Annual outages ensure operational reliability

3.7.2017

​Annual outages ensure the operational reliability and safety of the nuclear power plants. According to Outage Manager Jukka Wahala, careful planning guarantees the smoothness of the outage project that takes place every spring.
2017_05_15-110.jpgThis year's work started with the refueling outage at Olkiluoto 1 plant unit, which was concluded in early May. Besides refueling, routine maintenance work, repairs and tests were carried out at the plant unit.

As for Olkiluoto 2, the plant unit was disconnected from the national grid on 10 May.

“This time, the scope of the annual outage is greater than usually,” says the Outage Manager Jukka Wahala.

Among the more extensive maintenance and repair work to be carried out at OL2 are the repair of the reactor pressure vessel nozzles, replacement of the six recirculation pumps and their frequency converters, and the renovation of the power supplies and cable penetrations.

In addition, the heat transfer piping of the turbine condenser is renewed at OL2, among other things. The piping is also called tube packages, which condensate the turbine steam back to water. Also the high-pressure preheaters and systems related to residual heat removal are renewed.

Annual outages ensure the operational reliability and safety of the nuclear power plants. Periodic maintenance increases electricity production reliability, because stopping a failed plant would mean a need to acquire replacement energy from other sources.

“The annual outages at Olkiluoto 1 and 2 are planned in a way that on alternating years one plant unit undergoes a refueling outage and the other a more extensive annual outage. Besides routine maintenance work, longer outages include the replacement of equipment and modernising of the plant unit,” Wahala explains.
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Work based on scrupulous planning

The smooth running of annual outages requires careful background planning and skilled workforce. According to Wahala, planning for annual outages is taking place all the time, with the scheduling of each different measure put into a ten year time-frame. The plans set for each component and piece of equipment follow an exact schedule for maintenance and replacement.

“Methodical planning is important in that the plant units remain as good as new and that the outage work progresses as smoothly as possible. The most challenging works are the big renovations and modernisation of equipment."

The routine works during an outage are e.g. valve maintenance, calibration of measuring equipment and pump maintenance.

”Certainly maintenance work takes place also during plant operations but work on a lot of equipment and components can only take place during a maintenance outage,” says Wahala.

Finnish and foreign professionals

Professionals from all over Finland take part in the annual outages. The majority of the subcontractors comes from the Satakunta and Uusimaa regions. In addition, subcontractors come, for example, from Sweden and Germany. Those working in maintenance tasks specialise mainly in mechanical, electrical and I&C installations. Special nuclear power competence is needed, among other things, in maintenance and installation tasks related to the reactor.

“In practice, same professionals carry out the annual outages year after year. Many of the subcontractors working at Olkiluoto are also involved in the annual outages of Fortum’s Loviisa power plant units. Experienced technicians train new professionals for the tasks every year,” says Wahala.

This year, the annual outage slogan is “Recognise risks, avoid damage”.

“We emphasise the significance of safety to all workers participating in the annual outage. New workers undergo a thorough orientation.

Most of the work of the outage manager is done already before the annual outage.

“Well begun is half done. Actually, during the annual outage, my most important task is to take care that the work progresses according to plans and to resolve any possible questions and challenges that may come up during the annual outage,” says Wahala.

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Text: Timo Sillanpää
Photos: Hannu Huovila