The discharges of gaseous radioactive substances produced at the power plant are cleaned by filtering and slowing down their release before they can enter the environment around the nuclear power plant.

The aim is to keep the discharges as low as possible through practical measures. Gaseous radioactive substances are discharged via the plant’s tall ventilation chimney into the air.

Before the discharge, the level of radioactive substances is measured using a radiation meter. Samples of discharged air are also collected continuously for more precise analyses. Using precise measurement methods, nuclear power plant companies determine the composition and activity levels of the radioactive substances obtained from the air samples. Nuclear power plant companies report discharge data to the Radiation and Nuclear Safety Authority on a quarterly basis. The Radiation and Nuclear Safety Authority inspects the discharge reports received.

Methods of measurement of nuclear power plant discharges have been approved by the Radiation and Nuclear Safety Authority. The Radiation and Nuclear Safety Authority regularly inspects the power plants’ discharge systems.

In the analysis of the substances discharged into the air from nuclear power plants in Finland, an aver-age of ten to twenty different radioactive substances are detected each year. The most common nu-clides discharged into the air were tritium, carbon-14, argon-41, chromium-51, manganese-54, cobalt-58 and -60, silver-110m, antimony-122 and -124, iodine-131 and cesium-137. Argon-41 is a nuclide that is found in significant amounts only in the discharges from the Loviisa power plant. Other radio-nuclides detected at nuclear power plants in Finland include: iron-59, arsenic-76, bromine-82, different isotopes of krypton (-85m, -87 and -88), niobium-95, tellurium-123m, different isotopes of iodine (-132, -133 and -135), cesium-134 and different isotopes of xenon (-133, -133m, -135, -135m and -138).

The discharge data are used to evaluate the radiation exposure of residents around the nuclear power plant (the dose of the “most exposed person” in the environment). The amount of discharges has a direct impact on the radiation doses of the most exposed person in the environment.

No significant changes have been observed in the discharges of radioactive inert gases (Kr-87 equiv.) at the Loviisa power plant during the selected period. The prevailing substance in the discharges was argon-41, which is generated from the argon-40 in the air between the reactor pressure vessel and the main radiation protector.

There was variation in the iodine isotopes (I-131 equiv.) discharged into the air from the Loviisa power plant during the selected period. Small fuel leak in the power plant unit affected the levels of iodine discharges in 2013.

No significant changes have been observed in the discharges of radioactive aerosol particles during the selected period. The levels of aerosol discharges were higher than normal in 2013, due to the release of short-lived As-76 (arsenic) from both plant units during the additional shutdowns at the end of that year.

Variation was observed in the discharges of radioactive inert gases (Kr-87 equiv.) from the Olkiluoto power plant during the selected period. In 2014 and 2015 radioactive inert gases were below the detection limit. Small fuel leaks in the power plant units affected the levels of inert gas discharges between 2016 and 2019. The levels have been clearly under the annual release limits.

There was variation in the iodine I-131 isotope discharged into the air from the Olkiluoto power plant during the selected period. Small fuel leaks in the power plant units affected the levels of discharges between 2016 and 2019. The levels have been clearly under the annual release limits.

In the bar chart of the aerosol releases, the magnitude of the bars for the years 2011-2015 is 1.00E+7 Bq, for 2016 the magnitude of the bar is 1.00E+11 Bq, for 2017 1.00E+10 Bq and between the years 2018-2020 the releases have varied around the magnitude of 1.00E +8 Bq.