Comparison of fracture toughness of 9Cr-1W-0.3Ti ODS steel clad material evaluated using three different η and γ factors

9Cr-1 W-0.3Ti ferritic martensitic (FM) Oxide Dispersed Strengthened (ODS) steel is a candidate clad material for France’s future sodium-cooled fast breeder reactor. Fracture toughness of the FM ODS steel evaluated using pin-loaded tension (PLT) is already reported, which was evaluated using ηpl and γpl factors estimated by the domain integral (DI) method. The fracture toughness was re-evaluated again using ηpl and γpl factors estimated by the load separation (LS) method, and using ηpl and γpl factors reported in the literature estimated by the limit load (LL) method, and it was compared with the value already reported. The accuracy of the ηpl and γpl factors estimated by the LS method, relative to the DI and LL methods, is discussed in terms of their similarity to the compact tension specimen and the insensitivity of JIC obtained using LS-derived factors to a/W. Although the ηpl and γpl factors from the DI, LS, and LL methods differed, all three yielded nearly identical JIC values, indicating that any method can be used for single-value fracture toughness, while LS method derived factors are recommended when a complete J-R curve is required for safety analysis.