The Finnish Radiation & Nuclear Safety Authority (STUK – Säteilyturvakeskus) has completed an assessment of the concept of Steady Energy’s LDR-50 NPP. The concept assessment is a procedure proposed in the reformed Nuclear Energy Act whereby STUK can examine the prerequisites for designing and building a safe NPP, before any application for a construction permit is made. Steady Energy requested the assessment in late 2024.
Using the proposed safety assessment, STUK found that “nuclear and radiation safety, security arrangements, emergency arrangements and nuclear material safeguards solutions are such that they can be designed to meet safety requirements”.
Finland’s Steady Energy is a startup company spun out from the VTT Technical Research Centre of Finland in 2023 to provide engineering services to develop Steady Energy’s LDR-50 SMR. The LDR-50 district heating small modular reactor (SMR) has been under development at VTT since 2020.
The 50 MW LDR-50 is a simplified pressurised light water reactor specifically designed to operate at around 150°C and below 10 bar (145 psi). The reactor module comprises two nested pressure vessels, with their intermediate space partially filled with water. When heat removal through the primary heat exchangers is compromised, water in the intermediate space begins to boil, forming an efficient passive heat transfer route into the reactor pool. The system does not rely on electricity or any mechanical moving parts, which could fail and prevent the cooling function. It was awarded a patent in 2021.
The LDR-50, the size of a standard shipping container, is designed to be built underground for added safety and to free valuable real estate for key urban areas. It is optimised for district heating, industrial steam production, and desalination projects.
STUK said the design of the LDR-50 is so unfinished that it was impossible to make a concept assessment according to the current law. However, STUK used the draft concept assessment planned for the law as the basis for its assessment.
Minna Tuomainen, project manager on the outcome of the assessment, noted that the LDR-50 nuclear and radiation safety, security, emergency arrangements and nuclear safeguards solutions are such that they can be designed to meet safety requirements. The same goes for Steady Energy as an organisation. Although it is not yet a finished NPP supplier, it has the potential to develop into one.
Tuomainen said the assessment of the LDR-50 plant was useful for STUK in many ways. “First of all, we were able to get to know the facility at an early stage, for which we may be applying for a permit in Finland later”. He also found it useful that STUK was able to try out concept assessment in practice and to utilise the experiences in legislative development.
“We hoped for and received invaluable information from the evaluation to support our work. In addition, the assessment reinforces our belief that we are on the right path in terms of both technology and organizational development,” noted Juho Vierimaa, Head of Licensing and Quality at STUK.
“The result of the concept assessment supports our view of the development schedule of the LDR-50 nuclear power plant and confirms our previous view of the implementation schedule of the LDR-50 plants in Finland. We will continue to work closely with STUK,” said Steady Energy CEO Tommi Nyman.
The next step in the regulatory assessment is an international assessment of the facility, in which regulators from different countries work together and utilise the work already done by STUK. In accordance with the recommendation of the assessment, Steady Energy will demonstrate the operation of key safety features in a full-size pilot plant to be built inside the former coal-fired power plant of energy company Helen in Salmisaari, Helsinki. Construction is expected to start in late 2025.
The pilot will serve as a full-scale, operational model of the Finnish-designed SMR unit. Unlike the actual power plant, the pilot unit will use an electric element to produce heat inside the reactor capsule instead of nuclear fuel. The pilot investment is estimated to be around €15–20m ($16–22m).
Steady Energy has already signed agreements for 15 reactors in Finland and in December 2024 signed a contract with Belgian engineering firm Tractebel to provide engineering services to develop the LDR-150.
