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Darlington Unit 2 seen from above.

Unit power up

See how Ontario Power Generation works with project partners to power up Darlington Nuclear Generating Station’s reactors post refurbishment. It’s all part of the Darlington Refurbishment Project, one of the largest clean-energy projects in the country.

Getting ready to power up

After OPG’s refurbishment team has installed the final components and checked all systems, they begin the necessary steps to power up a newly refurbished reactor and return it to commercial service.

The Return to Service program is central to this phase, leading the refurbishment of a nuclear unit through many critical steps — from construction, to restoration, to full-power operation.

Along the way, workers refill the moderator with heavy water, load fuel into the fuel assemblies in the reactor core, and fill and pressurize the heat transport system.

With all of this complete, the nuclear fission process is started and the unit begins to warm up. Workers restore containment and then begin reconnecting the unit to the rest of the operating station.

The goal now is for the unit to achieve criticality — its normal reactor operating condition when nuclear fuel sustains a fission chain reaction.

After final high power testing, control room operators gradually raise the unit to full-power operation when it will once again provide Ontario with clean, low-cost and reliable energy for at least another 30 years or more.

Refurbishment in action

Watch how OPG is refurbishing Darlington Nuclear Generation Station.