Investigation of the Use of Micro-Mechanical Testing to Analyze the Mechanical Anisotropy of the Zr-2.5%Nb Pressure Tube Alloy

Maintaining a safe operation of nuclear power plants is the primary requirement of nuclear power generating organizations worldwide. This necessitates the use of highly effective methods for assessing the mechanical properties of reactor materials and components. This is important since all components located in a nuclear reactor core experience high levels of neutron irradiation which cause defects to be formed in the metals’ crystal structure. The density of these crystal defects increases with increasing exposure to neutrons and cause the crystalline metal to become harder and simultaneously more brittle. This change in mechanical properties is potentially detrimental to the safe performance of the nuclear reactor. I have evaluated the use of two micro-mechanical testing techniques for assessing the mechanical anisotropy of a common Zr-2.5%Nb alloy pressure tube material used in CANDU reactors. Three different types of experiments were performed; the first two were based upon the use of uniaxial compression of cylindrical pillars while the third was based on the use of spherical micro-indentation. The techniques, and their subsequent data analyses, are presented. It is then demonstrated how these techniques can be applied to assess the anisotropic yield stress and work-hardening behavior of the test material, both in its as-received and its Zr+ irradiated conditions, over a temperature range from 25oC to 300oC