Small specimen test technique for evaluating fracture toughness of blanket structural materials

Fracture toughness of blanket structural materials is one of the important material engineering properties to design structural components and evaluate the degradation during reactor operation. The present study showed that the master curve (MC) methodology to evaluate change in fracture toughness in the cleavage regime of a reduced-activation ferritic (RAF) steel before and after a thermal embrittlement treatment was applied by using sub-sized compact tension (CT) specimens. The reference temperature of MC for the JLF-1LN steel was estimated as −52 °C by using 1/2CT specimens. The shift of the reference temperature obtained by the MC methodology was judged to be somewhat larger than that of the ductile–brittle transition temperature shift obtained by the Charpy impact tests.