During the normal operation of nuclear reactors, the fuel–cladding gap may close, as a result of the different thermal expansion, creep and swelling of both the fuel and the cladding (pellet cladding interaction - PCI). In this equilibrium state, a significant increase of local power (like a transient power ramp in the order of 100 kW/m-h), induces tensile circumferential stresses in the cladding. In presence of corrosive fission products (e.g., iodine), and beyond specific material dependent stress threshold, cracks typical of stress corrosion appear and grow-up (stress corrosion cracking - SCC). The cracks may spread out from the cladding internal surface, causing the fuel failure. Among the operational and design limits developed to prevent this fuel failure mechanism, a recent review of the “Fuel Safety Criteria” evidenced that the limit on uniform cladding transient strain normally adopted as basic safety criterion for the avoidance of mechanical fracture of the cladding during transients due to pellet-cladding interaction is not fully reliable, especially for high burn-up fuels.