Decision

GDA Step 1 of the GE-Hitachi SMR: statement of findings public summary

Updated 17 December 2024

Applies to England and Wales

Executive summary

New nuclear power stations are an important part of the government’s plans for generating secure low carbon energy.

As regulators of the nuclear industry, the Environment Agency, Natural Resources Wales (NRW) and the Office for Nuclear Regulation (ONR) are working together to make sure that any new nuclear power stations built in the UK meet high standards of safety, security, environmental protection and waste management.

The generic design assessment (GDA) process enables the UK’s nuclear regulators to assess new nuclear power station designs at an early stage of the regulatory process and to provide confidence that these new designs can be constructed, operated and decommissioned in the UK. Early assessment of the design allows us to identify any potential regulatory concerns or issues and ask the reactor design company to address them. This will help to avoid potentially costly and time-consuming changes for regulatory reasons that are identified after construction has begun.

GE-Hitachi Nuclear Energy submitted the BWRX-300 small modular reactor (SMR) design to the UK government for entry into GDA in December 2022. Government ministers decided that GE-Hitachi Nuclear Energy was ready to enter GDA and asked the regulators (the Environment Agency, ONR and NRW) to begin the assessment process. The GDA of the BWRX-300 started on 25 January 2024.

GE-Hitachi Nuclear Energy International LLC (UK Branch) is the Requesting Party (RP) for the GDA and will manage the GDA process in the UK. GE Vernova Inc, is the ultimate parent company of GE-Hitachi Nuclear Energy International LLC overseeing the design of the reactor.

GE-Hitachi specialises in nuclear power station design, engineering and manufacturing. Its BWRX-300 SMR is being designed in the United States of America. GEH and Ontario Power Generation are developing the first BWRX-300 at Darlington, near Toronto. GE-Hitachi is taking part in the competition being held by Great British Nuclear (GBN) to select a SMR to be operated in the UK. GBN is a government company that has 2 potential sites for operation; one at Wylfa on Anglesey in Wales and the other at Oldbury on Severn in England.

The BWRX-300 design is a small modular reactor based on boiling water reactor (BWR) technology. It is being designed to generate 300 megawatts of electricity. This would be enough to power over 500,000 homes.

We have now completed Step 1 of GDA (Initiation) of the GE-Hitachi BWRX-300 design. We have concluded that it can progress to Step 2 of GDA - ‘Fundamental Assessment’.

GE-Hitachi Nuclear Energy has applied for a 2-step GDA.

This document summarises our main report and provides background on the GDA process, consents, our public engagement and next steps.

Illustration of BWRX-300 SMR. Copyright GE-Hitachi Nuclear Energy International LLC.

1. New nuclear power stations – government policy

UK energy policy, including the use of nuclear power, is a matter for government. The previous government’s policy was set out in the energy white papers that it published, including ‘Powering our Net Zero Future’ in 2020. This set out the need for nuclear power, among other measures, to help the UK achieve net zero by 2050.

In 2022, the then government published the British energy security strategy. This states an aim that by 2050, up to 24 gigawatts or a quarter of the electricity used in Great Britain will be from nuclear. This ambition was reinforced through the Civil nuclear roadmap, published in January 2024, which sets out the vision for the sector and important enabling policies to achieve this.

In 2024, a new government was elected and, as usual in these circumstances, existing policies continue to apply until/unless new policies are implemented.

2. New nuclear power stations – the environment agencies

The Environment Agency has published its own plan EA2025 creating a better place to guide its activities.

The 5-year action plan (EA2025) sets out 3 goals:

• a nation resilient to climate change
• healthy air, land and water
• green growth and a sustainable future

NRW has published a corporate plan to 2030, with a vision of nature and people thriving together. This will be achieved through collective action towards:

• nature’s recovery
• resilience to climate change
• minimising pollution

As enabling regulators, we will continue to engage with the government, regulatory partners, industry and others on nuclear energy matters, including policies, proposals and projects. We will make sure that people and the environment are properly protected. Nuclear is a low carbon energy source that could contribute significantly towards net zero goals and implementing the British energy security strategy.

