The Olkiluoto 3 plant unit has been granted permission for startup


The Radiation and Nuclear Safety Authority in Finland (STUK) has today on December 16, 2021 granted Teollisuuden Voima Oyj (TVO) the permission for making the reactor critical and conducting low power tests. The nuclear reaction in the OL3 EPR plant unit’s reactor will be initiated for the first time during December 2021. Electricity production will start at the end of January 2022 and regular electricity production in June 2022.

According to STUK, the commissioning tests conducted at the plant unit demonstrate that the unit works as planned, and the preconditions for its startup and conducting low power tests are fulfilled. STUK will verify the preparedness for startup at the plant unit before the reactor is made critical.

TVO can now proceed to first criticality, after which the reactor’s power will be gradually increased. TVO still needs permissions from STUK for proceeding forward from power levels at 5%, 30%, and 60% during power tests. Electricity production starts at a 30% power level.

– We are now moving step by step with a safety first attitude towards the moment we have waited for a long time. The preconditions for the startup of the reactor have been fulfilled, and soon we will be able to realize our promises on Finland’s greatest act for the climate, says Senior Vice President for Electricity Production, Marjo Mustonen.

OL3 EPR’s electricity production starts at the end of January 2022, which is a about a month earlier than previously communicated. The plant unit will produce electricity with varying power output during the test production phase. Regular electricity production starts in June 2022.

Output during the test production phase is communicated on TVO’s website at More detailed information about Olkiluoto 3 power output during test production phase will be published at latest 22.12.2021. A market message on any significant changes is released in NordPool.

The OL3 EPR plant supplier consortium is constructing the plant unit under a fixed-price turnkey contract. The supplier consortium companies, AREVA GmbH, AREVA NP SAS, and Siemens AG, have joint and several liability for the contractual obligations until the end of the guarantee period of the plant unit.

For further information and interview requests, please contact:

Johanna Aho, Head of Communications, Tel. +358 (0)40 729 0822