The combined effects of strain aging and elevated temperature (275 to 290°C) neutron irradiation to doses up to 3.1 × 10¹⁹ n/cm² (>1 MeV) on the Charpy V-notch (C_v) impact properties of commercial A533-B/A508 pressure vessel steels have been investigated. Neutron irradiation suppresses C_v transition shifts associated with nitrogen strain aging, and it is inferred that free nitrogen in the steel is trapped by irradiation-induced point defects or defect clusters. The results imply that strain aging C_v transition shifts need not be regarded as additive to radiation embrittlement shifts in nuclear vessel safety assessments.

The technique of small-angle neutron scattering has been used to study the radiation hardening processes in copper and phosphorus-doped A533-B alloys. The presence of copper leads to the creation of scattering centers ≤1 nm in diameter by irradiation; the volume fraction of scattering centers increases with increasing copper level and is further enhanced by enrichment of bulk nickel content. Addition of 0.07% phosphorus induces radiation hardening and neutron scattering effects comparable with 0.35% copper.