The first outage of the 1600 MWe EPR at unit 3 of Finland’s Olkiluoto NPP (OL3) has finally been completed after a series of extensions. Initially the outage was supposed to end on 8 April. Owner operator Teollisuuden Voima Oyj (TVO) said it was anticipated that the service outage after the first operating cycle “would be very laborious”. OL3 is the largest nuclear power plant unit in Europe, and the amount of equipment and components is extremely high. All in all, about 7,500 work phases were carried out during the outage.
“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,” TVO said.
The annual 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.”
Marjo Mustonen, Senior Vice President, Electricity Production, said many valuable lessons were learned during the service outage. “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.”
She added: “Although the pressures were high, this has also proven how well our organization was able to respond to unexpected situations. All planned works were completed, and most importantly, safely. The main objective in every annual outage is its safe execution.”
OL3 produces about 14% of all electricity produced in Finland. Two of the three units in Olkiluoto have now undergone their annual outage. In addition to OL3, the refuelling outage at OL2 was also completed and the annual outage of OL1 has now begun and is expected to take about 15 days.
