ON MECHANISMS CONTROLLING SWELLING IN FERRITIC AND MARTENSITIC ALLOYS

Ferritic and martensitic (FM) alloys are highly resistant to swelling in fast reactor irradiations. High self-diffusion rates and low dislocation bias may contribute to their intrinsic swelling resistance. Other factors, such as high sink densities, are metallurgically mediated and may not be permanent. Further, low helium generation rates in FM alloys may contribute significantly to the low swelling observed in fast reactor irradiations. Helium generation is environmentally mediated, and higher levels generated in mixed spectrum reactors increase void swelling. FM alloys also lose their advantageous helium-to-dpa ratio in fusion spectra. The implications of these factors are evaluated with critical bubble-to-void and rate theory swelling models using austenitic alloys as a reference base.