Global radioactive deposition on the Yenisey-river catchment and its contribution to the summary contamination of the valley

The results of the retrospective global radioactive contamination mapping of the Enisey-river catchment are presented. The maps of spatial , J 7 Cs distributions of 1964, 1974, 1986, 2000 are compiled using the geoinformation technologies in the Institute of Global Climate and Ecology. The territory of mapping is 2600000 km. The mapping is done from the airbome-gamma-spectrum data obtained at the beginning of 1960, of 1970 and 1990. In 2000 the global levels of I J Cs are 0.4-3 kBq/m. A small contribution of Chernobyl deposition can be registered on the maps built later 1986 (0.02-0.15 kBq/m). The levels of 2.5-3 kBq/m in the region of Severo-Eniseyski and Teya localities can be estimated as the tail part of the eastern Chernobyl partem. The present levels of 2.59-122 kBqVm are observed on the Enissey valley at distances of 0-1700 km from Krasnoyarsk-26. The parameters of runoff and soil erosion are estimated using the cartographic information, provided by the Laboratory of River Processes and Soil Erosion of the Moscow State University. A part of 1 3 Cs, accumulated in the Enisey-valley from early 1960 to 2000 with the transport of soil material from interfluve of all Enisey tributaries, will be estimated using a balance model of soil erosion. The contribution of I J T Cs from the catchment to the valley is estimated with respect to total l 3 7 Cs deposited in the valley. 1. HISTORY OF INVESTIGATIONS Functioning of the Krasnoyarsk Mining and Chemical Combine (MCC) is a main source of the radioactive contamination of the Enisey-river valley. Two production reactors equipped with only primary cooling system were put into operation in 1958 and 1964, respectively. In 1992 these two straight-through cooled reactors were decommissioned. The third reactor has a closed primary circuit and a secondary cooling system. It is still under operation [1]. Data on the radioactive contamination of the environment caused by operation of the Krasnoyarsk MCC, only recently become available in literature. First investigations of the radionuclide contamination in the Enisey-river were carried out in the early 1970 by the State Committee of Hydrometeorology of the USSR [1,16]. Data of this period revealed a considerable contamination of the bottom sediments and the river biota around the MCC. More intensive investigations of the radionuclide contamination in this region were begun in 1990 [2, 3, 9, 10, 11, 14]. The data were obtained in radioecological expeditions, which were carried out by institutions of the Hydrometeorological Service of Russia (SPA "Typhoon", Obninsk; Institute of Applied Geophysics, Moscow), and by the Siberian Branch of the Russian Academy of Sciences. The airbome-gamma-spectrum data were obtained in framework of the State Radiation Monitoring Program (a leading institution is Institute of Global Climate and Ecology) [4]. Interesting data were received in framework of several international projects, performed by the Kurchatov Institute and the Vernadski Institute [5, 11, 13, 15, 16]. Some results were summarized in the reports of the 1STCproject "Radiation Legacy" (RADLEG). Cl-18 RADIOPROTECTION COLLOQUES 2. GLOBAL FALLOUT IN THE CATCHMENT OF THE ENISEY RIVER Global fallout of radionuclides took place in Northern hemisphere mainly during period 1954-1970 with its maximums in 1959, 1963 and 1964. Spatial distribution of radionuclide is mostly determined by interaction between air masses and relief.