Our processes align with the goals in EA2025 because they help make sure that new nuclear power stations are designed, constructed and operated in ways that would minimise waste, consider sustainability and protect the environment.

3. Regulating nuclear power stations

The Environment Agency and NRW regulate the effects of nuclear sites in England and Wales on people and the environment. We do this by issuing environmental permits which cover activities required for:

• preparing the site and constructing the power station
• operating and decommissioning the power station

The Environment Agency and NRW also regulate other new and existing nuclear facilities in England and Wales. These can include fuel manufacturing sites, uranium enrichment plants, and waste management and disposal facilities.

We work closely with the ONR, which regulates nuclear safety, conventional health and safety, security and safeguards at nuclear licensed sites.

Our process for assessing and permitting new nuclear power stations can include 2 stages; generic design assessment and environmental permitting.

3.1 Generic design assessment (GDA)

GDA is where we assess the environmental aspects of a power station design that would be relevant to any site. This is based on a ‘generic site’ with characteristics defined by the Requesting Party. Later, when we assess applications for environmental permits, we use the actual characteristics of the specific site where the developer proposes building the power station. The site-specific characteristics may be different from those of the GDA generic site.

The Environment Agency and the ONR developed the GDA process. NRW participates in GDA where the company designing the nuclear power station advises that its design might be proposed for construction in Wales.

The GDA of a new design is not a mandatory requirement. Developers of nuclear power stations may choose to apply to the government to enter GDA to get an early view from regulators on their design. This helps to reduce risks to the developer over an entire project and enables the regulators to identify regulatory concerns and issues early so that these can be resolved before construction begins. The government asks the regulators to start a GDA if it decides that the nuclear power station design company is ready to enter GDA.

We’ve designed GDA as a flexible process with up to 3 steps. The assessment becomes increasingly more detailed with each step. At the end of each step, we will issue statements and reports about our findings. If the reactor design company still has significant issues to resolve after we have completed our planned assessments, we can add further steps to the process to resolve any remaining issues.

Step 1: Initiation

This is the preparatory part of the design assessment process when we make agreements with the reactor design company and agree the scope and the information it needs to provide. As part of this step, we carry out a readiness review and confirm that the reactor design company has put in place the arrangements and resources needed for the GDA process.

This is the step we have just completed for the GE-Hitachi Nuclear Energy BWRX-300 small modular reactor design.

Step 2: Fundamental Assessment

This is when the first technical assessments begin. It focuses on the environmental protection features of the design. The regulators will issue a Step 2 Statement at the end of the step. A Requesting Party may wish to stop the GDA at the end of Step 2 or proceed to Step 3. Getting to the end of Step 2 normally takes around 2 years.

GE-Hitachi Nuclear Energy has applied for a 2-step GDA and our assessment of the BWRX-300 is planned to stop at this point.

Step 3: Detailed Assessment

This is a detailed assessment of the environment case. Where a full GDA is being carried out we will run a public consultation, where we ask for comments on our assessment in Step 3. We consider all relevant responses before completing our assessments and making our decision on whether a SoDA should be issued. If a full Step 3 is not being carried out we will issue a Step 3 Statement. Getting to the end of Step 3 takes around 4 years.

Where a full Step 3 is being carried out (including public consultation), we will publish a decision document that sets out our decision on the design. Potential outcomes include:

Issuing a Statement of Design Acceptability (SoDA)

We will issue a SoDA if the design is acceptable. This means we:

• have not found any GDA Issues
• consider that the design is capable of being constructed, operated and decommissioned in a way that complies with our regulatory requirements and expectations
• believe that people and the environment will be properly protected

Issuing an interim Statement of Design Acceptability (iSoDA)

We will issue an iSoDA if we are broadly content with the environmental protection aspects, but there are still issues to be resolved and the Requesting Party has provided credible plans for addressing them. Normally, once it addresses these issues, we will issue a full SoDA.

