Bristol's Astral Systems raises €26M Series A to turn fusion reactors into a medical-isotope business

Bristol-based Astral Systems has closed a €26 million (£23 million) Series A — a first close — to commercialise medical isotopes made by its fusion reactors. The round was led by Mercia Ventures, with Tees River, Daphni and Blast Club joining alongside existing investors Speedinvest and Playfair. The financing takes Astral's total funding past €32 million (£28 million).

A fusion company that sells something today

The pitch that sets Astral apart is commercial, not just scientific. Founded in 2021 by Talmon Firestone and Dr Tom Wallace-Smith, the company builds compact multi-state fusion (MSF) reactors — but rather than waiting on the distant promise of fusion electricity, it puts those reactors to work producing medical isotopes.

Isotopes such as Actinium-225 and Lead-212 are the radioactive payloads of targeted cancer therapies: they are attached to molecules that home in on tumours and deliver radiation precisely where it is needed. Supply is chronically tight — these isotopes are hard to make and depend on a small number of ageing facilities — which makes a new, scalable source genuinely valuable. That scarcity is the market Astral is aiming at.

Revenue first, fusion alongside

Firestone is explicit that this reframes the company: "We are rewriting how we approach fusion and, in doing so, redefining what it means to be a fusion company... building a profitable, impactful fusion business." The key word is profitable. Where the fusion field is defined by long horizons and capital that has to wait, Astral is structuring itself around a product it can sell well before fusion power is on any grid.

The Series A funds three things at once: bringing its medical isotopes to market by early 2027, scaling modular MSF reactor production so capacity can grow in repeatable units rather than single mega-builds, and advancing the underlying fusion research at a new facility at the former Berkeley Power Station — a decommissioned nuclear site being repurposed for the work.

Why the structure matters

The modular approach is part of the bet. Building reactors as standardised units, rather than bespoke giants, is how a deeptech company turns a physics breakthrough into something it can manufacture and finance at scale. Paired with a near-term revenue product, it gives Astral a path that most fusion ventures lack: a way to fund its own long-term ambition from operating income rather than perpetual fundraising. The remaining question is execution — hitting the early-2027 market date and proving the reactors run reliably enough to supply a medical market where consistency is non-negotiable.