Monitoring of Individual Doses of Populations Residing in the Territories Contaminated after Chernobyl Accident

To provide instrumental validation of radioecological dosimetric models used for estimation of external doses to the Chernobyl population, about 1000 direct dose measurements were conducted in 1996-1997 in 54 settlements in contaminated territories of Ukraine. The areas covered by the measurements have 137Cs contamination density ranging from 55 to 491 kBq.m-2. Individual dose measurements were conducted using standard LiF dosemeters, type Harshaw 8814 (TLD-100), and automated TLD system Harshaw 8800. Relatively low contamination and, thus, an unfavourable 'Chernobyl/natural background' dose ratio, called for sophisticated analysis of experimental results. Linear regression of dose relative to 137Cs contamination density which was conducted in two different ways provided consistent results. Annual background dose, as derived from the results of individual dose measurements, is about 1.1 mSv per annum; the Chernobyl related component is expressed by the rate of 1.24-1.3 µSv per kBq.m-2 per annum. These results are in reasonable agreement with somewhat conservative modelling parameters which are assumed to be 1.91 µSv per kBq.m-2 per annum for the case of the rural population.