Japan Signs Nuclear Deal with Rolls-Royce to Build Modular Reactors
UK and Japan join forces to develop advanced, “meltdown-proof” reactors that can power factories, data centers, and military bases, as part of an £18 billion investment pact between the two nations.
LONDON / TOKYO — In a landmark agreement aimed at accelerating the next generation of nuclear power, Rolls-Royce has signed a deal with the Japan Atomic Energy Agency (JAEA) and the UK National Nuclear Laboratory (UKNNL) to develop Advanced Modular Reactors (AMRs), according to statements from the three parties.
The trilateral memorandums of cooperation were signed on Sunday, June 14, at 10 Downing Street during the UK visit of Japan’s Prime Minister, Sanae Takaichi . The agreements were unveiled as part of a broader £18 billion investment pact between the UK and Japan, which includes energy, technology, and defense cooperation .
The Technology: High-Temperature Gas-Cooled Reactors
Rolls-Royce’s AMR technology differs significantly from the company’s well-publicized Small Modular Reactor (SMR) design . While SMRs are essentially smaller versions of conventional water-cooled nuclear plants, AMRs operate at much higher temperatures and use different technology, making them suitable for industrial applications beyond just electricity generation.
Key specifications of Rolls-Royce AMRs:
| Specification | Details |
|---|---|
| Reactor Type | High-Temperature Gas-Cooled Reactor (HTGR) |
| Power Output | 15–35 MWe (electricity) plus high-grade heat |
| Operating Temperature | 700°C+ |
| Fuel Type | TRISO (Tri-structural Isotropic) particle fuel |
| Target Deployment | Demonstrator by mid-2030s |
The AMR design is viewed as “meltdown-proof” due to the inherent stability of its fuel and coolant . It will not use conventional uranium rods but rather TRISO particle fuel—microscopic uranium kernels encased in multiple layers of carbon and ceramic, which can theoretically cool itself without external intervention .
Applications Beyond Electricity
The high-temperature output of AMRs makes them suitable for decarbonizing heavy industry, which has been difficult to achieve with renewable energy sources. Potential industrial applications include :
- Steel-making (providing process heat for blast furnaces)
- Green hydrogen production (via high-temperature electrolysis)
- Cement manufacturing
- Plastics and fertilizer production (chemical feedstocks)
The reactors’ compact size also makes them suitable for military bases and remote industrial sites requiring “off-grid” power and heat .
Why Japan? Decades of Research Shared
Japan has been testing high-temperature gas-cooled reactor technology for decades, most notably through the Japan Atomic Energy Agency’s High-Temperature Engineering Test Reactor (HTTR) . Under the new agreement, JAEA will share its extensive safety data and operational experience with Rolls-Royce to help the British company build a demonstrator AMR in the UK by the mid-2030s .
Chris Cholerton, Group President of Rolls-Royce, called the agreements “a milestone moment for the UK’s nuclear sector,” stating that they will enable the parties to “jointly address technical challenges and accelerate the development of Advanced Modular Reactors” .
Masanori Koguchi, President of JAEA, added: “I hope that through our expertise in High Temperature Gas Reactor technologies, this collaboration will lead to their early deployment, a significant step towards net zero” .
The TRISO Fuel Factor
A central focus of the cooperation is the development and qualification of Coated Particle Fuel (CPF) , also known as TRISO fuel . This fuel type is critical to the safety case for AMRs. Within a TRISO particle, each microscopic kernel of uranium is surrounded by protective layers of carbon and ceramic, designed to contain fission products even under extreme temperatures .
This inherent resilience means that, unlike traditional reactors that rely on active cooling systems to prevent meltdown, AMRs fueled with TRISO can theoretically withstand a complete loss of coolant without catastrophic failure .
Julianne Antrobus, CEO of UKNNL, emphasized the historical significance: “Britain has a proud history, and is a current pioneer, in advanced nuclear technologies. This is a chance to honour that legacy by turning decades of research and international collaboration into real-world deployment” .
