Structural evolution features of the 42XNM alloy during neutron irradiation under VVER conditions

The paper presents the results of microstructural studies by transmission electron microscopy and atom probe tomography of the Ni-Cr-Mo (42XNM) alloy in the initial state, as well as after neutron irradiation, in the range of fast neutron fluence (0.9–1.5)• 10²⁶n• m⁻² (E>0.1 MeV) (5–12 dpa) at ~ 300°C. It was shown that during neutron irradiation, various defects were formed – dislocation loops and pores, the bulk density and size of the second phase precipitates (TiN and α-Cr) remained stable. Quantitative analysis of chemical composition for regions near the boundaries of austenitic grains was made, which showed typical effects for materials with an FCC lattice (which contains Ni and Cr) after neutron irradiation – nickel depletion of grain boundaries and enrichment in chromium. Similar studies were carried out for segregation processes on the Frank loop edges.