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Home  /  PRODUCTION  /  Plant units  /  OL1 and OL2  /  Annual outages and modernizations


The plant units have been developed in a systematic and methodical manner over the decades. TVO utilises the annual outages and specific modernisation projects for systematic modernisation of the OL1 and OL2 plant units. Solutions based on the most advanced technology are introduced throughout the lifespan of the plants in order to improve availability, productivity and safety.

Olkiluoto nuclear power plant is kept in a good condition at all times by means of annual refuelling and maintenance outages carried out in turns at the plant units. The annual outages take place every spring, usually starting with the refuelling outage where uranium fuel is replaced in the reactor and the necessary repair and maintenance activities are carried out, including any preparations required for the maintenance outage of the following year. Refuelling outages usually last about one week.

The annual outage then continues at the other plant unit where various major maintenance activities and modifications are implemented, in addition to refuelling. The normal duration of a maintenance outage is 2-3 weeks. Extensive modernisation and renovation projects have been implemented during maintenance outages at intervals of ca. 5 years.

Annual outages 2019

The annual outage carried out at the OL1 plant unit is a refuelling outage. Refuelling is the most important activity for this outage.

At OL2 plant unit significant works, in addition to refuelling, include the pressure test of primary circuit, renewal of the heat exchanger in the purification system of reactor water, the renewal of the low voltage bushings in the containment and the renewal of the 400 kV switchgear.