High temperature Young's modulus of IG-110 graphite

Data on Young's modulus of nuclear graphite at high temperature are required for the design and safety analysis of the VHTR. The purpose of the present experiment is to obtain Young's modulus data for the graphite materials used in the VHTR. An ultrasonic wave pulse method was applied up to a temperature of 1400 deg C. The Young's modulus of oxidized materials was also measured. The results were compared with tensile strength at high temperature to estimate the tensile strength non-destructively. Tensile tests were carried out at 600 deg C and 1000 deg C in a vacuum chamber. Specimens were oxidized to three weight loss levels (3.5 %, 5.0 %, 7.0 %) in air at 550 deg C. Young's modulus increased with increasing temperature. Temperature dependence of Young's modulus became less pronounced as the amount of oxidation increased. In the specimens oxidized to more than 5 %, the Young's modulus first decreased slightly with increasing temperature and the temperature at which the Young's modulus started to rise sifted to higher region with increasing weight loss. Young's modulus and tensile strength at high temperature up to 1000 deg C were correlated with each other using an equation: (σ/σ0) = (E/E0)1/2, where σ, σ0, E and E0 denote tensile strength at given temperature, tensile strength at room temperature, Young's modulus at given temperature, Young's modulus at room temperature, respectively. (author)