Discharge of radioactive substances into the sea

The liquid 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. Liquid radioactive substances are discharged along with the plant’s cooling water into the sea.

A sample is taken from every batch of liquid discharged from the power plant before it is released into the sea. The samples are used to analyse the radioactive composition and activity of the discharges. In addition, the activity of the discharges is measured through continuous radioactivity measurements. The methods used to measure nuclear power plant discharges are highly accurate. 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 sea from nuclear power plants in Finland, an av-erage of ten to twenty different radioactive substances are detected each year. The most common nuclides discharged into the sea were tritium, chromium-51, manganese-54, cobalt-58 and -60, niobium-95, zirconium-95, silver-110m, antimony-122 and -124, iodine-131 and -133 and cesium-134. The following radionuclides have also been detected in the discharges: sodium-24, potassium-42, iron-59, tin-125 and antimony-125. Other radionuclides have also been detected, but more rarely.

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

Gamma activity of the liquid effluents, Loviisa NPPThere was variation in the amount of gamma-active substances discharged from the Loviisa power plant between 2005 and 2014. In 2009 and 2013, as planned, the power plant discharged low-level evaporation waste into the sea, resulting in higher discharge levels than normal for these years. The quantity of the discharges was less than 0.01% of the annual discharge limit in 2014.

Gamma activity of the liquid effluents, Olkiluoto NPPThe amount of gamma-active substances discharged into the sea from the Olkiluoto power plant has been decreasing over the past few years. The quantity of the discharges was less than 0.03% of the annual discharge limit in 2014.

 

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  • Sovijärvi Jukka
    Section Head / SÄT tel. +358975988519