CHANGE IN THE PROPERTIES OF FE-CR-NI AND FE-CR-MN AUSTENITIC STEELS UNDER MIXED AND FAST-NEUTRON IRRADIATION

Detailed investigations are performed on mechanical properties, swelli ng and structure of different types of Fe-Cr-Ni and Fe-Cr-Mn austeniti c stainless steels irradiated in the SM-2 high-flux research reactor a nd BOR-60 fast reactor. Steel irradiation temperatures are ranging fro m 100 up to 800 degrees C and the maximum achieved level of damage dos es is 60 dpa for Fe-Cr-Mn steel (with 4-5% of Ni) and 30 dpa for steel s of the C-12Cr-20Mn-W-T type. Presented are dose dependencies of swel ling and mechanical properties of Fe-Cr-Ni and Fe-Cr-Mn steels. It is shown that at temperatures below 530 degrees C the investigated Fe-Cr- Mn steel systems are less susceptible to swelling as compared to Fe-Cr -Ni ones. Fe-Cr-Mn steels showed a lower value of irradiation embrittl ement after irradiation in the mixed spectrum at temperatures from 100 up to 400 degrees C and much higher embrittlement after irradiation f rom 350 up to 400 degrees C in the fast spectrum in comparison with Fe -Cr-Ni steels. Higher hardening rate of Fe-Cr-Mn steels after their ir radiation in BOR-60 is attributed to the presence of dislocation loops and defects of high density in the structure. The structural change f eatures in Fe-Cr-Mn steels under irradiation are considered taking int o account austenite stabilization in the initial state.