The gradual start-up of Unit 2 at the Bruce nuclear generating station in Tiverton has been delayed after a leak was discovered.
Bruce Power Media spokesperson John Peevers says with a unit that hasn't been operating for nearly 20 years, they expected a few hiccups along the way.
Peevers admits there was a moderator leak in the unit as it was being restarted over the weekend.
However, he says it was a minor leak of heavy water, but there was no exposure affecting workers and no impact on the general public.
The leaked moderator water entered the collection system which is designed for this purpose.
Unit two was returned to the shutdown state and the leak was stopped promptly.
It has now been isolated for repair, and Peevers says that should take just a few days.
The minor leak occurred just a day after Bruce Power received approval from the Canadian Nuclear Safety Commission to restart the unit.
The CNSC says Bruce Power staff took appropriate action.
Unit 2 is the first mothballed unit due to come back online.
The refurbishment of Unit 1 will also be complete soon and the project will cost nearly five billion dollars.