Darlington Nuclear Refurbishment Lands Under Budget and Four Months Early

Ontario Power Generation finished rebuilding four CANDU reactors on 2 February 2026, four months ahead of schedule and CAD $150 million under a CAD $12.8 billion budget. In an industry where nuclear projects are a byword for overrun, that outcome is the story.

Project Scope

The refurbishment replaced 1,920 fuel channels and 3,840 feeder pipes across Units 1 through 4, one unit at a time, with the station’s other reactors generating throughout. Unit 2 came out of service in October 2016. Unit 4, the last, took 968 days, the fastest of the four, and Unit 3 reconnected 169 days ahead of commitment.

OPG built the world’s first full-scale reactor mock-up before any tool touched a real vault, and the retube crews rehearsed on it until the sequence was muscle memory. Laurentis Energy Partners, OPG’s commercial arm, delivered a large share of the work, and BWXT’s Peterborough plant supplied fuel bundles.

Why It Matters

The refurbishment secures 3,512 MW for another thirty years, roughly a fifth of Ontario’s electricity, at a moment when data center and electrification load is arriving faster than new generation. It also produced a delivery record other utilities are already copying. The project averaged about 14,200 jobs a year, kept 96% of its spend inside Ontario, and generated an estimated CAD $90 billion in provincial economic benefit. OPG catalogued roughly 8,000 lessons learned and is applying them at Pickering and on the Darlington small modular reactor build next door.

One caveat belongs in the record. Unit 4 returned to service on 26 May 2026, ran near full capacity for about two weeks, and went offline again on 10 June. Post-refurbishment teething is normal on a machine this size and it is not a construction failure. But a refurbishment is not proven until the units run.

Project Team & Details