SSTC NRS Assessed Safety of New Finnish Designed District Heating Reactor

Experts from the State Scientific and Technical Center for Nuclear and Radiation Safety (SSTC NRS) together with colleagues from the State Nuclear Regulatory Inspectorate of Ukraine (SNRIU) have completed their work as members of the international expert group that assessed the safety of Steady Energy’s Finnish designed innovative small modular reactor (SMR) LDR-50. Following the Joint Early Review initiated by the Finnish Radiation and Nuclear Safety Authority (STUK) in October 2025, the summary report has been published.

As part of this international project, SSTC NRS as the technical support organization (TSO) to the Ukrainian regulatory body participated in the analysis together with experts from the Czech Republic (SÚJB and SURO), Poland (PAA), and Sweden (SSM). Ukrainian experts conducted an independent analysis of reactor concept for compliance with the national safety criteria and specific requirements of the regulatory framework.

Based on the analysis results, none of the participating international organizations including the Ukrainian party identified any critical safety or technical challenges that would prevent further development and implementation of the LDR-50 concept.

SSTC NRS experts together with their international colleagues identified several strengths of the Finnish project. Particularly, efficient implementation of the defense in depth concept (multiple successive safety levels) and extensive use of the passive safety systems that minimize human factor-related risks.

Despite overall positive assessment of the early design stage, SSTC NRS experts emphasize that a more detailed analysis will be required for future reactor licensing. In particular, the designers will need to provide more comprehensive justifications at the next stages regarding emergency response, plant-level safety analysis, as well as assessment of transboundary or local impacts.

Participation in this project enabled Ukrainian SSTC NRS experts to test approaches for adapting foreign safety reports (particularly, outputs of the Finnish Radiation and Nuclear Safety Authority STUK) to Ukrainian conditions.

Reference on LDR-50 design: the reactor was developed by Steady Energy. It is a 50 MW thermal power SMR operating at a temperature of approximately 150°C. Unlike conventional SMRs, LDR-50 does not generate electricity and is optimized exclusively for district heating, hot water supply, industrial steam, and water desalination. The company plans to commence construction of the first heating plant in 2029. Due to SSTC NRS review, Ukraine already has a clear understanding of safety characteristics of this technology, which may contribute to future modernization and decarbonization of the Ukrainian district heating sector.