Darlington Small Modular Reactor Programme 

Ontario Power Generation (OPG) is developing four GE Vernova Hitachi BWRX-300 small modular reactors (SMRs) at the Darlington Nuclear Generating Station in Ontario, at a total estimated cost of C$20.9 billion. The project is expected to be the first commercial SMR in Canada and the first in the G7. 

The Canadian Nuclear Safety Commission (CNSC) issued a licence to construct the first reactor on 4 April 2025, and the Province of Ontario approved the project on 8 May 2025. Construction of the first unit is targeted for completion by the end of the decade, with grid connection expected by the end of 2030. 

Overview 

The programme will consist of four 300 MWe BWRX-300 reactors with a combined generating capacity of 1,200 MWe, adjacent to the existing Darlington Nuclear Generating Station. 

The CNSC's April 2025 licence authorises construction of the first reactor and fuel-out commissioning, together with supporting infrastructure for up to four units. It does not itself authorise construction of all four reactors, which will each require separate approval. 

Key Facts 

Development 

OPG began site preparation in September 2022, ahead of formal licensing. The project is delivered under an integrated project delivery model bringing together OPG as licence holder and operator, GE Vernova Hitachi as reactor technology supplier, AtkinsRéalis as architect-engineer, and Aecon Kiewit Nuclear Partners as constructor. 

In March 2026, the CNSC removed the first of three regulatory hold points on the construction licence, relating to the reactor building foundation, allowing construction to proceed. 

Development Stage (June 2026) 

Status: First unit under construction 

• Construction licence issued and provincial approval received
• First regulatory hold point cleared, permitting continued construction
• Operating licence application submitted for the first unit 
•  Williams Treaties First Nations investment announced, with loan converting to equity on completion of all four units 
• Second, third and fourth units in the planning and definition phase 

Source: CNSC 

Timeline

Sources: OPG; CNSC; Major Projects Office; World Nuclear News 

Cost Summary

The total four-unit programme is estimated at C$20.9 billion in 2024 dollars, including interest, cost escalation and contingency.

OPG states that costs for the second, third and fourth units are expected to decline as efficiencies are gained, and that the total estimate will be refined as those units move through the definition phase. A firm cost breakdown for the remaining three units has not yet been published. 

Source: OPG Q1 2025 financial results 

Regulatory Status 

The CNSC issued the construction licence on 4 April 2025 following a two-part public hearing that concluded in January 2025. The licence is valid until 31 March 2035 and includes four facility-specific conditions. 

The Province of Ontario approved the project on 8 May 2025, and it was referred to the federal Major Projects Office on 11 September 2025. In March 2026, OPG applied for a 20-year operating licence for the first reactor. 

Sources: CNSC; Prime Minister of Canada 

Indigenous Participation 

The project sits on the traditional territory of the Michi Saagiig Anishinaabe people, on lands covered by the Williams Treaties between Canada and the Mississauga and Chippewa Nations. The Mississaugas of Scugog Island First Nation has held contracts at the Darlington and Pickering sites through its economic development arm, Voyageur Services, including site preparation work for the SMR project. 

On 23 June 2026, the seven Williams Treaties First Nations, comprising Alderville, Curve Lake, Hiawatha, Mississaugas of Scugog Island, Beausoleil, Chippewas of Georgina Island and Chippewas of Rama First Nations, announced a C$700 million investment in the project, structured through a jointly held investment limited partnership. 

The investment takes the form of a loan to Darlington New Nuclear Project LP for construction of the first unit, which converts to an equity stake once all four units are complete. The loan is backed by approximately C$715 million in guarantees from the Canadian Indigenous Loan Guarantee Corporation and Ontario's Indigenous Opportunities Financing Program, described by the federal government as the largest Indigenous loan guarantee in Canadian history. 

Sources: Major Projects Office; World Nuclear News; BNN Bloomberg 

Technical Specifications 

• Reactor: GE Vernova Hitachi BWRX-300
• Units: Four
• Capacity: 300 MWe each (1,200 MWe total)
• Design basis: Natural circulation cooling and passive safety systems, based on the licensed ESBWR design and GNF2 fuel
• Construction: Modular, factory-fabricated components assembled on site 

Source: Foro Nuclear 

Sources 

• Ontario Power Generation, Darlington SMR project page
• Ontario Power Generation, Q1 2025 financial results release
• Canadian Nuclear Safety Commission, Darlington New Nuclear Project page
• Canadian Nuclear Safety Commission, news release, 4 April 2025
• Major Projects Office, Darlington New Nuclear Project
• World Nuclear News, budget breakdown
• World Nuclear News, First Nations equity stake