Evaluation of Stainless Steel Pipe Cracking: Causes and Fixes

摘要

Leaks and cracks in the heat-affected zones of weldments in austenitic stainless steel piping and associated components of boiling water reactors (BWRs) have been observed since the mid-1960s. Since that time, cracking has continued to occur and indications have been found in all parts of the recirculation system, including the largest diameter lines. Proposed solutions include remedies primarily intended to produce a more favorable residual stress state, materials which are more resistant to stress corrosion cracking (SCC), and changes in the reactor environment which decrease the susceptibility to cracking. In addition to evaluating these remedies, it is also important to gain a better understanding of key variables such as residual stresses, crack growth rates, and the leak-before-break margin in flawed piping, which may impact regulatory decisions on operating plants. The main areas of effort during the past year have been (1) studies of impurity effects on susceptibility to intergranular stress corrosion cracking (IGSCC), (2) crack growth rate measurements, (3) finite-element studies of residual stress produced by induction heating stress improvement (IHSI) and the addition of weld overlays to flawed piping, (4) leak-before-break analyses of piping with 360 exp 0 part-through cracks, and (5) parametric studies on the effect of through-wall residual stresses on IGSCC crack growth behavior in large-diameter piping weldments. 5 references, 15 figures, 2 tables. (ERA citation 09:007851)