ВЛИЯНИЕ ПУЗЫРЬКОВ ГАЗА НА ЭРОЗИЮ СТАЛИ В СВИНЦЕ

Abstract

The erosion of the steel surface in lead-based coolants is a powerful factor that initiates corrosion of the structural material. In the conditions of cavitation effect of gas bubbles on the oxide coating, breaches of its integrity can be created, as a result of which an intensive influence of lead on steel occurs on the "bare" areas. This leads to a multiple increase in the rate of corrosion. The regularities of erosive action of lead or its alloys on structural materials have not been sufficiently studied. In the experiments of different authors, differing data of flow rates of lead or lead-bismuth, to cause the erosion of steel, were obtained. In general, this phenomenon is a combination of a number of simultane-ously occurring thermohydraulic and physicochemical processes. Erosion failure of structural materials in a heavy coolant is rapidly developing and occurs in places with increased coolant velocities, in the field of hydrodynamic disturbances, and so on. Protective coatings formed on steels based on oxide technology are vulnerable from the point of view of erosion wear. The erosion of protective coatings on steels can in turn cause peeling of fuel rod cladding with end-to-end sheath breaking, which can proceed more intensively than the front dissolution of unprotected shells.The most significant factor leading to the erosion of steel in lead is the hydrodynamic effect of the coolant flow. In the presence of gas bubbles in the coolant, erosion occurs at the lowest flow rates, and the erosive effect itself has a cavitation character. The present report presents the results of studies of erosion of steel in lead under gas cavitation. A methodology for appropriate erosion testing was developed. Experiments were carried out on the installation with a rotating cylinder at different cylinder speeds and at various temperatures. A numerical solution of the differential equation of motion of the bubble wall is performed for the different hydrodynamic parameters of the lead flow. The experimental and calculated data obtained make it possible to estimate the process parameters under which a cavitation damage of the oxide coating occurs on the steel surface in the flowing lead.