MiRESSO Raises $27M in Series A with New Low-Temperature Beryllium Process

MiRESSO, a Japanese startup developing beryllium manufacturing and sales capabilities, has announced the completion of its Series A funding round. The round raised ¥4.23 billion (approximately $27 million).

Founded in 2023, MiRESSO has developed a proprietary process that dissolves beryllium ore at around 300°C (572°F) — compared to the conventional method requiring temperatures exceeding 2,000°C (3,632°F).

Dissolving Beryllium Ore with Microwave Heating

MiRESSO’s push to commercialise a new beryllium refining process is driven by growing global interest in fusion energy.

Fusion reactions are generated by fusing deuterium and tritium. Deuterium is readily available from seawater, but tritium is virtually absent from nature.

One approach under consideration addresses this by using beryllium as a material for the blanket layer surrounding a fusion reactor. When a fusion reaction occurs, it releases neutrons; these neutrons collide with beryllium in the blanket and are multiplied. The amplified neutrons are then reacted with lithium to produce tritium. In other words, the reactor itself would generate its own tritium fuel.

Beryllium production, however, presents its own challenges. As noted above, conventional refining demands high temperatures exceeding 2,000°C and elevated pressure, which limits the number of viable manufacturers.

MiRESSO has addressed this by developing a process that dissolves beryllium ore at a low temperature of 300°C under atmospheric pressure, using an alkaline solution and microwave heating. The company says this can substantially reduce both costs and CO₂ emissions compared with conventional refining.

Beryllium ore (left) and beryllium fluoride recovered from it (right). (Source: MiRESSO press release)

In Oct. 2024, MiRESSO signed a design contract with JGC for its pilot plant, BETA. In Apr. 2025, the company also entered into a business partnership with Helical Fusion, a Japanese fusion reactor development startup, as it works toward commercialisation in 2027.

ITOCHU-Affiliated Fund, Mitsui & Co. Among Backers

The Series A round, including its first close, drew participation from 12 investors. Corporate investors outside the financial sector included ITOCHU Technology Ventures, NTT DOCOMO Ventures, Mitsui & Co., and Pacific Metals.

The proceeds will be used to construct BETA.

Rendering of the completed BETA facility. (Source: MiRESSO press release)

Masaru Nakamichi, CEO of MiRESSO, commented that the company aims to “accelerate the construction of a new beryllium supply chain in Japan, contributing to the social implementation of fusion energy.”