Dosimetric measurements at the former nuclear test site near Semipalatinsk/Kazakhstan

The joint projects performed since 1995 by Research Centre Juelich in cooperation with the Kazakh National Nuclear Centre in the region of the former nuclear test site near Semipalatinsk also involve the assessment of the current dose rate of the population at and around the test site in addition to the important retrospective determination of the dose rate of persons affected by the atmospheric tests. Present investigations include the assessment of external dose (area dose measurements, TLD dosimetry), the assessment of soil and air samples, urinary excretion analysis on the test site and in neighbouring locations as well as EPR measurements of teeth. First results from the last field mission in September 2000 are available for doses to individuals from a group of geologists and a group of herdsmen at the test site. For the first time, the individual dose was measured directly for these population groups with high-sensitivity dosemeters of the BICRON TLD 700H type. Detection limits of about one μSv permit informative measurements for wearing times of less than a fortnight. Herdsmen received a mean personal dose of 0.55 μSv per day, whereas geologists received a mean personal dose of 0.45 μSv per day. For an annual exposure period of typically about three months, the radiation dose received by the persons investigated in addition to the natural radiation exposure is thus below 0.1 mSv/a. During their work at the test site herdsmen and geologists live in small camps situated on the test site. Area dose rates in the camps were within the range of values normally observed worldwide from natural sources. (orig.)