Consultation outcome

Environmental permitting of Sizewell C: summary of decision

Updated 28 March 2023

1. Introduction

The Environment Agency is the independent environmental regulator for the nuclear industry in England. We make sure that nuclear power stations meet high standards of environmental protection.

Any company that wants to operate a nuclear power station must show that it can do the following safely and securely, while also protecting the environment:

• build, commission, operate and decommission the power station
• manage the wastes it produces

NNB Generation Company (Sizewell C) Limited applied to the Environment Agency for 3 environmental permits in May 2020. We consulted on the application from July to October 2020 and on our proposed decision and draft permits from July to September 2022.

We are grateful to everyone who took the time to respond to our consultation and attend our consultation events.

We have assessed the 3 permit applications and considered the responses we received from both consultations. We have now made a final decision about whether we should grant these permits, and if so, what conditions they should include.

The permits are:

• radioactive substances activity permit to dispose of and discharge radioactive waste

• combustion activity permit to operate standby power supply systems using diesel generators
• water discharge activity permit to discharge returned abstracted seawater from the cooling water system, and 2 fish recovery and returns systems, and other liquid trade effluents (including treated sewage effluent) to the Greater Sizewell Bay – North Sea

Our final decision is that we should grant all 3 permits. We consider that the limits and conditions in the permits are suitable to protect people and the environment.

NNB Generation Company (Sizewell C) Limited has applied for these permits many years ahead of the station operating. By granting these permits early in the project, it will help us to positively influence the design, procurement and commissioning of the power station where relevant to the permitted activity.

This document covers the final stage of our process to determine the environmental permit applications to operate the proposed Sizewell C nuclear power station. It provides a summary of our decisions. You can find more detailed explanations in the individual decision documents.

2. New nuclear power stations – the government’s view

Energy policy, including the use of nuclear power, is a matter for government. Government published an Energy white paper: Powering our Net Zero Future in 2020 that set out the need for nuclear power, among other measures, to help the UK achieve net zero by 2050.

In 2022, the government also published the British Energy Security Strategy. This states an aim that by 2050, up to a quarter of the power used in Great Britain will be from nuclear.

We have published our own plan, EA2025 creating a better place to guide our activities.

Our 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

We will continue to work with the government, regulatory partners, industry and others to help achieve net zero energy generation and the energy security strategy. And whilst doing this, we will make sure that people and the environment are properly protected.

3. Regulating nuclear power stations

The process for assessing and permitting new nuclear power stations is normally split into 2 stages.

3.1 Generic Design Assessment

The first stage is the Generic Design Assessment (GDA ), where we assess the environmental aspects of a power station design that would be relevant to any site. We carry out the GDA of a new design at the request of government. GDA allows us to begin scrutinising new nuclear power station designs well in advance of construction starting. This means that we can identify any potential design issues at an early stage and ask the applicant to address them. At the end of GDA, we provide a statement about the acceptability of the design.

We have previously carried out GDA on the design proposed for Sizewell C, known as EDF-Areva’s UK EPR™. This design is currently under construction at Hinkley Point C in Somerset.

3.2 Environmental permits

In order to build and operate a new power station at a specific site, a company must also apply for environmental permits from the Environment Agency. These permits cover:

• site investigation and preparation

• construction works and relevant ‘associated developments’ – such as workers’ accommodation

• operating and decommissioning the power station

In deciding whether to grant the permits, we will take into account matters relevant to the specific site as well as the GDA for the design proposed for the site.

4. Other site-specific permissions

For a future operator to build any new nuclear power station at a site, they must get the following necessary permissions from the relevant regulators.

4.1 Planning permission

A new nuclear power station as large as Sizewell C needs a Development Consent Order (DCO) from the Secretary of State for the government department for Energy Security and Net Zero, formerly called the Department for Business, Energy and Industrial Strategy (BEIS).

The Secretary of State for BEIS granted development consent to the Sizewell C project application in July 2022.

