Olkiluoto 1 returns to electricity production upon completion of annual outages

The annual outages have been concluded in Olkiluoto for this year. They ended today, Wednesday 19 June at 14:45 when the Olkiluoto 1 plant unit (OL1) returned to production. The refuelling outage at the Olkiluoto 2 plant unit (OL2) was completed already on 9 May and the service outage at the Olkiluoto 3 plant unit (OL3) on 16 May.

The service outage at OL1 started on 12 May and took 37 days and 21 hours. The duration of the annual outage was extended by a failure detected on the generator’s stator in the comprehensive service inspection. During the outage, a partial fracture was found in one of the terminal busbars of the main generator’s stator. The fracture has now been repaired. There are a total of 12 of these terminal busbars.
 
Apart from this repair, major work activities during the annual outage of OL1 included, for example, the maintenance of the main transformer and the generator switch, the replacement of the control rod drive mechanisms as well as servicing of the feedwater and condensate pumps and two main circulation pumps. Electrical feedthrough modules and reactor automation as well as fans of the emergency ventilation system were also replaced at the plant unit.

According to Plant Manager Nina Paaso, the annual outages went well at both the OL1 and the OL2 plant unit, despite the fact that the schedule had to be adjusted due to the generator fault.

-    Annual outages are carried out for the exact purpose of verifying the safety and operating capability of the plant during the operating cycle. The detection and repair of the fault during this outage is an example of this. Careful planning over a long span of time, unyielding professional skills, commitment and flexibility, as well as seamless cooperation across organisational boundaries are needed every year to ensure that the outage is carried out safely and to a high standard. We accomplished this also this year, Nina Paaso says. 

While for OL1 this year’s outage covered more extensive maintenance work, for OL2 this was the year of a refuelling outage. The two outage types are conducted at the OL1 and OL2 plant units in alternate years. During the first years of operation, Olkiluoto 3 will undergo a service outage every year, but later the plant unit can be operated also in longer operating cycles of 18–24 months. 

In addition to Teollisuuden Voima’s (TVO) own personnel, about a thousand subcontractors took part in the annual outage works of OL1 and OL2. About 150 experts in special fields arrived from abroad for the annual outages of OL1 and OL2. 

The refuelling and service outages carried out at the plant units annually ensure that a good level of production and operability is maintained at the Olkiluoto nuclear power plant at all times. About 30 percent of Finnish electricity is produced at the Olkiluoto nuclear power plant.

Teollisuuden Voima Oyj has produced electricity for its shareholders, Finnish industrial and energy companies, safely and reliably for over 40 years. The island of Olkiluoto produces about 30 percent of Finland's electricity needs. Climate-friendly nuclear electricity not only benefits society but also reduces the environmental impact of energy production. Moreover, the world's first final disposal facility for spent nuclear fuel is under construction in Olkiluoto.