Specific Features of Saturation with Deuterium of Vacuum-Arc Coatings Based on Iron
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SPECIFIC FEATURES OF SATURATION WITH DEUTERIUM OF VACUUM-ARC COATINGS BASED ON IRON H. D. Tolstolutska,1, 2 V. V. Ruzhytskyi,1 I. E. Kopanets,1 O. S. Kuprin,1 V. М. Voevodin,1 V. А. Bilous,1 and V. L. Vasylenko1
UDC 669.296.004.0772
We study the accumulation of deuterium in coatings made of FeCrAl alloys and stainless steel, as well as (for comparison) in the Zr1%Nb alloy under the conditions of their saturation with a hydrogen isotope (deuterium) from a gaseous medium. By the method of nuclear reactions, we measure the space distribution of the concentration of deuterium in the coatings after their saturation at a temperature of 450°C ( PD = 2 ⋅10 – 3 Pa for 120 min). It is shown that, for the investigated temperature and pressure, deuteri-
um does not penetrate into the bulk of the coatings and is adsorbed in their subsurface regions from which it is then desorbed at a heating temperature higher than the room temperature by 20–30°С.
Keywords: coating, zirconium, saturation, deuterium, distribution of concentration, chemical composition, morphology.
Introduction Alloys based on zirconium are extensively used in nuclear-power engineering due to the small capture cross section of thermal neutrons, good mechanical properties, and high corrosion resistance in water at normal working temperatures of up to 350°C [1]. The high chemical stability of these alloys is provided by a thin dense film of zirconium oxide. However, in the case of accidents occurring at high temperatures, the zirconium shell fails to serve as a reliable barrier, which blocks the penetration of fuel into the cooling liquid and ambient medium. The application of zirconium alloys in reactors of the fourth generation (Gen. IV) is also limited due to their low corrosion resistance in supercritical water [2, 3]. The situation is additionally complicated by the fact that, the interaction of zirconium with heat carriers (water or steam-water mixture) results in the formation of hydrogen, which is absorbed by the products. The absorbed hydrogen strongly deteriorates the mechanical properties of zirconium, lowers its creep resistance, increases the degree of dissolution of oxygen in the metal during the phase of oxidation in the case of an accident, and decreases its service life. All these factors enhance the loss of plasticity of the fuel shells made of zirconium alloys. As one of possible ways of decreasing the degree of saturation of zirconium alloys with hydrogen under the conditions of water-moderated water-cooled reactors, we can mention the creation of barriers for hydrogen diffusion. The development of new coatings is an actual problem not only in view of the necessity of creation of accident-tolerant fuels but also due to the formation of tritium in thermal reactors. Due to its high mobility, tritium 1 2
“Kharkov Institute of Physics and Technology” National Scientific Center, Kharkiv, Ukraine. Corresponding author; e-mail: [email protected].
Translated from Fizyko-Khimichna Mekhanika Materialiv, Vol. 56, No. 1, pp. 39–46, January–February,
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