Probabilistic safety assessment of components

Obviously, precautions against damage of components by operational and exceptional loads have to be taken. This is performed according to the procedures and standards of the nuclear regulations, e.g. by using the strength and fracture mechanical parameters (warranty parameters) of the involved materials. Within this integrity proof by calculation, however, the effects of the uncertainties in the input parameters cannot be evaluated quantitatively. By considering the possible parameter scatter in the geometrical dimensions and loads while performing the integrity proof, the failure probabilities, and hence the caused uncertainties, become quantifiable. In addition, postulated flaw sizes can be considered and the effects of operational measures can be evaluated. This requires, on one hand, exact knowledge about the scatter of the decisive parameters, and on the other hand knowledge about their effects on the employed methods, and hence on the result of the calculation.In this paper the applied reliability theory is described. Furthermore, the failure probabilities, especially of the weld joints of a feed water line, were calculated and the available partial safety factors were analysed.