EFFECT OF HYDROGENATION ON THE ANISOTROPY OF MECHANICAL PROPERTIES OF THE FUEL ELEMENTS PIPES OF AN ALLOY Zr-1% Nb

Mechanical characteristics of the fuel tube the alloy Zr-1% Nb Ukrainian production tensile in radial (annular samples) and longitudinal direction ("quasi-plane" samples) in the delivery state and after hydrogenation were defined. It is shown that the fuel tubes in the initial state possess significant anisotropy of mechanical properties: significant difference is observed for the proof stress, which in a tangential direction (with respect to the tube axis) is 20% higher than in the longitudinal direction. Hydrogenation of the fuel tubes increases anisotropy of mechanical properties: yield strength in the tangential direction by 20...40% higher than in the longitudinal direction. Tensile strength of the samples which have been deformed in the tangential direction exceeds the tensile strength in the longitudinal direction by 25...50%. The process of hydrogenation virtually has no effect on the plasticity of the ring samples, but it leads to embrittlement of quasi-plane samples. The cause of the anisotropy of the mechanical properties of the fuel tubes in initial state is the texture which is formed in the material in resulting in mechanical and heat treatments. Features of change of the strength and plastic properties of the hydrogenated material is associated with the formation of oriented zirconium hydride precipitates, which have different effects on the deformation of the tubes in the longitudinal and transverse directions.