The pilot plant will be a full-scale operational model of the Finnish-designed LDR-50 reactor, but instead of using nuclear fuel, it will use an electric element to produce heat within the reactor capsule. Its purpose is to test the reactor’s operational features and establish supply chains for future construction. The pilot facility will produce approximately 6 MW of heat for Helen's district heating network once completed.
Steady Energy, which spun off from the VTT Technical Research Centre of Finland in May 2023, emphasized that this pilot is the first physical test of a reactor module at full scale 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, the project manager for the pilot.
The LDR-50 reactor has been under development since 2020 and is designed for district heating, with a thermal output of 50 MW. It operates at about 150°C and below 10 bar (145 psi), conditions less demanding than traditional reactors. This simplifies the technical solutions required to meet high safety standards. Steady Energy also notes that its reactors are affordable enough for municipal utilities to invest in independently. The reactor module is designed with two nested pressure vessels, with the intermediate space partially filled with water. If heat removal is compromised, the water boils, forming a passive heat transfer route into the reactor pool, without relying on electricity or mechanical moving parts.
Helen, which ended coal usage earlier this year with the closure of the Salmisaari coal plant, aims to reduce Helsinki's carbon emissions by 30%. The company plans to achieve carbon neutrality by 2030 and eliminate combustion-based energy production by 2040. "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," said Helen CEO Olli Sirkka.
Helen launched the first phase of its nuclear programme in September 2024, aiming to build a combined heat and power plant or district heating plant in the 2030s. The company is evaluating business models, mapping potential plant sites, and preparing to select a plant supplier. Helen plans to publish the suitable plant sites by 2025 and choose the plant supplier later.
