On the methodology of fatigue assessment of nuclear power plant components

The fatigue assessment of components has to be considered as an essential module of the safety concept as well as the ageing and lifetime management of nuclear power plants. It is based on special safety requirements in the design phase as well as in the framework of the ageing and lifetime management. Considerable efforts of load identification (fatigue monitoring) as well as the strict code conformity are characteristic features. The predominance of thermal cyclic loadings as well as relevant stress/strain amplitudes in the low cycle fatigue regime (LCF) are peculiarities compared to other technical domains. The code based fatigue concept is explained in the first part of the contribution. Furthermore, potentials for the quantification of existing margins are shown. On this, a new approach of mechanistic simulation of the thermal cyclic fatigue process based on short crack fracture mechanics is described in the second part. (orig.)