OL3 Nuke plant resumes power generation after 74-day outage

The Olkiluoto 3 (OL3) nuclear power plant returned to electricity production on Thursday after first annual service outage, said the owner of the plant Teollisuuden Voima Oyj (TVO) in a press release early Thursday.

The resumption of power generation at the plant, however, delayed by several times due to glitches.

The plant was synchronized to the national grid on Thursday and the plant unit will be technically ready for a power increase.

About 7,500 work phases were carried out during the outage of OL3, the largest nuclear power plant in Europe.

In addition to refuelling, the most important activities carried out at OL3 during the annual outage included preventive maintenance on the protection system, washing of steam generators, generator maintenance, pressure equipment inspections, leak-tightness tests on containment isolation valves, and servicing of pressuriser safety relief valves.

The first EPR plant in Europe also underwent a significant number of different periodic tests and maintenance activities during the service outage.

The annual outage at OL3 took longer than originally planned. The outage was meant to take 37 days, but in the end lasted for about 74 days and 9 hours.

Additional days were required due to the shutdown process and the preparations for refuelling taking longer than expected and as a result of technical problems identified during maintenance activities.

Indications of a risk of foreign material in the fuel elements were also detected during the outage, and the inspections of the elements were therefore significantly more time-consuming than expected.

“The first annual outage at OL3 provided valuable knowledge about the duration of the various maintenance activities. We also gained a significant amount of data and maintenance experience which will benefit us in both the planning and the execution of future service outages. Cooperation with equipment manufacturers was another field where we gained experience,” said Marjo Mustonen, Senior Vice President, Electricity Production.

Olkiluoto 3 is by far the most efficient electricity production plant in Finland. It produces about 14 per cent of all electricity produced in Finland.

Two of the three nuclear power plant units in Olkiluoto have now undergone their annual outage.

In addition to OL3, the refuelling outage at OL2 was also completed on May 9 .

The annual outage of OL1 started on May 12. The duration of the OL1 outage is about 15 days.