There are several alternative strategies for the development of nuclear power [1,2]. One of the basic requirements imposed on the future nuclear power technology is its large scale, which presupposes a higher level of safety for all its elements ranging from reactor facilities to NFC technologies [3,4]. One direction for organizing a new technological platform for nuclear power, work on which is now being performed at the State Corporation Rosatom, is the development of innovative fast reactors which have extreme temperatures and dose loads and are cooled by sodium, lead and lead-bismuth [5,6]. In this connection, research on the properties of structural materials under irradiation has not lost its urgency.Metals and alloys irradiated by damaging particles become supersaturated with point defects and radiation-accelerated diffusion. As a result of radiation-induced segregation, the composition of the alloys becomes nonuniform near sinks for point defects (the boundaries of the samples and grains, dislocations, loops, pores and segregations). This is caused by two mechanisms: 1) the presence of a concentration gradient of point defects near sinks and the difference of the diffusion mobility of the components of an alloy and 2) the formation of complexes of certain chemical elements of the alloy with point defects and flows of point defects toward sinks.Alloys undergoing prolonged thermal soaking strive toward thermodynamic equilibrium when there are no concentration gradients of the components. Under irradiation, alloys strive toward 'kinetic' equilibrium (a stationary state), where the fluxes of the components equal zero but because of a concentration gradient of point defects concentration gradients of the components of the alloy arise and the alloy exhibits local nonuniformity. The phase composition of the alloy can change considerably as a result of radiation-induced segregation, irrespective of its initial state.Radiation-induced segregation was first predicted theoretically in 1971 [7] and it was first observed in 1973 [8] in the 18Cr-8Ni-1Si alloy irradiated by fast electrons. Subsequently, many experimental and theoretical studies showing its principal regularities in dilute and concentrated model alloys as well as in structural materials have been performed [9][10][11][12][13][14]. It was shown that the temperature range of the phenomenon (0.2-0.6)T melt coincides with that of vacancy swelling of metals and alloys.The data in [13] indicate the following features of radiation-induced segregation in structural materials: austenitic steel -enrichment with Ni, Si, P, and S and depletion of Fe, Cr, Mo, Ti, and Mn in regions near point defects; ferrite-martensite steel -enrichment with Ni, P, and Si in regions near sinks and the data on the behavior of chromium are ambiguous; vessel steel -enrichment with P, Ni, and Si in regions near sinks. It is evident in Fig. 1 that the radiation-induced segregation shifts into regions of higher temperature with higher rate of production of displacements (in dpa/sec).
