Numerical analysis of the influence factors of plastic failure in the cracked nozzle region of reactor pressure vessel

Abstract

The integrity of reactor pressure vessel (RPV) is greatly affected by pressurized thermal shock (PTS). Once crack appears in the nozzle region, the stress concentration around the crack tips may lead to crack propagation, and finally cause a serious security problem. When the transient temperature is above the nil-ductility reference temperature, elastic–plastic constitutive relations are considered in the fracture mechanics analysis. The temperature-related properties of the materials are introduced into a 3-D finite element model to establish the temperature field and stress field of a real RPV. Since the test and safety inspection for RPV with defects under PTS loads are quite difficult and dangerous, the process of the ductile crack propagation is simulated by the extended finite element method (XFEM), and the critical crack sizes for different base wall thicknesses are determined. Then, the quantitative analysis of the effect of the crack position on the ultimate bearing capacity is carried out. For the crack tips with different shapes, the crack propagation law and the shape effect on the ultimate bearing capacity of the whole structure are also analyzed. According to their crack propagation paths and damage degrees, a good agreement is obtained.