A leak-before-break assessment method for pressure vessels and some current unresolved issues

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

“…On the other hand, the critical crack length of the J R-Interface is the smallest, and that of the J R-Alloy52Mb is the largest. The lower ligament instability line and the smaller critical crack length will result in smaller safe margin of LBB behavior (Sharpie and Clayton, 1990;Bartholome and Wellein, 1995;Varfolomeev et al, 2010;Gong et al, 2013). This implies that for the A508/Alloy52Mb interface region cracks in the DMWJ, if the fracture resistance curve of base metal A508 or the buttering Alloy52Mb is used, the non-conservative (unsafe) LBB assessment results will be produced.…”

“…13 shows the LBB assessment diagrams under different maximum applied bending moments for the simplified model and actual model. The LBB behavior of a defect with size (a/t, 2Â) at the upmost severe bending moment load can be assessed and predicted by plotting the defect size and its propagation path in the LBB assessment diagram (Sharpie and Clayton, 1990;Bartholome and Wellein, 1995;Varfolomeev et al, 2010;Gong et al, 2013). It can be seen from Fig.…”

“…In LBB analyses, the LBB assessment diagram are usually built (Sharpie and Clayton, 1990; Bartholome and Wellein, 1995;Varfolomeev et al, 2010;Gong et al, 2013). There are two important lines in the LBB assessment diagram: the ligament instability line and critical crack length line.…”

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

“…Thus, constraint effect should be considered in the LBB analyses to modify the over-conservatism and increase accuracy of LBB assessments. In LBB analyses, the critical crack length is an important parameter, and it can be obtained from the LBB curves (Sharpie and Clayton, 1990;Bartholome and Wellein, 1995;Varfolomeev et al, 2010;Gong et al, 2013;Du et al, 2013). A conservatism factor Á can be defined to reflect the effect of constraint on the critical crack length for a given applied load:…”

A thermomechanical finite element tool for Leak‐before‐Break analysis

“…In addition to this, there are defence in depth arguments such as the Leak‐before‐Break (LbB) philosophy. It says that if there is a crack in a component, then it will be possible to detect a leak within a short enough time frame such that any corrective action may be taken before a catastrophic failure occurs . Essentially, this eliminates the possibility of a guillotine type fracture, which would normally be mitigated against with pipe whip restraints and jet impingement shields.…”