Irradiation Behaviors of Nuclear Grade Graphite in Commercial Reactor, (III) Mechanical Properties

Bending and compressive strengths, and Young's modulus were measured for Pechiney nuclear grade graphite irradiated in the temperature range 220∼400°C in the environment of CO2 in a commercial reactor, up to the neutron fluence 6.2 × 1019 and 2.2 × 1020n/cm2 (E>0.85 MeV), respectively. All of them increased owing to neutron irradiation, and the changes in both strengths were almost similar in the whole range of irradiation temperature, however the changes in Young's modulus depended on irradiation temperature. It was clarified in the present experiment that both strengths were related with Young's modulus and the relation could be expressed by the formula σ=kE n, where σ and E are strength and Young's modulus, respectively, and n is constant which has different value for bending or compressive strength and also for their measured direction.