An assessment by activation analysis of the influence of small nitrogen contents on electron-induced void swelling in Fe-Cr-Ni alloys

Abstract

Abstract Radiation-induced void swelling was studied in high-purity and nitrogen-doped Fe-16Cr-20Ni alloys by irradiation in a high-voltage electron microscope at 500°C. The nitrogen concentrations were determined at various stages of preparation by neutron and photon activation analysis. Although some contamination occurred during sample preparation the nitrogen contents in the samples ready for irradiation are similar to those found in the massive starting alloys. They are about 90 and 400 wtppm in the doped alloys and about or less than 10 wtppm in the pure alloys. Nitrogen significantly reduces the swelling. For 90 wtppm, the effect is mainly a delay in the beginning of swelling, whereas there is an important decrease of the swelling rate for 400 wtppm with almost no delay. Such minor concentrations of metalloidic impurities should be considered in the interpretation of the swelling behaviours of materials usually considered as highly pure.