Crack growth evaluation by XFEM for nuclear pipes considering thermal aging embrittlement effect

Since thermal aging embrittlement (TE) causes loss of fracture toughness and may lead to failure, it is one of structural integrity issues to be assessed in nuclear industry. In this study, crack growth simulation by using extended finite element method (XFEM) was carried out for CF8M base metal and ER316L weld metal, which are typical vulnerable materials. First, user subroutines were constructed to incorporate variation of mechanical properties of two materials due to the TE. In particular, with regard to ER316L, weld residual stress (WRS) distribution was considered. Second, validity of the subroutines and XFEM was confirmed by comparing with analytical and experimental data. Finally, crack growth analyses for nuclear pipes were performed by applying the verified methodology. Thereby, differences of the crack growth amounts and paths as the presence or absence of the TE and WRS were quantified and discussed.