Effects of local mechanical and fracture properties on LBB behavior of a dissimilar metal welded joint in nuclear power plants

Crack-tip constraint analyses and constraint-dependent LBB curves for circumferential through-wall cracked pipes

“…The internal pressure of pipes with mean radius-tothickness ratios, R m /t = 5, 10 and 20 was 17 MPa, 7 MPa and 4 MPa, respectively. A conventional mesh configuration having a focused ring of elements surrounding the crack front with a small initial root radius (2 m) at the crack tip (blunt tip) to enhance convergence of the nonlinear iterations (Wang et al, 2001;Cravero and Ruggieri, 2005;Gong et al, 2013;Du et al, 2013) was used in this study, as shown in Fig. 3(b).…”

“…In LBB analyses, the LBB curve shows dependence of the critical loading limit on the through-wall crack size, and it can be used in assessing safety of a through-wall crack (Stadtmuller and Sturm, 1997;Du et al, 2013). The J-R curves of standard fracture toughness specimens with high crack-tip constraint are generally used in LBB analyses (Gong et al, 2013;Du et al, 2013).…”

“…The J-R curves of standard fracture toughness specimens with high crack-tip constraint are generally used in LBB analyses (Gong et al, 2013;Du et al, 2013). However, as shown in Fig.…”

“…The leak-before-break (LBB) concept has been widely applied in the structural integrity assessments of pressured pipes in nuclear power plants (U.S. Nuclear Regulatory Commission, 1984;Stadtmuller and Sturm, 1997;Chattopadhyay et al, 1999;Gong et al, 2013;Du et al, 2013). In LBB analyses, the crack growth resistance curves (the J-R curves) of standard fracture toughness specimens, such as the single-edge notched bend (SENB) specimens with deep cracks to ensure high crack-tip constraint level are generally used to evaluate the LBB behavior.…”

Effect of thermal aging on the leak-before-break analysis of nuclear primary pipes

“…At present, the LBB analysis has been extended to new nuclear power technologies such as advanced passive 1000 (AP1000) and fast breeder reactors (FBRs). Gong et al (2013) and Du et al (2013) applied a LBB approach to a dissimilar metal welded joint connecting safe end to pipe-nozzle of an AP1000 reactor pressure vessel. Yoo and Huh (2013) and Wakai et al (2013) demonstrated that the LBB assessment procedure is applicable to piping systems of FBRs.…”