Examining the Experience of Revealing Delayed Deformation Corrosion Cracking

The problem of skipping iron-oxide–filled damages in the welding junctions between the collector and Dn1200 branch pipe of the PGV-1000 steam generator in a VVÉR-1000 reactor facility is considered. The mechanism of crack nucleation and development is described. A hypothesis that cracks filled with corrosion deposits exhibit minimum reflectivity has been proposed and confirmed. Results of theoretical research into transmission and reflection of ultrasonic waves in the presence of a thin layer of corrosion products surrounded by pearlitic steel are provided. The reflectances of longitudinal and transverse waves from corrosion damages have been calculated and proved the viability of the hypothesis.