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Sizewell C


On 30 June 2020, ONR received an application from NNB Generation Company Ltd (now Sizewell C Ltd) for a nuclear site licence to construct and operate a twin EPR™ power station at Sizewell in Suffolk, adjacent to the existing Sizewell B station.

ONR inspectors have now completed their assessment of the Sizewell C nuclear site licence application and a nuclear site licence has been granted, coming into effect from 7 May 2024. Further information is detailed below.

In addition to a nuclear site licence, before it can start construction, the applicant must obtain a number of site-specific permissions from other regulators and government.

ONR's regulatory responsibility starts at the point of granting of a nuclear site licence. Now a licence has been granted, we will use the powers available under the site licence to require the licensee to request our permission for starting nuclear safety related construction at Sizewell C. Similarly, the licensee will be required to seek ONR’s permission to proceed to subsequent, key construction and commissioning stages up to the start of commercial operation.

Our publication Licensing Nuclear Installations provides guidance on the licensing process and the factors that we may take into account when reviewing an application for a nuclear site licence.

We have undertaken our assessment activities in accordance with the guidance provided in the Licensing of Nuclear Installations document and ONR's Safety Assessment Principles, Technical Assessment Guides and Technical Inspection Guides.


Assessment reports

Progress statement – July 2022

On 11 July 2022, the Office for Nuclear Regulation (ONR) provided an update on its assessment of the nuclear site licence application for the proposed nuclear power station at Sizewell C in Suffolk.

Previous licensing matters explained

Security of tenure

Our regulatory guidance Licensing Nuclear Installations states that a nuclear site licensee is expected to have ‘full rights of access to and control of’ the site upon which the nuclear site will operate.

This stems from a requirement in the Nuclear Installations Act (1965).

NNB Generation Company (SZC) Ltd does not currently have such rights to the land proposed for the Sizewell development and this will need to be resolved prior to licence grant.

It is understood from engagement with the applicant that plans are in place to address this matter in due course.

Constraints of the current shareholder agreement

As the licensee should be able to exercise effective day-to-day control over all activities on the licensed site, it is essential there is clarity on how that responsibility can be exercised.

The current shareholder agreement for the development phase of the Sizewell C project places control of key policies relating to safety and security with NNB Holding Company (SZC) Ltd, rather than the licence applicant.

This is inconsistent with our regulatory expectations so we will require control of such policies to rest with the applicant prior to the granting of a licence.

It is understood from engagement with the applicant that the necessary amendments will be made to address this matter in due course.