Void swelling at low displacement rates in annealed 12X18HgT stainless steel at 4-56 dpa and 280-332 deg. C

Water-cooled fusion devices most likely will have austenitic components that operate at temperatures below the inlet temperatures characteristic of high flux fast reactors used to generate majority of data on void swelling. Many of these components will experience displacement rates of 10-7-10-8 dpa/s that are lower than that of most in-core fast reactor experiments. One question of particular interest is how to define the lower limit of the temperature range over which void swelling can occur at such low dpa rates. This question was addressed using a flow restrictor component irradiated at 4-56 dpa and 280-332 deg. C in the low-flux breeder zone of the BN-350 fast reactor in Kazakhstan. This component was constructed of annealed 12X18HgT, an alloy similar to AISI 321. Extensive sectioning to produce 114 separate specimens, followed by examination of the radiation-induced microstructure showed that void swelling in the range of temperatures and dpa rates of interest occurs down to ∼300 deg. C