Early Sunday morning, an emergency message was sent across Ontario alerting residents about an incident at the Pickering nuclear generating station east of Toronto.

The alert turned out to be an error but it raises questions about how prepared the province is in case of a nuclear incident.

Does Ontario have a plan for a nuclear emergency?

Yes. The Provincial Nuclear Emergency Response Plan, a 200-page document, dictates instructions to every municipality that has a nuclear facility within their jurisdiction.

It was last revised in 2017. Each of the five nuclear facilities located in and around Ontario also have their own plans.

What happens immediately following an incident?

If there's an incident at a nuclear facility, Ontario Power Generation would notify local and provincial governments within 15 minutes.

The provincial government's Emergency Management Ontario, which falls under the Ministry of the Solicitor General, is then responsible for public safety during nuclear emergencies and would determine the appropriate level of public action.

It will administer the Provincial Nuclear Emergency Response Plan and has overall responsibility for managing the off-site response to nuclear emergencies.

Local emergency responders: police, fire and ambulance crews, make sure emergency plans are implemented properly.

What kind of alerts are issued?

Guidelines and plans need to be in place to alert people within three kilometres of each reactor, said James Kilgour, director of Durham Emergency Management.

For example, in the immediate areas around Bruce Power, Pickering and Darlington, air sirens are utilized, he said.

Within 10 kilometres, residents receive indoor alerts — calls to their homes.

Kilgour said his region utilizes an auto-dialling system that calls everybody on landlines within 10 kilometres of the plant.

A jogger runs along the beach past the Pickering Nuclear Generating Station, in Pickering, Ont., on Sunday. (Frank Gunn/The Canadian Press)

The province controls the alert ready system, or amber alert, to contact mobile phone users.

Toronto also would use an indoor alert system — the city doesn't need sirens because it is not within three kilometres of the nearest plant.

Also, emergency bulletins would be issued regularly to provide updated information through radio, television and social media.

What about evacuations?

Those would likely occur in areas immediately surrounding a reactor facility, but additional evacuations of an expanded area could also be necessary as circumstances change, particularly if there are shifts in the wind.

"If we need to evacuate, the province makes the decision ... and then multiple agencies come together to start to operationalize the traffic movement," Kilgour said.

However, some people may be directed to remain indoors for a relatively short period of time if it's deemed that evacuating is too dangerous due to circumstances such as severe weather.

Are there any preparations for food contamination?

In case of a risk of contamination of food, water, milk, or commodities, the province may advise the public to take a number of measures. Those include protecting drinking water supplies that directly use rainwater, and restricting consumption and distribution of non-essential local produce, milk from grazing animals, rainwater and animal feed.

Can anything be used to help prevent radiation poisoning?

According to the Canadian Nuclear Safety Commission, potassium iodide can be used to protect the thyroid gland from radioactive iodine that may be released into the air in the event of a radiological emergency.

In 2015, the Canadian Nuclear Safety Commission and Ontario government agreed that every house, resident and business within 10 kilometres of all nuclear plants in Ontario would receive a free stock or inventory of potassium iodide.

Potassium iodide can be used to protect the thyroid gland from radioactive iodine that may be released into the air in the event of a radiological emergency, according to the Canadian Nuclear Safety Commission. ( Irene Thomaidis/CBC)

People who live between 10 and 50 kilometres from a plant who want potassium idodide, can order it online.

Residents can type in their postal code, and they will be informed as to whether they live within an area eligible for a free package. If so, it will be mailed out.

Who determines whether people should ingest the potassium iodide?

The chief medical officer of the province of Ontario, in consultation with other officials, decides whether or not people need to ingest potassium iodide.

According to the provincial plan, pills should be ingested two to six hours prior to or just after exposure to radiation. A single dose lasts approximately 24 hours.

Do municipalities run drills?

Yes. In Durham, for example, the region runs two drills a year, one in the spring and one in the fall, which include blaring sirens and indoor alerting, Kilgour said.

"That is accompanied by heavy public education and awareness, contacting the media, contacting the public to let them know that we're conducting these [tests]," he said.