Sizewell C
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15 Sep 2026
Insight
UK
In February 2026 the Department for Energy Security and Net Zero (DESNZ) published the Advanced Nuclear Framework. At its heart is the UK Advanced Nuclear Pipeline: a government-managed register of privately led advanced nuclear projects for small, advanced and micro modular reactors (respectively, SMRs, AMRs and MMRs) that DESNZ considers credible enough to be delivered.
The exception, which sits outside the Pipeline, is the delivery contract from the competition Rolls-Royce SMR won for the Great British Energy – Nuclear (GBE-N) programme at Wylfa. This was signed in April 2026 alongside a National Wealth Fund (NWF) loan facility of up to £599 million for Rolls-Royce SMR. The Pipeline is the route for everyone else. Submissions opened on 4 March 2026.
What the Pipeline is, and is not
Voluntary, with no closing date
The submission process is completely open-ended and optional, allowing developers to apply at any time without facing a fixed deadline.
Not restricted to Gen IV nuclear technology
“Advanced” is a policy label for the whole modular family (SMRs, AMRs and MMRs). Conventional Gen III+ light water designs such as Holtec’s SMR-300 and GE Vernova Hitachi’s BWRX-300 qualify alongside advanced Gen IV reactors like X-energy’s Xe-100 HTGR.
This is not a route for GW-scale reactors, though DESNZ reserves the right to extend it to other nuclear projects if there is sufficient market need.
Endorsement, not a guarantee
Membership is a “signal of limited in principle UK Government endorsement” designed to bolster investor confidence.
Not a funding mechanism or procurement tool
It is an assessment and endorsement process. Financial support, if any, comes through the separate levers described below.
The process: Three stages
Stage 1: Eligibility checkProjects must be for land-based fission (U-235 enriched up to 20%), deployment in England or Wales only with construction sought within 10 years of joining. Proposals must cover five core areas: technology and supply chain; developer capability; finance and funding; siting; and operator and end-user arrangements. |
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The Pipeline is not a competition and sets no preference between technologies, sites or operating models; it complements early regulatory engagement and the regulators’ Generic Design Assessment (GDA) rather than replacing them.
Developers entering the Pipeline will find the state on several sides of the table at once: assessor through DESNZ, prospective revenue counterparty, underwriter of political and uninsurable risk and, through the National Wealth Fund, lender and/or shareholder. Sizewell C showed those roles can be reconciled, but only with structuring that anticipates the conflicts rather than discovering them on the way to financial close.
Paul Butcher
Director of Public Policy
Potential support
Government support comes only where there is a credible delivery plan, value for money, and most economic risk staying with the developer. Three potential levers are referenced:
Revenue support (Pipeline projects only)
A CfD-style mechanism to stabilise future revenues, though none is expected during construction, reflecting an assumption of shorter modular build schedules.
High Impact, low probability risk protections (Pipeline projects only)
A Government Support Package, along the lines of those for Hinkley Point C, Sizewell C and UK CCUS projects: protection against asset stranding from sudden political or regulatory shifts, plus a last-resort backstop for uninsurable risks.
National Wealth Fund (open to all, Pipeline prioritised)
Designated the “natural home” of government finance for advanced nuclear, the NWF may offer debt, equity and hybrid instruments.
The first projects seeking entry to the Pipeline
- Centrica and X-energy submitted their proposal in early March 2026: an Xe-100 HTGR fleet of up to 6 GW, with Hartlepool the preferred first site (12 units, 960 MWe). X-energy applied in June 2026 to enter the Xe-100 into GDA, which it expects to conclude by the end of 2029.
- Holtec and EDF submitted their proposal in June 2026: up to four SMR-300 units (around 1.3 GW) at Cottam, with joint-venture Heads of Terms signed. The SMR-300 completed its two-step (fundamental) GDA in March 2026, with detailed assessment still to come.
- SGE (formerly Synthos Green Energy) announced its application in July 2026: 14 GE Vernova Hitachi BWRX-300 units across three sites, 4.2 GW in all. The BWRX-300 completed the same two-step GDA in December 2025.
The UK's new nuclear siting policy lets SMR developers bring forward their own sites. But each site still needs its own development consent order, through substantially the same process as a gigawatt station, and each is a target for legal challenge. The prize for the pipeline is repeatability: standardised applications, examinations that don’t relitigate settled questions, and courts that dispose of hopeless challenges fast.
Catherine Howard
Partner
Pages
- The Nuclear Narrative
- Rethinking nuclear: Grid, AI, industry, and energy security
- The UK Advanced Nuclear Framework: A new route to market
- The economics of small modular reactors: A primer for investors and policymakers
- EU nuclear: A €241 billion investment cycle takes shape
- Australia's nuclear frontier: Key contractual considerations for AUKUS industry participants
Key contacts
Steven Dalton
Partner, London
Paul Butcher
Director of Public Policy, London
Catherine Howard
Partner, London
Tom Marshall
Partner, London
Dr Silke Goldberg
Partner, London and Israel Group
Gavin Williams
Partner, Head of Infrastructure Sector, London
Matthew Job
Partner, London
Charlotte Whight
Partner, London
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The contents of this publication are for reference purposes only and may not be current as at the date of accessing this publication. They do not constitute legal advice and should not be relied upon as such. Specific legal advice about your specific circumstances should always be sought separately before taking any action based on this publication.
© Herbert Smith Freehills Kramer 2026
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