Interstitial loop nucleation and growth in solution-treated type 316 stainless steel irradiated to low doses with 22 MeV C2+ and 46.5 MeV Ni6+ ions

The nucleation and growth of interstitial dislocation loops have been studied in solution-treated type 316 steel irradiated to low doses in the Harwell Variable Energy Cyclotron. Specimens have been irradiated with 46.5 MeV Ni6+ ions and 22 MeV C2+ ions, after room temperature pre-injection with 10 ppm helium and without helium pre-injection, at temperatures in the range 300-6000C. The effects of these irradiation variables on the interstitial loop populations produced are discussed. At low doses, where loop intersection is rare and dislocation network formation is minimal, the number of interstitial atoms stored in loops can give an indication of the swelling rate in circumstances where voids remain sub-microscopic. It is shown that extrapolation for the low-dose swelling rates indicated by interstitial loop populations gives reasonable fit with experimentally determined high-dose void swelling values. (Auth.)