Through the DCO process, BEIS also carried out a Habitats Regulations assessment (HRA) for the planning permission. Any permission needed from the Marine Management Organisation to operate the site, for example the design and operation of the cooling water intake, was assessed as part of the HRA for the DCO.

The Environment Agency was a consultee in the DCO process and we provided advice throughout.

4.2 Nuclear site licence

We also work closely with the Office for Nuclear Regulation (ONR), which regulates the safety and security of nuclear sites.

Any organisation that wants to carry out nuclear activities must apply to ONR for, and be granted, a nuclear site licence. They must do this before they start building a new nuclear plant. 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, they must get a regulatory permission from ONR.

ONR received an application from NNB Generation Company (Sizewell C) Ltd for a nuclear site licence to construct and operate a twin EPR™ power station at Sizewell on 30 June 2020. ONR inspectors completed their assessment of the nuclear site licence application and issued a progress statement in July 2022. They concluded that the application has met almost all the regulatory requirements set out in regulatory guidance. However, there are 2 outstanding matters which need to be resolved before ONR can formally grant a licence.

4.3 Electricity generation licence

In February 2020, Ofgem, the regulator for the gas and electricity markets, granted NNB Generation Company (Sizewell C) Ltd an electricity generation licence.

4.4 Other permissions

The operator will also need agreement from government about a Funded Decommissioning Plan.

They also needed Regulatory Justification to use the UK EPR reactor. The Secretary of State granted this in October 2010.

Other requirements could include permits and licences from:

• the Marine Management Organisation

• Natural England

• Historic England

• East Suffolk Council

• Suffolk County Council

5. About Sizewell

The Sizewell nuclear power stations are in Suffolk, England on the North Sea coast, approximately 1.5km north-east of the town of Leiston.

Sizewell A was Sizewell’s first nuclear power station. It operated from 1966 to 2006 and is being decommissioned.

Sizewell B is a pressurised water reactor, the first to be constructed in the UK. It’s expected to stop generating electricity in 2035. However, it may carry on operating for a further 20 years, so we have assessed for a longer overlap with Sizewell C, up until 2055.

EDF nominated Sizewell as a potential site for a new nuclear power station. EDF’s new nuclear build company, NNB Generation Company (Sizewell C) Limited, is proposing a twin reactor nuclear power station, Sizewell C, at the site.

The image below shows an aerial view of the proposed Sizewell C development.

6. The UK EPR™ design

There are various types of nuclear reactors around the world, with over 440 in operation. One of the most common types is the pressurised water reactor (PWR), including the UK EPR™. Its twin reactors are capable of providing around 3,260 megawatts of electricity, enough to power more than 6 million homes on average. This design is currently under construction at Hinkley Point C in Somerset.

In the reactor core, some of the uranium atoms that make up the fuel, split in a process called nuclear fission. These fissions produce heat in a continuous process called a chain reaction.

The heat created by the nuclear fission is used to heat water inside the reactor, which is circulated by pumps in the primary circuit to a steam generator. In the steam generator, the very hot primary circuit water is used to heat water in the separate secondary circuit. This produces steam which is fed to a turbine. This makes the turbine spin and drives a generator that produces electricity.

The primary circuit of a PWR is at a very high pressure, giving this type of reactor its name. There is a third water circuit which is used to cool the condenser of the turbine, converting the steam of the secondary circuit back to water. The water is pumped back into the secondary circuit to flow through the steam generator again.

In UK nuclear power stations, sea water is usually used in the third water circuit.

Find out more on EDF’s website.

This image shows a simplified schematic of the EPR™ reactor

For each reactor, the main nuclear support facilities include a water filled pool for storing used (spent) nuclear fuel and water treatment systems for maintaining the chemistry of the primary and secondary water circuits. There are also some facilities shared by the 2 reactors, including an interim spent fuel store and an intermediate level radioactive waste store.

