MEASUREMENTS OF RADIOACTIVITY IN ENVIRONMENTAL-SAMPLES FROM THE SOUTHERN URALS

A region between Chelyabinsk and Ekaterinburg in the Southern Urals ha s been heavily contaminated due to operational and accidental releases from the first Soviet plutonium production facility Mayak. In 1992 an d 1993, the German Federal Office for Radiation Protection organized a measuring campaign involving two Russian institutes to assist with th e validation of former Soviet measurement data. The results of this me asuring campaign are reported here. Environmental samples were collect ed from areas affected by significant radioactive releases into the Te cha river, which started in 1948, and by fallout from the explosion of a fission product storage tank in 1957. Soil, sediment, water, milk a nd food samples were independently analysed for Sr-90, Cs-137 and plut onium by the three institutes involved. This paper presents data on th e present levels of environmental radioactivity. The highest contamina tion of areas accessible to the local population was found in the vici nity of the Techa river around Muslumovo. Activity concentration of fl oodplain samples reached up to 37 000 Bq.kg(-1 137)Cs, 5 600 Bq.kg(-1 90)Sr and 9.9 Bq kg(-1) Pu. Milk and potatoes from private farms in Mu slumovo showed low activity in the range from 0.7 Bq.kg(-1) to 25 Bq.k g(-1 90)Sr. The results of the three independent measurement teams sho wed sufficient agreement. One Russian laboratory obtained plutonium ac tivities that exceeded the results of the other laboratories by about 20%. Contrary to the International Chernobyl Project, there was no ove restimation of Sr-90 activities in the Russian analyses. Therefore, th e validity of earlier data sets acquired with same methodology and qua lity control can be considered a valuable basis for further assessment s and for dose reconstruction in epidemiological projects.