These web pages have been produced by the Office for Nuclear Regulation (ONR), Environment Agency and Natural Resources Wales (NRW). Regulators are working together to ensure any new nuclear power stations built in Great Britain meet high standards of safety, security, environmental protection and waste management, through a voluntary process called Generic Design Assessment (GDA).
Before a new nuclear power station can be built and operated in Great Britain the proposed operator must obtain permission from regulators and government in the form of:
- Site licensing and relevant consent to begin nuclear-related construction from ONR;
- Environmental permits from Environment Agency or NRW; and
- Planning permission from the Planning Inspectorate.
The voluntary GDA process is used by the nuclear regulators to assess the new nuclear power station designs. It allows the regulators to assess the safety, security and environmental implications of new reactor designs, separately from applications to build them at specific sites.
We have designed these pages so they are accessible to anyone with an interest in the GDA process, including the general public and other regulators. They also contain technical information for organisations submitting designs for GDA, which can be found in the assessment of reactors section.
Regulators assessment of civil nuclear reactors - update May 2026
Nuclear regulators publish new frameworks to streamline reactor design assessment
The Office for Nuclear Regulation, Environment Agency and Natural Resources Wales have published two new policies and approaches setting out how they will collectively simplify and speed up the process of assessing new nuclear reactor designs in Great Britain.
The UK government has given clear direction through the Prime Minister’s strategic steer and its acceptance of the principles of the Nuclear Regulatory Review to accelerate new nuclear deployment. The updated reactor design assessment framework and a new Leveraging International Regulators Judgements Policy reflect regulators' commitment to making regulatory activity more efficient, without compromising on safety standards.
The new reactor design assessment framework sets out updates to the Generic Design Assessment (GDA) being implemented now, as well as setting the direction for a single reactor assessment framework bringing together the existing GDA and Early Engagement processes, aligning with the ambition of delivering reactor design assessment in two years — a reduction that will help support the deployment of new nuclear technologies in the UK. This update is designed to provide clarity to reactor vendors and support the nuclear regulators' goal of launching updated guidance in Spring 2027.
The Leveraging International Regulators Judgements Policy sets out the principles we will follow when drawing on the work of international regulators, reducing duplication and making better use of assessments already carried out by trusted counterparts around the world. This includes work under the Transatlantic Partnership as well as collaboration with a broader range of international regulators. The policy includes case studies that demonstrate how these principles are already being applied in practice.
Together, the documents signal a significant step forward in our ambition to create a more streamlined regulatory environment that supports the UK's nuclear energy ambitions while maintaining the rigorous safety standards the public expects.
Regulators assessment of civil nuclear reactors - update September 2025
The Atlantic Partnership for Advanced Nuclear Energy announcement on 15 September 2025 includes commitments from nuclear regulators to significantly accelerate timeframes for decisions, by working much closer together on specific technologies where timeframes align.
We are currently reviewing our processes and guidance to enact this and ensure that we maintain standards, and retain our independent decision-making role. We anticipate this to be available in early 2026.
This will affect the Generic Design Assessment and Licensing Nuclear Installations processes and guidance. These processes remain valid for projects currently in progress, and we will work with those vendors and developers on an individual basis to explore acceleration opportunities.
For new projects we will use the early engagement processes to facilitate discussions on regulatory pathways whilst we develop revised processes and associated guidance.
Latest news
Holtec’s SMR-300 completes Generic Design Assessment
March 2026
Regulators have identified no fundamental safety, security, safeguards or environmental protection shortfalls with the Holtec SMR-300 design that would prevent its deployment in Great Britain.
GE Vernova Hitachi’s BWRX-300 completes Generic Design Assessment
December 2025
Our assessment has identified no fundamental safety, security or safeguards shortfalls with the design that could prevent its deployment in Great Britain.
Nuclear regulators renew transatlantic collaborative agreement
Nuclear regulators renew transatlantic collaborative agreement
Nuclear regulators have announced a new initiative to streamline regulation and accelerate the deployment of advanced nuclear reactors across UK and US markets.
ONR and the Environment Agency, alongside the NRC, will renew collaboration, reflecting a shared commitment to regulatory excellence, enabling safe, efficient, and timely deployment of next-generation nuclear technologies.
GE-Hitachi’s BWRX-300 completes the first step of generic design assessment
December 2024
The joint regulators have announced that they are progressing to Step 2 of their Generic Design Assessment (GDA) of the GE-Hitachi Nuclear Energy International LLC (GE-Hitachi) BWRX-300 reactor design.
Holtec International Small Modular Reactor design completes first step of regulatory assessment
August 2024
The joint regulators have announced that they are progressing to the next step of their assessment of Holtec International's SMR-300 Small Modular Reactor design. The GDA will look to actively explore opportunities to maximise the value of international regulatory collaboration and identify efficiencies in processes.
Rolls-Royce Small Modular Reactor design completes second step of regulatory assessment
July 2024
The joint regulators have announced that they are progressing to the next step of their assessment of Rolls-Royce SMR Ltd’s 470 MWe Small Modular Reactor design. The GDA will look to actively explore opportunities to maximise the value of international regulatory collaboration and identify efficiencies in processes.
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