Voluntary collaboration involved five European nuclear safety authorities
The Finnish Radiation and Nuclear Safety Authority (Stuk) has published a summary report of an international joint early review of Steady Energy’s LDR-50 small modular reactor (SMR) design
The review concludes that no fundamental issues were identified that would prevent the reactor concept from being further developed and deployed.
The review was a voluntary collaboration involving five nuclear safety authorities: Stuk, the Swedish Radiation Safety Authority (SSM), Poland’s National Atomic Energy Agency (PAA), the Czech State Office for Nuclear Safety (SÚJB) and Ukraine’s State Nuclear Regulatory Inspectorate (SNRIU).
Each independently assessed the LDR-50 reactor concept against their respective national regulatory frameworks.
Steady Energy said the review was not part of a formal licensing process and does not constitute regulatory approval or a licensing decision in any of the participating countries.
The assessment was based on LDR-50 design documentation first made available in early 2025 together with STUK’s early-stage concept assessment completed in the summer of 2025.
Steady Energy said that since then, the design has continued to mature significantly.
It said: “As expected for a concept at this stage of development, the review concluded that the available documentation was not yet sufficiently detailed to support the launch of a formal licensing process.
“At the same time, all participating regulators reached broadly consistent conclusions: none identified any fundamental nuclear safety issues that would prevent the concept from progressing to the next stages of development.”
PIlot Under Consruction In Helsinki
The LDR-50, the size of a shipping container, can be built underground in cities, and is designed to be particularly well suited to district heating.
A pilot version of the reactor is being built in the Finnish capital Helsinki, inside a decommissioned coal plant.
District heating, also known as a heat network, is a centralised system that generates heat in one location and distributes it – via a network of insulated underground pipes – to multiple residential, commercial, or public buildings for space heating and hot water. It acts like “central heating for cities”, eliminating the need for individual boilers in every home.
According to Finnish utility and nuclear operator Fortum, district heating is the most common heating method in Finland, providing heat to about 45% of residential, commercial, and public buildings.
