HELCOM MORS-PRO Radioactivity in the Baltic Sea Erkki Ilus STUK - Radiation and Nuclear Safety Authority, Finland

Sources of artificial radioactivity in the Baltic Sea Total injections of Cs-137 and Sr-90 into the Baltic Sea from different sources Source Cs ‑ 137 TBq Percent of total amount Sr ‑ 90 TBq Percent of total amount Chernobyl accident, incl. river discharges Nuclear weapons tests Discharges from nuclear reprocessing plants in Western Europe Discharges into the Baltic Sea from local NPPs, cumulative amount up to

Special features of the Baltic Sea increasing its radioecological interest Location close to one of the test areas (Novaya Zemlya) of the nuclear weapons tests carried out in the 1950s s Small volume of water Slow exchange of water Climatic conditions Large proportion of river waters Low salinity of water Scarce biota Sensitivity of the biota to changes in environmental circumstances

History of Radioecological studies / Monitoring of radioactive substances in the Baltic Sea National studies in different countries (in Finland since 1959) - bilateral and multilateral international cooperation Research programme on radioactive materials in the Baltic Sea coordinated by the IAEA (International Atomic Energy Agency) HELCOM MORS Expert Group (Monitoring of Radioactive Substances) - first meeting in Helsinki 8-11 April participated by 7 countries HELCOM MORS-PRO years projects - participated by 9 countries

HELCOM MORS-PRO All the Baltic Sea countries have ratified the Helsinki Convention Helsinki Commission (HELCOM) coordinates the international co- operation focusing on the implementation of the Convention Recommendation 26/3 of HELCOM defines the programme for Monitoring of Radioactive Substances (MORS) in the Baltic Sea All the Baltic Sea countries contribute to the monitoring with their own national programmes The results are reported annually to the HELCOM data base The results are published every five years in Periodical Assessment Reports of HELCOM Discharge data from all nuclear facilities operating in the Baltic Sea area are reported annually to the Discharge Register of MORS STUK is responsible for the Finnish part of the programme (~120 annual samples from sea water, bottom sediments and biota) STUK is responsible for maintaining the Discharge Register

”Radiologically, the sea most affected by the Chernobyl accident was the Baltic, since the first radioactive clouds from Chernobyl travelled to north and caused high deposition in the area” (Povinec et al., IAEA Bulletin 1/1996)

The average caesium- 137 activity of the surface seawater (Bq m -2 ) esti- mated for the reference year 1990 (Povinec et al., IAEA Bulletin 1/1996). (The average values for the sub-regions in the Baltic Sea (in brackets) are based on Finnish data from 1990).

Terrestrial deposition of 137 Cs in the Baltic Sea drainage area (kBq m -2 ); compiled by STUK.

Gamma-emitting radionuclides in Fucus vesiculosus (Bq/kg -1 dry weight) at sampling station Olkiluoto A in

Estimated average con- centrations of 137 Cs and 90 Sr (Bq m -3 ) in the Both- nian Bay, Bothnian Sea and Gulf of Finland in (IAEA-TECDOC-362)

Activity concentrations of 137 Cs in surface seawater at four stations in the Baltic Sea in The activity concentrations of 40 K in seawater: Bq m -3.

Activity concentrations of 137 Cs (Bq kg-1 dry weight) in Fucus vesiculosus along the Finnish coast in 1987 and the Chernobyl fallout in the drainage areas of the rivers Kokemäenjoki (A), Kymijoki (B) and Vuoksi (C).

Activity concentrations of 137 Cs (Bq kg -1 dry weight) in Fucus vesiculosus along the coasts of the Nordic countries in The activity concentrations of 40 K in Fucus: Bq kg -1 d.w.

Vertical distribution (Bq kg-1 d.w.) of 137 Cs in sediment profiles at a coastal station of the Gulf of Finland in

Total amounts of 137 Cs (Bq m -2 ) in bottom sediments of the Baltic Sea in 1998.

Activity concentrations of 137 Cs in Baltic herring and pike in four areas along the Finnish coast during

Ringed seal (Phoca hispida) Grey seal (Halichoerus grypus) Gulf of Finland May November 1988 SW coast of Finland ( ) ( ) Activity concentrations of 137 Cs (Bq kg -1 fresh weight) in seal flesh on the Finnish coast after the Chernobyl accident.

Radiation doses The exposure of the population to radiation caused by ingesting Baltic Sea fish and other marine products and living by the sea after the Chernobyl accident was evaluated in the EC/ Marina Balt Project in The dose for the Critical Groups living on the coasts of the Bothnian Sea and the Gulf of Finland peaked at 0.2 mSv in 1986 This can be considered a very low value, as on an average, a Finn receives an annual 3.7 mSv dose from other sources (2 mSv year -1 from indoor radon) Since 1986, the impact of the Chernobyl fallout has significantly decreased in the Baltic Sea At the same time, individuals in the critical groups had a dose rate of 0.7 mSv year -1 from polonium-210 occurring naturally in the sea. The average internal radiation dose from Baltic Sea fish to Finnish people was 0.01 mSv in 1986 and mSv in 2006.