Ontario Power Generation (OPG) has announced the successful completion of a major milestone at the Darlington Nuclear Generating Station in Clarington, as Unit 4 has been reconnected to Ontario’s electricity grid following a full refurbishment.
The completion marks the final phase of the Darlington Nuclear Refurbishment Project, a large-scale initiative that began in 2016 and is considered one of the most significant energy infrastructure projects in Canada.
Unit 4 had been offline since July 2023 while refurbishment work was carried out. According to OPG, the project was completed in 968 days, making it the first Darlington unit refurbishment to be finished in under 1,000 days.
Officials say the work was completed four months ahead of schedule and approximately $150 million under budget, highlighting the scale of planning and collaboration involved in the project.
OPG President and CEO Nicholle Butcher praised the thousands of workers and partners who contributed to the refurbishment.
“We give our thanks to all who made the Darlington refurbishment a resounding success — from our employees to our project partners and the province’s robust nuclear supply chain,” said Butcher. “They have helped set the standard and now we’re ready to keep delivering for Ontario’s future.”
The completion of Unit 4 also marks the final refurbishment of all four units at the Darlington nuclear station, concluding nearly a decade of work.
The modernized facility is now expected to continue producing clean electricity for Ontario for more than 30 years.
Darlington Nuclear Generating Station is one of the province’s largest power facilities, producing over 3,500 megawatts of electricity, which is enough to supply power to approximately 3.5 million homes across Ontario.
Beyond restoring power generation capacity, OPG says the project also provided valuable experience for future nuclear developments in the province.
During the refurbishment program, teams documented more than 8,000 lessons learned, which will help guide upcoming projects, including:
-
The refurbishment of the Pickering Nuclear Generating Station
-
The construction of four Small Modular Reactors (SMRs) at Darlington
-
A proposed large-scale CANDU reactor project in Wesleyville, located east of Darlington
Butcher said the success of the project demonstrates that large nuclear infrastructure projects can be completed efficiently.
“Through this project, we have demonstrated to the world that complex nuclear projects can be completed successfully, ahead of schedule and under budget,” she said.
Local leaders also praised the achievement and the workforce responsible for completing the project.
Clarington Mayor Adrian Foster called the completion an “extraordinary milestone” for both the community and the province.
“Completing the final phase of refurbishment nearly five months early is a remarkable accomplishment,” Foster said. “From trades and technical teams to engineers and planners, thousands of individuals helped deliver the world’s largest nuclear refurbishment project.”
Foster added that the project highlights the strength of Durham Region’s skilled workforce and its important role in Ontario’s energy sector.
With the refurbishment now complete, the Darlington nuclear station will continue to serve as a major source of reliable and clean electricity for Ontario residents and businesses for decades to come.
