Ontario Power Generation has confirmed that it plans to shut down Pickering's nuclear station within a decade, but will spend $300 million to keep it open for another 10 years.
When the Pickering plant is decommissioned, staff will have an opportunity to bid on jobs at the Darlington nuclear station.
Both nuclear plants are in Durham region, east of Toronto.
OPG also says it will proceed with a detailed planning phase for refurbishment of the Darlington nuclear station, with construction expected to begin in 2016.
The government-owned utility says the next phase for Darlington will include an environmental assessment and an integrated safety review to define the scope, cost and schedule of the project.
Critics say the decision to shut the Pickering plant shows nuclear power stations are too expensive to run.
However, Energy Minister Brad Duguid says Ontario still plans to build two new nuclear stations so nuclear power continues to provide about 50 per cent of the province's electricity supply.