Ontario Power Generation (OPG) said this week it has recompleted refurbishment of Unit 4 at Darlington Nuclear Generating Station in Ontario, Canada.
Darlington staff are currently doing final testing in preparation of returning Unit 4 to operation, OPG said Monday.
The major refurbishment project that cost $12.8 billion (US$ 9.3 billion) is on track to be completed four months earlier and at a lower cost than what the utility had once expected, OPG said in its press release. The Canadian utility said the project will be $150 million (US$109 million) under an earlier budget estimate.
“This is a momentous achievement for OPG, Ontario, and Canada,” Nicolle Butcher, OPG President and CEO, said. “Our experience on this refurbishment, and the thousands of lessons we have learned, will serve as our foundation as we advance nuclear’s future. Darlington’s refurbishment has given us the confidence, the tools, and the skills to forge ahead.”
The Darlington Nuclear Generating Station is composed of four CANDU pressurized heavy-water reactors and produces an output of 3,512 megawatts. OPG also has planned to add four small modular reactors (SMRs) to land adjacent to the site.
The decade-long project began in 2016 with the refurbishment of Darlington Unit 2. The second unit was refurbished and returned to operation in June 2020, while Unit 3 came back online in July 2023 and Unit 1 in November 2024.
With the construction for the fourth Darlington unit completed, the unit is expected to return online in the coming weeks. The unit was originally projected to come online by August this year.
OPG’s key partners in the Darlington refurbishment project were Aecon Group, Candu Energy, and the Government of Ontario.
According to Aecon’s Monday press release, throughout the refurbishment, the groups completed:
- 960 end fittings removed in each reactor
- 1,920 fuel channels installed in each reactor
- 3,840 feeder tubes removed and replaced across all four units
- 6,240 fuel bundles loaded into each reactor’s fuel channels
- 23 million hours of work executed without a lost-time incident
Coming off the Darlington refurbishment, Aecon said it will, along with Candu Energy, an AtkinsRéalis company, will work again with OPG in its refurbishment of the Pickering Nuclear Generating Station, which was approved in November 2025.