- TerraPower says its first British Natrium reactor could generate electricity in 2034, three years after the expected completion of its US demonstration.
- The reactor combines 345 MW of nuclear generation with thermal storage capable of raising output to 500 MW for more than five hours.
- The timetable is highly ambitious: there is no UK site, customer or disclosed financing package and the design is only at the start of regulatory assessment.
US advanced nuclear developer TerraPower is targeting electricity generation from a Natrium reactor in the UK by 2034, positioning the UK as the Bill Gates-backed company’s first market outside the US.
Chris Levesque, TerraPower’s president and chief executive, told media that progress at the company’s demonstration project in Wyoming meant “2034 nuclear electricity in the UK from Natrium is very possible”.
TerraPower has not selected a British site, although its UK subsidiary is likely to be based in Liverpool, close to the North West’s nuclear fuel and regulatory expertise.
The company estimates that a fleet of Natrium reactors could produce electricity for less than £100/MWh. That remains a developer forecast rather than the result of a UK procurement process and is not yet backed by a disclosed construction cost, offtake agreement or government support mechanism.
Nuclear with built-in storage
Natrium combines a 345 MW sodium-cooled fast reactor with molten salt thermal storage. The reactor can continue operating at a steady rate while heat is stored, allowing electrical output to rise to 500 MW for more than five hours when demand or prices are higher.
That flexibility distinguishes Natrium from conventional nuclear plants, which are generally designed to run continuously. On a system with large volumes of wind and solar, the ability to shift output towards lower-renewable periods could be more valuable than baseload generation alone.
The storage does not create additional energy, but it separates reactor heat production from electricity generation. TerraPower also argues that using liquid sodium rather than pressurised water enables passive cooling and reduces the size and cost of safety-related systems, although the design introduces unfamiliar materials and operating requirements for regulators.
The UK’s Office for Nuclear Regulation, Environment Agency and Natural Resources Wales began Step 1 of a three-stage Generic Design Assessment (GDA) in June. GDA examines a design’s safety, security, safeguards, waste and environmental implications, but is voluntary and does not approve a specific site.
The regulators say a conventional three-step assessment takes around four years, although they are developing routes towards two-year assessments and greater use of international regulatory work.
Even after GDA, a developer needs planning consent, environmental permits and a nuclear site licence. The regulatory timetable makes 2034 possible only if site selection, financing and assessment proceed substantially in parallel.
The fuel constraint
TerraPower received a US construction permit for its Kemmerer Unit 1 project in March, the first issued for a commercial-scale advanced reactor. Construction began in April, although an operating licence will still be required.
Current company messaging puts completion in 2031. That is around a year later than the 2030 date in TerraPower’s March permit announcement, underlining the schedule sensitivity of a first-of-a-kind project. A British reactor following only three years later would have limited opportunity to incorporate operating experience from Wyoming.
Fuel is another constraint. Natrium requires high-assay low-enriched uranium, or HALEU, which is enriched more highly than fuel for conventional reactors. Russia was previously the only large commercial supplier, prompting the US and UK to establish domestic production.
Urenco is targeting commercial HALEU operations at Capenhurst by 2031, closely aligned with, but leaving little contingency for, TerraPower’s proposed timetable.
The government’s Advanced Nuclear Framework gives private developers a structured route to early engagement and possible support, but it does not guarantee funding or market access.
TerraPower’s announcement should therefore be read as a serious bid for a place in Britain’s advanced nuclear pipeline, rather than a committed project schedule. Its strategic proposition is compelling: flexible firm power with storage. Whether 2034 is credible will depend on a site, an investable revenue model and evidence that the Wyoming plant can be delivered close to its revised programme.
