Construction of dose estimation model for low dose radiation exposurefor residents living around the Semipalatinsk Nuclear Test Site

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Since 1994, we have concentrated our energies on assessing the radiation dose for human effect and environmental contamination by the nuclear testings at the Semipalatinsk (SNTS) in Kazakhstan. For this purpose, residual long-lived radionuclides such as 137Cs and Pu isotopes have been measured for environmental samples from various areas. At first, works were focused on Dolon village contaminated heavily and external radiation dose for resident was already estimated by detailed soil samplings where were carried out along a line perpendicular to the supposed center of plume of the first atomic bomb (Aug. 1949). In this works, such works were directed to Sarzhal, Karaul and Kainar villages located in the southern direction from the SNTS. Although the obtained data in Sarzhal and Karaul varied largely, overall, peak-like distributions similar to Gaussian function were observed for both 137Cs and 239,240Pu even after about 60 years from atomic bomb. Within the Sarzhal village, being about 5 km away from the center-axis, upper range is 5000-7000 Bq/m^2. Pu is around 2000 Bq/m^2. By using these data, external radiation doses in both villages were successfully estimated. On the other hand, in Kainar, Gaussian-likedistribution was not observed,137Cs inventory was not so high, now its inventory was around 4000 Bq/m^2. The levels are nearly same as Karaul, but somewhat higher sites like hot-spot were in places existing. Now, further works in Kainar are continuing.