Espoo’s nuclear reactor is now decommissioned, and the site has been cleaned of radioactivity

The research reactor FiR 1 operated in Otaniemi, Espoo, from 1962 to 2015. The small reactor, acquired for research and educational use, was initially owned by the Helsinki University of Technology and, from 1971 onward by VTT. VTT was also responsible for decommissioning and dismantling the facility. The dismantling of the reactor and the management of nuclear waste were carried out by VTT in cooperation with Fortum between 2023 and 2025.

The Radiation and Nuclear Safety Authority (STUK) supervised the planning and execution of the decommissioning from the beginning. The supervision ended last December when STUK decided to release the research reactor from regulatory control. After the decision, the research reactor is no longer considered a nuclear facility. The dismantled reactor area and premises in Otaniemi do not differ in any way from the surrounding area in terms of radiation safety.

Later this year, inspectors from the European Commission and the International Atomic Energy Agency (IAEA) will verify the situation.

VTT’s old research laboratory was also decommissioned

At the same time as FiR 1 was released from regulatory control, STUK also released VTT’s materials research laboratory, located in the same building, from oversight.

The research laboratory had conducted studies on radioactive materials since the 1970s. The operation and decommissioning of the FiR 1 research reactor were regulated by nuclear energy legislation, whereas the laboratory’s activities were governed by radiation act. The decommissioning of the laboratory was also subject to radiation act and was carried out by VTT alongside the decommissioning of FiR 1.

VTT delivered the radioactive waste generated from the dismantling and decontamination of the laboratory to Fortum for disposal at the repository located at the Loviisa nuclear power plant, just as with the reactor’s waste. Before releasing the laboratory from oversight, STUK confirmed that the premises were free of radioactive contamination.

Lessons and experience for dismantling large nuclear power plants

Kai Hämäläinen, a principal advisor at STUK, notes that because the decommissioning of the Otaniemi nuclear reactor was the first of its kind in Finland, it also provided an important opportunity for the authority to learn and gain experience.

Although the Otaniemi reactor was not a nuclear power plant, the same radiation and nuclear safety factors applied as in larger facilities — only on a much smaller scale. The decommissioned FiR 1 contained, for example, spent nuclear fuel, radioactive internal components, and radioactive concrete structures.

The decommissioning of nuclear power plants is not expected in Finland in the immediate future, but preparations must still be made. Finland is currently reforming its nuclear energy legislation and the complementary STUK regulations.

According to Kai Hämäläinen, the lessons learned from dismantling the Otaniemi research reactor and supervising the process have been valuable in this work. “Until now, the law and regulations have not described the final stages of a nuclear facility’s life cycle and the technical requirements for decommissioning in much detail. The experience gained has now been used in drafting the new law and in writing STUK’s regulations,” Hämäläinen says.