Quantitative Estimation of the Growth of Environmentally Assisted Cracks at Flaws in Light Water Reactor Components

Since environmentally assisted cracking (EAC) is an important degradation mechanism affecting the structural materials of nuclear power plants, numerous EAC experiments have been performed in the past three decades using standard specimens in simulated high temperature water environments to evaluate the various core materials used in light water reactors (LWRs). However, the environment, the condition of the material, and the mechanical properties near flaws in LWR components are not absolutely equivalent to those near the crack tip in standard specimens; thus, more research needs to be done before EAC growth in an actual LWR component can be accurately estimated using existing experimental EAC data. By combining the film slip-dissolution/oxidation model with the elastic-plastic finite element method and existing experimental EAC data, we have derived a method by which an estimation of EAC growth at flaws in actual LWR components can be made. In this paper we propose and discuss the use of this method. The results show that this new method basically concurs with the Fracture Research Institute (FRI) model in evaluating EAC growth across a semi-elliptic crack front under a simple tensile load and is also in approximate agreement with the experimental results obtained in evaluating EAC growth along a semi-elliptic crack front under complex loading conditions. The approach is expected to form a bridge between predicting EAC growth rate in core materials and evaluating EAC growth in key structural components in LWRs, and it is also expected that it can be used as a pre-analytical tool for EAC experiments using nonstandard specimens.