The VTT Technical Research Centre in Finland announced that it has started the development of a small modular reactor (SMR) for district heating in Finland.

The first phase, to be carried out this year, involves developing a concept-level plan for a nuclear heating plant suitable for the heating networks of Finnish cities.

This will be followed by a longer phase, including more engineering work, then commercialisation of a small modular reactor for district heating.

The project aims to create a new domestic industry around SMR technology.

Licensing system for SMRs in Finland

Petteri Tiippana, director general of the Radiation and Nuclear Safety Authority (STUK), said that traditional nuclear power companies Fortum and TVO, municipal energy companies and, to some extent, the process industry are all interested in small-scale nuclear plants.

He added that there is also a lot of international interest with Russia already operating  the floating Akademik Lomonosov nuclear power plant. China is also developing small-scale nuclear plants. One small reactor (the NuScale SMR) is currently being licensed in the USA, while in Canada, several small reactors are being officially investigated, he noted.

In the autumn, the Ministry of Employment and the Economy set up a working group to review legislation on nuclear power plants. Currently, permits must be obtained for each power plant separately.

“We have the opportunity to change practices in the licensing system," said Liisa Heikinheimo, chair of the working group from the Ministry of Employment and the Economy.

“There seems to be quite a lot of interest on the heating because of the need for energy companies to consider alternatives to fossil fuels. The amount of interest has been surprising, but commercially available approved reactors are not yet available,” said Heikinheimo.

Tiippana believes licensing of small reactors requires regulatory flexibility.

“The starting point is that when applying for permission to build and operate a single reactor, it must also be taken into account that there will be several similar reactors,” he said.

The licensing of small reactor modules individually is not appropriate. Rather, the solution is to license the reactor type which would then be approved for use in Finland.

"The power company could choose how many reactors the company wants to build," said Tiippana.  The reactors could also be located in a decentralised manner. For example, Helsinki has thermal power plants all around the city.

Tiippana emphasised that the safety of small reactors must be at least as good as that of current large reactors. He noted that plant suppliers insist that small reactors are by definition safer than large reactors. "This may be the case, but we have not looked at the different technologies in depth," he said. However, he added that, when properly applied, passive safety factors can be better utilised than in large power plants.

At the end of January, STUK published a report on the preconditions for safe operation of small reactors. The report addresses specific issues of safety assessment and licensing. Small plants have the advantage of being more flexible to operate. Large power plants need a maintenance outage once a year when the plant is offline. With an SMR comprising several units, fuel switching can be sequenced so that the plant produces energy even when one reactor is in service, said Tiippana. "Through flexibility and usability, modular construction brings the greatest benefits to the user," he added.

The goal of decarbonising the district heating system

VTT noted that decarbonising the district heating system is a "significant challenge". Most district heating is currently produced by burning coal, natural gas, wood fuels and peat, but Finland aims to phase out its use of coal in energy production by 2029.

In 2019, emissions from district heating production alone in Finland were over four million tonnes of carbon dioxide. In many cities, cleaning up heat production is one of the major climate challenges.

The aim is to create a new industrial sector around the technology in Finland that would be capable of manufacturing most of the components needed for a district heating reactor.

Design of the reactor will require expertise from a wide range of Finnish organisations, VTT said.

"The schedule is challenging, and the low-cost alternatives are few," noted Ville Tulkki, research team leader at VTT. "To reach the target, new innovations and the introduction of new technologies are required. Nuclear district heating could provide major emission reductions."

VTT will use its in-house calculation tools and multidisciplinary competence in modelling and high-fidelity numerical simulation to develop the SMR.

The organisation, which has around 200 researchers working with nuclear energy and related applications, has been involved in various projects examining the opportunities for deployment of SMRs over the past five years.

At the European level, VTT is coordinating the European Licensing of Small Modular Reactors (ELSMOR) project, launched in 2019. It is also leading one of the work packages of the European Research and Innovation project McSAFE, which is developing the next generation calculation tools for the modelling of SMR physics.