This paper creatively chooses ASTM E793, E2585 and E1461 Standards to study the confirmed material relocation during Pellet to Cladding Interaction (PCI) phenomenon. In this paper, there are two thermal properties used to analyze the material relocation phenomena caused by this interaction between pellet and cladding: one is the melting temperature which is the onset of material relocation; the other is the thermal diffusivity, the primary driver of the material relocation. These two kinetic parameters of the PCI can be established into the fuel center-line melting criterion for assuring that the axial or radial relocation of molten fuel would not be allowed to contact with the cladding in Fast Reactor design. Moreover, the fuel melting temperature shall be used as a cladding failure criterion for some design basis accidents and for those postulated accidents. The total number of rods that experienced the center-line melting is assumed to fail from the point view of radiological dose (J/g) or heat generation calculation.