At a glance
OPG is now constructing North America’s first commercial, grid-scale Small Modular Reactor (SMR) at its Darlington Nuclear site.
The first of four SMRs is expected to be in service by the end of 2030, providing enough reliable, low-carbon power for about 300,000 homes.
Recent important work to prepare for nuclear construction has included site preparation and procurement of long-lead materials.
This massive tunnel boring machine—nicknamed Harriett Brooks after Canada’s first female nuclear physicist—will help carve the path for OPG's SMR project. The machine arrived in parts to the Port of Oshawa in June.
OPG is now building North America's first commercial, grid-scale SMR.
On May 8, the Province of Ontario gave OPG the green light to begin construction on the first of four SMR units at its Darlington New Nuclear Project (DNNP) 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, while serving as a growth platform for Canada’s nuclear supply chain.
“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.
OPG's Darlington SMR will be Ontario's first new nuclear build in more than three decades.
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.
Nicolle Butcher
President and CEO, OPG
Nicolle Butcher, OPG's President and CEO
Deploying and operating four SMRs is expected to increase Canada’s GDP by $38.5 billion over 65 years, according to the Conference Board of Canada. And over the next 65 years, OPG’s SMR fleet is expected to sustain, on average, about 3,700 jobs per year, including 18,000 jobs per year during construction. About 80% of project spending will go to some 80-plus companies across Ontario and construction of the SMR fleet is expected to drive $500 million annually into the province’s supply chain.
“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.
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 condenser cooling water system is now being constructed in Lake Ontario for the Darlington New Nuclear Project.
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.
"Harriet Brooks" arrives on site
In June, the project’s heralded tunnel boring machine (TBM)—nicknamed “Harriett Brooks” after Canada’s first female nuclear physicist—arrived at the Port of Oshawa from the Netherlands. Over the summer, the massive machine's parts arrived by truck to the DNNP site, where they will be stored until assembly begins in early 2026. When operational, the TBM will bore and line the 3.4-kilometre-long condenser cooling water tunnel—an essential element for bringing OPG's SMR fleet online.
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.
As key components and equipment begin to arrive on site, it’s essential the right people and trades are also lined up to support the project’s next phase of work. Over the past few months, OPG has started to welcome about 700 new employees who will be required during SMR construction.
The first round of new arrivals has been made up of iron workers, millwrights, and boilermakers, hailing from across Ontario and neighbouring provinces.
The site is prepared, parts are in motion, and the team is assembled. OPG is ready to build the future of nuclear, right here in Ontario.
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