Annual outages completed at Olkiluoto nuclear power plant

18.7.2017

The annual outages of 2017 at the Olkiluoto nuclear power plant were completed on Friday 14 July at 08:06, when the Olkiluoto 2 plant unit was restored to electricity production.

The full power level will be achieved at OL2 by the end of the week. The annual outage carried out at OL2 this year was the longest ever in the history of the plant unit. The total duration of the outage was 64 days, 14 hours and 8 minutes. OL1 was this year up for a short fuel replacement outage that took ten days. The annual outages started on 23 April.

Major works during the annual outage started at OL2 on 10 May included replacement of the reactor recirculation pumps and their frequency converters, renewal of the neutron flux calibration system as well as modernisation of the heating system that contributes to residual heat removal. The turbine condenser was also renewed. Some repair work was carried out in the reactor pressure vessel, as well. The pipe nozzles of the pressure vessel were repaired using a method never before used in Finland.

TVO started the planned repair of the pipe nozzles during the annual outages of 2017 by repairing the cracks found on the nozzles of OL2. The repair was implemented by machining the weld on the inside of the nozzle and welding a new deposit coating using a weld metal less susceptible to stress corrosion.

All in all, the duration of the annual outages took 24 days longer than expected. The complex welding works on the pipe nozzles were the cause for the delay. In all other respects the annual outages were carried out according to plans. This year a total of up to 1 100 contractor employees took part in the outage works in addition to TVO's own personnel.

- Over the years, our annual outages have always been executed successfully. We especially emphasise the highlighting of safety issues. This year the annual outages included some exceptionally complex works, but once again, we succeeded, owing to our good attitude. Thanks for this are primarily due to our professional and committed employees, says Mikko Kosonen, Senior Vice President, Electricity Production.

The Olkiluoto nuclear power plant has been modernised over the years in extensive modernisation projects as well as the refuelling and maintenance outages carried out at the plant units on alternating years. The OL1 and OL2 plant units play an important part in the base load production and implementation of the national energy and climate strategy in Finland. The plant units have been producing electricity for almost 40 years. Today, the electricity produced at the plant units accounts for about 17 percent of the Finnish electricity consumption and about 22 percent of the electricity produced in Finland.

For more information, please contact:
Mikko Kosonen, Senior Vice President, Electricity Production, tel. +358 2 8381 2100

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