A Flaw Sizing Technique for Austenitic Stainless Steel Welds Using Creeping Wave Probe

One of the most important subjects in nuclear power plants is sizing of flaws which are detected during InService Inspection (ISI), since reliability of flaw sizing is very important to estimate the life of the structure or pressure equipment. The most difficult matter for applying the flaw sizing techniques mentioned above is how to identify the flaw tip signal, especially in the case of natural cracks such as stress corrosion cracking (SCC). At present, the identification of the flaw tip signal depends on technical skill, related knowledge and experiment of UT personnel. This paper proposes a new technique using echo locus curves on B-scan image for flaw sizing. The technique was applied to welds test specimens with simulated SCC and advantages of the technique were confirmed experimentally. As a result, it is clear that flaw sizing can be conducted with higher accuracy and misjudgment or measuring error due to personnel ability can be reduced.