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Estimating the population’s exposure

Exposure to radiation among residents of the area around nuclear power plants is assessed annually based on power plants’ discharge data and environmental samples as well as meteorological measurements.

Discharges from nuclear power plants are effectively absorbed into the massive amounts of air and water around them; that is, into the atmosphere and the sea. For this reason, only very tiny amounts of radioactive substances accumulate in the environment around plants. These can only be detected with highly sensitive measurement methods (see the results of environmental radiation monitoring). The amount of substances discharged from the plant during normal use is so small that it is impossible to measure the radiation dose to which the population is exposed. For this reason, radiation doses are determined through analytical estimation.

The radiation exposure of the population is calculated by defining an individual from the “critical group” (a person representing the group of people most exposed), for whom the largest possible radiation doses can be determined based on the individual’s place of residence and lifestyle. It is not a real person. The calculations are made using an imaginary person who lives in the vicinity of the nuclear power plant. This person’s diet consists mainly of natural produce from the area around the power plant, including berries, mushrooms and fish, as well as milk from a nearby farm and local grain and meat products. In addition, the person spends a lot of time on the shores near the nuclear power plant and swims in the sea. The results of the calculations are very conservative—in practice, it is the largest possible radiation dose that a person can be exposed to when living in the vicinity of the nuclear power plant. In reality, people living near nuclear power plants are exposed to much smaller radiation doses.

If plants discharged so much radioactive material that it increased the radiation levels in the vicinity, the situation would be detected immediately by the monitoring networks surrounding the plants. The networks are made up of measuring stations located 1–5 kilometres away, from which information is sent directly to the computers at the plants and can be checked at any time by the Radiation and Nuclear Safety Authority. If the dose rate at a plant increases above the alarm limit of 0.4 microsieverts per hour, the system sends an alert to STUK’s emergency team. In Finland, background radiation varies from 0.05 to 0.30 microsieverts per hour (µSv/h).


The calculated dose of the most exposed individual in the environment at Loviisa has remained below 1 μSv during 2012–2021, ranging between 0,1 and 0,3 μSv.

Radiation dose calculated for an individual from the most exposed (critical) group in the environment around the Loviisa nuclear power plant has remained under 1 percent of the 100 μSv limit set in the Nuclear Energy Decree (161/1988). In 2013, 2017 and 2021 the Loviisa plant discharged low-level evaporation waste, as planned, into the sea. For this reason, the doses of the critical group are slightly higher compared to the other years.


The calculated dose of the most exposed individual in the environment at Olkiluoto has remained clearly less than 1% of the 100 μSv limit set in the Nuclear Energy Decree (161/1988), ranging mainly between 0,2 to 0,4 μSv. In 2016, the annual dose was the highest (0.51 microsieverts).

Radiation dose calculated for an individual from the most exposed (critical) group in the environment around the Olkiluoto nuclear power plant. Despite the fuel leakages during the years 2016-2019, the radiation doses from Olkiluoto were still very low, less than 1% of the 100 μSv limit set in the Nuclear Energy Decree (161/1988).


Radiation dose calculated for an individual from the most exposed (critical) group in the environment around both the Loviisa and Olkiluoto have been significantly higher in the 70’s and 80’s. During the years 1979-1990 in Olkiluoto the dose has varied between 0,5-2,7 mikrosieverts when the variation has been between 0,2 – 0,5 mikrosieverts during the years 1991- 2021. During the years 1978-1992 in Loviisa the dose has varied between 0,8-2,7 mikrosieverts. During the years 1993-2021 the variation has been between 0,1 – 0,5 mikrosieverts, excluding the year 1998, when the dose was about 1 microsievert.

Radiation dose calculated for an individual from the most exposed (critical) group in the environment around both the Loviisa and Olkiluoto nuclear power plants since the start of operation. Due to several significant discharge restrictions, both sites have been able to significantly reduce the radiation dose calculated for an individual from the most exposed (critical) group in the environment.

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