Swedish nuclear startup Blykalla has submitted what it claims is the first-ever application to the Swedish government to build a commercial advanced nuclear reactor park in Norrsundet, two hours north of Stockholm. The proposed park is envisioned to consist of six of Blykalla’s lead-cooled SEALER reactors, with a total capacity of approximately 300 MWe. The project is expected to generate 300-400 direct jobs, as well as several thousand indirect employment opportunities in the region.
Blykalla founded in 2013, is a spin-off from the KTH Royal Institute of Technology in Stockholm. Its SMR prototype SEALER (Swedish Advanced Lead-cooled Reactor) design is a fast compact reactor with passive safety. Each reactor will have a 55 MWe capacity, which can be increased by installing multiple units at the same location. The reactor is designed with the smallest possible core that can achieve criticality in a fast spectrum using 19.9% enriched nitride fuel. It broke ground in February 2025 for the construction of an electrical small modular reactor pilot facility near Oskarshamn to test proof of concept of its SEALER technology.
Blykalla chose Norrsundet in the municipality of Gävle as the location for the facility because of its strategic location between two key bidding zones (SE2 and SE3), an existing port, key infrastructure, and industrial heritage. This should reduce construction complexity while addressing regional power shortages with predictable baseload power.
“This application is a historic first for Sweden. We’re not just planning an advanced reactor park – we’re building Sweden’s energy future and putting the country at the forefront of the global nuclear power renaissance,” said Blykalla CEO Jacob Stedman. “Building new energy infrastructure is critical, and the energy systems of the future need to be predictable, reliable and fossil-free. As AI and electrification grow worldwide, we need to accelerate the deployment of predictable, clean baseload power. That’s exactly what Blykalla’s technology does, and we are uniquely positioned to meet this moment.”
According to Sweden’s Ministry of Climate & Enterprise, the government will assess whether the application meets the requirements and whether the proposed activity is justified. It will also consider whether there are conditions for preparedness and for handling nuclear material and nuclear waste.
The government review launches a comprehensive approval process involving multiple agencies, including the Land and Environmental Court and the Swedish Radiation Safety Authority. The government will then produce a facility plan to guide decisions on land and water use. The municipality of Gävle needs to approve both the plan and the application before the government can make a decision.
Blykalla’s application comes about two months after SMR developer Kärnfull Next submitted the first application under Sweden’s new Act on Government Approval of Nuclear Facilities for a proposed SMR campus in the Valdemarsvik Municipality. The act is one of several reforms the Swedish government has adopted to spur new nuclear deployment. Sweden is currently home to six operational power reactors: one at Oskarshamn, two at Ringhals, and three at Forsmark.
In March, Blykalla signed a Joint Development Agreement (JDA) with fabrication technology company ESAB AB The agreement formalises an industrial partnership to develop and industrialise Blykalla’s proprietary Alumina Forming Steels (AFS) for the SEALER. Blykalla is also collaborating with NEEXT, an engineering firm based in Belfort, France, to optimise the performance of the conventional island for SEALER.
Meanwhile, Blykalla has opened an office in New York marking “a decisive step in our mission to bring Swedish lead-cooled reactor technology to the North American market”. Blykalla said the US “currently offers a uniquely favourable policy environment for advanced nuclear innovation”.
In 2025, Blykalla partnered with US nuclear start-up Oklo to collaborate in the areas of materials, components, nonnuclear supply chain sourcing, fuel fabrication, and licensing. Oklo is developing a sodium-cooled fast reactor.
Blykalla has an ambitious timeline, aiming to begin serial production of its commercial SEALER-55 units in the early 2030s. Construction of an electrical (non-nuclear) prototype began in 2024 at Oskarshamn, Sweden, to test the lead-cooled systems. A pilot nuclear plant, SEALER-One, is planned to achieve criticality by 2029. A letter of intent is in place with Studsvik to build this at its Nyköping site.
A key challenge for lead cooling is its tendency to corrode stainless steel. Blykalla uses a patented aluminium-alloyed steel that forms a self-healing protective layer of alumina on its surface, allowing for long-term commercial operation. The reactor uses 19.9% enriched nitride fuel. This fuel has a 40% higher uranium density than standard fuels, enabling it to last for up to 25 years without replacement or refuelling. While technical corrosion hurdles are being overcome with the new alloys, Blykalla’s timeline could be at risk because of the need to obtain regulatory approvals from the Swedish Radiation Safety Authority and the non-availability of high-assay low-enriched uranium (HALEU) fuel, which is the raw material for its planned nitride fuel.
However, nitride fuel needs to use enriched Nitrogen-15, and the only possible supplier is the Aria Project in Sardinia slated for commissioning in 2026. As yet there is no official public contract yet between Blykalla and the Aria project. There is currently no commercial-scale factory for uranium nitride fuel and Blykalla has no such infrastructure.
While Blykalla’s website has details of the overall design, fuel and the safety features for SEALER, there are no details about the fast reactor technology. This is currently only operational in Russia, where the world’s first ever lead-cooled fast reactor is now nearing completion after decades of government supported research and development on a site that already has a nitride fuel manufacturing facility, with a used fuel recycling facility under construction.
