Blykalla
🇸🇪 Stockholm, SE · Founded 2013 · Active
Blykalla is a Swedish reactor developer founded in 2013 as a spin-off from the Royal Institute of Technology (KTH) in Stockholm, where its founders researched lead-cooled reactors. Its design, SEALER, is a small reactor cooled by liquid lead that is never refuelled during operation; the company says a patented aluminium-alloyed steel solves the corrosion that has held back lead cooling. With Uniper, OKG, KTH and a 99 million kronor Swedish Energy Agency grant, it is building an electrical prototype of the reactor at the Oskarshamn nuclear plant, where work began in February 2025. It plans a first nuclear demonstration reactor, FJÄLL, to be developed in the US with Oklo, followed by 55 MW commercial SEALER-55 units, which it expects to produce serially in the early 2030s.
- Sector
- Fission
- Technology
- Lead fast reactor
- Fuel
- High-assay low-enriched uranium
- Role
- Reactor developer
Terms
- Lead fast reactor
- Molten lead or lead-bismuth coolant, fast and unmoderated. Does not burn in air or react violently with water, unlike sodium, at the cost of weight and corrosion engineering. Fuel is typically nitride or mixed-oxide.
- High-assay low-enriched uranium
- High-assay low-enriched uranium: uranium enriched to between 5% and just under 20% uranium-235, as the US Department of Energy defines it. It is still formally low-enriched, because the international line for highly enriched uranium is 20%, which is why many designs specify 19.75%. The binding supply constraint for many advanced reactor designs. The 5 to 10% part, which carries lighter US physical-security requirements than material from 10% up, is also tagged as LEU+. A developer calling fuel in that band 'LEU' is making a labelling choice, not describing a different enrichment.
Designs
| Design | Developer | Approach | Electrical output per unit | Size class | Licensing stage |
|---|---|---|---|---|---|
| SEALER-55 SEALER | Blykalla | Lead fast reactor | 55 MWe planned | Small modular reactor | No milestone recorded |