Maintenance works to suspend production at OL3 nuke plant

The Olkiluoto 3 plant unit (OL3) will be disconnected from electricity production on Saturday for a service outage, said the owner of the plant Teollisuuden Voima Oyj (TVO) in a press release on Friday.

The estimated duration of the outage is about 37 days. It will be the first annual outage at the new plant unit. Production at full power output started at OL3 in March 2023.

The long duration is explained by the technical characteristics of the plant type and the large number of periodic tests and maintenance activities to be carried out during the service outage.

As OL3 is the largest nuclear power plant unit in Europe, there is a considerable number of components and equipment that need to be serviced.

The plan for the OL3 service outage includes some 1,900 different work activities with almost 6,500 work phases.

In comparison, the work list for the annual outage of OL2 shows about 550 activities with a total of 1,200 work phases.

At OL3, the most important activities apart from refuelling include preventive maintenance on the protection system, software upgrades in the I&C systems, leak-tightness tests on the containment isolation valves, and the maintenance of the pressuriser safety relief valves.

Work is carried out during the service outage in compliance with a precise schedule and around the clock in several shifts.

“Annual outages are large-scale, meticulously planned processes at nuclear power plant units, and the safe execution of the outages to a hight standard requires professional expertise from both TVO’s own employees and subcontractors and the plant supplier,” said Marjo Mustonen, Senior Vice President, Electricity Production, for TVO.

In addition to TVO's own personnel, this year about 1,400 employees of subcontractors take part in the annual outage works. The majority are Finnish, but a total of 550 experts in special fields arrive also from abroad, especially for the service outage of OL3.

The Olkiluoto nuclear power plant is the most significant producer of electricity in Finland. Last year, about 31 per cent of all of Finland’s electricity was produced in Olkiluoto.

OL3, which is the first unit to undergo the service outage, covers about 14 per cent of the demand for electricity in Finland.

At Olkiluoto 2 (OL2), a refuelling outage will start on 28 April and last for about 11 days. The last one of the plant units is Olkiluoto 1 (OL1) where a service outage with a duration of about 16 days will start on 12 May. All annual outages are expected to be completed by 28 May.