Relationship of the characteristics of radiation-induced porosity in steel Kh16N15M2GTR (ChS-68) with the temperature and dose of neutron irradiation

Transmission electron microscopy (TEM) was used to study the radiation-induced porosity of steel ChS-68 (Kh16N15M2GTR) (16Cr15Ni2MoMnTiB) employed for fuel elements, which was cold-deformed and irradiated with fast neutrons in a BN-600 reactor at temperatures of 410-600°C to different damaging doses in a range of -20-90 dpa. It was shown that, in the fuel-element claddings, the formation and growth of voids differing in size and in the time and mechanism of nucleation occur depending on the temperature and irradiation dose. The dependences of the average sizes and concentrations of all types of voids on the damaging dose of neutron irradiation for different temperatures were obtained. It was found that, with an increase in the damaging dose to a certain value, the concentrations of all types of voids increases. On reaching the damaging dose at which the concentration and size of voids become considerable, void coalescence begins, which results in a decrease in their concentration. The average size of voids of all types increases; the growth rate of coarse voids is higher than that of fine voids. The contribution of voids of different types into swelling is analyzed.