Evaluation of environmental fatigue lifetime for nuclear welded structure based on structural stress and fracture mechanics approach

In this paper, a new analysis procedure for LWR (light water reactor) environmental fatigue lifetime of nuclear welded structure is proposed based on a structural stress/fracture mechanics approach. Validity of the mesh-insensitive structural stress procedure presented by Dong is identified comparing the structural stresses calculated for various FE (finite element) models. Fatigue crack initiation cycles are determined by using the structural stresses and the fatigue crack growth model considering LWR environmental effect. Also, in order to compare the new fatigue analysis procedure with the existing procedures such as Fen methods and Battelle's structural stress/fracture mechanics approach, the fatigue crack initiation cycles are determined by using the existing procedures. Environmental fatigue test is also performed to identify validity of the fatigue analysis procedures. As a result of comparison of analysis results with test data, it is found that the new fatigue analysis based on structural stress/fracture mechanics approach is the most reliable procedure for environmental fatigue. Finally, the additional requirements for developing the more reliable and applicable new fatigue analysis procedure, which is based on structural stress/fracture mechanics, are presented. (authors)