Holtec SMR-300 clears step 2 of UK generic design assessment

British regulators have reached a decisive stage in the assessment of Holtec International's SMR-300 reactor. The Office for Nuclear Regulation (ONR), the Environment Agency and Natural Resources Wales have published a Generic Design Assessment (GDA) statement confirming no fundamental shortfalls in the reactor's design with respect to safety, security, safeguards and environmental protection. The assessment covered 21 technical topic areas. The step opens the path to potential deployment of the reactor in Great Britain.

A regulatory process completed across two steps

Step 1 of the GDA for the SMR-300 began in October 2023 and was completed in July 2024. Step 2, launched the following month, involved a rigorous regulatory assessment examining the fundamental adequacy of the reactor design, its safety case and methodologies. Tim Parkes, ONR's Head of the Holtec SMR-300 GDA, states the assessment has identified no fundamental shortfalls across the 21 technical topic areas examined. Fourteen regulatory observations were nonetheless issued, to which Holtec has responded constructively according to the regulators. New Hampshire issues executive order to assess advanced nuclear reactor deployment, reflecting a broader regulatory momentum around advanced nuclear technologies.

Saffron Price-Finnerty, the Environment Agency's New Reactors Programme Manager, describes the milestone as an important step for the Holtec SMR-300 project. Paul Gibson, Natural Resources Wales Nuclear Team Leader, highlights the effective collaboration between Holtec and the regulators throughout the process. The GDA process is voluntary and non-mandatory in Great Britain. The global nuclear industry awaits decisive milestones from Rooppur to Onkalo in 2026, amid a broad resurgence of interest in nuclear energy.

A 300 MW pressurised water reactor in development since 2011

The SMR-300 is a pressurised water reactor producing about 300 MW of electrical power, or 1,050 MW of thermal power for process applications. Holtec has been developing the reactor since 2011. Richard Springman, Holtec's President of Global Clean Energy Opportunities, describes the UK validation as a key derisking milestone for the SMR-300 international deployment programme, adding that the design also meets the requirements of the US Nuclear Regulatory Commission (NRC). The company positions the SMR-300 as a globally deployable design.

In the United States, Holtec plans to deploy two SMR-300 reactors — named Pioneer 1 and 2 — at the Palisades Nuclear Generating Station site in Michigan. The Construction Permit Application for Pioneer 1 and 2 was submitted to the NRC at the end of 2025. On February 13, the NRC officially accepted the application for review, with an expected schedule anticipating completion of safety evaluations and the environmental impact assessment by early to mid-2027.

Cottam project: a partnership with EDF Energy for data centres

In the United Kingdom, Holtec has signed a memorandum of understanding with EDF Energy and real estate partner Tritax Management to develop an SMR-300 at the former Cottam coal-fired power plant in Nottinghamshire, England. The project aims to provide power to new, advanced data centres on the site. The partners indicate the initiative would also enable foreign direct investment into the UK.

The GDA Step 2 statement does not constitute final deployment approval. Should Holtec wish to continue plans to build an SMR in England or Wales, a further period of detailed design assessment will be conducted by the regulators, either as part of a future Step 3 or as part of a site-specific development. The UK's Department for Business, Energy and Industrial Strategy had opened the GDA process to advanced nuclear technologies, including small modular reactors (SMRs), in May 2021.