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Taking into account the mechanism of pitting corrosion in the heat transfer tubes of steam generators discussed earlier, as well as the background related to measures for preventing and controlling such corrosion, the following are typical real-world cases that are available in public records: The pitting corrosion case in the steam generator of a 1300MW unit in France. After investigating the deformation and rupture of the heat transfer tubes in the steam generator of that 1300MW unit, EDF determined that the cause of the incident was the residual welding slag from the electrodes and grinding debris left behind during the on-site welding of the circumferential welds of the secondary tank, which were not completely removed before the unit started operating. During operation, these ferrous compounds are oxidized to form large amounts of magnetic iron oxide; this expansion then presses on the expansion section of the heat transfer tubes, causing pitting corrosion. Ultimately, excessive stress on the inner wall leads to intergranular stress corrosion cracking in the primary side. Early cases of dent corrosion in U.S. pressurized water reactor steam generators: At the end of 1975, routine eddy current testing at several nuclear power plants in the United States revealed that the wall surfaces of the heat transfer tubes in the support plate areas of the steam generators were dented, preventing the eddy current probes from passing through properly. Such notches are formed as a result of the corrosion products accumulated in the gaps of the carbon steel support plates pressing against the tube walls; in severe cases, this can cause the cross-section of the heat transfer tubes to take on a renal shape. This condition easily leads to intergranular stress corrosion on the primary/secondary sides during subsequent operation, and it also increases the risk of high-frequency fatigue failure in the U-shaped elbow areas.