Background: Dissimilar metal welded joints（DMWJs） were indicated to be vulnerable components in the primary systems

an accurate structural integrity assessment for such DMWJ is needed.Purpose: Understand the fracture performance of the welded joint containing defects

determine if appropriate to assess the defects in the weld joint with the present codes.Methods: The fracture tests of the initial crack located in the different positions of Alloy 52M DMWJ specimens were carried out by using single-edge notched bend（SENB） method.Results: Different crack resistance and crack propagation path were obtained for the SENB specimens

and the cracks always deviate to the materials with lower strength.Conclusions: The crack path deviation is mainly controlled by strength mismatch

rather than toughness mismatch.The J-resistance curves with larger crack path deviation only reflect the apparent fracture resistance along the crack growth region

rather than the intrinsic fracture resistance of the initial crack-tip region material.Without considering the local fracture resistance properties of heat affected zone（HAZ）

interface region and internal affected region（IAZ）

following present assessment codes will unavoidably produce non-conservative or excessive conservative assessment results.In most cases

the assessment results will be potentially non-conservative.