Study on Underclad Cracking in Reactor Pressure Vessel Steels

摘要

Underclad crackign (UCC) in pressure vessel steels and their assessment on structural integrity is reported important. The residual strength of a clad is reduced by UCC, hence it's innocuity/behaviour needs to be demonstrated. Fabrication and test experience shows that SA 508 is susccessptible for UCC. Stainless steel mateirla like SA 304 and Incolloy 825 cladded with Sa 508 were studied. Reliable generation of UCC was performed through weld cladding. Detection of UCC is possible by a special ultrasonic testing but assessment of its risk extended by fatigue and subsequent fracture in pressure vessels is considered equally important. Hence, a combination of nondestructive evaluation (NDE) and destructive testing (DT) becoems inevitable. The crack growth and its influence on base metal - clad interface was attempted trough acoustic emission testing (AE). An experimental -analytical hybrid type of investigation on freacture parameter J compare qualitatively. Based on the results, the significance of UCC on structural integrity is discussed.