At a glance
OPG and its project partners are progressing construction of North America’s first commercial SMR, which will provide 300 megawatts of low-carbon, reliable power for Ontario’s future.
In October, OPG secured up to $3 billion in equity financing for the project from the Canada Growth Fund and Building Ontario Fund.
Over the summer, the project’s massive tunnel boring machine completed its final journey to the Darlington site, marking a major milestone.
Ontario Premier Doug Ford, OPG President and CEO Nicolle Butcher, and Prime Minister Mark Carney attend an announcement at Darlington Nuclear, Oct. 23, 2025.
It was a busy summer for OPG’s Darlington New Nuclear Project (DNNP) as construction work continued on the G7’s first commercial, grid-scale Small Modular Reactor (SMR).
Since getting the go-ahead from the Province of Ontario in May to begin building, OPG’s project team has marked several major milestones.
This includes the arrival of all components for a massive tunnel boring machine that will help bring online Canada’s first new nuclear build in over three decades.
And the milestones continued into October, as OPG secured up to $3 billion in equity financing for the DNNP via an innovative financing agreement. This includes up to $2 billion through the Canada Growth Fund and up to $1 billion from the Building Ontario Fund, with each taking minority ownership positions in the project. The landmark financing agreement was announced at an event at Darlington Nuclear on Oct. 23 attended by Prime Minister Mark Carney and Premier Doug Ford.
“OPG and Ontario are now building the foundation for not just Canada’s first SMR, but also future SMRs in this country and beyond,” said Nicolle Butcher, OPG’s President and CEO. “We are doing this with the help of skilled Ontarians and local supply chain companies. Our team, our people, and our partners are now building the capacity and the model for new reliable, low-carbon nuclear power for our future.”
In July, after months of meticulous planning and coordination, the project’s tunnel excavating machine, named Harriet Brooks after Canada’s first female nuclear physicist, finished its journey from overseas to the project site.
Each piece of this big digger, from the massive cutterhead to the smallest bolt, will be safely stored until its assembly begins in early 2026.
The highly specialized excavating machine will be critical for boring a cooling water path for OPG’s planned fleet of four SMRs.
Once operational, the 6.97-metre-width Harriet Brooks tunnel boring machine will be used to bore and line a 3.4-kilometre-long tunnel for the project’s condenser cooling water system—a key operational feature critical to bringing the first SMR online.
In October, through a first-of-a-kind agreement, OPG secured up to $3 billion in equity financing for its DNNP project. The agreement includes up to $1 billion from the Building Ontario Fund and up to $2 billion through the Canada Growth Fund. Together, this financing will ensure successful completion of this critical project.
Elsewhere on the project, OPG and its partners, with the help of skilled trades from across Ontario, have been hard at work fabricating the structural components of the building that will house the reactor itself.
Production of these components, called diaphragm plate steel composite (DPSC) modules, are progressing at an offsite fabrication shop, with the first assemblies that make up the Basemat module—the foundation of the reactor building—being delivered to site. Once the reactor building shaft is completely excavated, a heavy crane will lift the Basemat and place it at the bottom of the shaft, 35 metres in the ground.
Meanwhile, construction of the on-site pre-assembly building is now complete and ready for use. The sprawling facility will support the final assembly of reactor building structural components for the first SMR unit.
The fabrication building—where final assembly of modular building components will take place—is also now complete, as is foundation work for the radiation waste building and control and service buildings.
Excavation work is continuing on the reactor building shaft, forebay shaft, and the condenser cooling water launch shaft, while site grading for three additional SMR units has officially been completed.
In parallel to the on-site progress, OPG continues to advance planning and licensing activities for the subsequent SMR units in its planned fleet.
Advancing Ontario’s first nuclear build in over three decades
On May 8, the Province of Ontario approved OPG to begin construction on the first of four SMR units at its DNNP site. The Province has also approved OPG’s plan for building three more SMR units at the site.
A piece of the massive tunnel boring machine, nicknamed Harriet Brooks, that will be used in the Darlington New Nuclear Project.
This followed the issuance of a Licence to Construct the first SMR unit from the Canadian Nuclear Safety Commission in April.
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 (and pending regulatory approvals), 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.
The reactor may be small, but the economic impact of this project is expected to be massive.
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.
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 in early 2026. The company will also incorporate lessons learned from the construction of the first SMR to the rest of the fleet.
Learn more about the Darlington New Nuclear Project.
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