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Insights Darlington nuclear generating station | maintaining our nuclear energy

AtkinsRéalis is proud to be part of the joint venture working on Darlington – Canada’s largest clean energy project. It’s also the country’s second largest nuclear facility by total energy output. Four CANDU pressurized heavy water (PHWR) reactors produce up to 31 million MWh annually.

Refurbishing a vital resource

Nuclear is a reliable, low carbon energy source that accounts for 60% of Ontario’s energy. Darling produces 20% of the province’s power supply or enough to power 2.5 million households! To ensure CANDU reactors remain in good working condition throughout their expected life, they need a mid-life refurbishment or life extension.

Careful project planning

Planning for this Retube and Feeder Replacement (RFR) project has taken our teams several years. We started back in February 2010 when OPG announced plans to proceed. The sheer size of the project makes it complex and consisted of two phases: the Definition and Execution phases.


AtkinsRéalis ’s engineers created a full-scale reactor mock-up which provides:
• Simulations of the refurbishment’s key elements
• An employee training program
• A space to develop, source and test specialized tooling solutions
• A comprehensive estimate and full schedule for the project


Our teams began execution in YEAR with Darlington Unit 2. The remaining three units will see their reactor cores retubed in a sequential basis using the tools and methods developed and tested during the Definition phase. Each of Darlington CANDU reactors will be taken out of service for approximately three years to allow for the replacement of fuel channels, feeder pipes, calandria tubes and end fittings.

Proud of our CANDU teamwork

As stewards of CANDU technology our people bring specialized knowledge of this Canadian-developed nuclear technology. We are also responsible for a range of services and tooling, as well as training and procurement of critical resources. We’re extremely pleased by our people’s excellent planning and innovative thinking. Two years into the first reactor refurbishment (Unit 2), the project remains on time and on budget. The old reactor components have been removed, the calandria has been inspected and the fuel channels have all been replaced.

Transforming local economy

We exist to transform the world through sustainable technology but also by uplifting communities wherever we go. This project will create up to 11,800 jobs for more than 180 companies across Ontario. Once fully refurbished, the reactors will continue to produce approximately 20% of the province’s energy for at least another 30 years. It will also fully comply with current nuclear safety regulations and policies that have come into place since Fukushima.

Excited about uplifting Canada’s future through nuclear? Join us here.

Project statistics:

$12.8 billion
refurbishment of four CANDU reactors

2.5 million
households powered a year

jobs created by the Darling project

local companies will benefit from the project