Broader Economic Context: £18bn Investment Pact
The Rolls-Royce AMR deal is part of a larger economic package between the UK and Japan announced during Prime Minister Takaichi’s visit. Over 10 commercial and government agreements were expected to be signed, totaling approximately £18 billion in investment, including a £9 billion offshore wind deal .
UK Prime Minister Keir Starmer welcomed the agreements, stating that they would create “tens of thousands of jobs” and deepen the strategic economic partnership between the two nations ahead of the upcoming G7 summit .
Comparison: AMR vs. SMR
Rolls-Royce is pursuing a dual-track nuclear strategy—developing both SMRs and AMRs concurrently . While these technologies share the principle of modular factory fabrication, they serve different markets and are at different stages of development.
| Feature | Rolls-Royce SMR | Rolls-Royce AMR |
|---|---|---|
| Power Output | 470 MWe | 15–35 MWe |
| Reactor Type | Pressurized Water Reactor (PWR) | High-Temperature Gas Reactor (HTGR) |
| Primary Use | Grid electricity | Industrial heat, hydrogen, off-grid power |
| Fuel | Conventional uranium pellets | TRISO particle fuel |
| Safety | Active safety systems | “Meltdown-proof” passive safety |
| Status | Preferred bidder for UK sites (Wylfa) | Demonstrator planned by mid-2030s |
The company’s SMR design—a 470 MWe pressurized water reactor—has already been selected as the preferred bidder by Great British Energy – Nuclear (GBE-N) to build the UK’s first SMRs at Wylfa on Anglesey . By contrast, the AMR technology remains in the research and development phase, with the JAEA partnership intended to accelerate its commercialization .
Looking Ahead: The Race to Commercialize
The UK-Japan agreement places Rolls-Royce in a competitive race with other global players seeking to be the first to commercialize AMR technology . Unlike SMRs, which face established global competitors, the AMR market is still emerging, with first-mover advantages potentially significant.
Lord Vallance, UK Minister for Science, Innovation, Research and Nuclear, stated: “We are bringing together crucial expertise through our Advanced Nuclear Framework to deliver a golden age of nuclear and boost our energy security. These agreements build on Britain and Japan’s proud legacies of leading innovation in nuclear technologies” .
The agreements also include provisions for supply chain development and skills training, with Rolls-Royce, UKNNL, and JAEA committed to using their joint expertise to “sustain and develop the people and skills needed for the nuclear industry” .
Frequently Asked Questions (FAQs)
Q1: What type of reactor is Rolls-Royce building with Japan?
A: Rolls-Royce is developing an Advanced Modular Reactor (AMR) based on High-Temperature Gas-Cooled Reactor (HTGR) technology. It will use TRISO particle fuel, which is considered inherently safer than conventional nuclear fuel and can theoretically cool itself without external intervention .
Q2: When will these reactors be operational?
A: The parties aim to build a demonstrator AMR in the UK by the mid-2030s. Commercial deployment would follow successful demonstration .
Q3: What will the reactors be used for?
A: Unlike larger SMRs designed primarily for grid electricity, AMRs are designed to provide both electricity and high-temperature heat for industrial applications such as steel-making, hydrogen production, cement manufacturing, and chemical production. They can also power military bases and data centers .
Q4: Is this Rolls-Royce’s only nuclear project with Japan?
A: No. Rolls-Royce SMR has a separate agreement with Japan’s Yokogawa Electric Corporation, signed in February 2026, for Yokogawa to supply the data processing and control systems (“central nervous system”) for Rolls-Royce’s SMR fleet . The new AMR deal focuses on research and development of reactor technology itself.
Q5: How much will the reactors cost?
A: Specific costs have not been disclosed. However, the agreements are part of a broader £18 billion UK-Japan investment pact, and Rolls-Royce has reportedly held discussions with the UK government about potential support, which could include taxpayer-backed loans, debt financing, or direct investments .
Q6: Are AMRs safer than traditional reactors?
A: Yes, according to the developers. The combination of TRISO fuel—which encases uranium particles in protective layers that can withstand extreme temperatures—and gas cooling means the reactor can theoretically cool itself without active safety systems, leading to claims of being “meltdown-proof” .
