Living up to its slogan

The phrase “Thankfully, we have Olkiluoto” highlights our importance. Without the production from Olkiluoto, we would be missing a significant chunk of domestic electricity: a good 30 per cent, and even more than that on windless days. This means that we have a lot on our shoulders these days.

News or not?

The electricity production of our three plant units is generally very steady and reliable. In other words, it is base load power that does not depend on the time of day or the weather. Some may snort at reliability of production being associated with Olkiluoto. After all, you could get a different impression from the headlines.

This is explained by media logic, and especially by the news value. As a rule, an exception to the prevailing situation becomes news. Something exceptional is good news, while something normal is weak news – if it is news at all.

This rings very true with regard to our plant units. Any changes in our production are quickly reported in the media, even within a few minutes. We are strongly in the “Breaking News” category.
On the other hand, all the normal production days, when electricity is fed into the national grid as planned, are left unmentioned. They are not on the media radar because they lack the deviations to fuel the news logic.

In reality, most of our everyday work consists of these basic days when we generate base load power.

Data on production

Let’s dig a little deeper into the production figures of our plant units for the current year. Since we want to include whole months, we will use the figures accumulated up to the end of October 2024.
And since we want to keep it simple, we have calculated one indicator below: which proportion of the time the plant unit has been producing electricity this year, by the end of October:

OL1 – 87.5%
OL2 – 87.7%
OL3 – 75.3%

Service outages are the main reason why the above figures are not 100%. If those are subtracted, the remaining number of hours is rather minuscule. The service outage times for 2024 look as follows:

OL1 – 38 days
OL2 – 11 days
OL3 – 74 days

Thus, apart from the annual outages, unavailability at our plant units has only amounted to the following:

OL1 – 0 hours
OL2 – 645 hours (27 days)
OL3 – 13 hours

All of these figures are quite impressive, even by international standards. OL1 and OL2, which we have been operating for more than 40 years, have been clocking in factors of around 90 per cent for quite some time. Of course, the OL2 rotor replacement carried out in autumn 2024 took several weeks.

OL3’s first years of regular electricity production, in turn, have been an excellent early performance. It is good to remember that during the first years of operation of OL1, for example, there were over 50 failures that affected production. At OL3, it has been possible to count their number on one hand, and in 2023, the plant was only down for 84 hours due to such failures.

The numbers for 2024 have been even better. By the end of October 2024, OL3 had been out of production for less than 13 hours outside of the annual outage. To use a well-worn expression, we are off to a good start.

Importance of annual outages

Annual outages are key to the plant’s operational reliability and steady production. They are executed to ensure that the plant operates with as few interruptions as possible between the outages.

The necessity of annual outages also stems from the fuel, which needs to be replaced from time to time even at nuclear power plants. This coincides with the annual outages, during which some of the fuel is replaced with new fuel.

The annual outages bring a large number of subcontractors to Olkiluoto. For example, in the summer of 2024, approximately 1,400 subcontractor employees participated in the annual outages in addition to TVO’s in-house personnel. This gives a nice boost to the regional economy, as quite a few of these subcontractors are staying, eating and filling up the tanks of their vehicles either in Eurajoki or the Satakunta area in general. For many local entrepreneurs, this translates to major activity at the cash register.

The service work carried out annually at the plants helps extend their service life. At Olkiluoto, we are now analysing whether the current service life of the OL1 and OL2 plant units, which have been in operation for 45 years, could be extended by 10 or 20 years. This kind of an analysis would certainly not be conducted if we had taken the easy way out when it comes to the annual outages. Not even if it sometimes means extra days for service activities.

The article was originally published in the Uutisia Olkiluodosta (News from Olkiluoto) magazine on 27 November. In November, the OL3 plant unit was out of production for 95 hours due to a malfunction in the seal oil system.


Text: Ville Kulmala
Photo: Tapani Karjanlahti