Research on Test and Theoretical Analysis Methods on Stability of LBB Circumferential Through-Wall Crack in Austenitic Stainless Steel Pipe under Dynamic Load

Judging whether the circumferential through-wall crack of pipe is stable is one of the criteria to judge whether the pipe meets the Leak-Before-Break (LBB) design criteria. In order to ensure the safety and reliability of LBB technology, the stability of circumferential through-wall crack of pipe under dynamic load is studied and analyzed by experiment. The horizontal impact machine was used to carry out the impact test on the pipe with circumferential through-wall crack without operating pressure at high temperature with the loading speed of 1.22 m/s, 2 m/s, 3 m/s, 4 m/s in order to obtain the test limit load values at each strain rate, and then compared with the engineering theoretical analysis and calculation results. The results show that the failure mode of circumferential through-wall cracks in austenitic stainless steel pipe under dynamic load is plastic instability. Through the verification of the test, when LBB analysis is carried out for austenitic stainless steel pipe under dynamic load in the project, the theoretical analysis method of limit load in the standard review plan 3.6.3 leak-before-break evaluation procedures (SRP 3.6.3) of the NRC has high engineering safety. If the mechanical properties of materials under quasi-static state are adopted at the same time, the engineering safety is higher.