[en] During HTGR operation, the dimensions and material properties of nuclear graphite, which appears as a moderator, reflector, core structural materials, and a fuel block, are changed by neutron irradiation as a function of irradiation dose and temperature. These changes lead to significant component stresses and distortions deteriorating and limiting the integrity and lifetime of graphite components. In this sense, knowledges and database on irradiated nuclear graphite properties are important for the design of nuclear graphite components, and safe operation and life management of a HTGR. Accordingly, present state-of-the-art-report has been prepared to analyze the most up-to-date informations on irradiated nuclear graphite properties and relevent technologies. It appeared that international collaborations and IAEA nuclear graphite database membership are needed to prepare the high temperature (≥950 .deg. C), high dose (≥15 dpa) dimensional change and internal stress prediction data in view of the importance of these data on the graphite component life prediction