Deuterium Permeation Through Reduced Activation V-4Cr-4Ti Alloy and V-4Cr-4Ti Alloy with AlN/Al Coatings

Vanadium alloys are considered as candidate structural materials for thermonuclear fusion reactors (FR) and fast neutron reactors. Some properties of vanadium alloys are especially attractive for FR: fast decay of induced activity, durability in liquid lithium, high temperature strength. At the same time vanadium alloys absorb and dissolve hydrogen isotopes, and hydrogen fluxes through them are quite high. Hydrogen affects on plasticity of vanadium alloys and significantly decreases it at high concentrations. This should be taken into account considering the possibility of vanadium alloys usage as the material of fusion and fission reactors, especially if these materials are assumed to be in contact with radioactive tritium. In this work deuterium permeation through V-4Cr-4Ti alloy with deposited AlN coatings on an adhesion sublayer of Al on it was investigated. Deposition of insulating coatings on blanket structural materials allows to reduce the influence of strong magnetic fields of the tokamak on liquid metal coolant (e.g., lithium flow). It has been demonstrated that the coatings also reduce deuterium permeating fluxes by several times in comparison with V-4Cr-4Ti covered with natural oxide film and about 3–4 orders of magnitude in comparison with literature data for vanadium and its alloys with oxide-free surfaces. Taking into account thermomechanical and insulating properties, moderate swelling under neutron irradiation, thermal conductivity an order of magnitude higher than that of oxide coatings AlN coatings seem to be attractive for application in FR both as insulating and as a coating for hydrogen permeability suppression.