Development of an evaluation model for the thermal annealing effect on thermal conductivity of IG-110 graphite for high-temperature gas-cooled reactors

Sumita, Junya ; Shibata, Taiju ; Nakagawa, Shigeaki  ; Iyoku, Tatsuo; Sawa, Kazuhiro

Thermal conductivity of graphite components in HTGR is reduced by neutron irradiation. The reduced thermal conductivity is expected to be recovered by thermal annealing when irradiated graphite component is heated above irradiation temperature. In this study, the thermal conductivities of IG-110 graphite for the VHTR were measured systematically and thermal annealing effect was evaluated quantitatively. As the results, the thermal conductivities of IG-110 graphite were recovered up to 80% of unirradiated ones at maximum and the thermal annealing effect of IG-110 on thermal conductivity could be evaluated quantitatively using proposed thermal annealing evaluation model based on experimental results. Moreover, the calculated thermal conductivities of IG-110 with modified thermal resistance model were good agreement with experimental ones more than irradiation temperature. It implies that modified thermal resistance model can predict the thermal conductivity of IG-110.