Unit 3 is the second of four Candu units at the site to undergo refurbishment in a 10-year project that will enable the station to continue operations until 2055.
The first major work at Darlington-3, defuelling, involves the remote-controlled removal of 6,240 fuel bundles from the reactor over the course of 90 days.
OPG said workers will place these bundles inside water-filled fuel bays for up to 10 years of safe storage. Once the bundles have been removed, the team will drain heavy water from the unit’s reactor systems.
Darlington-2 was the first of the station’s four units to undergo refurbishment. All four units are beinge refurbished in a phased CAD12.8bn ($9.3bn, €8bn) project which is scheduled for completion by 2026.
Each of the four units is being taken out of service for three years for work to be carried out.
The project began in 2016 after nearly a decade of planning and preparation, with the support of hundreds of companies and thousands of workers. The team undertook more than 765,000 training hours in the project’s mockup and training facility to safely shut down, defuel, disassemble and reconstruct the reactor.
OPG said the 10-year project is expected to generate a total of nearly CAD90bn in economic benefits for Ontario.
In response to the coronavirus pandemic, OPG postponed the start of Unit 3 refurbishment from May 2020, allowing the unit to continue delivering electricity to the grid.