نبذة مختصرة : The fracture properties of nuclear graphite and their effects on the structural failure process threaten the integrity and safety of High Temperature Gas-cooled Reactor structures. This study aims to develop close-form solutions to determine the size-independent tensile strength and fracture toughness of graphite from small-sized specimens, and thus to predict its structural failure behaviors. Firstly, the scale coefficient and dispersion coefficient are introduced to reflect the heterogeneity of graphite; these are estimated to be 21.0 and 16.8, respectively, in accordance with the meso-structural characteristics and macro-mechanical responses of the graphite. The fracture parameters of geometrically non-similar IG-11 graphite specimens are statistically analyzed with a normal distribution to determine the true fracture toughness and tensile strength, in the form of analytical solutions. Thus, a complete fracture failure curve is constructed to evaluate its fracture behavior. Then, the proposed method is employed to obtain the fracture responses of geometrically similar IG-11 graphite specimens. Good consistency in the calculation results of two types of specimens are observed, verifying the accuracy and size-independence (including absolute and relative sizes) of the proposed method for determining the fracture parameters of graphite. Finally, the structural failure loads of IG-11 and IG-110U graphite specimens with different sizes are predicted within an error margin of 15%. The minimum size requirements of graphite specimens satisfying the condition of linear elastic fracture mechanics are discussed, and the relationship between the fracture behavior of small-sized graphite specimens in the laboratory and the structural failure of actual large-sized graphite members is established.
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