Tuesday, February 3, 2026
The Government of Ontario announced the completion of construction on the refurbishment of the Darlington Unit 4 nuclear reactor. The unit is now complete and will be returning to service four months ahead of schedule, the overall refurbishment project coming in $150 million under budget.
Originally expected to return to power in August 2026, the unit has received approval from the Canadian Nuclear Safety Commission to enter the initial power testing, which is expected to begin on February 12, and will be at full power shortly after.
“Ontario is proving to the world that we can deliver major nuclear energy projects on-time and on-budget,” said Stephen Lecce, Minister of Energy and Mines. “Last year we returned another refurbished unit at Darlington four months ahead of schedule, and today we’ve done it again. Completing the full Darlington refurbishment on-time and under-budget is a made-in-Canada win for our economy, generating $90 billion in economic benefits and supporting 14,200 good-paying jobs.”
The Darlington Nuclear Refurbishment is No. 6 on ReNew Canada’s 2026 Top100 Projects report.
The Darlington refurbishment project involved the complete overhaul of all four nuclear reactor units, extending the station’s operating life to at least 2055. With all four units refurbished and ready to be brought back online, this marks the completion of the world’s largest refurbishment project to-date, with the Darlington Nuclear Generating Station ready to deliver more than 3,500 megawatts (MW) of clean, reliable, emission-free electricity — enough to power 3.5 million homes — for at least 30 more years.
The Darlington refurbishment project was completed by over 6,000 Ontario workers, including skilled tradespeople, support services workers and project managers. Refurbishment work included replacing thousands of fuel channels, feeder tubes, calandria tubes, and end fittings, as well as rehabilitating other critical components. The project also included system improvements and plant upgrades to meet current regulatory requirements.
“Bringing the Darlington refurbishment in ahead of schedule and under budget will clearly demonstrate our team’s ability to deliver large and complex nuclear projects,” said Nicolle Butcher, president and CEO, Ontario Power Generation. “The skills we developed and lessons we learned during this project are invaluable as we proceed with refurbishing Pickering Nuclear Generating Station, continue construction on the G7’s first Small Modular Reactor at the Darlington New Nuclear Project, and study the potential for up to 10,000 MW of new nuclear at Wesleyville.”
Featured image: (Government of Ontario)
