The evolution of helium-vacancy bubbles in austenitic steels under neutron irradiation

Highlights: • An equation for the growth condition of a helium–vacancy pore nucleus is obtained. • Evolution of the helium–vacancy pores in austenitic steel is described. • Theoretically calculated pore growth rate and experimental results are compared. The paper describes an evolution model for helium-vacancy bubbles in austenitic steels under neutron irradiation. A condition for the growth of helium-vacancy void nucleus was found using the model of point defect migration. An equation to determine the critical diameter, when a nucleus transforms into a vacancy void was obtained. The critical diameter value under irradiation in the fast reactor spectrum was calculated. The found characteristics were compared to the experimental data obtained from samples of the austenitic reactor steel (Russian Grade EK-164) cladding operated in the fast BN-600 reactor. It has been shown that radiation porosity growth leads to increase in critical diameter, thus significantly affecting the swelling process.