LEAK-BEFORE-BREAK ANALYSIS OF THERMALLY AGED NUCLEAR PIPE UNDER DIFFERENT BENDING MOMENTS

摘要

Cast duplex stainless steels are susceptible to thermal aging during long-term service at temperatures ranging from 280 degrees C to 450 degrees C. To analyze the effect of thermal aging on leak-before-break (LBB) behavior, three-dimensional finite element analysis models were built for circumferentially cracked pipes. Based on the elastic-plastic fracture mechanics theory, the detectable leakage crack length calculation and J-integral stability assessment diagram approach were carried out under different bending moments. The LBB curves and LBB assessment diagrams for unaged and thermally aged pipes were constructed. The results show that the detectable leakage crack length for thermally aged pipes increases with increasing bending moments, whereas the critical crack length decreases. The ligament instability line and critical crack length line for thermally aged pipes move downward and to the left, respectively, and unsafe LBB assessment results will be produced if thermal aging is not considered. If the applied bending moment is increased, the degree of safety decreases in the LBB assessment. Copyright (C) 2015, Published by Elsevier Korea LLC on behalf of Korean Nuclear Society.