An analysis of leak-before-break for nuclear piping with stress corrosion cracking

Studies on structural safety of nuclear piping system in the presence of large flaws have been of much importance because of discoveries of stress corrosion crackings in several BWR plants. One important concept in consideration of structural integrity of piping with such a flaw is the so-called leak-before-break concept. The assessment of this concept requires understanding of fracture condition and development of estimation method. In this paper, studies on these problems are reviewed. First of all, a criterion of ductile crack growth is studied with the finite element analyses for plates and pipes. Next, crack growth behavior from a part-through crack is estimated using the criterion above. Finally, using the practical methods, leak-before-break condition is estimated for the actual piping