This study presents a comprehensive investigation into the mechanical and thermophysical properties of various grades of nuclear graphite, essential for their application in Generation IV high-temperature reactors (HTR). The research highlights the significant variability in properties such as density, elastic modulus, tensile strength, compressive strength, and thermal expansion, attributed to microstructural characteristics, manufacturing processes, and differing source materials. Utilizing a large dataset exceeding 24,000 data points, the analysis employs the three-parameter Weibull distribution to characterize the stochastic behavior of these properties, emphasizing the need for a probabilistic approach in material qualification. The results demonstrate that fine-grained, isostatically molded graphite grades exhibit superior tensile strength due to their smaller pore sizes and isostatic processing, while extruded graphite reveals higher variability in strength due to anisotropic behavior. Furthermore, the thermal properties indicate minimal variation across grades, suggesting a common thermal response influenced by graphite's crystalline structure. These findings enhance the understanding of nuclear-grade graphite's unirradiated performance, facilitating the development of reliable materials for advanced nuclear reactor applications.
