Olkiluoto Nuclear Power Plant Unit 3, Finland

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Olkiluoto Nuclear Power Plant’s Unit 3 in Finland has started producing electricity. This is according to Finnish plant operator Teollisuuden Voima Oyj (TVO).

The regular output comes more than a year after the plants’ test phase began. The test production phase according to TVO comprised 3,300 tests with more than 9,000 test reports collated.

Olkiluoto Nuclear Power Plant, which is Europe’s largest nuclear power plant, will boost Finland’s energy security. This will be achieved by increasing domestic production and will operate for the next 60 years.

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According to TVO president and CEO Jarmo Tanhua, the production of Olkiluoto 3 stabilizes the price of electricity. In addition, he said it plays an important role in the Finnish green transition.

The project team and contractual end

The Olkiluoto Nuclear Power Plant’s Unit 3 project resulted in the employment of people from more than 80 different nations. Its highest manpower on the site was 4,500.

The projects supplier consortium consists of AREVA GmbH, AREVA NP SAS, and Siemens AG. The contractual end of the Olkiluoto Nuclear Power Plant’s Unit 3 project will occur once the analyses from the latest test production phase are completed.

Project Background

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.

The unit whose construction began 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.

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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.

December 2021

TVO applied to Finland’s Radiation and Nuclear Safety Authority (STUK) for permission to bring the Olkiluoto 3 (OL3) EPR to first criticality and conduct low-power tests. The Finnish nuclear power company said that the OL3 EPR project has progressed faster than previously communicated and that the facility’s commercial operation may be brought forward from the previously announced date of January 2022.

Mid-December 2021

TVO received permission from Finnish Radiation and Nuclear Safety Authority (STUK) to bring the Olkiluoto 3 (OL3) EPR to first criticality and conduct low-power tests.

The unit is expected to begin generating electricity at the end of January 2022, with regular electricity production starting in June of that same year.

March 2022

Finland’s Olkiluoto 3 nuclear reactor linked to the national power grid

Finland’s Olkiluoto 3 nuclear reactor has been linked to the power grid for the first time 12 years late and on a significantly inflated budget. The 1.6-gigawatt (GW) reactor, which was developed by the French-led Areva-Siemens partnership, was supposed to start up in 2009.

It being the first nuclear power plant built in Europe after the 1986 Chernobyl tragedy, Olkiluoto-3 was supposed to be a showpiece of French-German expertise, with more power and improved safety thanks to the third-generation European Pressurized Reactor (EPR) type technology.

However, the project was beset by technical issues and cost overruns. The frequent delays resulted in a bitter compensation dispute between the Finnish operator TVO and Areva, with the latter eventually agreeing to pay TVO slightly over US$ 493M in March 2018. According to the 2019 World Nuclear Industry Report, its cost increased from an early estimate of Us$ 3.27bn to close to US$ 12.1bn.

A new awakening 

With its commissioning, Olkiluoto 3, located on Finland’s west coast,  becomes the country’s first new nuclear reactor in more than four decades, and Europe’s first in nearly 15 years. It will eventually be the most powerful reactor in Europe since it will be built alongside two existing reactors.

According to TVO, after normal energy production begins in July, the reactor will provide around 14% of Finland’s electricity at a capacity of 1,650 megawatts, and lower prices by reducing the demand for electricity imports from Russia, Sweden, and Norway.

“OL3 considerably increases Finland’s electrical self-sufficiency and aids in the achievement of carbon neutrality targets,” according to the operator. Finland’s net electricity imports have averaged 13 terawatt-hours (TWh) in recent years, but with Olkiluoto-3 in service, that number should reduce to about half by 2025.

Nov 2022

Commercial start of Olkiluoto 3 nuclear reactor postponed to late Jan ’23

TVO, a Finnish nuclear operator has postponed yet again the planned commercial start of its 1.6 GW Olkiluoto 3 nuclear reactor to late January. The facility was initially expected to start commercial operations in July.  This date was pushed to December and now to January next year.

The recent push is reportedly due to cracks found in the feedwater pumps at Olkiluoto 3’s turbine island. It will allow plant supplier Areva-Siemens to carry out an investigation and analysis of the reasons behind the damaged feedwater pumps.

According to the Finnish utility, the potential restart dates are highly uncertain. While the investigations of the damage will continue for several weeks, potentially lasting until the end of the year, the repairs could take several months especially if the parts need to be manufactured separately.

Test production is to continue on 11 December

The third-generation European pressurized reactor (EPR), started test production in March, almost 13 years behind schedule. This was after the facility was linked to the national power grid.

However, 7 months later, in October the facility went offline due to the feedwater pump issues. According to TVO, the test production could continue on 11 December at the earliest.