There are 12 stand-by diesel generators that would provide power if there was a loss of electricity from the National Grid.

7. Our consultations

We aim to build and maintain confidence in our decision-making processes through our public engagement and consultation. It is our responsibility to make decisions about the environmental permit applications for Sizewell C, but we consider that our decisions are better informed through consultation.

We can all help to protect and improve the environment by being actively involved. Our public participation statement shows how our process is open, transparent and consultative. We would like people to understand our role, what we are doing and why it’s important.

When we consulted, we explained that the consultations were not about the need for nuclear power, UK energy policy or policy relating to the siting of nuclear power stations.

During the consultations we shared information with people, explained our proposed decisions and considered the feedback we received.

We emphasised that we would not make any final decisions until we had considered all relevant responses to the consultation.

Our approach to consultation is in line with the government’s published consultation principles and our public participation statement. We also published our engagement plan before starting the consultation.

Our consultations were open to everyone and, in particular, we invited the following groups to take part:

• the public

• local councillors

• the energy industry

• academics with an interest in nuclear power, energy or the environment

• non-governmental organisations

• other organisations and public bodies

We publicly consulted on:

• NNB Generation Company (Sizewell C) Limited’s 3 operational permit applications from July to October 2020
• our proposed decisions and draft permits from 4 July 2022 to 25 September 2022

For our 2020 consultation on the permit applications, we received 79 consultation responses. These were from:

• members of the public

• local councils

• non-governmental organisations (NGOs)

• environmental groups

• public bodies

• government agencies

• other interested parties

For our 2022 consultation on the proposed decision and draft permits, we received 133 consultation responses. These were from organisations and members of the public.

You can find more detailed information about our consultation activities in the document Summary of our 2020 and 2022 consultation activities.

Information about which organisations responded and how each response has been considered is included in our final decision documents.

All responses to our consultation (if the respondent gave permission) are published on our consultation website.

We used the relevant responses to help inform our decisions on whether to grant each permit and what conditions they should include. We are grateful to everyone who took the time to respond to our consultation and attend our consultation events.

Evaluating our consultations helps us to learn lessons and share our experiences with others. We will use the findings from these evaluations to improve our work on future nuclear projects and other relevant consultations that we carry out.

8. Our decision

Our final decision is that we should grant the permits for the 3 operational activities. The limits and conditions attached to the permits will make sure that people and the environment are protected from the 3 operational activities under normal operation.

In reaching our final decision, we have considered the following:

• the relevant legislation

• government policy and guidance

• our own guidance

• the relevant responses to our consultations on both the applications and our proposed decision and draft permits

In reaching our decision we completed these assessments and published the findings:

• Radiological impact assessment
• Habitats Regulations assessment (HRA)
• Countryside and Rights of Way Act (CRoW) SSSI assessment
• Water Framework Directive (WFD)

We have assessed the risks to designated habitats and species and consider that the proposed activities will not have an adverse effect on national network sites, or damage Sites of Special Scientific Interest (SSSI).

We assessed the company’s proposals for managing radioactive waste and concluded that these are consistent with the use of the best available techniques (BAT) to minimise the:

• creation of waste

• discharge of radioactive waste to the environment

• impact of discharges and disposals on the environment

We assessed the company’s management arrangements and concluded that these were suitable and that the company is a suitable operator.

9. The permits and their conditions and limits

This section provides information about what the permits are for and the limits and conditions in the permits.

9.1 Permit for managing radioactive waste

Radioactive waste is produced by activities associated (directly or indirectly) with operating, maintaining and decommissioning the nuclear reactors. When we permit radioactive substances activities, we require operators to minimise the activity and volume of radioactive waste produced and its impact on the environment and public. They must do this by using BAT.

Radioactive wastes produced by operating the nuclear reactors include the following types.

