National Research Nuclear University “MEPhI” (Moscow Engineering Physics Institute), Moscow, Russia:
B. A. Kalin, Head of a Chair of Physical Problems of Materials Science
M. S. Staltsov, Assistant Professor
A. G. Tishchenko, Student
I. I. Chernov, Professor, e-mail: i_chernov@mail.ru

This article gives a brief overview of the development of vanadium alloys as structural materials for fast and fusion reactors in future. The most important properties of vanadium alloys are considered with respect to the properties of austenitic and ferritic-martensitic steels. Vanadium is sufficiently spread in nature metal, and series alloys have good processability. Short-term strength properties of vanadium alloys remain at a high level up to the temperature of 970 K. In the high-temperature strength properties (thermal creep, long-term strength) vanadium alloys significantly exceed similar characteristics of austenitic and ferritic-martensitic reactor steels. Vanadium-base alloys are characterized by higher melting point and lower density than steels, and have a lower linear thermal expansion and higher thermal conductivity. At the same time, vanadium alloys are able to withstand higher heat loads due to better thermal and physical properties than steels. Analysis of the nuclear physical properties shows that the helium production rate is 2–3 times lower in vanadium alloys than the one in austenitic and ferritic-martensitic steels (as well as hydrogen production). At the same time nuclear heating rates are lower for the vanadium alloys compared to both steels. These effects provide a significant advantage to vanadium alloys as compared with steels. Alloys V – (4–5) Cr – (4–10) Ti have the highest potential in long-term radioactivity and show the advantages over low activation steels. From the point of view of radiation embrittlement, it is concluded that the temperature of 700 K should be taken as the lower limit of the operating temperature for vanadium alloys when they are used as a reactor structural materials. The data on radiation creep of vanadium alloys are extremely limited and contradictory. The ways are noted of solving the existing problems: helium and hydrogen by corresponding alloying, the sensitivity to impurities using high-purity vanadium and/or special alloying, compatibility with liquid sodium using the composite material “steel – vanadium alloy – steel”.

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