Overview of strontium-89,90 deposition measurements in Finland 1963―2005

Abstract In Finland the deposition of strontium-89 ( 90 Sr) and strontium-90 ( 90 Sr) has been monitored since the early 1960s. The measured cumulative 90 Sr deposition in 1963–2005 is on average 1200 Bq m −2 , of which 150 Bq m −2 originates from the Chernobyl accident. Adding to this the deposition in 1945–1962 produces a value of 2040 Bq m −2 for the cumulative deposition in Finland. The nuclear explosion-derived deposition up to 1985 obtained in this study, 1850 Bq m −2 , is in good agreement with the zonal 90 Sr deposition of 1740 Bq m −2 in the 60°N–70°N latitude band estimated by UNSCEAR. The regional deposition patterns of 89 Sr and 90 Sr following the Chernobyl accident resemble those of the refractory nuclides such as 239,240 Pu and 95 Zr. The total deposition of Chernobyl-derived 90 Sr in Finland was about 5.3 × 10 13  Bq. This activity corresponds to 0.027% of the reactor core inventory and 0.66% of the atmospheric emissions from the accident. The corresponding figures for 89 Sr are 4.5 × 10 14  Bq, 0.023% and 0.56%, respectively.