Bruce Power Unit 4: Rebuilding a Reactor Core Inside 1970s Containment

Rebuilding a CANDU reactor core means pulling out 480 fuel channels, 960 end fittings, the calandria tubes, the feeder tubes and eight steam generators, then putting it all back inside a containment structure built in the 1970s. Bruce Power is on its third one.

Unit 4’s Major Component Replacement outage began on 3 February 2025 and runs about three years. It follows Units 6 and 3 through the same sequence, and in September 2025 the unit hit its key milestone and moved into the removal-and-replacement series.

Project Scope

Shoreline Power Group holds the work, a joint venture of Aecon, AtkinsRéalis and New Jersey-based United Engineers & Constructors, now an Aecon subsidiary. Shoreline won a CAD $1.3 billion fuel channel and feeder replacement contract in May 2023 covering Units 4, 5, 7 and 8. The earlier Unit 3 package alone ran about CAD $400 million. BWXT Canada manufactures the replacement steam generators in Cambridge, Ontario, eight per unit.

The whole life-extension program is a CAD $13 billion effort. That makes it Canada’s third-largest infrastructure project and pushes station operation past 2064.

Why It Matters

Unit 3 is why this schedule is worth watching. It went into outage in March 2023 and returned to service in June 2026, more than seven months ahead of plan, with roughly CAD $150 million in savings flowing back to Ontario ratepayers as a power-price reduction starting April 2027. Aecon and Shoreline credited the crew learning curve carried over from Unit 6.

That is the number the rest of the nuclear construction market keeps citing. Refurbishment spent decades as a byword for schedule risk, and Bruce is assembling the counter-example one unit at a time. U.S. utilities weighing restarts and uprates now point at these outages when they argue that repeat execution, rather than first-of-a-kind engineering, is what makes nuclear predictable.

Worth noting for anyone pricing similar work: Bruce Power has not published a separate contract value for Unit 4 on its own. The figures above are program and multi-unit totals.

Project Team & Details