Darlington Nuclear returns Unit 4 to service, marking completion of refurbishment project

At a glance

• Darlington’s Unit 4 has been reconnected to the grid at 100% power.
• This marks the completion of OPG’s four-unit Darlington Refurbishment project, delivered $150 million under budget and four months ahead of schedule.
• Unit 4 began its refurbishment in July 2023.

OPG is celebrating a milestone 10 years in the making!

Unit 4 at Darlington Nuclear Generating Station has been reconnected to the grid at 100% power, generating low-carbon, reliable power for Ontario for the first time since July 2023, when the unit was taken offline for its refurbishment.

With this, the four-unit Darlington Refurbishment project, which kicked off in October 2016, officially comes to a close — $150 million under budget and four months ahead of schedule. The renewed station is now set to power Ontario for more than 30 years.

Unit 4’s refurbishment was completed in 968 days, making it the first Darlington unit to be completed in under 1,000 days. The unit’s return to service is a culmination of meticulous planning and preparation, millions of hours worked, and the dedication of thousands of people.

“We give our thanks to all who made the Darlington Refurbishment a resounding success – from our employees to our project partners to the province’s robust nuclear supply chain. They have helped set the standard and now we’re ready to keep delivering for Ontario’s future,” said Nicolle Butcher, OPG’s President and CEO.

With approximately 8,000 lessons learned from the Darlington Refurbishment, OPG will continue to leverage this experience to successfully execute future projects, including the Pickering Nuclear refurbishment, the deployment of four Small Modular Reactors at Darlington, and the proposed large nuclear development in Port Hope.

“Through this project, we have demonstrated to the world that complex nuclear projects can be completed successfully, ahead of schedule and under budget,” said Butcher. “Our experience on this refurbishment, and the thousands of lessons we have learned, will serve as our foundation as we advance the future of nuclear. Darlington’s refurbishment has given us the confidence, the tools, and the skills to forge ahead.”

Learn more about this project and look back at its journey below.