New UK nuclear rules pave way for US reactor developers

Great Britain is overhauling nuclear regulation just as U.S. developers step up plans for projects in the UK. Electricity demand in Britain is forecast to rise by 40% by 2035, according to the National Energy System Operator.

The British government aims to conclude an overhaul of its nuclear regulations by the end of 2027, as part of efforts to quadruple nuclear output to 24 GW by 2050.

The Office for Nuclear Regulation (ONR), Environment Agency (EA) and Natural Resources ​Wales (NRW) aim to cut reactor design approval periods from roughly three or four years to around two years.” alt=”” />

The UK-U.S. Atlantic Partnership for Advanced Nuclear Energy, signed in September 2025 to “turbocharge” the deployment of next-generation nuclear technology, could help achieve that ‌target. It enables the two countries to share regulatory assessments for new reactor applications to avoid duplicating work.

Efforts to streamline regulations follow the 2025 Nuclear Regulatory Review, which identified fragmented oversight, “overly conservative and costly” regulatory decisions, and unnecessarily complex legislation as major obstacles to nuclear development.

It made 47 recommendations, such as better coordination between regulators, more proportionate safety assessments, and a fleet-based approach that would reduce repeated scrutiny of identical reactor designs.

The government also wants to streamline planning and environmental approvals for nuclear projects, which have contributed to long development times and high costs.

These reforms could allow leading U.S. small modular reactor (SMR) developers, including Holtec, TerraPower, Westinghouse, and X-energy, to ​gain a foothold in the rapidly growing British market.

Holtec will provide an early test case on whether bilateral cooperation can accelerate regulatory approvals.

UK authorities have identified Holtec’s two-unit SMR-300 project at Palisades, Michigan, as the input reference design for the company’s Generic ​Design Assessment (GDA) – a regulatory review of a nuclear reactor design’s safety, security and environmental acceptability, independent of a specific site.

The regulatory reviews that would allow Holtec to obtain a GDA for the SMR-300 reactor will therefore ⁠draw on information and analysis developed for Palisades.

Holtec submitted its Preliminary Safety Analysis Report for Palisades to the U.S. Nuclear Regulatory Commission (NRC) on September 30.

“Our intention is to apply the U.S. design and safety analysis in the UK,” said Patrick O’Brien, Executive Director, Government Affairs and Communications at Holtec ​International.

Holtec wants to treat its U.S. and British ventures as “a single continuous deployment rather than two separate engineering projects,” O’Brien told Reuters Events.

Holtec completed Step 2 of the GDA for its SMR-300 with the three British regulators – ​ONR, EA and NRW – in March 2026. The company plans to deploy up to four SMR-300s with EDF and Tritax at Cottam, a former coal-fired power station in Nottinghamshire, in the East Midlands, providing around 1.3 GW of generating capacity.

Replicating the Palisades project would reduce first-of-a-kind engineering risks and improve schedule and cost predictability, O’Brien said.

Cottam could therefore provide “a test case” of how effectively ONR and NRC can work together to improve regulatory timescales and efficiency, Simon Stuttaford, Partner at law firm White & Case, told Reuters Events.

It remains to be seen whether projects that have already obtained a design license in the U.S., or feature “more mature” nuclear technology, can move rapidly through the ​GDA regulatory process, Stuttaford said.

“A lot of this will turn on the willingness of the ONR to accept or otherwise regulatory information from the U.S.,” he added.

Westinghouse’s 300 MW AP300 reactor entered the GDA process in August 2024. TerraPower’s Natrium reactor formally began the GDA application process in ​June 2026, and X-energy’s Xe-100 in September.

TerraPower has not yet chosen a site for its first UK deployment, but the company’s CEO, Chris Levesque told Reuters in September that by “2034 nuclear electricity in the UK from Natrium is very possible.” It would be the first Natrium reactor outside the U.S., the company said.

The ‌GDA remains rigorous, covering ⁠safety, security, safeguards and environmental acceptability, an X-energy spokesperson told Reuters Events.

However, its generic nature allows developers to establish that their technology “is acceptable early in the development and deployment process before significant site-specific expenditure is incurred,” the spokesperson said.

X-energy sees a parallel with NRC standard design certification, where projects can reference a technology-level assessment rather than revisit every design question, the spokesperson said.

“The practical opportunity is licensing efficiency: reducing duplication by recognising work already done under U.S. assessments,” they noted.

X-energy has chosen Centrica as its partner to develop up to 6 GW of UK advanced nuclear capacity, starting with a proposed 12-reactor, 960 MW project at Hartlepool in northeast England.

Centrica owns 20% of Britain’s operational nuclear fleet and holds a 15% stake in the 3.2 GW Sizewell C project in Suffolk.

The X-energy spokesperson described the partnership as “genuinely market-leading,” in part because Centrica is an experienced nuclear developer with access to capital ​and a long-term presence across energy assets, they said.

X-energy is working with ONR and NRC ⁠to map U.S. assessments onto UK requirements. ONR, EA and NRW’s May 2026 Leveraging International Regulators’ Judgements Policy is a legal framework that allows these regulatory agencies to use assessments by trusted overseas bodies.

ONR is increasingly willing to use work already undertaken by the U.S. NRC, potentially making parts of GDA “confirmatory due diligence rather than a completely ground-up review,” said Malcolm Parry, Partner at law firm Hogan Lovells Cadwalader.

“The direction of travel is towards ​regulatory recognition rather than regulatory duplication,” Parry told Reuters Events.

U.S. developers face government-backed UK competition. Great British Energy-Nuclear, a government-run body to accelerate nuclear deployment, has contracted Rolls-Royce SMR to deliver three reactors with ​combined generating capacity of 1.4 GW at ⁠Wylfa, a former nuclear site on Anglesey in North Wales, although the site could eventually accommodate eight units.

Initial work at Wylfa is due to begin this year, with the first reactor due to become operational in the mid-2030s. The government has committed more than 2.5 billion pounds ($3.3 billion) to its wider SMR programme, which includes Wylfa.

Government support for Wylfa gives Rolls-Royce a headstart over U.S. rivals. The company also has an established British supply chain, having spent more than 300 million pounds with suppliers since 2021, at least 70% of it with UK businesses.

Holtec is evaluating the business case ⁠for a UK factory ​that could become a regional hub for component production, O’Brien told Reuters Events.

U.S. developers can also draw on international manufacturing networks while building local partnerships, potentially allowing them to ​replicate reactor designs without duplicating production facilities.

Westinghouse in September 2025 signed agreements with six British suppliers to support the construction of AP1000 and AP300 reactors in the UK and elsewhere.

Yet Stewart Forbes, Counsel at Hogan Lovells Cadwalader, told Reuters Events that U.S. developers could gain an advantage from their much larger domestic market.

“The ​economics of SMRs depend on repeat production and standardisation,” he said.

UK government support for both pressurised-water SMRs and Generation IV advanced modular reactors, and the large size of the British energy market suggest that nuclear developers will be able to deploy “multiple fleets of different reactor designs,” the X-energy spokesperson said.