Creep behavior of EUROFER97–3 steel during neutron irradiation at 325 °C and 550 °C to 7–24 dpa

• Creep properties of EUROFER97–3 steel using pressurized tube specimens during irradiation at 325 °C and 550 °C with damage doses ranging from 6.8 to 24.1 dpa were studied. • Lower effective strain and steady-state creep rates at both irradiation temperatures for EUROFER97–3_1100/700 heat treatment compared to EUROFER97–3_980/780 were observed. • The effective strain and the steady-state creep rate are at 550°С higher compared to irradiation temperature of 325°С for both heat treatments. • The irradiation creep modulus is slightly higher than that from literature for irradiated ferritic steels of comparable irradiation temperatures and effective stresses. Irradiation experiments on pressurized creep specimens of EUROFER97–3 steel were conducted using two heat treatment conditions, EUROFER97–3_1100/700 and EUROFER97–3_980/780, in the BOR-60 reactor at temperatures of 325 °C and 550 °C, reaching damage doses of 18–24 dpa. During three reactor shutdowns, intermediate unloading and outer diameter measurements of the creep specimens were performed at three different dose intervals. The results showed that, at both irradiation temperatures, the effective strain and steady-state creep rate of EUROFER97–3_1100/700 specimens were lower than those of EUROFER97–3_980/780. At 550 °C, both the effective strain and the steady-state creep rate were higher compared to 325 °C for both heat treatments. The irradiation creep modulus of EUROFER97–3 was found to be slightly higher than values reported in the literature for irradiated ferritic steels under comparable irradiation temperatures, effective stresses, and damage doses. However, in this study, the modulus exhibited a decreasing trend at damage doses exceeding 20 dpa.