Radiation consequences of a hypothetical failure of a dam at the coolant reservoir of the chernobyl nuclear power plant

Abstract

The coolant reservoir at the Chemobyl nuclear power plant is an artificial filling reservoir with area 22.7 km 2, volume 0.16 km 3, and average depth 7 m. The reservoir was tbrmed by collapsing part of the walls of the Pripyat' River valley and building with sand dams with sloping beaches. The Pripyat' River is diverted from the reservoir by an artificial navigable channel along the eastem dam. Water losses due to evaporation and filtration axe replenished by pumping from the Pripyat' River. There is no direct runoff from the reservoir into the Pripyat' River. At the low water point, the water level in the reservoir reaches a height of 7.8 m above the water level in the river. A long flow-control dam, intended for optimizing the thermal regime of the coolant, has been constructed within the coolant reservoir. The old bed of the Pripyat' River, which is now partially filled with silt, passes along the bottom. There are also old soil excavations which were used for filling the dam. Flooded dams are also located in the water area. One such dam is a remnant of an enclosure of the tirst reservoir, and a second one is intended for optimizing the circulation water flows (Fig. 1 ). During the period of operation, the bottom of the reservoir was coated with silt deposits up to 10 cm thick. As a result of the accident at the No. 4 unit of the nuclear power plant, additional radionuclides precipitated into the reservoir, settled on the bottom, and mixed with the silt. From the standpoint of contamination, the bottom of the reservoir can be divided conditionally into three zones, differing by the density distribution of the radioactive contamination [ 1 ].