National Research Nuclear University “MEPhI”, Moscow, Russia:

S. N. Nikitin, Engineer, Applied-Research Laboratory 709 

B. A. Tarasov, Engineer, Applied-Research Laboratory 709 

D. P. Shornikov, Senior Researcher, Applied-Research Laboratory 709, e-mail: mephi200809@yandex.ru

V. G. Baranov, Professor of a Chair “Physical Problems of Materials Science”, Head of Research Laboratory 709

Nowadays, one of the most promising types of nuclear fuel for fast reactors is metallic fuel, based on Uzr, UPuZr and UMo alloys, having such advantages as high thermal conductivity, high density and excellent neutron- physical properties. Ferritic-martensitic steels, such as HT-9 and 9Cr, are offered as claddings with such fuel. These steels are exposed to little swelling during irradiation. Their advantages are good mechanical properties at high temperatures and resistance to metal coolants. During the exploitation, metal fuel comes into tight contact with metal sheath (because of swelling), which promotes the fuel-diffusion interaction at high temperature of the shell to form a liquid phase and fuel rod failure. Alloying of ferritic steels by barrier layer forming elements (Al, Si) is the promising way to improve the compatibility of metallic fuel with ferritic steels. This paper studies the diffusion interaction between UZr and UMo alloys with iron alloys. These results show that ferritic chromium steels have higher compatibility with metallic nuclear fuel, based on uranium-zirconium alloy, compared with austenitic chromium-nickel steel. Introduction of aluminum into Fe (13% (wt.) of Cr) leads to decrease in the rate of interaction of UZr core with the shell by more than 4 times. It was found that iron alloying with aluminum leads to a sharp reduction of interaction speed by forming a protective zirconium-enriched layer, which suppresses the formation of liquid phase to the temperature of 800 ^oC. In addition, there is shown the possibility of obtaining of in-situ protective coatings on ferritic chromium steel, which was alloyed by aluminum, using nitriding method.

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