Fish monitoring analysis completed for the cooling water used at Olkiluoto
Monitoring of fish in the cooling water was performed at Olkiluoto in 2023 and early 2024. The aim of the monitoring was to prepare an analysis of the types and number of fish that are being carried into the power plant with the cooling water. Drawing up a new analysis became necessary, since there are now three operating plant units instead of the previous two.
The conditions of the water permit granted for the power plant require that TVO perform fish stock analyses. It is a commitment to analysing the fish and fingerlings that are carried to the power plant with cooling water. A similar study was last conducted in 2010. The present analysis is more detailed than the previous one.
- The inclusion of fingerlings of less than 1 centimetre in length was a new addition to the study, and we tried to catch them in the inlet water channels of the plant units. No fingerlings were caught, however, says TVO’s fishery researcher Ilkka Tammela.
Fish samples were taken from the flushing channels of sea water plants at all three plant units. The flushing channels collect all the so-called screenings that are carried in by the cooling water. In addition to algae, mussels and fish, screenings comprise water fauna and polyps.
Electricity generation at Olkiluoto does not significantly affect fishery in the area
For the analysis, a total of 26 samples were obtained of screenings and fish for each plant unit. According to the analysis, the total number of fish carried into the plant units at Olkiluoto during the monitoring period, which lasted slightly more than one year, was approximately 27.6 million (an estimated 42.4 tonnes in total weight).
Nowadays, more fish is being carried into the plant units with the cooling water as the cooling water flow of the plant units has been increased since the previous fish monitoring study and the Olkiluoto 3 plant unit has been commissioned.
- The number of individual fish is massive, of course, but it does consist of very small specimens. Based on the results from the monitoring, 95% of the fish carried in by the cooling water weighed less than or equal to 3 grams. Approximately 87% of the fish were economically non-significant fish species, Mr Tammela explains.
The three most common species of fish at the Olkiluoto 1 plant unit were the three-spined stickleback, nine-spined stickleback and gobies of the genus Pomatoschistus. At Olkiluoto 2, they were the three-spined stickleback, nine-spined stickleback and smelt and herring fingerlings, while at Olkiluoto 3 the most common species were the three-spined stickleback, herring and nine-spined stickleback.
A new invasive species in the Baltic Sea, the moss animal Conopeum chesapeakensis, was also discovered in the screenings during the monitoring, as we reported in early 2024: TVO - Environmental monitoring at Olkiluoto once again demonstrated its efficiency. Indeed, the island of Olkiluoto is one the most researched areas in Finland, and its diverse nature has been charted in detail. Environmental research has been conducted on the island since the 1970s, years before electricity production was launched.
The screenings that gather at the plant units are collected and delivered for appropriate processing at the composting plant. Removing the screenings also eliminates nutrients from the water, which reduces eutrophication.
The results of the study have been presented to the Centre for Economic Development, Transport and the Environment. TVO is also performing test fishing, age and growth determinations for fish, fishing for record-keeping purposes and surveys among professional and recreational fishermen in the waters near Olkiluoto.
Teollisuuden Voima Oyj has produced electricity for its shareholders, Finnish industrial and energy companies, safely and reliably for over 40 years. The island of Olkiluoto produces about 30 percent of Finland's electricity needs. Climate-friendly nuclear electricity not only benefits society but also reduces the environmental impact of energy production. Moreover, the world's first final disposal facility for spent nuclear fuel is under construction in Olkiluoto.
