Methods of improving the high-tempera ture strength and corrosion resistance of vanadium and certain alloys used in reactors

Abstract

We present new evidence for the high-temperature strength of vanadium and low-alloyed (up to 15 at. %) vanadium-based alloys under conditions of prolonged (up to 5000 h) high-temperature (973-1173 K) exposure to vacuum, helium, lithium and sodium melts, modeling reactor heat-transport media (10 Pa). The kinetics of phase transformations in alloys of the systems V-Zr-C, V-Nb-Zr-C, V-Mo-Zr-C, and V-Ti-O in the process of prolonged aging under stress is analyzed. It is established that the process of pre-decay of a solid solution has many stages and is intensified by the action of stresses. The corresponding isothermal diagrams of the decay of VTsU (V-Zr-C) alloy are constructed. We give recommendations as to the choice of alloying elements with the aim of enhancing the high-temperature strength of vanadium and vanadium alloys used for reactors. New alloys developed on the basis of the systems V-Ti-O, V-Nb-Zr, V-Ta-Hf, V-Cr-Sc, and V-Cr-Nd and a new method of hardening thermochemical treatment of vanadium-titanium alloys with the use of oxygen from air have found application in pilot-engineering developments for high-temperature nuclear power plants.The strategy of the development of power engineering consists of increasing the power of existing nuclear reactors, transferring to the use of the energy of fast neutrons, bringing controlled thermonuclear fusion to a commercial level, and increasing the safety margin of energy production to the maximum possible extent [1][2][3]. The analysis of the principles of selection of materials for the operating and promising fast-neutron nuclear power plants and for fusion-type reactors shows that one of the methods of upgrading their efficiency consists of raising the operating temperatures of the processes of energy conversion and transmission up to 900-1400 K and using unconventional high-temperature media. The experience in the operation of reactors and the predictions of many scientists allow one to separate the following promising media [4][5][6][7][8][9]. For fast-fission reactors, these are heat-transport media based on sodium, helium, and, in some cases, on lithium. For fusion-type reactors, we mention lithium (blanket), eutectics (tritium-reducer), helium (heat-transport medium), and vacuum (vacuum wall). For this to be realized, the development of new materials and the improvement of the reliability and serviceability of tested high-temperature metallic materials are required. These materials should meet the requirements of not only the physics of nuclear fission and lusion, but also the physicochemical requirements that are imposed by their prolonged interaction with reactor media and related ones under the simultaneous action of high temperature and loads. In this respect, according to the predictions of world-famous scientific-research centers specializing in the field of reactor materials science, the application of refractory metals, in particular, vanadium and low-alloyed vanadium alloys (up to 15 at. %) [9][10][11][12], nickel-based alloys, and special steels [...

Formation and structure of V–Zr amorphous alloy thin films

“…This is because these two individual elements have good creep resistance [1], high melting temperatures, high thermal conductivities, tailorable low densities, relatively small thermal neutron cross-sections [2] and low thermal expansion [3]. Zr-based alloys are already extensively used for structural, in-core applications for the current generation of fission reactors [4], while V-based alloys are under consideration for structural components in fusion reactor environments, particularly the first-wall blanket [5].…”