Not issuing a SoDA or iSoDA

We will not issue a SoDA or iSoDA if the design is unsuitable and would not provide the right levels of environmental protection. This could also be because there are GDA Issues but no credible plan to resolve them. We would issue a Step 3 Statement if this was the case.

Our GDA guidance for the reactor design company sets out in detail the process that we follow.

Completed GDAs

We have previously carried out generic design assessment on 4 different reactor designs:

• EDF-Areva’s UK EPR, completed in December 2012, and there are 2 reactors currently under construction at Hinkley Point C in Somerset – it is also proposed for use at Sizewell C in Suffolk
• Westinghouse’s AP1000, completed in March 2017
• Hitachi-GE’s Advanced Boiling Water Reactor (ABWR), completed in December 2017
• General Nuclear System Limited’s UK HPR1000, completed in February 2022

Current GDAs

We are currently assessing the following reactor designs:

• Rolls-Royce SMR Limited’s small modular reactor
• Holtec International’s SMR-300 small modular reactor
• GE-Hitachi Nuclear Energy’s BWRX-300 small modular reactor

Ministers have requested the regulators carry out a GDA of Westinghouse’s AP300 SMR.

The regulators have introduced a new additional process to enable early engagement with reactor vendors where their designs are not yet ready to enter GDA. We are now engaging with several companies in this process.

3.2 Environmental permits

In order to build and operate a new power station at a specific site, a company must apply for environmental permits from the Environment Agency in England, or NRW if the site is in Wales.

These permits cover site investigation and preparation, construction works and associated developments such as workers’ accommodation, operation and decommissioning.

Site preparation and construction works permits include activities such as:

• drilling boreholes
• abstracting groundwater (such as from dewatering of excavations)
• discharging effluents (including groundwater and concrete batching plant waters)
• using mobile diesel electricity generators
• flood risk activity permits (for work near rivers and flood defence assets)

Operational permits are needed to:

• dispose of and discharge radioactive waste
• operate standby power supply systems using diesel generators
• discharge returned abstracted water (from the cooling water system and fish recovery and returns system) and other liquid trade effluents (including treated sewage effluent) to the sea or inland water body

If we receive permit applications, we will decide whether or not to grant the permits and, if so, what conditions we should apply. When making decisions about site-specific permit applications, we will take account of matters relevant to the specific site as well as the GDA for the design proposed for the site.

For some permit applications we will also carry out a public consultation before deciding whether to grant permits for a specific site. We will make our decision once we have considered the comments we receive in the consultation. We may also receive applications for changes (variations) to the environmental permits and, where appropriate, we will consult on these.

4. The BWRX-300

There are currently around 415 nuclear reactors operating around the world. The BWR is a common type of reactor in operation, with 41 operating worldwide. There are also 2 BWRs under construction, 19 BWRs not generating currently, and 53 in permanent shutdown.

There are a range of sizes and potential uses for BWRs, but all operating BWRs are used for power generation.

The BWRX-300 is a BWR which is being designed to generate 300 megawatts of electricity (MWe). This would be enough to power over 500,000 homes.

The BWRX-300 is still being designed and is, therefore, not yet in operation. The design has completed the vendor design review process with the Canadian Nuclear Safety Commission (CNSC) and it has now received an application for a licence to construct in Canada. New aspects of the design have also been reviewed by the United States Nuclear Regulatory Commission (US NRC) as part of pre-licensing activities and GE-Hitachi expects a submittal for a construction permit to be filed with the US NRC in 2024 for the Tennessee Valley Authority’s Clinch River site. GE-Hitachi is also progressing early regulatory activities in Poland and the Czech Republic.

How does a BWR reactor work?

When a uranium-235 atom absorbs a neutron, it can split into 2 or more smaller atoms, release energy and emit several neutrons. This is the fission process. In a reactor, these fissions happen in a controlled process called a chain reaction, which provides a continuous heat source.

This heat is removed from the reactor core by circulating water through it. The water boils into steam which is dried in the ‘stream drier’ at the top of the reactor vessel. The steam is then used to power a turbine which drives a generator to produce electricity. After passing through the turbine, the steam is condensed back to water, using a separate cooling water circuit. This cooling water system is the same as for any power station. The cooling water circuit can use seawater, freshwater or circulating water through cooling towers. The water from the condensed steam is returned to the reactor core to start the heat removal process again.

