The continuous evolution of heavy-duty gas turbines, with the aim of improving the machine performance, implies a significant increase of its working conditions. Regarding turbine expander, front blades & vanes have to withstand extremely harsh operating conditions that lead to damage mechanisms as creep, fatigue and oxidation, which play an important role in the crack initiation and propagation. At Ansaldo Energia Group, it has been studied, by means of Linear Elastic Fracture Mechanics (LEFM) approach, the evaluation of crack propagation behaviour at the most critical locations of a GT second vane for power generation (F-class). Furthermore, it has been developed a Mechanical Integrity (MI) assessment on the FE model where the required creep limits of the material were overcome, according to FE calculations.