Olkiluoto 3

The newest nuclear power plant unit in Finland is Olkiluoto 3, which is located in Olkiluoto, Eurajoki, Finland, owned by Teollisuuden Voima Oyj (TVO).STUK has supervised the project from the design of the plant unit through manufacturing and construction to the start-up and commissioning of the reactor. From the start of commercial operation, the unit will be monitored as part of the supervision of the Olkiluoto nuclear power plant.

Safety oversight of the Olkiluoto 3 project


2020–2023: Nuclear commissioning

2023: The trial phase ends and regular electricity production starts on 16 April 2023. 

Regulatory oversight by STUK

  • 468 person-years
  • More than 100 experts
  • Several thousand factory inspections in around 30 countries
  • More than 10 000 on-site inspections
  • More than 20 000 applications

2021: STUK concludes that OL3 meets its safety requirements and that the safety and emergency arrangements of the plant unit are sufficient for fuel loading. STUK grants a loading licence for the new unit on 26 March 2021 and a licence for the start-up of the reactor on 16 December 2021. The criticality and low power tests for the commissioning of the reactor start.

2022: STUK supervises the commissioning tests of OL3 and issues permits to increase the reactor power in stages.

2020: TVO toimittaa STUKille OL3:n ydinpolttoaineen latauslupahakemuksen huhtikuussa 2020.

OL3 unit design and construction period


2016–2019: Operating licence

2019: STUK carries out a safety assessment and issue its opinion on the operating licence application in February 2019. The Government grants the operating licence for the plant unit in March 2019.

2016: TVO submits an application for a licence to operate a new nuclear power plant unit in 2016.


2006–2018: Construction period

STUK supervises the construction of the new nuclear power plant unit and the manufacture of components, and carries out safety assessments. For example, in 2014 STUK will supervise the pressure and leakage test of the containment building and in 2015 the automation testing in Germany.


2004–2005: Construction licence

2005: As a result of the examination of the documents submitted by TVO, STUK issues a statement and a safety assessment of the OL3 power plant unit on 21 January 2005. On 17 February 2005, the Government grants a construction licence for the plant.

2004: TVO submits the application for a construction permit in January 2004. TVO submits to STUK the first documents required by Article 35 of the Nuclear Energy Decree. STUK starts to prepare the safety assessment.


2000–2003: Design Design of a nuclear power plant unit

2002: On 17 January 2002, the Government adopts a decision in principle on a new nuclear power plant unit, which is confirmed by Parliament on 24 May 2002.

2001: The then Ministry of Trade and Industry asks STUK for a preliminary safety assessment of the OL3 application for a decision in principle. In February 2001, STUK submits a preliminary safety assessment for the Council of State's decision in principle, evaluating the preliminary plans for the plant and highlighting the major safety issues.

2000: TVO submitted an application to the Government for a decision in principle under the Nuclear Energy Act for the construction of a new nuclear power plant unit in November 2000. The application for a decision in principle includes a description of the safety systems of the plant at the principle level.


STUK's press releases about Olkiluoto 3 can be found on the Finnish website.