Gaseous radioactive waste

Gaseous radioactive waste (after treatment) would be discharged to the environment mostly via 2 main outlet stacks, one for each reactor

Aqueous radioactive waste

Aqueous radioactive waste (after treatment) would be discharged with the cooling water into the North Sea, at a point approximately 3.4 kilometres offshore.

Solid radioactive waste

Solid radioactive waste would be produced during the treatment of gaseous and liquid waste, and during the operation and maintenance of the power station. Low-level solid radioactive wastes, oils and solvents would be transferred to off-site treatment and disposal facilities. Higher activity solid waste would be stored on-site until it decays to low-level waste (allowing it to be disposed of) or until suitable disposal facilities become available.

We are satisfied that the radiation dose rates to the public and wildlife associated with permitted discharges from the Sizewell C site would be well below these limits:

• the UK’s statutory radiation dose limit for members of the public of 1,000 microsieverts a year (µSv/y)
• the source (300μSv/y) and site (500μSv/y) dose limits
• our guideline level for non-human species of 40 microgray an hour (μGy/hour)

We have assessed the total dose to the representative person from discharges of radioactive waste and direct radiation from the proposed Sizewell C station as 4.7μSv a year.

We have also assessed the total dose to a representative person from both past and future discharges of radioactive waste from all 3 Sizewell stations (A, B and C sites) at the permit limits as 28μSv/y.

Our radioactive substances activity permit includes limits on gaseous and liquid discharges of radioactive waste. There are 16 requirements to provide additional information, which will help make sure that NNB Generation Company (Sizewell C) Limited builds and operates the proposed power station according to the commitments it made in its application.

9.2 Permit for using diesel generators

The combustion activity will consist of 12 backup diesel generators with a combined net thermal input of 227MW, associated fuel storage tanks and interconnecting pipework. The generators will be housed in 4 purpose-built concrete buildings. Each building will contain 2 x 23.1MWth essential diesel generators (EDG) and one 10.53MWth ultimate diesel generator (UDG).

The diesel generators will be safety classified standby equipment and would only be operated in the event of a power failure and during periodic testing.

The main emissions will be to the air, through exhaust stacks measuring 27.2 metres high. Emissions will consist of combustion gases containing particulates as well as oxides of sulphur, nitrogen and carbon. We assessed the environmental impact of these emissions in 3 operational scenarios – commissioning, routine testing and loss of off-site power (LOOP).

The main issues arising during our assessment were air quality and the dispersion of emissions to air, and the impact of these emissions on the local environment.

Our assessment of the air dispersion modelling has concluded that it is unlikely that the relevant air quality objectives and environmental assessment levels will be exceeded. We have also concluded that operating the generators would have no adverse effect on European sites’ integrity and would not damage the special features of the Sites of Special Scientific Interest (SSSIs).

Our combustion activity permit limits the operational hours of the generators to 500 hours a year and includes 5 pre-operational requirements and 4 improvement measures. These will help make sure that the proposed power generators are commissioned and operated according to the commitments made in the application.

9.3 Permit for discharging water

This permit regulates the operational water discharge activities (WDAs) from Sizewell C, which relate to discharging the following non-radioactive liquid effluents:

• returned abstracted cooling water from the turbine condensers and other cooling systems – including using biocide to control biological fouling of the cooling systems (biological fouling is the potential growth of bacteria, fungi, biofilms or other species such as mussels)
• trade process effluents from the various plant systems (including those that maintain water purity and chemistry to keep the best operating conditions and maximise efficiency)
• treated sewage effluent (from staff welfare facilities)
• returned abstracted seawater through 2 fish recovery and return (FRR) systems

The cooling water discharge is the main WDA from Sizewell C (approximately 11.4 million cubic metres (m³) per day) and represents approximately 99% by volume of the total overall daily non-radioactive liquid discharges.

After being used within the power station, the abstracted seawater (combined with the various trade process effluents and treated sewage effluents) would then be discharged back to the Greater Sizewell Bay. This would be done through a single cooling water discharge tunnel (which incorporates 2 cooling water outfall heads). The average temperature would be 11.6°C above the background seawater temperature.

