Last week, MiRESSO, a Japanese fusion startup, announced the first close of its Series A funding round, securing ¥1.83 billion (~$12 million). This brings its total financing to ¥4.28 billion (~$28.5 million), enabling the company to develop and expand its beryllium refining technology.
MiRESSO specializes in a low-temperature refining process that dramatically reduces the cost and energy required to produce beryllium, addressing a major bottleneck in the deuterium-tritium (D-T) fusion fuel cycle.
The Series A was led by Spiral Capital, with strategic participation from Pacific Metals Co. (PAMCO), a major Japanese metals manufacturer. Notably, Genesia Ventures, MiRESSO’s seed round lead investor, also participated.
Why MiRESSO’s Raise Matters for Fusion Supply Chains
MiRESSO’s technology addresses a pressing challenge for designs like Commonwealth Fusion’s ARC: the availability of beryllium for tritium breeding blankets. As fusion reactors like ITER and DEMO ramp up, the demand for beryllium is expected to surge, far outstripping the current global supply.
Beryllium plays a pivotal role in tritium breeding. When high-energy fusion neutrons strike beryllium nuclei, they release additional neutrons. These extra neutrons increase the flux available to interact with lithium in the breeding blanket, boosting tritium production and helping achieve a tritium breeding ratio >1.
Illustration of beryllium’s function as a neutron multiplier.
MiRESSO’s low-temperature refining process, using chemical processing and microwave heating, reportedly allows beryllium to be produced at just 300°C, compared to the much higher temperatures required by conventional methods. This would significantly reduce the cost and energy required to produce beryllium in the quantities needed for future reactors.
Beyond tritium breeding, beryllium is also used in divertors and other plasma-facing components, which manage excess heat and high-energy particles. Its high melting point, thermal stability, and low activation properties make it ideal for handling reactor-grade conditions.
This combination of attributes underscores why MiRESSO’s focus on beryllium refining could secure its role in the fusion industry for years to come. The company’s near-term goal is to establish a pilot production plant (BETA) in Aomori, Japan, with a target output of 1 ton per year by 2027. As a demonstration project, BETA will be a crucial step toward MiRESSO’s long-term vision of a full-scale beryllium plant capable of producing 100 tons per year by the early 2030s, aligning with the anticipated scale-up of fusion reactors worldwide.
Go-Forward Strategy & Key Partnerships
MiRESSO plans to use the Series A funding for constructing the BETA plant and scaling its refining technology. At the same time, the startup is developing a parallel business platform, licensing its technology to address challenges in mineral resource refining and expanding into other high-value markets such as rare metals and molten-salt reactor materials. This diversification ensures MiRESSO’s near-term revenue streams and strengthens its commercial viability while prototype fusion reactors are still in development.
MiRESSO’s partnership with Pacific Metals further supports this strategy. By hosting the pilot plant at PAMCO’s industrial site, MiRESSO gains access to PAMCO’s expertise in materials science and processing, which could significantly reduce its capital expenditure and accelerate the timeline to scaled production.
In addition to industry support, the startup also benefits from national government backing. MiRESSO’s success aligns with Japan’s Fusion Energy Innovation Strategy, which aims to position the country as a leader in both fusion research and industrialization. A notable portion of MiRESSO’s total funding comes from government grants, notably the MEXT SBIR Phase 3 award of up to ¥2 billion, granted in 2023. The startup also stands to gain from Japan’s strong materials science base and public-private partnerships.
Closing Thoughts
MiRESSO’s Series A strengthens its first-mover advantage, positioning the startup to capitalize on the growing demand for critical fusion materials. By focusing on beryllium, MiRESSO targets a niche market poised for rapid growth if D-T reactors succeed.
However, beryllium and related refining services have existing markets, and MiRESSO’s ability to generate revenue before commercial fusion power is realized offers it a distinct strategic edge. This, coupled with key partnerships and national support, could position the company to play a pivotal role in the emerging fusion supply chain.