Japan’s Kyoto Fusioneering and industrial ceramics and metals manufacturer NGK Corporation are partnering to develop and commercialise FLiBe – a molten salt of lithium fluoride and beryllium fluoride for use in fusion power plants. The partnership brings together Kyoto Fusioneering’s fusion plant engineering expertise with NGK’s beryllium handling and refining technology.
Bringing fusion to commercial reality depends on more than plasma-confinement technology. Developers must also solve how to extract heat from the plasma, how to breed and recover the tritium fuel that fusion reactions consume, and how to engineer the surrounding circulation systems that tie the plant together. This collaboration bridges advanced material manufacturing with fusion plant engineering to build a stable commercial supply chain.
FLiBe can be used as a liquid blanket material by circulating through the inner walls of a fusion reactor to absorb energy, breed fuel, and shield structures. It operates in a molten liquid state, typically at temperatures between 500°C and 700°C. This eliminates the structural stress and thermal cracking risks associated with solid breeding blankets.
FLiBe has emerged as one of the leading candidate materials for this role. As a molten salt, it can simultaneously carry heat away from the reactor and breed the tritium fuel needed to sustain the fusion reaction. Realising that potential, however, requires mastering the safe handling, purification, and quality control of beryllium, a rare and technically demanding material, along with the engineering of circulation systems that can operate reliably with molten salt over the long term.
The fusion reaction between deuterium and tritium releases 80% of its energy in the form of high-energy, 14.1 MeV neutrons. As these neutrons pass through the liquid FLiBe blanket, they collide with lithium and beryllium atoms. These collisions slow down the neutrons, converting their kinetic energy into thermal energy. The molten salt heats up and is pumped out to a heat exchanger to drive turbines for electricity generation.
Fusion reactors require tritium, an isotope of hydrogen that does not exist in abundant quantities. FLiBe solves this by breeding its own fuel through nuclear reactions when neutrons hit the lithium atoms in the salt. A single fusion reaction uses one tritium atom and releases one neutron. Because some neutrons are inevitably absorbed by structural walls or escape, a reactor needs a “neutron multiplier” to ensure a tritium breeding ratio (TBR) greater than 1.0. The beryllium inside the FLiBe salt acts as this multiplier. When a fast neutron hits a beryllium nucleus, it releases two neutrons instead of one. This doubles the available neutrons, guaranteeing there are always enough neutrons to react with lithium and breed a surplus of tritium fuel.
FLiBe does not boil or vaporise easily at high temperatures. This prevents high-pressure build-ups inside the reactor casing, reducing the risk of explosive pipe ruptures. Moeover, FLiBe does not react violently with air or water. This minimises fire risks in the event of a structural leak. As a liquid, FLiBe cannot suffer from the structural radiation damage (such as swelling or embrittlement) that degrades solid blanket components over time.
However, despite these advantages there are challenges. Under neutron bombardment, the fluorine atoms in the salt can form hydrofluoric acid (HF), which is highly corrosive to metal reactor walls. Redox potential control systems must be used to mitigate this. In addition, FLiBe solidifies at roughly 459°C. The reactor systems must be constantly kept hot to prevent the salt from freezing and blocking the circulation loops. Also. beryllium is highly toxic to humans if inhaled as dust, requiring strict containment protocols during manufacturing and handling.
NGK has supplied and manufactured beryllium-containing materials since 1958. For more than six decades, NGK has built deep expertise in the safe handling, quality control, and refining and analysis of beryllium. KF is a specialist in fusion plant engineering. From plasma heating systems to plant-wide system design, thermal-hydraulic analysis, and tritium breeding and recovery systems, KF has built expertise in the field, and provides technology and knowhow through partnerships with government agencies, research institutions, and organisations worldwide.
Through the partnership, the two companies will advance FLiBe-related technology for fusion plant applications with a view to future commercialisation and supply-chain development. NGK and KF will work together from material manufacturing and refining to real-equipment application including circulation systems in line with specifications based on customer requirements.
KF will lead the engineering design (including engineering, procurement, and construction) of the FLiBe production and refining facility which will be hosted at NGK’s beryllium facility. NGK will contribute its beryllium safety and handling-related expertise and will be responsible for raw material sourcing and operation of the FLiBe production and refining facility.
KF, drawing on its close engagement with the fusion research community and understanding of fusion industry requirements, will guide the partnership in developing low-activation, low-corrosion FLiBe suited for the long-term operation of fusion power plants. KF will also evaluate the resulting fusion-grade FLiBe using its dedicated FLiBe Research Japan Advanced (FREJA) Loop, ensuring the material meets the rigorous performance and quality standards required for fusion applications. The FREJA Loop is a specialised, laboratory-scale test platform used to validate and certify that manufactured FLiBe meets strict nuclear and structural standards.
“Under our Long-Term Management Plan 2026–2035, NGK has positioned 2035 as the midpoint toward our NGK Group Vision: Road to 2050, and we remain committed to research, development, and societal implementation aimed at future commercialisation in the carbon-neutral space,” said Takeshi Otsu, NGK Vice President and Head of NV Business Development, NGK Corporation. “This strategic partnership with Kyoto Fusioneering is an important step in that direction.”
He added: “By applying NGK’s safety management and technical knowhow in beryllium handling, together with our FLiBe-related technology, we are taking on the challenge of creating new technological value that supports the practical realisation of fusion energy in the carbon-neutral field. We will continue to advance technology development toward the societal implementation of FLiBe-related technology and contribute to making fusion energy a reality.”
Kyoto Fusioneering President and COO Kiyoshi Seko noted: “At Kyoto Fusioneering, we are working to establish fundamental technology needed to bring fusion energy into practical use at the earliest possible stage. FLiBe is a critical material in that effort, serving multiple functions — breeding, cooling, and tritium recovery. Because it contains beryllium, handling it safely calls for advanced safety management and refining technology. By combining the beryllium-handling expertise NGK has built over many years with the system-integration knowhow we have accumulated through fusion plant design, we aim to accelerate the industrial foundation for FLiBe-related technology and take an important step toward the societal implementation of fusion energy.”
