Effect of the Neutron Irradiation Characteristics on the Irradiation-Induced Swelling in a Kh18N9 Steel

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Abstract—The swelling of Kh18N9 steel fragments cut from the reactor internals after irradiation at 370–442°C and an atomic displacement generation rate of 4.8 × 10^–9–4.16 × 10^–8 dpa/s are determined by hydrostatic weighing. The vacancy migration energy for a Kh18N9 steel (1.24 eV) is estimated using the energies for austenitic steels (ChS68, EK164) with various nickel contents. The neutron irradiation-induced void growth in a Kh18N9 steel during its operation in the BN-600 nuclear power reactor internals is analyzed in terms of a point defect migration model with allowance for the estimated vacancy migration energy. The vacancy void growth rate at the beginning of the transient swelling stage is used as a characteristic of the susceptibility to radiation swelling. This rate is diameter independent for the samples under study.