Federal State Budget Educational Institution of Higher Education “Nizhny Novgorod State Technical University named after R.E. Alekseev”

The article presents the results of experimental studies of the durability of protective oxide coatings of 12X18N10T stainless steel in a lead coolant environment, when simulating an emergency situation of “inter-circuit leakage of a steam generator”. The tests were carried out on the FTM-2023 NSTU stand in a lead coolant with a temperature of up to 430—450 °C, without circulation. The tube bundle for simulating a steam generator leak during the outflow of the light phase is two rows of 22x3.5 pipes welded to a plate with a pitch of 33 mm. The data were obtained for tube bundles with two different types of holes for the outflow of the vapor phase: a slit hole of 13x1 mm and a round hole with a diameter of 4 mm. The processing and analysis of the results allowed us to conclude that when a steam-water mixture enters the HLMC circuit, the oxide coatings become thinner depending on the location of the tube in the bundle and the shape of the discharge hole. There is a noticeable decrease in microhardness (by 49 HV for a tube bundle with a round discharge hole and by 23 HV for a tube bundle with a rectangular discharge hole), which is more pronounced when approaching the discharge hole and depends on the orientation of the tube surface onto which the mixture enters, relative to the leak. The obtained data are recommended for use in assessing the consequences of a large leak in a horizontal steam generator in installations with heavy liquid metal coolant.

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