In a BWR the heat removal process takes place in a single circuit, unlike in pressurised water reactors (PWRs) where the water is kept in a liquid phase under pressure and heat is exchanged to a secondary circuit via a steam generator before passing through a turbine. BWRs do not have steam generators or a pressuriser as for PWRs.

The GE-Hitachi BWRX-300 has other features in common with most other types of nuclear power station, including:

• a spent (used) fuel storage pond
• spent fuel dry store (not in GDA scope)
• water treatment systems for maintaining water circuits and their chemistry in good condition
• radioactive waste treatment and storage facilities
• back-up systems for providing power in the event of a loss of electrical supply from the grid

The BWRX-300 would be mostly constructed and assembled in factory-built modules. GE-Hitachi has submitted the design into a competition being held by Great British Nuclear to select technologies to be taken forward into site-specific developments.

Find out more on the GE-Hitachi Nuclear Energy website.

5. About Step 1 (Initiation) and our decision

We began GDA on GE-Hitachi Nuclear Energy’s BWRX-300 design in January 2024. We completed Step 1, the Initiation stage in December 2024.

The objectives of Step 1 were to:

• agree the scope of the GDA
• agree the processes that will be followed in the GDA, including the environment case information GE-Hitachi Nuclear Energy needs to provide for assessment
• confirm if the company is ready to proceed to Step 2

During Step 1, we carried out a joint assessment with the ONR of the GDA project management arrangements to give us confidence in the quality of the GDA submissions that we will receive in Step 2.

We also provided feedback and advice to GE-Hitachi Nuclear Energy on:

• the proposed GDA scope
• the proposed schedule for submitting information
• the structure of the submissions being made to regulators
• the information we expected the Requesting Party to include in the parts of the submissions relevant to the environment case
• the proposed GDA website and comments process

We also agreed detailed working arrangements with GE-Hitachi Nuclear Energy covering matters such as:

• tracking documents
• how the company will document its environment case and submit it for assessment
• how the company will address any gaps in meeting our regulatory requirements
• the arrangements for the public comments process

Our Step 1 review concluded that:

• the proposed scope of the GDA should be sufficient for GE-Hitachi Nuclear Energy to aim for a meaningful Step 2 Statement to be issued after Step 2
• the documents provided adequately address all of the information requirements set out in our GDA guidance for Requesting Parties for Step 1 and also the requirements applicable to the Environment Agency relating to the project delivery, as detailed in appendix 2 of the ONR guidance to Requesting Parties.

Our review also concluded that GE-Hitachi Nuclear Energy has carried out the necessary gap analysis and readiness review to demonstrate it is ready to progress to Step 2.

We carried out a review of GE-Hitachi Nuclear Energy’s readiness to enter Step 2 and have decided that the arrangements and resources the company has put in place to carry out the GDA will be adequate. We have also considered our own readiness to progress to Step 2 and we have sufficient resource in place to assess the expected submissions.

We have concluded that we can progress to Step 2 of GDA. Our GDA Step 1 of the GE-Hitachi Nuclear Energy BWRX-300: statement of findings full report provides more detail.

The ONR has also concluded that it can progress to Step 2 of GDA and its Step 1 report is available on the ONR website.

6. Permissions and consents for a nuclear power station

Any company that wants to build and operate a new nuclear power station must obtain several site-specific permissions. These include:

• environmental permits from the Environment Agency or NRW
• a nuclear site licence and relevant consents from the ONR
• planning permissions from the Planning Inspectorate

GE-Hitachi Nuclear Energy has been selected by Great British Nuclear to advance to the next phase of the small modular reactor competition for innovative nuclear technologies. Once Great British Nuclear completes its technology selection process it is expected to announce its technology partners and the sites for development it has allocated to them.

Currently, no developers have identified a site and applied for environmental permits to use the BWRX-300 in the UK.

