The problem
Europe needs a lot of new clean, firm electricity as it electrifies heating, transport and industry. Nuclear power can provide it, but recent large reactors, such as Olkiluoto 3, Flamanville 3 and Hinkley Point C, have run years late and billions over budget. Much of that risk comes from building one-off, giant structures on site.
Small modular reactors (SMRs) aim to change that by making reactors smaller and standardised, and by moving most of the work into factories, where quality and cost are easier to control. The challenge is to prove that the factory model really cuts costs, because no SMR of this kind has yet been built in Europe.
The product
The Rolls-Royce SMR is a three-loop pressurised water reactor, based on the PWR technology used in hundreds of reactors worldwide. It generates up to 470 MWe from 1,358 MW of heat. It uses standard uranium dioxide fuel, enriched to no more than 4.95% uranium-235, in a 17x17 assembly. Each fuel cycle lasts 18 to 24 months, with refuelling outages of about 18 days (Rolls-Royce SMR GDA).
Unlike most PWRs, it does not use dissolved boron to control reactivity in routine operation, which simplifies chemistry and reduces waste. The whole power station is made of about 1,500 modules in three types: heavy pressure vessels; mechanical, electrical and plumbing modules; and civil engineering modules. Each unit fits under a site canopy of about 21,500 square metres. About 90% of the plant is to be built in factory conditions (WNN).
How it works
- Fission: fuel assemblies in a forged steel reactor pressure vessel heat water to about 300°C.
- Pressure: a pressuriser keeps the primary circuit at about 15.5 MPa, about 155 times atmospheric pressure, so the water does not boil.
- Steam: reactor coolant pumps send hot water through three steam generators, where it boils water in a separate secondary circuit.
- Power: the combined steam drives a turbine at up to 3,000 rpm and a generator connected to the grid.
- Cooling: steam condenses back to water using a third, separate cooling circuit and cooling towers.
- Safety: active and passive safety systems are designed to bring the core to a safe state without human intervention, for up to three days.
Timeline
| Date | Milestone |
|---|---|
| 1 Apr 2022 | UK Generic Design Assessment (GDA) Step 1 begins |
| 30 Jul 2024 | Step 2 completed; Step 3 (detailed assessment) begins the next day |
| Oct 2024 | ČEZ selects Rolls-Royce SMR for up to 3 GW and takes a 20% stake |
| Jun 2025 | Great British Energy - Nuclear (GBE-N) selects Rolls-Royce SMR |
| 13 Nov 2025 | Wylfa named as the site for three units |
| 13 Mar 2026 | UK regulatory justification granted, a first for an SMR |
| 13 Apr 2026 | Contract with GBE-N for Wylfa; National Wealth Fund loan of up to £599 million |
| 24 Apr 2026 | Early works contract with ČEZ for Temelín |
| Dec 2027 | GDA Step 3 due to finish |
| 2029 | Final investment decision for Wylfa expected |
| Mid-2030s | First power targeted at Wylfa |
Impact and numbers
- Output: each unit is designed to produce enough low-carbon electricity for about a million homes for 60 years. The three Wylfa units would provide at least 1,400 MW.
- Public funding: the UK allocated £2.6 billion in the 2025 Spending Review for the contract and wider programme, plus the National Wealth Fund loan to finish the generic design (WNN).
- Supply chain: GBE-N has signed a £300 million contract with the Amentum and Cavendish Nuclear joint venture, Litmus Nuclear, as owner’s engineer for Wylfa.
- Waste: Rolls-Royce SMR says one unit produces about 285 cubic metres of spent fuel over 60 years, about the size of a tennis court.
- Europe: Rolls-Royce SMR is the only SMR vendor with firm contracts for units in two European countries: three at Wylfa and up to six in Czechia (Rolls-Royce SMR).
