Irradiation creep in austenitic and ferritic steels irradiated in a tailored neutron spectrum to induce fusion reactor levels of helium

A series of six austenitic stainless steels and two ferritic alloys were irradiated sequentially in two research reactors where the neutron spectrum was tailored as a function of time to produce a He production rate typical of a fusion device, Irradiation began in the Oak Ridge Research Reactor where an atomic displacement level of 7.4 dpa was achieved and was then transferred to the High Flux Isotope Reactor for the remainder of the irradiation to a total displacement level of 19 dpa. Temperatures of 60 and 330 degrees C are reported on. At 330 degrees C irradiation creep was found to be linear in stress and fluence with rates in the range of 1.7-5.5 x 10(-4)% MPa(-1) dpa(-1). Annealed and cold-worked materials exhibited similar creep rates. There is some indication that austenitic alloys with TIC or TiO precipitates had a slightly higher irradiation creep rate than those without. The ferritic alloys HT-9 and Fe-16Cr had irradiation creep rates about 0.5 x 10(-4)% MPa(-1) dpa(-1). No meaningful data could be obtained from the tubes irradiated at 60 degrees C because of damage to the tubes.