Monday, June 30, 2025
Ontario Power Generation (OPG) has received the green light to build North America’s first commercial, grid-scale small modular reactor (SMR).
On May 8, the Province of Ontario approved OPG to begin construction on the first of four SMR units at its Darlington New Nuclear Project site. This represents the first new nuclear build in Ontario in more than three decades.
Once in service by the end of 2030, the first BWRX-300 SMR unit will be capable of generating 300 megawatts (MW) of safe, low-carbon, reliable, Ontario-made power—enough to power about 300,000 homes. In total, OPG’s SMR fleet will be capable of producing 1,200 MW of electricity to help support Ontario’s electrification.
“This is truly a historic moment,” said Nicolle Butcher, OPG’s president and CEO. “This made-in-Ontario project will support provincial companies, create jobs for Ontarians, and spur growth for our economy. OPG is proud to be leading this first-of-a-kind project. With the province’s robust nuclear supply chain and our successful track record on nuclear projects, particularly our Darlington Refurbishment, we are confident we will be able to deliver the first SMR unit for Ontario, on-time and on-budget.”
The reactor may be small, but the economic impact of this project is expected to be massive.
“As a first mover on SMRs, Ontario will also be able to market our capabilities and nuclear expertise to the world to further grow our domestic industry,” said Butcher.
“This nation-building project being built right here in Ontario will be led by Canadian workers using Canadian steel, concrete and materials to help deliver the extraordinary amount of reliable and clean power we will need to deliver on our ambitious plan to protect Ontario and unleash our economy,” said Stephen Lecce, Minister of Energy and Mines.
Aecon Kiewit Nuclear Partners, a general partnership between Aecon and Kiewit Nuclear Canada has been awarded an alliance construction contract by OPG for the execution phase on the Darlington New Nuclear Project.
The project is being delivered under an Integrated Project Delivery model. During the execution phase, Aecon Kiewit Nuclear Partners will work collaboratively with partners OPG (owner and licence holder), GE Vernova Hitachi Nuclear Energy and AtkinsRéalis.
Aecon Kiewit Nuclear Partners’ scope of work during the execution phase includes project management, construction planning and execution, with completion and commercial operation expected in 2030.
“OPG’s Darlington New Nuclear Project is a trailblazing undertaking—leading the way in delivering the next generation of nuclear plants across North America and internationally,” said Jean-Louis Servranckx, president and CEO, Aecon Group Inc. “Aecon is proud to bring its diverse nuclear expertise and multidisciplinary capabilities to play a prominent role in safely executing this exciting project to meet the energy demands of future generations in Ontario.”
“With dozens of Ontario-based suppliers contributing to this project, we’re not just building a reactor—we’re generating thousands of good-paying jobs, driving investment into communities across the province, and reinforcing Ontario’s global leadership in clean energy technology,” said Lisa McBride, country leader, GE Vernova Hitachi SMR Canada.
To ensure a successful buildout, OPG will be leveraging more than 7,000 lessons learned from its Darlington Refurbishment project, which remains on track to be completed by 2026. The company will also incorporate lessons learned from the construction of the first SMR to the rest of the fleet.
The Province’s approval to proceed comes after OPG received a Licence to Construct the first SMR unit in April from the Canadian Nuclear Safety Commission.
On the ground, the project team has been busy preparing for this pivotal moment, including advancing site preparation work and procuring long-lead components.
Since Fall 2022, dozens of trucks have been busy relocating clean soil across the site to level out the lands intended for the future SMR units. Crews have also been busy installing various utilities, including fire lines, water lines, sanitary sewer lines, and network cabling. Construction on a few important buildings, including the on-site fabrication building, is also progressing well.
Meanwhile, the team continues to excavate for the Reactor Building shaft—a critical milestone—in preparation for construction of the reactor building.
To support a fleet of SMRs, the DNNP team has worked to secure several long-lead items, including the reactor pressure vessel. As the SMR’s largest component, the vessel will contain the reactor core, coolant, and support structures. Measuring over 30 metres in length and over six metres in diameter, and weighing 550 tonnes, this is a positively massive piece of equipment.
Meanwhile, the generator rotor—a key component of the turbine-generator system that converts heat from the reactor into electrical power—has been forged and is now undergoing pre-machining. It’s expected to arrive at the project site by summer 2027.
Finally, later this summer, the project’s heralded tunnel boring machine—nicknamed “Harriett Brooks” after Canada’s first female nuclear physicist—will arrive from Germany at the new nuclear site for storage until assembly in early 2026. Once operational, the massive machine will be used to drill the condenser cooling water tunnel, which will measure 3.4 kilometres long and 6.05 metres in diameter.
[This article appeared in the July/August 2025 issue of ReNew Canada.]
Featured image: The Darlington New Nuclear Project site, future home of North America’s first small modular reactor. (OPG)
