Olkiluoto 3

Finland's newest nuclear power plant unit is Teollisuuden Voima Oyj's (TVO) Olkiluoto 3 in Olkiluoto, Eurajoki. The plant has been supplied to TVO by a consortium consisting of AREVA GmbH, AREVA NP SAS and Siemens AG.

The start-up of Olkiluoto 3 is in progress and according to the schedule announced by TVO 29.4.2022, commercial operation starts in September 2022.

The operation of the plant is considered to have started with the loading of nuclear fuel into the reactor. TVO started the loading after receiving permission from STUK in March 2021.

After the loading of fuel was carried out successfully, pre-criticality tests were performed at the plant to test operations and features that cannot be tested before the fuel is loaded but do not require the criticality the reactor.

TVO submitted an application for a criticality permit to STUK on 8 December, which STUK approved by its decision on 16 December. After being made critical, the plant will be operated at low power and a nuclear test operation will be started with low power tests.

Low power tests ensure that the reactor core behaves as anticipated and that the plant and its systems are functioning as planned also when the reactor is working in power operation. After the low power tests, the power of the plant will be increased gradually.

Power tests after low-power tests ensure that the plant functions in different power levels as planned and, if possible, the plant behaviour in case of operating problems is also tested. The regular electricity generation and commercial operation of the plant will start after the nuclear commissioning phase.

The Radiation and Nuclear Safety Authority supervises

The nuclear safety supervision tasks of the Radiation and Nuclear Safety Authority (STUK) and participation in the licensing are described in detail on STUK’s supervision of nuclear safety website. The licensing model has four phases (decision in principle, construction license, operating license and decommissioning).

In addition to these permits, a permit issued by STUK is required before the nuclear fuel is loaded into the reactor and, before the first criticality. TVO also needs permits issued by STUK to perform criticality and low-power tests as well as during power tests at power levels of 5%, 30% and 60%.

STUK's task at all licensing stages and continuous monitoring is to ensure that there are sufficient requirements for the use of nuclear energy and that these requirements are complied with when using nuclear energy.

Phases of the OL3 project

Teollisuuden Voima Oyj initiated investigations concerning the construction of a new plant at the Olkiluoto nuclear power plant area in Eurajoki at the end of the 1990s, and filed an application for a Government decision-in-principle with the Government in November 2000. In February 2001, STUK provided a preliminary safety assessment for the Government decision-in-principle, in which the preliminary plans and designs related to the plant were assessed and the major safety concerns were raised. The Government issued a favourable decision-in-principle in 2002, which was subsequently ratified by Parliament.

At the beginning of 2004, TVO filed an application for a construction license with the Finnish Government, which was granted in February 2005. The construction of the third nuclear power plant unit in Olkiluoto at the western end of the Olkiluoto island, next to the OL1 and OL2 units, was commenced in June of the same year.

In the spring 2016, TVO filed an application for an operating license with the Finnish Government, which was granted in March 2019. The operation of the nuclear power plant begins when the nuclear fuel loading has been started. The launch of the loading requires a separate loading authorisation from STUK, which STUK granted in March 2021. The loading launches the nuclear commissioning phase of the plant during which the operations of the plant will be tested as a whole for the parts that could not be tested before the fuel loading and criticality. After the nuclear commissioning, the commercial operation of the plant begins.