As a result of the direct cooling of the Sizewell C power station with seawater, the 2 EPR™ units will each incorporate a FRR system (2 FRR systems in total) to minimise the risk of injury to fish that are drawn into the cooling water system. The FRR systems will return the fish to the Greater Sizewell Bay. Each of the 2 FRR systems is served by a dedicated discharge tunnel and outfall. These will discharge at locations where fish are not likely to be returned to the 4 cooling water intake heads.

Following our assessment of the impact of the combined cooling water and trade effluent discharges through the 2 cooling water outfalls (outfalls 1 and 2 in the WDA permit), we have included limits in the WDA permit on:

• volume

• rate

• temperature

• total residual oxygen (TRO)

• hydrazine

• other chemicals

This is to make sure that the receiving environment within the Greater Sizewell Bay is protected.

Following our assessment of the impact of the 2 fish recovery and return system (FRR) discharges, we have also included limits on volume, rate and the combined biomass discharged from the 2 FRR system outfalls (outfalls 3 and 4 in the WDA permit).

We have concluded that the proposed Sizewell C operational WDAs would have no adverse effect on the:

• integrity of the European sites

• designated features of the relevant European sites

• functionally of linked land and features

We have also concluded that the proposed WDAs will not cause the current status of the Water Framework Directive (WFD) water bodies to deteriorate, nor prevent them from achieving their objectives.

The permit regulates the operational WDAs from Sizewell C and only allows discharges during:

• the commissioning of the power station, known as hot functional testing (HFT)

• an approximate 60-year operational timescale (up until when site decommissioning begins once electricity production stops)

The permit includes 19 pre-operational conditions which need Environment Agency approval before the proposed power station can be commissioned or begin to operate. This is to make sure that NNB Generation Company (Sizewell C) Limited builds and operates the proposed power station according to the commitments made in its permit application.

10. Publishing our final decision

You can read detailed explanations of our decisions in the individual decision documents for each permit. Each document explains how we have considered the permit application and the relevant consultation responses, and why we have included the specific conditions in the permit we are issuing. It is our record of our decision-making process, to show how we have considered all relevant factors in reaching our decision.

You can find our decision documents on GOV.UK and the Environment Agency’s consultation website.

We have published the following documents:

• permit for radioactive substances activity
• decision document for radioactive substances activity
• permit for water discharge activity
• decision document for water discharge activity
• permit for combustion activity
• decision document for combustion activity

We have republished the following documents with minor edits:

• Independent dose assessment
• Water Framework Directive assessment

We have not updated the following documents:

• Habitat Regulations assessment – covers all 3 permits
• SSSI assessment – covers all 3 permits

11. Next steps

11.1 Future opportunities to have your say

There will be further opportunities to input into our decision-making for environmental permits for this site.

NNB Generation Company (Sizewell C) Limited will need to apply for a range of environmental permits relating to site investigation, construction works and for relevant ‘associated developments’ such as workers’ accommodation.

Where appropriate, we will consult on the applications for these permits. We will make our decision once we have considered the comments we receive in the consultation. Construction activities are not unique to nuclear developments and are time limited, so we will deal with these permit applications as we would for other types of construction sites. This is a proportionate approach that will help us exercise the best regulatory control on rapidly changing construction activities.

We may also receive applications for changes (variations) to the 3 operational permits and for other environmental permits related to work at the site. Where appropriate, we will consult on these.

11.2 Future engagement

We will continue our programme of communications and stakeholder engagement for Sizewell C and other nuclear developments and projects. This includes holding events with communities and stakeholders.

You can read our engagement plan for Sizewell C.

Find out more about our work at Sizewell C.

11.3 Contact us

You can feed back on this document or our work in regulating Sizewell C. Email your questions and comments to nuclear@environment-agency.gov.uk.