Analysis and crack growth behavior of nuclear piping materials using experimental and J-contour integral methods

In case of Nuclear power plant, Primary Heat Transport (PHT) piping components are subjected to high pressure and large amplitude cyclic loads during the design basis accidents that are Safe Shutdown Earthquake (SSE).Their fracture assessment is essential for demonstration of Leak Before Break capability and safety margins against the fracture failure, under the SSE loading. The emphasis is made here to understand the effect of cyclic loading on fracture resistance of the material. Studies have been carried out on stainless steel pipes to demonstrate the leak before break, design criterion and validate the analytical procedures. Fatigue crack initiation, fatigue crack growth rate and fracture resistance behaviour of the pipes have been experimentally and analytically evaluated. The tests have been carried out on pipes of outer diameter 168mm and 14.6mm wall thickness having a part through notch in the circumferential direction. It has been observed that the analytical and experimental results compare well. The fatigue crack growth curve da/dn obtained from various analytical calculations and pipe tests have been compared with the fatigue crack growth curve (ASME Section XI). The comparison shows that use of the ASME curve in analysis of components gives a better result in comparison to the curves obtained from the actual pipe tests.