Dual ion irradiation of commercial and advanced alloys: Evaluating microstructural resistance for high dose core internals

Ten alloys including austenitic stainless steels 316L and 310; Ni-base alloys X750, 718, 725, 690, 625, and C22; and advanced ferritic alloys T92 (optimized) and 14YWT were irradiated in dual ion mode at 400 °C with ∼5 MeV self-ions to a damage level of 150 dpa and with degraded 2 MeV helium to a concentration of ∼13 appm He/dpa. Irradiation-induced dislocation loops and nanoscale cavities were observed across the alloys, but with only modest swelling. Pre-existing γ ^′ and γ ^″ precipitates were dissolved or chemically disordered by irradiation, while irradiation-induced phases (e.g., Ni ₂ Cr, G-phase) did not form. In terms of microstructural change, the ferritic alloys, as a class, showed the best radiation resistance while the austenitic stainless steels showed the worst. Radiation resistance among the Ni-base alloys varied significantly, with precipitation-hardened alloys performing worse and dislocation loop content increasing with iron content. These findings were in broad agreement, qualitatively and quantitatively, with past dual beam and in-reactor irradiations of structural materials, demonstrating the utility of dual ion irradiations to capture key evolution quickly and accurately.