Pilot non-nuclear SMR plant to be built in Finnish coal-fired plant

Tuesday, 6 May 2025

Steady Energy and energy firm Helen have signed an agreement to lease the decommissioned Salmisaari B power plant building as a space for Steady Energy's small modular reactor (SMR) pilot plant. The lease runs until 2028. The pilot facility is to be built within the turbine hall of the power plant. 

Construction is scheduled to start in late 2025, with a budget of EUR15-20 million (USD17-23 million), funded by capital investments already raised by Steady Energy.

The pilot plant will serve as a full-scale, operational model of the Finnish-designed LDR-50 reactor design. 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 main purpose is to test operational features and to establish the necessary supply chains with various manufacturers to construct actual plants. It will be used to produce heat for the Helen district heating network with an output of about 6 MW when completed.

Steady Energy - which was spun out in May 2023 from the VTT Technical Research Centre of Finland - said this will be the first instance of physically testing a reactor module at full scale, beyond simulation environments, before actual construction.

"The primary objective of the pilot facility is to demonstrate that the core passive safety system of the LDR-50 functions effectively at full scale," said Antti Teräsvirta, Steady Energy's project manager for the pilot facility.

_{A multiple LDR-50 unit plant (Image: Steady Energy)}

The LDR-50 district heating SMR - with a thermal output of 50 MW - has been under development at VTT since 2020. Designed to operate at around 150°C and below 10 bar (145 psi), Steady Energy says its "operating conditions are less demanding compared with those of traditional reactors, simplifying the technical solutions needed to meet the high safety standards of the nuclear industry". It noted that its reactors are affordable enough for municipal utilities to invest in independently.

The LDR-50 reactor module is made of 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 company said. The system does not rely on electricity or any mechanical moving parts, which could fail and prevent the cooling function.

"When implemented, the pilot plant will be a very concrete step in the advancement of small-scale nuclear power, and it is symbolically great that it is being built in Salmisaari, which has just finished using coal," said Helen CEO Olli Sirkka. "The location of the pilot plant is also suitable to support our nuclear energy programme, as we will be able to examine the development of a small-scale nuclear reactor on our own site, and in addition, utilise the clean energy generated during the pilot operation to heat Helsinki."

Helen ended coal usage in energy production earlier this year with the closure of the Salmisaari coal power plant, reducing Helsinki's carbon emissions by about 30%. The company aims to achieve carbon neutrality by 2030 and entirely combustion-free energy production by 2040.

Helen launched the first phase of its nuclear programme in September last year, the goal of which is to build either a combined heat and power plant or a district heating plant to achieve non-combustion energy production in the 2030s. The programme is currently evaluating business models, mapping potential plant sites in the Helsinki metropolitan area and preparing the selection of a plant supplier, for which Helen has invited suitable suppliers to a competitive bidding process. Helen will publish plant sites identified as suitable based on the research during 2025. It said the selection of the plant supplier will take place at a later date.

Article researched and written by WNN's Warwick Pipe