Major Component Replacement – or MCR – involves removing and replacing key reactor components including steam generators, pressure tubes, calandria tubes and feeder tubes and adding 30-35 years to the reactor’s operating life. Bruce 3 was taken offline to begin its MCR outage in March 2023, with Bruce Power announcing the completion of the construction phase of the project in February.
Regulatory hold points are mandatory checkpoints beyond which reactor operation cannot proceed without approval from the Commission. The Canadian Nuclear Safety Commission (CNSC) applies four hold points to reactor refurbishment projects: loading fuel into the reactor; removing the guaranteed shutdown state and starting the reactor; exceeding 1% full power; and exceeding 35% full power.
Ramzi Jammal, Executive Vice-President and Chief Regulatory Operations Officer at the Canadian Nuclear Safety Commission, notified the company on 2 June of the regulator’s decision to remove the final regulatory hold point after CNSC staff confirmed that the company had met all of its commitments and remained in compliance with its licence conditions.
Bruce Power Director, Community & External Affairs Maggie Tieman confirmed that the unit has been restarted. “Today at 1:34 a.m. Unit 3 was successfully synchronised to Ontario’s electricity grid. As we move forward, we will continue power ascension in Unit 3 and complete the remaining testing and approvals required for commercial operation,” she told World Nuclear News.
The Bruce site comprises eight operable Candu reactors divided equally between two plants: units 1-4 make up Bruce A, and units 5-8 are Bruce B. At Bruce A, units 1 and 2 have already been refurbished, returning to operations in 2012. Unit 4 is currently undergoing an MCR which began in February 2025. The four units making up Bruce B are also being refurbished: unit 6’s MCR was completed in 2024; units 5 is expected to begin its MCR later this year, according to the CNSC’s timeline, with overlapping MCR projects scheduled to begin at units 7 and 8 in 2028 and 2030 respectively.
