Reconstruction of individual doses to the Semipalatinsk historical cohort subjects : preliminary results

At present scientists from Russia, Japan, the U.S. and Kazakhstan take part in an international scientific research on reconstruction of individual doses for the population of 10 settlements: Dolon, Kanonerka, Mostik, Cheremushki, Znamenka, Kainar, Karaul, Sarzhal, Kaskabulak and Kundyzhdy, included in the so-called Semipalatinsk historical cohort. All the calculations are conducted in accordance with a U.S./Russian joint methodology. Individual input data, such as date of birth, ethnicity and so on, are obtained from the register of the residents who lived on the territory of local radioactive fallout due to the nuclear tests on the Semipalatinsk Nuclear Test Site. This register was created by the scientists in both Kazakhstan and Japan. The register contains data on 11,370 persons, lived in the above mentioned settlements at the time of the most significant nuclear tests. In addition, the register contains data on the persons who were born or arrived to the above mentioned settlements after the most significant tests. Individual whole body doses from external irradiation and internal doses to thyroid due to the ingestion of 131I and 133I for more than 11,000 persons included in the Semipalatinsk historical cohort have been estimated. According to the preliminary results of dose assessment, the maximum whole body dose (260 mGy) was received by adult non Kazakh residents of Dolon. In turn, the maximum thyroid dose (310 mGy) was received by 3-7 years old Kazakh residents of Kainar. Evacuation of the residents of villages Sarzhal and Karaul has been taken into account. Due to evacuation either whole body or thyroid dose to the residents of Sarzhal and Karaul were substantially less than they could have been without evacuation. Dose reduction factor in case of whole body dose was estimated to be equal to 4.6 (Sarzhal) and 2.8 (Karaul), while in case of thyroid dose — 10.6 (Sarzhal) and 4.6 (Karaul).