Assessment of Coalescence Criteria for Steam Generator Tubes with Triple Axial Through-Wall Cracks

Abstract

Recently, detection of diverse cracks has been increased world-widely in operating nuclear components such as reactor pressure vessels, SG(Steam Generator) and piping. Even though lots of efforts have been devoted to secure structural integrity of them, further researches are necessary especially for thin-walled SG tubes with multiple cracks. In this study, a preliminary assessment was conducted on dual axial through wall cracks(TWCs) in a representative SG tube and its validity was proven by comparing FE(Finite Element) analysis results with corresponding test data. Subsequently, by employing the assessment method, systematic FE analyses were carried out for triple axial TWCs in the same tube. Typical analysis conditions were selected on the basis of ASME B&PV code and main assessment was performed to examine whether the triple axial TWCs are behaved independently or merged. The details and key findings are fully discussed in this paper to decide the present criteria are appropriate or not, which can be used to develop further realistic coalescence diagrams of the multiple cracks.