emergency planning at Canada's power plants

Canada's seven nuclear generating stations are located at five sites in Ontario, Quebec and New Brunswick, which have relatively low levels of seismic activity but have experienced damage-causing earthquakes in the past.

According to Natural Resources Canada, Eastern Canada, which includes those provinces, averages three earthquakes a decade of magnitude greater than 5, the level considered damage-causing.

The Canadian Nuclear Safety Commission (CNSC) says all of the country's nuclear power plants have been "designed and built or refurbished to meet seismic standards."

The plants use the Candu type of reactor, a Canadian-built pressurized heavy-water power reactor. As a condition for licensing, the reactors have to be built to withstand the strongest earthquakes recorded for the site where they will be used.

"Withstand" does not necessarily mean "not suffer any damage." The CNSC says each Candu reactor has multiple safety systems in place to ensure that the surrounding area is not adversely affected should there be an earthquake. In an emergency, Candu reactors are supposed to automatically shut down and cool the core without a release of radiation.

2 accidents at Pickering plant

The most serious nuclear accidents in Canada happened at the Pickering nuclear facility east of Toronto, which has two generating stations with four reactors each, in 1974 and in 1983. In each case, pressure tubes — which hold fuel rods — ruptured. The CANDU design uses much smaller pressure vessels than other types of nuclear reactors, so when a pressure tube fails, it can be replaced without taking the entire reactor off-line.

An aerial view of the Pickering, Ont., nuclear plant, which has two generating stations with four reactors each, two which are currently out of operation. (Kevin Frayer/Canadian Press)

In the Pickering accidents, some coolant escaped but was recovered before it left the plant, and there was no release of radioactive material from the containment building. The plant staff were able to shut down the reactor without having to rely on the automatic shutdown systems that would kick in during a nuclear accident.

Emergency preparedness and response is a shared responsibility between all levels of government and the operator of a given plant, which all regularly participate in nuclear emergency exercises in which they practice responding to a given scenario.

Municipal governments are generally the ones overseeing emergency operations while provincial authorities are responsible for public health, safety and environmental aspects.

Ontario's emergency plan

The highest concentration of nuclear power plants in the country is east of Toronto — the Pickering and Darlington nuclear power plants. They are located in Durham Region, and it is the Durham Emergency Management Office that is responsible for carrying out the area's emergency response plan.

Part of that plan includes:

Alerting the public. A system of sirens is in place to warn people within a three-kilometre radius of the Darlington and Pickering power plants should there be an emergency. When the sirens go off, residents are supposed to go indoors and tune in to local radio or television stations, which will be relaying emergency information.

Automated telephone-dialing system. Everyone who lives within a 10-kilometre radius of the power plants in Durham Region will receive an automated call advising them of an emergency.

Potassium iodide pills. People who live within three kilometres of the plants will have access to free potassium iodide pills at designated pharmacies. The tablets prevent or reduce the absorption of radioiodine, a byproduct of nuclear fission, through the thyroid gland.

Evacuation. In a worst-case scenario, residents will be advised to leave the area and go to designated facilities, following evacuation routes established by the province.

Emergency Management Ontario also recommends people develop their own emergency plans.

Not all of Canada's nuclear plants are fully operational. New Brunswick's Point Lepreau nuclear generating station, which is near a fault line but not one that is likely to cause a major earthquake, is undergoing refurbishment, and the Pickering facility has only six of its eight reactors online.

Aside from nuclear power plants, Canada also has several research reactors across the country operated by Atomic Energy Laboratories Canada or universities, some of which are used for various medical and industrial purposes. Those, too, are overseen by the nuclear safety commission when it comes to adhering to seismic safety standards.