Environmental Radioactivity Problem around the Former Soviet Union's Semipalatinsk Nuclear Test Site

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This paper is a report on our survey of residual radioactivity, Pu isotopes and ^<137>Cs, within and without the territory of the Semipalatinsk nuclear test site. Soil samples within the test site were collected at approximately' 30 sites along the roads connecting Kurchatov City, ground zero for the first USSR nuclear test, Balapan, Degelen Mountain and Salzhal settlement. Furthermore, outside the test site, the soil was sampled at about 20 sites, including some settlements (Mostik, Dolon, Tchagan, etc.), forest and pasture areas, along the roads from Semipalatinsk City to Kurchatov City and north Korosteli settlement. The contamination levels of long-lived radionuclides, ^<137>Cs, ^<238>Pu and ^<239,240>Pu as well as ^<240>Pu/^<239>Pu atomic ratio in the soil were determined by non-destructive gamma-spectrometric method and radiochemical sepatation followed by alpha -spectrometic and/or ICP-MS methods, respectively. The resutls showed that although ^<137>Cs was within typical environmental levels except for an areas near ground zero and Balapan, ^<239,240>Pu was elevated levels contaminated with weapons-grade plutonium in all area we visited . From the stepwise leaching of Pu from the soil, 50-80% of total ^<239, 240>Pu in most samples was found to be tightly incorporated into the soil components which might have been melted at time of detonation.