Due to the interaction of welding residual stress (WRS) and salt environment, cracks can be generated and grow in the Spent Nuclear Fuel (SNF) Canisters. In this paper, two fracture mechanics parameters, stress intensity factor and J-integral, for the canisters with axial cracks subjected to the mechanical loading are calculated by finite element analysis. The structural integrity assessment codes, API 579-1 and R6, are used to verify the procedure. For every external surface crack and through-wall crack, the stress intensity factor follows well the existing evaluation codes, API 579-1. The reference stress-based J-integral prediction of R6 procedure is the most accurate to use the tresca-based limit load as the reference stress.