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Olkiluoto Nuclear Power Plant Unit 3 project timeline and all you need to know

Olkiluoto Nuclear Power Plant Unit 3 project involves the construction of a third reactor, one of the largest of its kind in the world with the capacity to generate at least 1,600 MW of electricity, at Olkiluoto Nuclear Power Plant, one of Finland’s two nuclear power plants located on Olkiluoto Island, on the shore of the Gulf of Bothnia, in the municipality of Eurajoki.

The plant is owned and operated by Teollisuuden Voima Oyj (TVO) a Finnish nuclear power company owned by a consortium of power and industrial companies, the biggest shareholders being Pohjolan Voima and Fortum. It consists of two boiling water reactors (BWRs), each producing 890 MW of electricity, together comprising 22% of the country’s electricity generation as of 2020.

An overview and construction of Unit 3

The unit whose construction begun back in 2005, is the first EPR (European Pressurized Reactor), the direct descendant of Areva’s N4 and KONVOI reactors, to have gone into construction. It has a total of four steam generators (one for each of the four heat removal loops) making up the primary system.

Steam generators are heat exchangers that receive heat from the nuclear reactor on their primary side and deliver it to the non-nuclear part of the facility on the secondary side. The secondary heat then produces steam to power the turbine that generates electricity.

At the start of construction, the main contractor for the Olkiluoto Nuclear Power Plant Unit 3 project was Areva NP, a joint venture of Areva Nuclear Power Company, a French multinational group specializing in nuclear power and renewable energy whose name was changed to Orano Group, and Siemens AG, a German multinational conglomerate and a focused technology corporation headquartered in Munich.

However, in 2009, Siemens sold its one-third share of Areva NP to Areva, which is now the main contractor and the former (Siemens AG) remained on the project as the subcontractor with the main responsibility for constructing the turbine hall.

Areva Nuclear Power Company later sold its majority stake in Areva NP now known as Framatome, its nuclear reactor and fuel business, to Électricité de France (EDF), a French multinational electric utility company largely owned by the French state.

Olkiluoto Nuclear Power Plant Unit 3 project timeline


The project reached a milestone in June 2010, following the installation of the reactor pressure vessel in the reactor building. This marked the beginning of the installation activities of nuclear components, coinciding with the start-up testing of electromechanical systems.

Also Read: The Hinkley Point C nuclear power plant and all you need to know


By February 2011, the heavy components of the reactor such as steam generators and pressurizers were installed.


In February, Framatome signed a series of service contracts with TVO for the long-term operation of the Olkiluoto 3 EPR. These contracts cover nuclear plant outage and maintenance scopes, including engineering, I&C, and non-destructive testing services over an extended period of time.


In March, TVO was granted a permit by the European country’s Radiation and Nuclear Safety Authority (STUK) to load fuel into the reactor of the Olkiluoto 3 (OL3) EPR.

STUK said that by issuing the permit, it had verified that OL3 meets the safety requirements set for it, and TVO’s security and emergency arrangements and procedures were sufficient for loading nuclear fuel into the reactor.

In May 2021, TVO announced that it had reached a consensus with the Areva−Siemens consortium regarding the terms of the Olkiluoto NPP (OL3) project. Electricity production at the unit was to start in October 2021, when the plant is connected to the national grid and regular electricity production is to start in February 2022.

In June, TVO signed a contract with Hitachi ABB Power Grids to construct one of Europe’s largest battery energy storage systems at the Olkiluoto nuclear power plant. The 90 MWe system will act as a fast-start backup power source to ensure the stability of the country’s energy network in the event of an unplanned shutdown of the Olkiluoto 3 (OL3) EPR unit.

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