Swelling behavior of austenitic stainless steels in a spectrally tailored reactor experiment: Implications for near-term fusion machines

Abstract

Abstract Current designs for engineering test reactors such as the International Thermonuclear Experimental Reactor propose to use an austenitic stainless steel for the first wall. Most of the available swelling data have been derived from neutron-irradiation experiments in which helium generation rates are very low (fast breeder reactors) or very high (mixed spectrum reactors). Recently a spectrally tailored experiment was concluded in the Oak Ridge Research Reactor in which the helium generation rate and damage rate were maintained at values typical of a fusion reactor operating at ~ 1 MW/m 2 . It was found that the swelling behavior of a titanium-modified stainless steel (PCA) in both the cold-worked and solution-annealed conditions differed significantly from the behavior observed in earlier experiments in which the He/dpa ratio was either ~ 0.5 or ~ 50. The results suggest that there is a strong dependence of microstructural evolution on the He/dpa ratio. The data are shown to be consistent with earlier theoretical predictions of swelling behavior that is a non-monotonic function of the He/dpa ratio. Finally both the present data set and a larger collection of low-temperature swelling data are discussed in the context of near-term machines.