Bruce Power has removed all four of Bruce B’s operating units from service for the generating station’s planned Vacuum Building Outage (VBO) in close collaboration and co-ordination with the Independent Electricity System Operator (IESO) and Hydro One.

The eight pressurised heavy-water Candu reactor units at the Bruce site in Ontario (Bruce A – units 1-4, and Bruce B – units 4-8) began commercial operation between 1977 and 1987. Bruce Power’s CAD13bn ($10bn) Life Extension Programme, which includes Asset Management and Major Component Replacement (MCR), began in 2016. MCR, which started with unit 6 and also includes units 3-8, will extend the life of the site until 2064. Units 1&2 have already been refurbished and were returned to service in 2012. Work began on unit 3 in March 2023 and is progressing on schedule using innovation and efficiencies gained in unit 6.

Vacuum buildings are unique to multi-unit CANDU generating stations and are part of their robust safety systems, providing an additional protective barrier to the release of radioactivity to the environment. All four operating units must be shut down approximately once every decade to allow for inspections and maintenance to the vacuum building, the culmination of extensive planning, resourcing and co-ordination. The VBO represents an investment of CAD190m ($138m) over less than three weeks to ensure maintenance and inspection work can be carried out safely and successfully by Bruce Power, its partners and skilled tradespeople.

“Bringing all of the station’s operating units off-line at once is a large undertaking and our team has been planning for years to ensure it is completed safely,” said Bruce B Vice-President Adrian London. “The Vacuum Building Outage removes about 15% of the capacity available to the Independent Electricity System Operator grid, so the people of Ontario are counting on us to bring our units back online successfully to continue to provide clean, reliable power.” Bruce A's vacuum building underwent a similar outage in 2022.

Bruce Power works closely with the IESO to ensure the timing of these outages can be accommodated to meet the needs of the province’s electricity grid. VBOs are scheduled during periods of the year when demand is expected to be low – usually the spring or autumn. Before being taken off-line April 18 for a planned outage, unit 7 marked its historical record run of 646 consecutive days operation, which is the Bruce site’s second longest after Bruce A unit 1’s post-refurbishment run of 694 days in 2020.