Abstract
The accident at the Chernobyl nuclear power plant (NPP) in Ukraine on April 26, 1986 led to a considerable release of radioactive material resulting in environmental contamination over vast areas of Belarus, Ukraine and western Russian Federation. The major health effect of the Chernobyl accident was an increase in thyroid cancer incidence in people exposed as children and adolescents, so much attention was paid to the thyroid doses resulting from intakes of (131)I. Because cow's milk consumption was the main source of (131)I intake by people, it was important to measure the (131)I activity concentrations in cow's milk to calculate, or to validate, the thyroid doses to the exposed population. Almost 11,000 measurements of total beta-activity in cow's milk were performed using a DP-100 device during the first month after the Chernobyl accident in the most contaminated regions of Belarus. Using an ecological model and calibration coefficients for the DP-100 device the activity concentration of (131)I in cow's milk was derived as well as the activity concentrations of the other radiologically important radionuclides, namely (134)Cs, (137)Cs, (89)Sr and (90)Sr. The activity concentrations of other radionuclides, such as (90)Y, (132)Te, (132)I, (133)I, (136)Cs, (140)Ba, (140)La, (141)Ce and (144)Ce, in cow's milk were also estimated and were shown to be of minor importance. The concentrations of (95)Zr, (95)Nb, (103)Ru and (106)Ru in cow's milk were negligible. The data obtained in this study were validated by comparing derived (131)I and (137)Cs concentrations in cow's milk with gamma-spectrometry measurements performed in milk produced in the same location close to the same date. The results of this study were essential to assess and validate the radiation doses received by the subjects of epidemiological studies related to the health consequences of the Chernobyl accident.