6.1 Environmental permits

We provide information on these in Section 3.2.

6.2 Nuclear site licence

The ONR regulates the nuclear safety, conventional health and safety, security and safeguards at nuclear sites. Any organisation that wants to carry out nuclear activities must apply to the ONR, and obtain a nuclear site licence. It must do this before it starts building a new nuclear power station. Granting a nuclear site licence is a significant step, but, on its own, it does not give an organisation permission to start nuclear-related construction. For that, it must get further regulatory permission from the ONR.

6.3 Planning permission

A developer using the BWRX-300 needs a Development Consent Order from the Secretary of State for the Department for Energy Security and Net Zero. The Secretary of State makes a decision having received a recommendation from the Planning Inspectorate.

The environment agencies are consultees in this process and provide advice throughout.

6.4 Electricity generation licence

An operator would need an electricity generation licence from Ofgem, the regulator for the gas and electricity markets.

6.5 Regulatory justification

Regulatory justification is required for any process involving radiation exposure. In essence, regulatory justification requires that the benefits of that process exceed health detriments. This is not a site-specific requirement but is carried out for new nuclear power station designs. The justifying authority for new nuclear power stations is the Secretary of State for the Department of the Environment, Food and Rural Affairs (Defra). No application for regulatory justification has yet been made for the BWRX-300.

6.6 Other permissions

An operator will also need approval from the government for a Funded Decommissioning and Waste Management Plan for its site. This is to ensure that there are funds to decommission and dispose of the waste from a site at the end of its life.

Many other regulatory permissions can also be required depending on the location and local environment of a site and a developer’s proposals. This could include marine licences from the Marine Management Organisation (England), species licences from Natural England (England) and the equivalent permissions in Wales from NRW.

7. Public and stakeholder engagement for this GDA

We have set up our GDA process to be open and transparent.

Public comments process

GE-Hitachi Nuclear Energy is expected to publish design information on its website and to update it as new information becomes available. Anyone can view that information, comment and ask questions about it.

GE-Hitachi Nuclear Energy is required to respond to questions and comments about its design. Regulators see the questions and the responses, and, where relevant, use these to help inform our assessments. Comments can also be made to the nuclear regulators’ Joint Programme Office.

GE-Hitachi Nuclear Energy’s comments process was launched at the start of Step 2 (Fundamental Assessment) on 12 December 2024, so that the public can view and comment on the information the company is submitting for GDA.

GE-Hitachi Nuclear Energy has published the information it is submitting for GDA (apart from any sensitive nuclear or commercially confidential information) on its website, allowing people to make comments through the website or by post.

GE-Hitachi Nuclear Energy is promoting the publication of this information, the comments process, and the new website.

The nuclear regulators are also publicising the second step of GDA and the comments process being available through the media and directly to stakeholders.

The regulators will consider any comments received up to 31 August 2025, and GE-Hitachi Nuclear Energy’s responses to those comments, during our Step 2 assessments.

There is also information about GDA and the comments process on:

• the joint regulators’ webpage
• the getting involved webpage
• the Environment Agency webpage on assessing reactor designs for new nuclear power stations
• the ONR’s webpage on new reactors
• NRW’s webpage on how it regulates the nuclear industry

Get involved

You can get involved in our GDA by:

• reviewing the information and commenting through GE-Hitachi Nuclear Energy’s website
• talking to us at public, stakeholder and industry events

The regulators have published an approach to engagement for this GDA on their joint webpages.

If you have any comments on the plan, please email nuclear@environment-agency.gov.uk.

8. GDA timetable and next steps

The planned duration of the GDA of the BWRX-300 overall is currently 24 months.

Step 1 (Initiation) started in January 2024 and finished on 12 December 2024.

Step 2 (Fundamental Assessment) started on 12 December 2024 and is expected to finish in December 2025.

At the end of Step 2, we will publish a Step 2 Statement. This will be the end of the GDA process for the BWRX-300.

9. Contact us

You can feed back on this document or our work on assessing this design.

Email your questions and comments to nuclear@environment-agency.gov.uk.