Honest caveats. No Rolls-Royce SMR has been built yet, so the promised savings from factory construction are unproven. The design has not finished its UK regulatory assessment; earlier reports expected Step 3 to end in 2026, while Rolls-Royce SMR’s own GDA site now gives December 2027 (GDA process). The total cost of the Wylfa project and the price of its electricity have not been published, and the investment decision is still three years away. In June 2026, the regulator ONR said site-specific technical talks on Wylfa were only due to start in its 2026/27 year (ONR). At 470 MWe, the unit is “small” only compared with gigawatt reactors, so site works remain substantial. Funding may rely on a regulated asset base model that adds charges to consumer bills. Spent fuel will need the UK’s geological disposal facility, which has not yet been sited. Finally, the Temelín contract covers design, permitting and preparation, not construction.
What’s next
At Wylfa, Rolls-Royce SMR will now develop the site-specific design, start ordering long-lead components and work on licensing and planning with GBE-N. In Czechia, ČEZ and Rolls-Royce SMR plan to submit a site application for Temelín in 2026. Rolls-Royce SMR also hopes to sell further units; in Sweden, Vattenfall’s Videberg project shortlisted the Rolls-Royce SMR and the GE Vernova Hitachi BWRX-300 for new reactors at Ringhals (Neutron Bytes).
Why it matters for Europe / green buyers
The Rolls-Royce SMR is Europe’s most advanced home-grown SMR design, and its two first projects are designed to share a UK and Czech supply chain. If it is delivered on time, it could give European utilities and industrial users a standard, repeatable nuclear product, rather than a new megaproject each time. For green buyers, it is one of the main options for long-term clean power purchase agreements in the 2030s. For governments, the Wylfa project will test whether the factory approach can deliver lower costs than large reactors.
India is pursuing its own small reactors. Its 2025 Nuclear Energy Mission set aside ₹20,000 crore for research on SMRs, with a goal of at least five indigenous SMRs operating by 2033, and NPCIL has invited Indian industry to finance 220 MW Bharat Small Reactors. Rolls-Royce SMR’s experience with factory modules and regulation will be a useful reference.
Sources & image credits
- World Nuclear News, “Contract signed for delivery of UK’s first SMRs”, 13 April 2026: https://www.world-nuclear-news.org/articles/contract-signed-for-delivery-of-uks-first-smrs
- Rolls-Royce SMR, “Our technology” (GDA website): https://gda.rolls-royce-smr.com/our-technology
- Rolls-Royce SMR, “GDA process” (GDA website): https://gda.rolls-royce-smr.com/gda-process
- GOV.UK, “Rolls-Royce Small Modular Reactor design completes second step of regulatory assessment”, 30 July 2024: https://www.gov.uk/government/news/rolls-royce-small-modular-reactor-design-completes-second-step-of-regulatory-assessment
- Rolls-Royce SMR, “Rolls-Royce SMR achieves major milestone with regulatory justification decision”, 13 March 2026: https://www.rolls-royce-smr.com/press/rollsroyce-smr-achieves-major-milestone-with-regulatory-justification-decision
- Rolls-Royce SMR, “Rolls-Royce SMR secures Czech contract to deliver Small Modular Reactor Programme”, 24 April 2026: https://www.rolls-royce-smr.com/press/rolls-royce-smr-secures-czech-contract-to-deliver-small-modular-reactor-programme
- World Nuclear News, “UK selects Wylfa to host at least three Rolls-Royce SMRs”, November 2025: https://www.world-nuclear-news.org/articles/uk-selects-wylfa-for-at-least-three-rolls-royce-smrs
- Office for Nuclear Regulation, “Wylfa SMR project communications” (FOI release), June 2026: https://www.onr.org.uk/publications/corporate-publications/foi-releases/2026/06/onr-wylfa-smr-project-communications
- Neutron Bytes, “UK & Rolls Royce sign deal for three SMRs at Wylfa”, 19 April 2026: https://neutronbytes.com/2026/04/19/uk-rolls-royce-sign-deal-for-three-smrs-at-wylfa/
Images:
- “Wylfa nuclear power station - geograph.org.uk - 1717137” by David Dixon, licensed under CC BY-SA 2.0 (https://creativecommons.org/licenses/by-sa/2.0), via Wikimedia Commons: https://commons.wikimedia.org/wiki/File:Wylfa_nuclear_power_station_-_geograph.org.uk_-_1717137.jpg
