Study on 137Cs adsorption by soils around Qingshan and Daya Bay Nuclear Power Plants

The patterns of 137Cs adsorption and percolation are studied by 137Cs solution through soil cylinder samples collected from seven sites around Qingshan and Daya Bay Nuclear Power Plant. The top soils (0 ∼ 20 cm) are put into plastic tubes after being sieved. Three different ways are taken in the experiments. (1) 137Cs solutions with the same specific activity (3.7 x 104 Bq/L) and same volume (40 mL) pass through the soils. (2) 137Cs solutions with different specific activity (3.7 x 103, 3.7 x 104, and 3.7 x 105 Bq/L) and with same volume (40 mL) pass through the soils. (3) 137Cs solutions with same specific activity (3.7 x 104 Bq/L) and with different volumes (40, 80, 120 mL) pass through the soils. The results show that the relationships of specific activity on the top 1 cm soil to the specific activity of solution is conformed to y = AxB, to the volume of solution is conformed to y = A + Bx. The upper 0 to 1 cm soil adsorbs 137Cs over 90-95%, and upper 0-5 cm soil adsorbs 100% 137Cs. When the depth is greater than 5 cm the activity of filtered solution is background. From this experiment, it shows that the contamination can be eliminated by removing top soil when the soil is contaminated by 13'7Cs solution