Press Release 9.6.2011: TVO's most extensive maintenance outage successfully completed
The most extensive annual maintenance outage ever carried out at TVO's nuclear power plant has completed in 8th of June. Revision was completed in the evening when Olkiluoto 2 plant unit was connected to the Finnish national grid.
The plant upgrades executed at Olkiluoto 2 improved further on the technical reliability of plant unit. An enhanced efficiency of the turbine island is about to increase the net electrical output of the plant unit by almost 20 Megawatts. Olkiluoto 1 underwent a similar major maintenance outage last year.
- Olkiluoto 2 plant unit's outage, which took a bit less than 29 days, was the most comprehensive ever carried out at TVO's plant history. The most significant projects completed were replacement of low-pressure turbines, steam extraction lines, generator and its cooling system, I&C for condensate clean up system, inner isolation valves of main steam lines, low voltage switchgears and main seawater pumps, explains Senior Vice President responsible for production, Mr. Mikko Kosonen.
The annual outages of 2011 started on the evening of the May Day, when Olkiluoto 1 was disconnected from the national grid. This year Olkiluoto 1 underwent a short refueling outage, which was completed in nine days. In addition to refueling, some periodic maintenance work as well as inspections and tests were carried out.
The outages were executed by up to fifteen hundred subcontractor employees in addition to TVO's own personnel.
Findings in over pressure protection system
During the routine and planned inspections, some indications and wear were noticed in the safety and relief valves of Olkiluoto 2 plant unit.
Altogether, 12 valves were inspected during the maintenance outage at Olkiluoto 2. Indications of flaws were found after closer inspection. The flaws had not caused inoperability of the valves.
TVO has reported the findings to the Finnish National Radiation and Nuclear Safety Authority, STUK, and proposed further actions to be taken before taking the plant unit in operation. STUK approved TVO's proposal.
TVO has also proposed STUK that the safety classification of the notification would be the lowest level 1 in the international nuclear event scale, INES. STUK has confirmed this classification.
As a consequence of findings at Olkiluoto 2, the corresponding valves at Olkiluoto 1 plant unit will be inspected and replaced if required in June 2011. Valves at Olkiluoto 2 unit will be replaced later in the summer 2011.
For more information:
Senior Vice President, Production, Mr. Mikko Kosonen, tel. +358 (2) 8381 2100.
TVO is a Finnish non-listed public company founded in 1969 to produce electricity for its shareholders at cost price. The Company owns and operates two nuclear power plant units on the west coast of Finland, which together produce slightly more than 16% of all the electricity consumed in Finland. A third nuclear power plant unit is under construction. Additionally, TVO owns 45% of the Meri-Pori coal-fired power plant.