Separation of strontium from calcium by the use of sodium hydroxide and its application for the determination of long-term background activity concentrations of Sr-90 in 100 km area around Kozloduy Nuclear Power Plant (Bulgaria)

摘要

The method for the determination of Sr-90 which employs sodium hydroxide for the separation of strontium from calcium was further improved introducing the use of elevated temperatures. The results from 11-year study of background activity concentrations of Sr-90 in different environmental objects in 100 km zone around Kozloduy Nuclear Power Plant (Bulgaria) are presented as an application of the analytical method. The measured mean values are as follows: air precipitation - 0.0015 +/- 0.0009 Bq(m(2.)d), tap water - 0.0017 +/- 0.0012 Bq/L, soil - 1.90 +/- 1.26 Bq/kg, grass - 1.54 +/- 0.80 Bq/kg, milk - 0.023 +/- 0.012 Bq/L and for the Danube river: water - 0.0046 +/- 0.0026 Bq/L, bottom sediments - 0.64 +/- 0.60 Bq/kg, algae - 1.99 +/- 1.56 Bq/kg. The calculated transfer coefficients (soil-grass) are in the range of 0.33-0.84. Between 2 and 5 times reduction in actual background activities of Sr-90 is observed compared to 1972-1974.