The company said the 817 MWe (net) pressurised heavy water reactor had recently achieved criticality - a sustained fission chain reaction. This followed Canadian Nuclear Safety Commission approval in May to begin releasing the unit from a Guaranteed Shutdown State which enables the many commissioning activities to be completed on the newly installed systems to verify everything is working as expected.
"This is a key step in returning the reactor to service, as it prepares to resume supplying clean, reliable electricity to the people, hospitals and businesses of Ontario for decades to come," Bruce Power said.
Unit 6 is the first of six Candu reactors at the site in Ontario to undergo refurbishment in a privately funded investment that will extend the life of the site through 2064. The company noted that the unit 6 MCR remains on track despite challenges faced during the COVID-19 pandemic.
The construction phase of the unit 6 MCR, completed with execution partner Shoreline Power Group as well as tradespeople from the Ontario Building Trades, included the removal and replacement of 960 feeder tubes, 480 fuel channels, and 480 calandria tubes. Steam generator work was completed earlier this year by SGRT, a joint venture of Aecon and Framatome and United Engineers & Constructors partnership SGT.
Refuelling the unit with 5760 fuel bundles began in May. The reactor is expected to be reconnected to the grid in the fourth quarter of this year.
Welcoming the restart of the unit, Bruce Power President and CEO Mike Rencheck said: "This is great progress, made possible by years of planning, preparation and execution by Bruce Power and our partners. We are now in the final stages of returning unit 6 to service and we're applying all of our learnings, innovation and experience from unit 6 to future MCRs to ensure our strong performance continues and improves."
Bruce 3 became the second unit to begin the MCR process in March this year when it was taken offline for defueling. "Work on the unit 3 MCR outage is also progressing on track," Bruce Power said.
The refurbishment of Bruce units 3-8 is scheduled to be fully completed by 2033 (units 1 and 2 at the site have already been refurbished). The MCR project and Bruce Power's Life-Extension Program will extend the operational life of each reactor by 30 to 35 years, helping to mitigate predicted increases in greenhouse gas emissions from the electricity grid, the company said. The work is also being coordinated with the Project 2030 programme, which aims to leverage innovation and new efficient technology to increase site capacity to over 7000 MWe of net peak output in the early 2030s, once all units have completed their MCRs.
