Influence of interaction among multiple cracks on crack propagation in nozzle corner of reactor pressure vessel

Abstract

This paper analyzes the interaction effects and the propagation (growth) behavior among three semi-elliptic corner cracks. Those interacting cracks are assumed to be in the stress concentration area of the inlet of the AP1000 reactor pressure vessel (RPV). The results suggest that the dominant crack will stop first under the interaction. One of the subsidiary cracks will become a long crack while the other will become a short crack. In the simulations, the interaction factor (γ) of the dominant crack and the stressintensityfactors (SIFs) of the subsidiary cracks are calculated respectively by changing the horizontal and vertical distances. The results show that the value of γ decreases with the increase of the propagation steps. With larger horizontal distances among the cracks, the maximum value of γ will rise. In addition, the maximum value of γ will rise if the subsidiary cracks are moved up vertically. Otherwise, the maximum value of γ will decrease. When the cracks get closer together, the increasing rate of the SIF of the long crack will increase while the increasing rate of the short crack will decrease, whether the subsidiary cracks are moved up or down.