Oxidation damage evaluation by non-destructive method for graphite components in High Temperature Gas-cooled Reactor

Shibata, Taiju ; Tada, Tatsuya; Sumita, Junya ; Sawa, Kazuhiro

To develop non-destructive evaluation methods for oxidation damage on graphite components in High Temperature Gas-cooled Reactors (HTGRs), the applicability of ultrasonic wave and micro-indentation methods were investigated. IG-110 and IG-430 graphites, candidates for Very High Temperature Reactor (VHTR), were uniformly oxidized for experiments. (1) Ultrasonic wave velocities were decreased with increasing the oxidation. It can be expressed empirically by exponential formulas to oxidation weight loss. (2) A wave propagation analysis with a wave-pore interaction model showed slightly less velocity reduction than experimental data of the oxidized IG-110. The possibility of the non-uniform oxidation effect was suggested. (3) Although micro-indentation characteristics were changed to show oxidation-induced degradation, it is necessary to assess the variation of the test data with statistic method to specify the oxidation damage in the next study.