Fatigue Testing and Lifetime Assessment of Components Under Variable Amplitude Loading in Operation Conditions

Abstract The fatigue assessment of nuclear reactor internals and piping is of high importance with regard to safety, reliability and long-term operation of nuclear power plants. Due to their excellent mechanical and technological properties as well as their corrosion resistance austenitic stainless steels are often used for reactor internals and piping systems. These are subject to mechanical and thermo-mechanical loading in all fatigue regimes (Low Cycle, High Cycle and even Very High Cycle Fatigue). For this purpose, numerical simulations of thermo-mechanically loaded components with focus on their welded joints as fatigue relevant locations are conducted. With special regard to the toes of weld joints the multiaxiality is investigated by means of advanced energy-based fatigue damage parameters. A multilinear kinematic elastic plastic material model is used in connection with experimental data of the investigated materials. In addition, fatigue testing of the Control Rod Guide Assembly Support component (replica) and pipes (extracted from the spray line of Ringhals nuclear power plant in Sweden) is conducted in order to further validate the methods of multiaxial fatigue lifetime assessment under operating conditions of nuclear power plants. The applied variable amplitude loading resembles loads measured in real operational components. With the presented work the design guidelines can be further improved by comparing experimental fatigue lifetime with analytical fatigue lifetime prediction.