Process concludes technology offers clear climate and economic benefits
The UK government has approved the nuclear justification for the small modular reactor (SMR) design developed by Rolls-Royce SMR, marking an important regulatory step for the deployment of the technology.
The decision, announced by environment secretary Emma Reynolds, means the benefits of the Rolls-Royce SMR design outweigh potential health or environmental risks linked to the use of ionising radiation.
The justification covers the generation of power using low-enriched uranium dioxide fuel in a light-water cooled and moderated pressurised water reactor. Officials said the design could deliver significant climate and socio-economic benefits to the UK while presenting only limited potential health risks, with radioactive waste and environmental impacts considered manageable within existing regulatory frameworks.
A statement said th decision follows a public consultation held between October and December 2025 and an internal government assessment of the technology’s benefits and risks.
In July 2024, the UK Nuclear Industry Association submitted an application for the justification of Rolls-Royce’s SMR design, marking the first time a UK reactor design has been presented for the regulatory process.
Justification is a regulatory process required before any new class of nuclear technology can be introduced in the UK. The process is separate from the UK’s generic design assessment (GDA), which evaluates the safety, security and environmental aspects of reactor designs.
A justification decision is one of the required steps for the operation of a new nuclear technology in the UK, but it is not a permit or licence that allows a specific project to go ahead.
Rolls-Royce SMR welcomed the decision, saying it represents an important step in the regulatory pathway for deploying the company’s small modular reactor technology.
Helena Perry, safety and regulatory affairs director at Rolls-Royce SMR, said the decision was “a key step in our regulatory journey to deploying the UK’s first small modular reactors”.
Rolls-Royce has said its SMR will be factory-built, enabling easier transportation, reduced completion risk and increased certainty on construction schedules. The plant will have an output of 470 MW.
The company has received UK government funding of £210m as part of a project to develop the SMR design. This has been supplemented by £280m of private capital.
According to the UK Office for Nuclear Regulation, Rolls-Royce SMR is since August 2024 in Step 3, or detailed assessment phase, of the UK’s GDA process. Completion is expected in August 2026.
The GDA is not site-specific and is a voluntary, pre-licensing process to assess new nuclear power plant designs before actual permitting begins.
