Ductile crack growth test for surface cracked plates of carbon steel piping material

Until recently, light-water reactors have been provided with safety equipment such as pipe-whip restraints on the assumption that double ended unstable fractures might occur in many portions of the piping system. Recently, however, such safety equipment obligations have been relaxed for same piping systems in the Federal Republic of Germany and the United States based on the idea that this assumption is not realistic from the viewpoint of mechanical properties of piping materials which lead to leak-before-break (LBB) tendency (Schulz 1983, USNRC 1984 ). Extensive research is also under way for the improvement of the methods used in the LBB evaluation ( Wilkowski et al. 1985 ).