A view of the Darlington Nuclear Generating Station in Courtice, Ont., in May, 2023.Carlos Osorio/The Globe and Mail
The fourth and final refurbished reactor at Darlington Nuclear Generating Station in Clarington will return to service four months early, the Ontario government said Monday, concluding a multibillion-dollar, decade-long overhaul intended to extend the station’s life by another 30 years.
Construction work on the station’s Unit 4 officially ended on Jan. 19, and initial power testing of the unit is scheduled to begin later this month.
The government said the project as a whole cost $150-million less than its original $12.8-billion budget. Unit 1, which was overhauled previously, returned to service five months ahead of schedule.
The Globe went inside the control room that keeps reactor work at the Darlington nuclear-generating station safe and on track in 2023.
Such an outcome is rare among complex capital projects generally, and particularly in the nuclear industry, which has long been notorious for failing to deliver projects as promised. Provincial officials cite Ontario Power Generation’s performance at Darlington as justification for granting the utility permission to build new plants, including four new small modular reactors adjacent to the station.
“OPG is emerging as the most credible nuclear operator and builder on Earth,” Energy Minister Stephen Lecce said in an interview with The Globe and Mail last week.
“We’re the only ones building on time, and we’re building on budget. Unit 1 was one case study. Unit 4 will be the next frontier of our demonstration we can do this.”
But there is a wrinkle: Additional costly work is required at Darlington in the near future to maintain safe, reliable operations.
In a rate application made public last month, OPG reported that turbine rotors at the station need to be replaced, at an estimated cost of $2-billion.
“The need for this project arose from detailed inspections conducted during the Darlington Refurbishment Program of components not typically accessible during regular planned outages,” the application stated.
OPG also identified more “emergent” maintenance: The stators on the generators of Darlington Unit 1 and 2 have degraded and must be rewound (an additional $300-million), primary moisture separators must be replaced on the station’s steam generators ($235-million), and the turbine control and auxiliary system on Unit 2 must be upgraded ($115-million).
The utility said in 2018 that inspections had shown the station’s steam generators were in “excellent condition” and were ready for 30 more years of service.
Darlington, which has historically produced around one-fifth of Ontario’s power, was built in the 1980s and ’90s. Candu reactors originally had a stated design life of 30 years. After a decade of planning, the refurbishment began in October, 2016.
Though not quite as challenging as building a new plant from scratch, a midlife refurbishment is a major undertaking. It inevitably involves removing the nuclear fuel and replacing hundreds of pressure tubes – often described as the heart of a Candu reactor. But all equipment must be assessed to determine which components can endure further decades of service, and which ones must be replaced.
Experience has shown that misjudgments can be costly. OPG’s previous refurbishment, of the four oldest units at Pickering Nuclear Generating Station, was discontinued after the first two units came in late and massively overbudget.
OPG learned lessons from those failures, contributing to its success at Darlington. The utility said it learned thousands of lessons during the project, which were applied to save time and money.
Critics expected a worse outcome. In a 2010 report, the Ontario Clean Air Alliance calculated the province’s average historical nuclear project cost overruns at 2.5 times original estimates; on that basis, it warned the Darlington refurbishment could cost as much as $35-billion, nearly three times its ultimate cost.
Other recent major nuclear projects, particularly in the United States, have followed disastrous trajectories, resulting in huge cost and schedule overruns and abandonment of half-constructed reactors.
The government said the refurbishment will extend Darlington’s operating life until at least 2055. Bruce Power is in the midst of its own refurbishment of six units at its station in Kincardine, Ont. That project, which is scheduled to wrap up in 2033, is also reportedly on time and on budget.
In November, the government granted OPG permission to refurbish the four newer reactors at Pickering, with a budget of $26.8-billion – more costly, in nominal terms, than Darlington and Bruce combined.
Editor’s note: A photo caption in a previous version of this article misidentified its subject as the Darlington Nuclear Generating Station in Clarington, Ont. It depicted OPG's future headquarters in Oshawa, formerly owned by General Motors of Canada. The image and incorrect caption have been replaced.