Abstract
The Dolon village is located 60 km from the border of the Semipalatinsk Nuclear Test Site (SNTS) in Kazakhstan where more than 450 nuclear tests were performed by the former USSR from 1949 to 1989. Dolon is known to be heavily contaminated by the radioactive plume from the first USSR nuclear test in 1949. To investigate thyroid dose, 131I contamination is important. So far no radioactive iodine measurement has been available around the SNTS because of the short half-life of 131I (8.02 d). It seemed to be possible, however, that other radioiodine, 129I could be measured due to the long half-life of 129I (1.57 x 107 y) by using accelerator mass spectrometry (AMS). Soil core samples around Dolon were taken in October 2005 by the joint university expedition team and 14 samples were measured at Tandem Accelerator of Mutsu Facility, Japan Atomic Energy Agency. The 129I/127I atom ratio was obtained to be from 3.3 x 10-9 to 3.3 x 10-7. These values are similar to the current background level in the environment (10-9 - 10-7) in Europe including contributions from global fallout of atmospheric nuclear tests and nuclear industries. The 129I atom inventory measured in soil was ranged from 1.2 x 1013 to 1.5 x 1014 atoms m-2, the average of which (7.3x1013) was slightly larger than the background level of (2 – 5) +/- 1013. Considering that the global fallout level of atmospheric nuclear tests and nuclear industries around the Semipalatinsk area is two to three times less than those in Europe and Russia, about 80 % of 129I in soil samples from Dolon were deposited as local fall from the SNTS. These are the first results of our 129I AMS measurement about the radioactive contamination around the SNTS.
