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The results of tests of the compatibility of nickel-based alloys and metal-fluoride melts are generalized for molten-salt reactors. The structure and strength characteristics of the alloys Kh80MTYu, KhN80M-VI, and MONIKR in the initial state, after thermomechanical treatment and quenching, exposure for 1200 h to thermal convection loop filled with 58NaF-15LiF-27BeF 2 with heating by 100°C, are investigated. A method for removing impurities from the melt has been developed. The results of corrosion tests performed on samples of nickel-based alloys in a setup with natural circulation with maximum melt temperature up to 700°C and redox potential of the system 1.25-1.33 V relative to a beryllium comparison electrode are presented. It is shown that deep removal of oxidizing impurities from the melt and maintaining a low redox potential give slow uniform corrosion (less than 5 µm/yr) of Kh80MTYu and KhN80M-VI samples. After the tests were completed, none of the alloys studied exhibited any tendency toward intercrystallite absorption.The use of molten salts as working fluids in fourth-generation reactors requires solving certain urgent scientifictechnical problems. The key problem is finding or developing new structural materials which are compatible with molten fluorides under operating conditions. No less important is the problem of developing a technology which ensures the required purity of the circulating melt.The first fluoride-salt melts were developed in Oak Ridge National Laboratory (USA) for molten-salt reactors with circulating fuel, which operate in uranium-thorium and uranium-plutonium cycles [1][2][3][4]. The prototypical structural material for molten-salt reactors became nickel-molybdenum alloy Hastelloy H (Table 1), developed for the experimental MSRE with fuel salt LiF-BeF 2 -ZrF 4 -UF 4 . Experience in operating this reactor showed that fission products (tellurium) give rise to intercrystallite corrosion of the alloy, substantially limiting the service life of the reactor, and for neutron fluence >5·10 20 cm -2 the alloy is subjected to high-temperature radiation embrittlement.