FRACTURE-TOUGHNESS OF CANDIDATE MATERIALS FOR ITER FIRST WALL, BLANKET, AND SHIELD STRUCTURES

Although the design of the International Thermonuclear Experimental Reactor is still in an evolutionary phase, the most probable choice for a structural material is a 300 series austenitic stainless steel. An experiment was carried out in the High Flux Isotope Reactor to quantify the effects of neutron irradiation on the fracture toughness properties of a range of austenitic stainless steels. The alloys investigated were provided by programs in the European Community, United States, and Japan; they included 316, 316L, and titanium-stabilized steels in cold-worked, annealed, and welded conditions. Subsize disk compact tension specimens were irradiated to a dose of about 3 dpa and 50 appm helium (the expected fusion value) at temperatures of either 60 to 125 degrees C or 200 to 300 degrees C. With the exception of a cold-worked air-melted heat of 316, all materials retained excellent fracture toughness, with K-J values varying from 150 to 400 MPa root m over the test temperature range from 90 to 250 degrees C.