The present paper is dedicated to the quantitative determination of oxygen-containing impurities in the LiF–NaF–KF eutectic using electrochemical (cyclic and square-wave voltammetry) and reduction melting methods. The LiF–NaF–KF melt was analyzed before and after purifying electrolysis. The amount of oxygen-containing impurities removed from the salt during purification was determined. It was found that after electrolysis, the concentration of oxygen-containing impurities decreased by 7 times. The results obtained via electrochemical techniques and reduction melting were well-correlated, which made it possible to evaluate the quality of the LiF–NaF–KF F melt. To verify the analysis conditions, mechanical mixtures of LiF–NaF–KF containing Li₂O were analyzed using the reduction melting method. The oxygen concentration in the mixtures varied from 0.672 to 2.554 wt. %. Based on the analysis results, the dependence approximated by the straight line was obtained. These data may be used to draw calibration curves and to further develop the procedure of oxygen analysis of fluoride melts.

The problem of tailoring the structural materials for MSR is solved by continuously overcoming the shortcomings of widely used materials and finding new ones. The materials commonly used in engineering may not be applicable for MSR due to their high corrosivity. Experiments were carried out to determine the corrosion rate of stainless steel 12Cr18Ni10Ti with different concentrations of oxide ions (by adding lithium oxide to the melt in the concentration range from 0 to 0.8 wt.%) in a FLiNaK melt. The formation of a protective oxygen-containing layer with a thickness of 1 micron has been realized. The corrosion rate decreases by an order of magnitude at the concentration of oxygen anions in the melt, in the range from 0.2 to 0.4% by weight, which may indicate high-temperature passivation of the material due to modification of the composition of the fluoride melt and reduction in its corrosion activity. In addition, the corrosion type of stainless steel in fluoride melts changes from the intercrystalline and pitting that is usually harmful to reactor material structure to total corrosion when lithium oxide is added. This is due to the “healing” of individual corrosion defects formed on the surface of the studied material by oxygen-containing compounds.

СРАВНЕНИЕ СКЛОННОСТИ К ПИТТИНГОВОЙ КОРРОЗИИ ОТЛИВОК ИЗ ЭКСПЕРИМЕНТАЛЬНЫХ СПЛАВОВ Al6Ca, Al1Fe, Al6Ca1Fe И ПРОМЫШЛЕННОГО СПЛАВА AK12M2

The supercritical water-cooled reactors (SWCR) belong to Generation IV of reactors. These reactors have a number of advantages over currently operating WWERs and PWRs. These advantages include higher thermal efficiency, a more simplified unit design, and the possibility of incorporating it into a closed fuel cycle. It is therefore necessary to identify candidate materials for the SWCR and validate the safety and effectiveness of their use. 12Cr ferritic-martensitic (F/M) stainless steel is considered a candidate material for SWCR internals. Radiation embrittlement and corrosion cracking in the primary circuit coolant environment are the main mechanisms of F/M steels degradation during SWCR operation. Here, the stress corrosion cracking (SCC) in supercritical water at 390 and 550 °C of 12Cr F/M steel irradiated by neutrons to 12 dpa is investigated. Autoclave tests of specially designed disk specimens in supercritical water were performed. The tests were carried out under different constant load (CL), temperature 450 °C, and pressure in autoclave 25 MPa. The threshold stress, below which the SCC initiation of irradiated 12Cr F/M steel does not occur, was determined.

This article, which is based on the materials of a paper presented at the General Meeting of RAS Members on December 8, 2020, formulates new materials-science and technological approaches to ensure the safety and economic efficiency of the operation of new-generation nuclear power plants. The importance of the complementary application of multilevel modeling, accelerated radiation tests of the properties of materials and products in support of design solutions, and the need to create an advanced regulatory framework and standards for the introduction of new methods of design of materials and production technologies are emphasized. It is noted that a number of promising projects for the development of new materials are successfully being implemented in cooperation with the institutes of the Russian Academy of Sciences. The main directions of cooperation between industrial research institutes and academic institutes in the interests of nuclear energy are listed.

This article discusses adjustment of processing modes of selective laser melting of powdered 03Kh16N15M3 steel allowing fabrication of lattice structures with steady parameters. On the basis of statistical analysis of sizes of cells, ribs, and nodes in cross section parallel to the growth direction of lattice structures of two sizes of ribs and voids (400 × 1000 and 300 × 600 μm), the process variables providing fabrication of items with the most stable sizes along the height of the structure have been determined. The sizes of the main elements of the lattice structure have been determined using a scanning electron microscope; the crystallographic texture and material structure have been determined using X-ray structural analysis. It has been determined that increase in laser power leads to increase in distortions in crystalline structure and decrease in the lattice constant of the material of lattice structures. The highest distortions of the structure have been detected in ribs of lattice structures as well as in items with smaller sizes of ribs and voids. The material of the considered lattice structures is characterized by axial texture, for which crystallographic axes are oriented parallel to the growth direction. The degree of manifestation of the axial texture component depends on the laser power used for growing of lattice structures. The samples obtained by minimum radiation power are characterized by a scattered axial texture, which is dictated by an increase in the number of chaotically oriented grains with a simultaneous decrease in the bulk of strictly oriented columnar crystals, located mainly in the vicinity of the axis of the ribs of the lattice structure. The texture sharpness in lattice samples with voids of small size is higher than that in samples with voids of large size.