Vertical distributions in the Kapachi soil of the plutonium isotopes (238Pu, 239,240Pu, 241Pu), of 241Am, and of 243,244Cm, eight years after the Chernobyl accident

This study has been realized on samples of an agricultural soil taken in the 30 km exclusion area of Chernobyl. The study is focused on the determination of the actinides Pu, Am and Cm, their vertical distributions in the soil as well as relative movements with regard to each other. Therefore, a sample campaign was realized in spring 1994 in the Kopachi village, located just a few kilometers away from the damaged reactor. Four samples in the form of 30 cm long cores with a diameter of 4•7 cm were taken on a 1 m2 surface. The soil was then cut in successive sections of 1 cm thickness. These samples were dried in an oven, homogenized, weighted and analysed in order to determine their respective content of actinides. The results show the presence of actinides in quantities that can be measured until a maximum depth of 5 cm, beyond which the limits of detection were reached. 241Pu remains the preponderant isotope: its total activity is approximately 177 kBq m−2 in a soil section of 6 cm depth. 243,244Cm is also present, but in a lower ratio compared to the 241Pu. The total activity of all these actinides is present in the first 3 cm depth.