In large components such as rotors defects due to manufacturing processes have to be taken into account and crack assessments based on findings of non-destructive evaluation are necessary. Similar approaches are used in remaining life estimations. The Time Dependent Failure Assessment Diagram (TDFAD) approach is currently being developed within the R5 procedures as an alternative to conventional methods for predicting incubation and the early stages of creep crack growth. A similar Two Criteria Diagram approach has been developed independently in Germany to assess creep crack incubation in ferritic steels. Both approaches have been investigated in a study initiated by ECCC Working Group 1.2 “Creep Crack Initiation”. Calculations and parameters used for the analysis such as reference stresses and fracture mechanics parameters have been compared for two materials, a ferritic 1CrMoV steel and an austenitic steel of type 316H.