The pilot facility will feature a full-scale model of Steady Energy’s LDR-50 reactor module, a 50 MW pressurized light water reactor designed to operate at approximately 150°C and below 10 bar (145 psi). The LDR-50, developed by Steady Energy after spinning out from the VTT Technical Research Centre of Finland in 2023, uses a dual pressure vessel system with water-filled intermediate space for passive heat transfer, eliminating reliance on mechanical parts or electricity. A patent for this design was granted in 2021.
The pilot plant will not use nuclear fuel; instead, electrical resistance elements will heat water in the reactor loop, simulating about one-tenth of the LDR-50’s power output. Housed entirely within the turbine hall, the facility will not alter the building’s external appearance. Steady Energy’s CEO, Tommi Nyman, stated: “We minimise cost and time risks by testing the plant thoroughly before selling it. Private investors see this approach as a major reason to trust us.”
Antti Teräsvirta, project manager for the pilot facility, said: “The primary objective of the pilot facility is to demonstrate that the core passive safety system of the LDR-50 functions effectively at full scale.” This marks the first full-scale physical testing of an SMR module before commercial construction, which will occur underground.
Helen’s CEO, Olli Sirkka, noted: “It’s fantastic that the pilot facility will be situated at Salmisaari, precisely where coal usage recently ceased. As landlords, we can closely follow the facility’s development and, as a bonus, gain about six megawatts of additional emission-free capacity to our grid.” Helen ceased coal-based energy production at Salmisaari earlier this year and launched the first phase of its nuclear program in September 2024, aiming to develop a combined heat and power or district heating plant by the 2030s.
The project supports Helsinki’s transition to sustainable energy, with Helen exploring business models and potential sites in the metropolitan area. The pilot facility will validate the LDR-50’s innovative safety features, paving the way for commercial SMR deployment and contributing to Finland’s clean energy goals.
