The first of four BWRX-300 small modular reactors (SMRs) under construction at the Darlington nuclear site in Canada will not be on schedule or to budget, Ontario Power Generation (OPG) has said.
OPG said in its 2026 third quarter financial results that it had previously noted that the Darlington New Nuclear Project (DNNP) is subject to “inherent risks and uncertainties that could affect project cost and schedule”.
OPG said: “While OPG is undertaking a comprehensive assessment of the project cost and schedule, DNNP Unit 1 is no longer expected to achieve the previously disclosed commercial operation date target of October 2030 or be completed within the previously disclosed estimated cost of $7.7 billion, inclusive of required systems and services that would be common to all SMRs planned as part of the project.
“This reflects GE Vernova Hitachi (GEVH) Nuclear Energy’s ongoing engineering for its first-of-a-kind SMR, which has impacts on construction execution and supply chain performance.
“OPG is working with GEVH to complete outstanding engineering scope and move the project forward as quickly as possible.”
GEVH designed the BWRX-300, a 300-MW boiling water reactor that uses established boiling water reactor technology but incorporates significant design simplifications.
OPG said it is continuing construction of the first Darlington BWRX-300, which “remains central” to Ontario’s plan to meet growing electricity demand with reliable and clean power.
It said the project has achieved important construction milestones, including installation of the basemat – the first nuclear foundation laid in Canada in more than 30 years.
During the third quarter of 2026, assembly was completed of the tunnel boring machine ahead of tunnelling activities expected to commence in the last quarter of 2026. The machine will bore and line the condenser cooling water tunnel, an essential element for bringing Canada’s first SMR online. The project also completed the first turbine building pour, marking a key milestone for the building foundation.
According to OPG, the Darlington BWRX-300 plant will be the first SMR in the G7 group of nations.
Canada’s federal nuclear regulator issued a construction licence to OPG for the unit in April 2025.
Site preparation works began in the autumn of 2022 and several long-lead items, including the reactor pressure vessel, have been procured.
