Recent NDE experiences with PWR steam generator tubing inspection

The focus of steam generator tubing inspection by eddy current has shifted in the last decade from the detection and characterization of denting and wastage to more complex tube wall degradation mechanisms. The newer degradation mechanisms consist of intergranular attacks, stress corrosion cracks, mechanical wear, and pitting in the presence of copper. The affected areas include anti-vibrational bar locations in the U-bend, a free span region between the tube sheet top and the first support plate, at the first and second tube-to-tube support intersections, and the tube sheet crevice regions, including the roll transition/roll expansion areas. Brief overviews of the different corrosion and mechanical damage mechanisms are presented, followed by the presentation of more recent eddy current nondestructive evaluation (NDE) experiences. To substantiate NDE capability, selected eddy current results are compared directly with actual metallographic analyses of pulled tubes