from the conferences organized by TANGER Ltd.
Long-term operation of nuclear power plants requires reliable monitoring of material degradation while minimizing the amount of material removed from components for the assessment of their current condition, residual lifetime, and structural integrity. Monitoring of changes in key material properties should include all degradation mechanisms occurring during operation, with thermal ageing being one of the main factors affecting these properties. To evaluate the rate of property changes, predict their trends, and assess the period of safe operation, it is essential to determine the initial (reference) properties of materials in their unexposed condition. This paper describes the evaluation procedure and provides data on the initial properties of the base material of new (non-operated) main circulation piping of the new units of the EMO34 nuclear power plant. The study also presents the application of the Small Punch Test (SPT) as an additional mechanical testing method for monitoring the properties of austenitic main circulation piping material. The initial properties of the unexposed material were determined using a combination of standard mechanical tests (tensile test and Charpy impact test) and SPT performed on small discs with a diameter of 8 mm and a thickness of 0.5 mm in accordance with EN 10371:2021. The SPT methodology was applied to determine yield strength and ultimate tensile strength from characteristic forces on the load-displacement curve, as well as fracture-related SPT energy calculated as the integral under the curve up to specimen perforation. The presented dataset demonstrates that SPT can be effectively applied in long-term surveillance programs, particularly in cases where only a limited amount of material is available.
Keywords: Small Punch Test, thermal ageing, nuclear power plant, primary circuit piping, mechanical properties© This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.