External radiation in Dolon village due to local fallout from the first USSR atomic bomb test in 1949

Abstract

Dolon village, located about 60 km from the border of the Semipalatinsk Nuclear Test Site, is known to be heavily contaminated by local fallout from the first USSR atomic bomb test in 1949. External radiation in Dolon was evaluated based on recent 137Cs data in soil and calculation of temporal change in the fission product composition. After fitting a log-normal distribution to the soil data, a 137Cs deposition of 32 kBq m-2, which corresponds to the 90th-percentile of the distribution, was tentatively chosen as a value to evaluate the radiation situation in 1949. Our calculation indicated that more than 95% of the cumulative dose for 50 y had been delivered within 1 y after the deposition. The resulting cumulative dose for 1 y after the deposition, normalized to the initial contamination containing 1 kBq m -2 of 137Cs, was 15.6 mGy, assuming a fallout arrival time of 3 h and a medium level of fractionation. Finally, 0.50 Gy of absorbed dose in air was derived as our tentative estimate for 1-year cumulative external dose in Dolon due to local fallout from the first USSR test in 1949.