THE FRACTURE-TOUGHNESS DATABASE OF FERRITIC ALLOYS IRRADIATED TO VERY HIGH NEUTRON EXPOSURES

A summary is presented of the entire fracture toughness database for HT9 and modified 9Cr-1Mo generated at Hanford. Fracture toughness tests were recently performed on miniature specimens of HT9 and modified 9Cr-1Mo irradiated in the Fast Flux Test Facility (FFTF) to exposures ranging from 35 to about 100 dpa. At test temperatures ranging from 20 to 430-degrees-C, values of toughness and tearing modulus at 35 to 100 dpa were no lower than those obtained previously in tests conducted on specimens irradiated in the Experimental Breeder Reactor-II (EBR-II), despite differences in orientation between the EBR-II and FFTF specimens. The data imply that the fracture toughness of HT9 is adequate to exposures on the order of 100 dpa at temperatures typical of fast reactor operation. Fracture toughness data generated on material irradiated in the High Flux Isotope Reactor, however, demonstrate that both alloys are unsuitable for use even to low neutron exposures at temperatures on the order of 50-degrees-C.