Irradiation effects on thermal shock resistance and fracture toughness of HTGR-graphite

This paper describes changes in the thermal shock resistance and the thermal shock fracture thoughness in addition to the usual mechanical properties including the diametral compressive strength and fracture toughness of four varieties of graphite for the high temperature gas-cooled reactor due to neutron irradiations of (1.6 2.3) × 10²¹ n/cm² (E > 0.18 MeV) at 600 850°C. These experiments are carried out by using small disk specimens which can be conveniently loaded into a capsule for irradiation in the Japanese Materials Testing Reactor. Both the thermal shock resistance and the thermal shock fracture toughness of graphites after irradiation decreased markedly despite of the increase in mechanical strength.