Migration of ¹³⁷Cs and ⁹⁰Sr from Chernobyl Fallout in Ukrainian, Belarussian and Russian soils.

Studies carried out inside the 30-km restriction zone of the Chernobyl Nuclear Power Plant (ChNPP) and in other contaminated regions of Ukraine, Belarus and Russia have shown that much of the ¹³⁷Cs and ⁹⁰Sr deposited by the accident in 1986 has been retained in the superficial layers of the soil and is likely to remain there for a long time. However, in wet organic soils, there has been considerable downward movement. Between 1987 and 1993, laboratory and field experiments were carried out in order to determine the vertical distribution profiles of ¹³⁷Cs and ⁹⁰Sr in undisturbed soils at various locations and in various soil types. The data from these experiments were then used to calculate the vertical migration rates of the two radionuclides by two types of model.