Ontario nuclear unit ends record continuous run of more than 3 years

New York — Ontario Power Generation's Darlington Unit 1 has set a world record for continuous operation, running for more than 1,000 days before being taken offline Feb. 5 for planned maintenance.

The 878-MW unit was taken down for its final inspection and maintenance outage before it is refurbished in 2022 as part of an overhaul of the 2,634-MW Darlington nuclear facility. The CANDU reactor that powers the generator is a pressurized heavy-water machine that has been in service since 1992, according to data compiled by S&P Global Market Intelligence. Darlington Unit 1 eclipsed the previous world record of 962 days in September 2020, surpassing India's Kaiga power station for continuous operation. Last brought online on Jan. 28, 2018, it ran for a total of 1,106 days.

The maintenance outage will include a full inspection, upgrades to the reactivity control systems and preparation for the planned refurbishment. Ontario Power Generation credited earlier preventive maintenance work for the unit's record run. The Darlington complex is located on the shore of Lake Ontario, about 70 km southwest of Toronto.

"Unit 1's record-setting run highlights the excellent work carried out by our dedicated nuclear professionals throughout the pandemic to ensure Ontarians and frontline workers battling COVID-19 can count on a steady supply of power 24 hours a day, seven days a week," Ontario Power COO Sean Granville said in a posting on the company's website. "It also highlights the effectiveness of our preventive maintenance programs, and the overall reliability of our nuclear fleet."

Ontario Power Generation plans to overhaul all four units at Darlington by 2026. The refurbishment of Unit 2 was completed in June 2020 after it was taken offline in 2017 to be defueled, disassembled and reconstructed. A similar refurbishment of Unit 3 was started in the third quarter of 2020 with a planned completion by the first quarter of 2024. Unit 4 will be the last to be refurbished, with an anticipated offline date in the third quarter of 2023. All of the units have a nameplate capacity of 934 MW and net capacity of 878 MW, according to S&P Global data.