CONTRIBUTION FROM THE YENISEI RIVER TO THE TOTAL RADIOACTIVE CONTAMINATION OF THE KARA SEA

An attempt is made to estimate the contribution from the Yenisei River and, therefore, the Krasnoyarsk Mining and Chemical Plant (MCP), whic h discharged wastewaters to the Yenisei, to the total contamination of the Kara Sea using results from a study of the radioactive contaminat ion of the Yenisei River, Yenisei Bay, Yenisei Gulf and the Kara Sea i tself. Radionuclides generated from using river water in cooling circu its of production reactors make the largest contribution to the total activity. The radioactive contamination of the river decreased by more than 20 times after two of the three operating reactors were shut dow n. Only several wetlands are actually affected by MCP hundreds of kilo meters from the discharge point. The contents of Sr-90, Cs-137, and Pu -239,Pu-240 in river water is fractions of a percent of the permissibl e concentration. The content of these radionuclides in water and sedim ents of the lower river is nearly always comparable with the global le vel typical of this region. The studied long-lived radionuclides settl e mainly in sediments of the Yenisei estuary and the Rapa Sea. The con tents of Cs-137 and Pu-239,Pu-240 in sediments in the mixing zone of r iver water and saline Kara Sea waters increase owing to hydrolysis and extensive coagulation of hydroxides, fine suspensions, and radionucli des absorbed by them. The contents of Cs-137 and Pu-239,Pu-240 im sedi ments of the Kara Sea itself vary within limits typical for these radi onuclides that are due to global radioactive fallout. In combination w ith our investigations of the radionuclide distribution in the Yenisei and Ob river systems, this fact suggests that the entry of radionucli des into waters of the Yenisei and Ob did not substantially affect the contamination level of sediments in this aquifer. The low content of radionuclides in Kara Sea sediments and the reported low concentration s of radionuclides in this aquifer are consistent with an insignifican t injection (until now) of radionuclides from radioactive wastes dumpe d in the Kara Sea.