Airborne and deposited radioactivity from the Chernobyl accident : a review of investigations in Finland

The Chernobyl nuclear accident happened in the former Soviet Union on 26 April 1986. The accident destroyed one of the RBMK-1000 type reactors and released significant radioactive contamination into the environment. At first the emissions were transported north-westwards over Poland, the Baltic States, Finland, Sweden and Norway. During 27 April 1986 emissions were spreading to eastern-central Europe, southern Germany, Italy and Yugoslavia. Radioactivity mapping over Finland between 29 April and 16 May 1986 showed that the ground deposition in Finland covered southern and central parts of the country but had an irregular distribution. The highest (over 100 μR h ―1 [1 μSv h ―1 ]) contamination disclosed by the mapping was around the city of Uusikaupunki in western Finland and the city of Kotka in southeastern Finland. The Uusikaupunki region was an area of heavy fallout associated with the air mass that was located in the Chernobyl area at the time of the accident. The fallout pattern of reftractory nuclides, e.g. plutonium isotopes, had their spatial maximum in this region. Medical consequences in Finland were luckily mild, the most important symptoms being psychological ones. No increase in thyroid cancer or birth defect occurrence has been observed. The Chernobyl accident boosted the radioecological research which had already been calming down after the last atmospheric nuclear test in China in October 1980. Important new results concerning e.g. hot particles have been achieved. The most important effects of the accident in Finland were, however, the increase of public awareness of environmental issues in general and especially of nuclear energy. In Finland, the nuclear energy programme was halted until 2002 when the Parliament of Finland granted a licence to build the fifth nuclear reactor in Finland.