PNNL

Abstract

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 same locations will also experience displacement rates that are also lower than that of most in-core fast reactor experiments, 10-7 to 10-8 dpa/s. One question of particular interest is how to define the lower limit of the temperature range over which void swelling can occur, especially at such lower dpa rates. This question was addressed using a flow restrictor component from the low-flux breeder zone of the BN-350 fast reactor in Kazakhstan. This component was constructed of annealed 12X18H10T, 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 approximately 300 degrees C. At 330 degrees C the swelling reached approximately 1 percent at 20 dpa. Comparison of these data with other published data on this steel from Russian light water reactors at less than 10 dpa confirms that the lowest temperature that stainless steels can begin swelling also appears to be approximately 300 degrees C. Since fusion and LWR spectra generate similar levels of hydrogen and helium, it is expected that these conclusions are equally applicable to both types of reactors when operating at comparable dpa rates.