Small modular reactors

STUK is preparing for the possibility that there will be desire want to build smaller nuclear power plants with an electricity output of less than 300 megawatts and small nuclear power plants intended solely for heat production in Finland. STUK is familiarising itself with different types of small nuclear power plants and their specific characteristics, and is participating in international cooperation.

1

Safety remains a fundamental prerequisite for the use of nuclear energy

Whatever the type and size of reactor, the safety of people and the environment must be ensured. Small nuclear power plants must also be shown to meet the safety objectives set out in the regulation. However, there may be differences in the suitability and application of the more detailed technical requirements between small nuclear power plants and existing large nuclear power plants.

The management of nuclear waste is part of safe use of nuclear energy. Finland is the first country in the world to build a final disposal facility for spent nuclear fuel. Similar nuclear waste disposal solutions will also work for water-cooled small reactors. No solutions are yet available for the disposal of spent fuel from other types of reactors.

2

Safety must always be assessed on a case-by-case basis

Many small nuclear power plants have safety benefits. Low power means lower reactor-specific residual heat and radioactive material, which is beneficial for safety. Low power makes it easier to use passive systems, such as gravity flow of water instead of pumps. This can reduce the dependence on electricity supply and human and equipment activity. However, safety is affected by many factors and must therefore always be assessed on a case-by-case basis.

3

A small nuclear power plant could potentially be located closer to residential areas than existing power plants

Small nuclear power plants can be located close to residential areas if the safety of the location is justified. For example, in the case of district heating, the plant producing heat must be located relatively close to the population. The safety of the location of the plant must be justified - the plant must not pose a risk to its environment.

4

The current regulation allows for conventional technology small nuclear power plants

In Finland, the nuclear regulations are designed for large nuclear power plants and are not fully adapted to small reactors. Finnish nuclear energy legislation is currently being reformed. The goal is that the new legislation would be better suited also to new types of nuclear reactors and power plants, including small modular reactors. The licensing and oversight of a small modular reactor based on conventional light water technology would not differ significantly from that of existing plants.

A new pre-licencing step would be the conceptual design assessment, in which STUK evaluates whether the design can meet the Finnish safety requirements and is mature enough to proceed to the construction licence phase. As part of the reform of the legislation, STUK is renewing its own regulations. The renewal reduces the level of detail in the requirements and makes them more goal-oriented, which gives room for different solutions.

International cooperation takes place in several forums

The International Atomic Energy Agency's (IAEA) Nuclear Harmonization and Standardization Initiative (NHSI) aims at common safety assessments and allows other authorities to use their own safety assessments to support their own.

The SMR Regulators Forum is a forum for cooperation between interested IAEA member countries to exchange information and experience on the regulatory control of small nuclear power plants among nuclear safety authorities. It also identifies the specificities of the regulatory framework for small nuclear power plants.

STUK also participates in the OECD's Nuclear Energy Agency (NEA) working group on new technologies and in WENRA's Reactor Harmonisation Working Group.

STUK also participates in bilateral and multilateral cooperation with nuclear safety authorities in other countries.

Discussions with designers and other actors in the field of small modular reactors

In 2025, STUK conducted a pre-assessment of CAL-30 reactor concept of the French company Calogena. The assessment was completed in December 2025 and STUK provided Calogena with feedback that it can use in further development of the design. STUK will use the lessons and experiences gained from the pre-assessment conducted in preparing for activities under the revised Nuclear Energy Act and its subordinate regulations, in particular in developing the conceptual design assessment proposed in the new licensing model.
Together with the French and Czech nuclear safety authorities, STUK is assessing selected features of the Nuward reactor developed by the French energy company EDF. The project will provide STUK with an opportunity to reflect on how current nuclear energy legislation applies to small nuclear power plants at a concrete level. The lessons learned will be used to develop nuclear energy legislation.
In 2022, Fortum launched a study on the conditions for building new nuclear power in Finland and Sweden. Fortum and STUK meet regularly to discuss the study.
Rolls-Royce SMR is exploring opportunities for cooperation with Fortum in the field of small nuclear power in Finland and Sweden. As part of this work, Rolls-Royce SMR is in preliminary discussions with STUK on the small reactor it is developing.
LUT University has a Memorandum of Understanding with the US company Ultra Safe Nuclear Corporation to build a small gas-cooled high-temperature reactor in Lappeenranta. STUK is holding preliminary discussions with LUT and USNC on the project.
Steady Energy, which was separated from VTT into its own company, requested a preliminary safety assessment from STUK for the LDR-50 small nuclear power plant it is developing. The assessment was completed in June 2025.

Small modular reactors