Corrosion of the Second Contour of Power-Generating Units of Nuclear Power Plants with WWÉR-1000 Reactors

We present a survey of experimental investigations of the mechanisms of erosion-corrosion damage to the heat-exchange equipment of power-generating units with WWÉR-1000 (water-cooled, watermoderated) reactors. By using metallographic methods, we study the in-service defects of different regions. It is shown that the nature of defects in thick-walled structures made of pearlitic steel of the 10GN2MFA type is initially explained by the pitting corrosion caused by the electrochemical interaction of the metal with particles of the sludge, i.e., products of the corrosion-erosion wear of the equipment made of copper alloys. We make a conclusion that the complex interdependent processes of corrosionerosion wear of the equipment are running under the conditions of the second circuit. In their final stage, we observe the development of stress-corrosion cracking. Hence, for the prevention of in-service defects of equipment of the second circuit, it is necessary to remove copper-containing structures.