Abstract
Structural integrity assessment for nuclear power components is one of the most important policies for improvement of safety and reliability of nuclear power plants. When the flaws are detected by in-service inspection, fatigue crack growth analysis shall be performed as a part of structural integrity assessment for the technical judgment on continuous service based on the Rules on Fitness-for-Service for Nuclear Power Plants of the Japan Society of Mechanical Engineers Code (JSME FFS Code). However, fatigue crack growth analysis for BWR components consisted of Ni-base alloy is not able to be performed since the fatigue crack growth rate curve for Ni-base alloy in BWR water environment is not specified yet in the JSME FFS Code. In this study, fatigue crack growth tests in BWR water environment were performed for Ni-base alloy weld metal. Based on the test data, effects of stress ratio and rising time of cyclic loading on the fatigue crack growth behavior were evaluated. Furthermore, reference curves of fatigue crack growth were formulated with consideration for the scatter of data. And the values of ΔK_<th> were quantified.
