Long-term transfer from soil to plant of radioactive corrosion products.

The uptake by swards of three activation products ((54)Mn, (57)Co and (63)Ni) was studied in a long-term field experiment. Some of the soils used in the investigation were sampled in the vicinity of four Swedish nuclear power plants, while the others represented the most frequent types of agricultural soils occurring in Sweden. Data on the uptake by clover and timothy during a 9-year period were used for the calculation of soil-plant transfer factors of these nuclides. The temporal distribution of the transfer factors and the variations exhibited by the different nuclides were examined, as well as the differences between crops. The increased uptake at the early stage of the experiments (first year effect) observed in clover is discussed. Regression analyses employed to quantify the dependence of uptake on soil parameters showed that the soil characteristics that most influenced the uptake are the pH and the soil contents of calcium and potassium.