First concrete has been poured for Finland’s first small nuclear heating pilot plant. The pilot facility, developed by the Finnish nuclear technology developer Steady Energy, is being built inside a decommissioned coal-fired power plant in Salmisaari, Helsinki city centre, owned by energy company Helen. Minister of Climate and the Environment Sari Multala attended the ceremony marking the launch of construction of Steady Energy’s pilot facility.
“This pilot project advances Finland’s strategic objective of becoming a clean‑energy superpower. Affordable cost and stable production, together with world‑leading technological expertise, form the foundation of our competitiveness,” said Multala.
“The first concrete is a major milestone for all the professionals involved in developing Steady Energy’s small nuclear heating plant. We are one step closer to the first Finnish small nuclear heating facility,” said Steady Energy CEO Tommi Nyman.
The pilot is a 1:1 full-scale replica of the LDR‑50 small nuclear heating reactor. Instead of a reactor core, the pilot uses an electric resistor that simulates the decay heat which would be produced by the reactor. The main purpose of the pilot is to demonstrate that safety features operate as designed.
During the testing period, the heat generated as a by-product will be supplied to Helen’s district heating network. The reactor module fits entirely inside the turbine hall and will not be visible in the cityscape. The project also prepares future supply chains and paves the way for industrial‑scale deployment.
The LDR‑50 is the size of a shipping container, and it will be constructed underground. Steady Energy has several projects underway in Finland, and new projects are also planned in Poland, Sweden and South Korea.
At the beginning of 2026, Steady Energy and Fortum signed an agreement on exclusive operation and maintenance services in Finland and Sweden, and Fortum invested €2.1m ($2.5m) in Steady Energy as part of its Innovation & Venturing activities, alongside state-owned Finnish Industry Investment among others. The pilot plant has a budget of €20m, while the final nuclear version would cost around €100m per unit, Nyman said.
In 2023, Steady Energy partnered with Helen, which decided to invest in a new small or medium-sized nuclear unit after shutting down Finland’s last coal-powered plant in active production in 2025. “Our plant-supplier tender process currently includes about half a dozen Western plant suppliers, among them reactors that produce heat only as well as those that generate electricity and heat,” Helen Nuclear CEO Pekka Tolonen told Reuters.
