Radioactive pollution of the Ob river system from Urals nuclear enterprise 'MAJAK'

The Techa river belongs to the Iset-Tobol-Irtysh-Ob river system. Around 1950 the Techa was contaminated with medium and high level radioactive waste from the MAJAK nuclear installation. The total discharge amounted to 100 PBq; 90Sr and 137Cs contributed 11.6% and 12.2% respectively. Presently the Techa contains about 0.3 TBq 90Sr, more than 6 TBq 137Cs and about 8 GBq 239,240Pu. The levels of the radionuclides upstream are several orders of magnitude higher than those expected from global fallout. The activity concentrations decrease exponentially or by power functions with distance. The study has shown that the contamination of the soil of the Techa flood plain is 15-85 times higher than global fallout levels. There is an unexplained radioactive contamination in the Iset river after confluence with the Techa. (author)