International review of Finnish nuclear power plant concept completed

The Finnish Radiation and Nuclear Safety Authority (STUK) coordinated the Joint Early Review (JER) of the Finnish Steady Energy's LDR-50 nuclear power plant concept by the nuclear safety authorities of four countries. The review was a voluntary cooperation process in which each authority independently assessed the plant concept based on its national requirements. The review is not part of the licensing procedure and does not produce binding decisions or a joint position on the plant concept. 

Launched in October 2025, the review involved radiation authorities from Ukraine (SNRIU), Poland (PAA), Sweden (SSM) and the Czech Republic (SÚJB). The review made use of the early assessment of the plant concept completed by STUK in the summer of 2025. 

Leveraging previous assessment by the authorities is possible but not straightforward 

The key objective of the review was to support nuclear facility design at an early stage and to provide non-binding feedback to support the facility design process. At the same time, it was tested in practice how the safety review of new nuclear power plant concept (Small Modular Reactors, SMR) carried out by an authority of one country can be leveraged in independent reviews carried out by other countries. 

National reviews by the authorities may support early safety reviews in other countries, serve as useful reference material for others and help identify key needs for further examination in new plant concepts. At the same time, it is also a demanding and time-consuming process. 

“The work showed that leveraging a national safety assessment in other countries is not straightforward but requires significant preparations and clear approaches. Making leverage possible must be taken into consideration already at the point of preparing the national assessment,” says Teemu Soukki, inspector responsible for the project at the Radiation and Nuclear Safety Authority. 

Based on the experiences, the successful leverage of a completed assessment requires front-loaded planning, clear reporting practices and good traceability to the assessment findings and justifications. 

Results of the review of the LDR-50 nuclear power plant concept

The international review was based on the materials provided by Steady Energy on the LDR-50 in 2025 and the preliminary assessment completed by STUK in June 2025 on the basis of the materials. Based on the international experiences obtained now, it can be noted that the conclusions drawn by the authorities in different countries were broadly in line with each other. 

Several strengths were identified in the safety solutions of the LDR-50 nuclear power plant concept, such as a defence-in-depth safety approach (several successive safety levels that secure each other) and the utilisation of passive safety solutions. In the early planning phase, the concept was considered largely appropriate, but not yet sufficient from a licensing perspective. 

None of the authorities involved in the Joint Early Review identified any fundamental obstacles in the areas examined that would prevent the further development of the concept. At the same time, the reviews emphasised that the actual licensing phases require significantly more detailed analyses, justifications and more detailed planning, for example in connection with safety analyses, handling of emergencies and plant-level impacts. 

The summary report of the Joint Early Review is available on the website of the Radiation and Nuclear Safety Authority. 

Previous press releases on the topic:

• STUK practices nuclear power plant safety assessment based on proposed model for new nuclear energy law (includes a link to STUK’s assessment of the conceptual design of the LDR-50 reactor)
• Authorities from five countries assess the safety of a Finnish nuclear power plant concept