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 of Loviisa NPPRadiation dose calculated for an individual from the most exposed (critical) group in the environment around the Loviisa nuclear power plant. In 2013, the radiation dose was approximately 0.07 microsieverts, or less than 0.1 percent of the 100 μSv limit set in the Nuclear Energy Decree (161/1988). The average radiation dose to which people in Finland are exposed each year is around 3200 microsieverts (µSv) (3.2 millisieverts). In 2009 and 2013, the Loviisa plant discharged low-level evaporation waste, as planned, into the sea. For this reasons, the doses of the critical group were higher than in previous years.

The calculated dose of the most exposed individual in the environment of Olkiluoto NPPRadiation dose calculated for an individual from the most exposed (critical) group in the environment around the Olkiluoto nuclear power plant. In 2016, the radiation dose in the vicinity of Olkiluoto was the highest since 1997 due to the fuel leaks, among other issues. The radiation doses from Olkiluoto were still very low or less than 1% of the 100 μSv limit set in the Nuclear Energy Decree (161/1988).

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  • Sovijärvi Jukka
    Section Head / SÄT tel. +358975988519