In May, OPG of Canada reported it had received the green light to build a BWRX-300 at its Darlington site, which it describes as “North America’s first commercial, grid-scale SMR”, also billed as the “G7’s first grid-scale SMR.”
One person who might take issue with this claim is Bill Gates, whose company Terrapower started construction work on a 345 MW Natrium sodium-cooled fast reactor in Kemmerer, Wyoming, USA, in June last year.
However, BWRX-300 developers would argue that Kemmerer is a demonstration project rather than commercial, and that construction there is currently confined to the non-nuclear portion of the plant.
The Province of Ontario has approved OPG to begin construction on the first of four SMR units at its Darlington New Nuclear Project site. What we can say for sure is that this is the first new nuclear build in Ontario for more than three decades.
Essential to the SMR cause, of course, is that these early projects are successful in terms of implementation, economics and, looking ahead, operating performance. But OPG is optimistic. “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,” says Nicolle Butcher, President and CEO, OPG. And “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,” Butcher believes.
To ensure a successful buildout, OPG says it will be leveraging more than 7000 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, OPG says the project team has been busy preparing for “this pivotal moment”, including advancing site preparation work and procuring long-lead components.
Since autumn 2022, dozens of trucks have been relocating clean soil across the site to level out the areas 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 of buildings, including the on-site fabrication building, is also progressing.
Meanwhile, says OPG, 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 Darlington New Nuclear Project team has worked to secure several long-leadtime items, notably the reactor pressure vessel. As the SMR’s largest component, the vessel – over 30 m in length and 6 m in diameter, and weighing 550 tonnes – will contain the reactor core, coolant, and support structures.
The generator rotor has been forged and is now undergoing pre-machining. It’s expected to arrive at the project site by summer 2027.
Later this summer, the project’s tunnel boring machine — named “Harriett Brooks” after Canada’s first female nuclear physicist — will arrive from Germany for storage until assembly in early 2026. The machine will be used to drill the condenser cooling water tunnel, which will be 3.4 km long and 6.05 m in diameter.
Candu Energy Inc., an AtkinsRéalis company, has been awarded a $450 million “execution contract” by OPG, for the first SMR unit at Darlington. The scope includes project management, licensing, engineering, design, procurement, construction support and commissioning, as well as digital delivery capabilities for both the nuclear island and balance of plant. “Our trusted relationship with OPG supporting hydropower assets and refurbishing CANDU reactors at Darlington and Pickering will support this project’s successful completion by 2030,” the company asserts. Nicolle Butcher would seem to agree: “AtkinsRéalis is a long-time trusted partner to OPG, including on the on-time, on budget Darlington Refurbishment Project,” she says. “We will draw on our shared experience for similar success as we build the first small modular reactor in the G7 at the Darlington New Nuclear Project site.”
AtkinsRéalis has been the architect-engineer on the Darlington New Nuclear Project alliance team since 2023, working alongside GE Vernova Hitachi Nuclear Energy and Aecon Kiewit.
“Ontario’s power demand is expected to surge by 75% by 2050 and we’ll need all sources of cleaner power to meet the need, including large and small nuclear reactor technology,” said Joe St. Julian, President, Nuclear, AtkinsRéalis. AtkinsRéalis also continues to support SMR projects outside Canada, including in the UK, USA, and Poland.
TVA project
Significantly, Tennessee Valley Authority has selected the BWRX-300 for an SMR project at its Clinch River site (which back in the 1970s was to have been the location of a 350 MWe liquid metal cooled fast breeder reactor).
On 20 May, TVA announced that it had submitted a construction permit application to the NRC for the BWRX-300 project, making it the first utility in the USA to submit such an application for an SMR. TVA sees the project as a step towards “establishing America’s energy dominance to power artificial intelligence, quantum computing and advanced manufacturing.”
“TVA has put in the work to advance the design and develop the first application [in the USA] for BWRX-300 technology, creating a path for other utilities who choose to build the same technology,” said Don Moul, TVA President and CEO. “
TVA believes it has “the best path to deploying a commercial BWRX-300 based SMR in the USA” because it holds the nation’s first and only early site permit for SMRs from the NRC at its Clinch River site.
In 2023, TVA joined a global collaboration to speed up the design and development of BWRX- 300 technology and now leads a “strong coalition of industry partners” in submitting an application for an $800 million US Department of Energy grant to accelerate BWRX-300 development and is also seeking an $8 million DOE grant to support the NRC licence review cost. TVA has already completed the environmental report for the Clinch River site and submitted it to the NRC. Preliminary SMR site preparation could begin as soon as 2026.
BWRX-300 cutaway.
Source: GE Vernova Hitachi Nuclear Energy compared with other SMR designs and it aims to reduce construction and operating costs below other nuclear power generation technologies. In particular, it will leverage a combination of existing commercially available fuel, plant simplifications resulting in reduced concrete and steel requirements, use of proven components as well as a design based on an already licensed reactor (as already noted).
Other features of the BWRX-300 include: fuel enrichment, 3.81% (avg)/4.95% (max); refuelling cycle, 12-24 months; design life, 60 years.
Also notable is an estimated construction duration of 24-36 months (presumably first nuclear concrete to fuel loading). With the nuclear power industry notorious for overoptimistic construction schedules, it will be interesting to see whether anything like this can be achieved in practice.
USA looks to nuclear renaissance 23 May 2025 saw the signing by President Trump of executive orders designed to “usher in a nuclear renaissance”, and directing the US Department of Energy to take a leading role in “unleashing” it, with a focus on accelerating advanced nuclear technologies. After “decades of stagnation and shuttered reactors”, President Trump is said to be providing a path forward for nuclear innovation. The May executive orders encourage reactor design testing at the Department of Energy’s (DOE) National Labs, clear the way for construction on federal lands to protect national and economic security, and remove regulatory barriers by requiring the Nuclear Regulatory Commission to issue timely licensing decisions.
“For too long, America’s nuclear energy industry has been stymied by red tape and outdated government policies, but thanks to President Trump, the American nuclear renaissance is finally here,” said Energy Secretary Chris Wright. “With the emergence of AI and President Trump’s pro-American manufacturing policies at work, American civil nuclear energy is being unleashed at the perfect time. Nuclear has the potential to be America’s greatest source of energy addition. It works whether the wind is blowing, or the sun is shining, is possible anywhere and at different scales. President Trump’s executive orders today unshackle our civil nuclear energy industry and ensure it can meet this critical moment.”
“Over the last 30 years, we stopped building nuclear reactors in America – that ends now. Today’s executive orders are the most significant nuclear regulatory reform actions taken in decades. We are restoring a strong American nuclear industrial base, rebuilding a secure and sovereign domestic nuclear fuel supply chain, and leading the world towards a future fueled by American nuclear energy. These actions are critical to American energy independence and continued dominance in AI and other emerging technologies,” said White House Office of Science and Technology Director Michael Kratsios.
“President Trump’s executive orders expand America’s Energy Dominance agenda. As energy demand continues to surge, expanding our existing nuclear fleet and investing in advanced nuclear technologies ensures we have reliable energy to power our homes, fuel for President Trump’s manufacturing revolution, and a stronger electric grid,” said Interior Secretary Doug Burgum.
This article first appeared in Modern Power Systems magazine.
