Second refurbished Darlington reactor back online

19 July 2023

The refurbished unit 3 of the Darlington nuclear power plant has been reconnected to the grid 169 days ahead of schedule, Ontario Power Generation (OPG) announced. Unit 3 is the second of four Candu units at the site to undergo refurbishment in a 10-year project that will enable the plant to continue operations until 2055.

Darlington 3's turbine hall (Image: OPG)

Refurbishment of a Candu reactor involves removing all the reactor's fuel and heavy water and isolating it from the rest of the power station before it is dismantled. Thousands of components, including those that are not accessible when the reactor is assembled, are inspected, and all 480 fuel channels and 960 feeder tubes are replaced during the high-precision rebuild.

Refurbishment of Darlington 3 began in September 2020 and was originally slated for completion in the first quarter of 2024. However, in December 2022 the Canadian Nuclear Safety Commission allowed OPG to proceed with fuel loading and in May this year gave the go-ahead for the reactor to be restarted.

Unit 3 is now operating at 100% capacity, OPG announced, "providing clean, reliable energy for Ontarians during these peak summer months". It noted the early return of unit 3 will produce an extra 3 TWh of electricity - enough to power 350,000 homes for an entire year. It will also avoid up to 1 megatonne of greenhouse gas emissions, or the equivalent of taking 300,000 cars off the road for an entire year.

The Darlington units are being refurbished in a CAD12.8 billion (USD9.7 billion) project that will enable the station to operate for an additional 30 years. The refurbishment of all four units is scheduled to be completed by the end of 2026. Unit 2 was the first to be refurbished and returned to service in June 2020.

"Thanks to the quality of refurbishment work, in the three years since its return to service, unit 2 has experienced a record 529-day continuous run," OPG said. "This is industry-leading performance for a Candu reactor post-refurbishment. Overall generation was also 10-plus percent better than target."

The refurbishment of unit 1, which began earlier this year, is approximately 60% complete and is currently in the reassembly phase. It is expected to be completed in mid-2025. Unit 4, the final unit to be refurbished, will come offline shortly to begin its refurbishment.

"Through this project, OPG is demonstrating that with detailed planning and preparation, large nuclear projects can be completed not only on time, but ahead of time and with great quality," said OPG President and CEO Ken Hartwick. "This would not be possible without the performance, expertise, and commitment from our refurbishment project team, project partners, industry experts, energy professionals, and skilled tradespeople."

OPG said an assessment for refurbishing the Pickering plant will be complete later this year.

Researched and written by World Nuclear News