Studies of activation products in the terrestrial environments of three Swedish nuclear power stations

Samples of sewage sludge, lichen, soil and ground-level air have been analysed for activation products released into the atmosphere from three Swedish nuclear power stations. The activity concentration of the activation products in the sludge can be arranged in the following sequence: 60Co > 65Zn > 58Co approx.= 54Mn. There is agreement between the time variation of the activity concentration in the sludge and the reported releases to the air from the power stations. The 58Co/60Co activity ratio measured in the sludge does not differ significantly from that reported in the releases to the air. The activity concentration in sludge sedimented from incoming waste-water has been used to get better time resolution than that obtained using only digested sludge from the final stage of the plant. These studies have shown that the 60Co activity concentration increases substantially with the first rain runoff that reaches the sewage plant, and then falls off rapidly. Measurements on samples of lichen and underlying soil show that the radioactive cobalt isotopes 58Co and 60Co have a short mean residence time in the lichen carpet compared with most fission products present in the global fallout. (author)