Helena Perry, Safety & Regulatory Affairs Director for Rolls-Royce SMR Rolls-Royce SMR has welcomed the decision by the UK Secretary of State for Environment, Food & Rural Affairs, Emma Reynolds, to provide regulatory justification for the Rolls‑Royce Small Modular Reactor (SMR) design – the first SMR to receive this approval in the UK.
While a justification decision is a required step for the operation of a new nuclear technology in the UK, it is not a permit or licence that allows a specific project to go ahead. It is a generic decision based on a high-level evaluation of the potential benefits and detriments of the proposed new nuclear practice as a pre-cursor to future regulatory processes.
However, this regulatory milestone is a major step toward deploying Rolls-Royce SMRs in the UK, as it confirms that the social and economic benefits of the reactor design outweigh any potential health risks from ionising radiation under The Justification of Practices Involving Ionising Radiation Regulations 2004. Without this approval, no new nuclear technology can be legally deployed. It provides the high-level policy “go-ahead” that allows specific sites to then apply for environmental permits and nuclear site licences.
Gaining this approval early in the UK Generic Design Assessment (GDA) process helps de-risk the project for investors and ensures that regulatory hurdles do not pile up at the end of the development phase. Rolls‑Royce SMR is currently progressing through the third and final stage of the GDA.
The Department for Environment, Food & Rural Affairs (DEFRA) acts as the “Justifying Authority” for new nuclear energy technologies. This involves assessing the evidence provided by the industry and weighing the benefits (carbon reduction, energy security, jobs) against the “detriment” (radiological risks to workers and the public). Once the Secretary of State makes a positive decision, it must be given legal effect through secondary legislation approved by both houses of parliament.
The Nuclear Industry Association (NIA) submitted the application to the DEFRA for the Rolls-Royce SMR design in July 2024. A public consultation was held from October to December 2025, allowing statutory consultees, such as the Office of Nuclear Regulation and Environment Agency, as well as the public to provide feedback on the design’s benefits and risks.
NIA as the representative body of the UK civil nuclear industry, often makes justification applications. NIA was applicant for the Advanced Boiling Water Reactor (ABWR) designed by Hitachi, the Advanced Passive 1000 (AP1000) reactor designed by Westinghouse and the European Pressurised Reactor (EPR) designed by AREVA (now Framatome). However, this was the first ever application specifically for a UK-designed Small Modular Reactor.
The Rolls-Royce SMR design is a three loop PWR with an output of 470 MWe derived from 1,358 MWt. The Rolls-Royce SMR concept is centred on modularisation of reliable and proven technology, allowing maximum use of the factory environment to combine standard components with advanced manufacturing techniques. The factory-built modularisation approach is expected to drastically reduce the amount of on-site construction while its compact footprint and modular design means it can be located alongside energy intensive industrial processes.
After a multi-year competition managed by Great British Nuclear (now Great British Energy-Nuclear), Rolls-Royce was chosen as the primary technology partner and preferred bidder in June 2025. The Final Investment Decision (FID) is expected in 2029 Between now and then, the government and Rolls-Royce must agree on a revenue
In November 2025, the government confirmed Wylfa on the island of Anglesey in North Wales would be the lead site for the SMR rollout. This was a strategic pivot after previous large-scale projects at the site failed. In 2024, the government spent £160m ($213.8m) to buy the Wylfa site back from Hitachi (who had abandoned their Wylfa Newydd project in 2020). This gave the state direct control over who builds there.
