Ageing of Nuclear Power Plant’s Equipment. Assessment of Reactor Pressure Vessel Ageing Effect

Ageing of materials stands for the change in their mechanical properties, due to thermodynamic imbalance of the initial condition, and gradually bringing the structure to equilibrium in the presence of sufficient diffusive mobility of the atoms. The current paper presents the main mechanisms of degradation of the mechanical properties of the nuclear power plant equipment metal, as well the models for ageing. The ageing effects and ageing indicators typical for the equipment are defined. The ageing process may cause loss of the appropriate functions. It is important to recognize the ageing effects, as well the ageing indicators. Testing methods are defined for every ageing indicator. The paper considers different national approaches to ageing management of structures, systems, and components (SSCs) at nuclear power plants (NPPs).