UK nuclear regulators have announced that the GE Vernova Hitachi (GVH) BWRX-300 nuclear reactor design has completed Step 2 of the Generic Design Assessment (GDA). Through the GDA, UK regulators assess the safety, security and environmental implications of new reactor designs. The two- or three-step process is carried out by the Office for Nuclear Regulation (ONR), the Environment Agency (EA) and Natural Resources Wales (NRW). Completion of the process results in the issue of a Design Acceptance Confirmation from the ONR and a Statement of Design Acceptability from the EA. GE Vernova Hitachi chose the two-step version for the BWRX-300.
The BWRX-300 is a single unit, direct-cycle, natural circulation, boiling water reactor with generating capacity of 300 MWe and is designed to have an operational life of 60 years. ONR noted that the BWRX-300 design assessed in GDA is predominantly based on the ‘standard’ BWRX-300 design being developed by GVH as it was in March 2024. “Whilst the design has been fixed for the purposes of GDA, GVH has continued to develop the design in support of its other international projects.”
The two-step GDA began with Step 1 in January 2024 – a year-long initiation phase, during which regulators worked closely with GE Vernova Hitachi to establish a robust foundation for the assessment process. Under Step 2, which began in December 2024 regulators complete a comprehensive and rigorous assessment of the BWRX-300 reactor design. This phase has focused on evaluating the fundamental adequacy of the design and its safety, security, safeguards and environmental protection documentation.
“The assessment concluded with the issue of two GDA statements that set out our regulatory conclusions on the BWRX-300 design and its supporting documentation,” the regulators said. They confirmed that their assessment has identified no fundamental safety, security, safeguards or environmental protection shortfalls with the design that could prevent its deployment in England and Wales.
“GE Vernova Hitachi opted for a shorter two-step GDA, making it the first requesting party to take advantage of the flexibility we introduced in our modernised GDA process,” said Rob Exley, ONR’s Head of the BWRX-300 GDA. “This means it is the quickest GDA engagement completed to date, facilitated by GE Vernova Hitachi’s responsiveness, the quality and maturity of its submissions, learning from previous GDAs, and our active collaboration with regulatory colleagues in the US and Canada who have been evaluating the BWRX-300 in parallel to our assessment.”
Saffron Price-Finnerty, the Environment Agency’s New Reactors Programme Manager, said: “The accelerated pace of this first two-Step GDA was enabled by the delivery of a complete set of documentation by GE Vernova Hitachi at the start of Step 2. This helped our assessment team to plan their work effectively and efficiently. Their assessments were targeted and proportionate in ensuring that there were no fundamental shortfalls in environmental protection. It has been a considerable effort from both the Requesting Party and regulators, resulting in a quality outcome in such a short timeframe.”
Currently, there are no plans to deploy the GE Vernova Hitachi BWRX-300 design in England and Wales, and no sites have been identified for its deployment. Any organisation seeking to progress plans to deploy the BWRX-300 design would require the regulators to undertake a further period of detailed design assessment before safety-significant construction could begin and environmental permits could be issued. This assessment could be conducted on a generic basis with GE Vernova Hitachi returning to the GDA process to complete Step 3. Alternatively, it could be undertaken with a licensee or constructor as part of a site-specific development in the UK.
ONR and the EA have each issued GE Vernova Hitachi with a GDA statement. The statement provides an indication of our confidence in the design, based upon the assessment conducted to date, and our judgement on whether the design is potentially capable of being built and operated on a site bounded by the generic site envelope, in a way that is acceptably safe and secure and properly protects the environment. It also identifies any matters which might be in conflict with UK government policy.
ONR noted that, based upon assessment to date it “has not identified any significant issues that: may prevent ONR from issuing a Design Assessment Confirmation (DAC), might prevent ONR granting permission for the construction of a nuclear power plant based upon that design, or which might be in conflict with relevant government policy”.
This judgement “does not guarantee that ONR will grant permission for the construction of a power station based on the BWRX-300 design at a particular site in Great Britain. Any organisation intending to build and operate a BWRX-300 in Great Britain must first obtain from ONR a nuclear site licence”. The judgement is valid for ten years and “will be taken into account by ONR in any subsequent work as part of a GDA or to grant a future permission”.
The statement of the Environment Agency and Natural Resources Wales Step “concluded that no fundamental environmental protection shortfalls in the design have been identified so far”. However, it identified one potential environmental protection shortfall. “We think that further work will be needed to prove that the decision not to sort and segregate waste ion exchange resins demonstrates the best available techniques.” This information would be required as part of a site-specific permit application.
It noted: “The agreed GDA scope is comprehensive with regards to environmental protection from radioactive substances and contains all the systems, structures and components that have a bearing on the generation and management of radioactive waste for the life cycle of the plant. The life cycle encompasses design through operations to decommissioning and site clearance.” It added: “We have not been requested to carry out Step 3 of GDA, Detailed Assessment, and so this conclusion is subject to carrying out that detailed assessment and any future developer gaining the necessary site-specific permissions.”
To date, GDAs have been completed for the EDF/Areva UK EPR, the Westinghouse AP1000, the Hitachi-GE UK ABWR and the CGN/EDF/GNI UK HPR1000 (Hualong One) designs. Assessments are underway for Rolls-Royce SMR Limited’s small modular reactor design and Holtec International’s SMR-300. Westinghouse’s AP300 was accepted for a GDA review in 2024 and TerraPower recently submitted its Natrium sodium-cooled fast reactor and energy storage system to undergo the GDA process.
