OL3 nuke power plant goes under service outage on March 1

The Olkiluoto 3 plant unit (OL3) will be disconnected from electricity production on March 1 for a service outage, said the owner of the plant Teollisuuden Voima Oyj (TVO) in a press release on Wednesday.

The estimated duration of the outage is 63 days.

This will be the first time the plant unit undergoes a service outage for an operating cycle of 18 months.

The annual outages at Olkiluoto 1 and Olkiluoto 2 are carried out one after the other, starting in May and ending in mid-June.

This time, the service activities at the plant unit are designed in preparation for a longer operating cycle. The next annual outage at OL3 will not take place until in September 2026.

As OL3 is the largest nuclear power plant unit in Europe, the amount of equipment and components to undergo maintenance is high.

The maintenance plan for OL3 includes some 1,700 work activities with about 5,000 work phases.

Apart from refuelling, the most important activities during the annual outage of OL3 include a containment leak-tightness test, work on the reactor pumps, warranty work caried out by the plant supplier as well as steam generator washes and inspections.

In addition to TVO's own personnel, this year about 1,000 employees of subcontractors take part in the annual outage works at OL3, about half of them arriving to Olkiluoto from abroad.

The activities to be implemented during the annual outages of all the Olkiluoto plant units have been planned and scheduled in detail and work is carried out in several shifts, 24 hours a day.

“The annual outages are a major, carefully planned effort which employs a significant number of nuclear professionals. The most important aspect of the annual outages is the high standard and safety of implementation. This contributes for its part to uninterrupted electricity production that is stable but also flexible, if need be,” said Marjo Mustonen, TVO’s Senior Vice President, Electricity Production.

The refuelling outage at Olkiluoto 1 (OL1) will start on 11 May and it takes about 11 days.

The last one of the plant units in turn is Olkiluoto 2 (OL2) which will undergo a service outage starting on 25 May with a duration of about 21 days.

In addition to the refuelling, OL2 will undergo, for example, a containment tightness test, testing during the annual maintenance of the new loading machine, replacement of electrical penetrations in the containment building, and tightness tests of isolation valves.

The annual outages of the Olkiluoto plant units will be completed on 15 June.

At Olkiluoto 1 and Olkiluoto 2, annual outages will also in the future be implemented every year. The Olkiluoto nuclear power plant is the most significant producer of electricity in Finland. Last year, Olkiluoto produced about 28 percent of all electricity consumed in Finland.