Analysis On Crack Propagation Characteristics Of AP1000 Pressure Vessel Under Seismic Load

The reactor pressure vessel will withstand various loads such as high temperature and high pressure during service,so damage and various defects will inevitably occur,and cracks will occur in the defective parts.Earthquake is a very serious disaster in nature and an irresistible factor in nuclear accidents,at the same time the earthquake load will increase of defective parts of the pressure vessel crack extension.Therefore,it is necessary to study the response of the reactor pressure vessel under seismic load,and carry out three-dimensional crack growth calculation.This has important research value in practical engineering applications.The article mainly uses finite element software for numerical simulation and also compares with theoretical calculations.Analyzing three-dimensional crack propagation of reactor pressure vessel with internal crack under seismic load.Compared with two-dimensional model,using the three-dimensional model can better show the changing law of the stress intensity factor along the crack front.The main research contents and results of the reactor pressure vessel containing internal cracks under seismic load are as follows:Firstly,establishing the finite element model of the pressure vessel AP1000.Using the method of applying hydrostatic pressure to analyze the stress of pressure vessel under seismic load.The results show that the stress concentration area of the pressure vessel is the intersection area of the inlet pipe and the cylinder body,and the peak stress of the stress concentration node is greater than the yield strength of the material,the pressure vessel enters the yield stage and prone to crack.Then,establishing the finite element model of angular crack at the inlet joint inside the reactor pressure vessel.Using FRANC3D to calculate the changing law of stress intensity factor along the crack front,and comparing the results with those calculated by the IFM recommended in ASME code.The results show that the stress intensity factor at the inlet joint Angle crack under different loads is smaller than the fracture toughness of the material.When the internal pressure is small,the value of K1 which obtained by the finite element method is not significantly different from the Ki obtained by the IFM.When the internal pressure is large,the K1 calculated by the IFM is close to the maximum value calculated by the finite element method.Finally,calculating three different types of original inlet pipe crack for crack propagation:① The crack was located in the longitudinal section of the inlet pipe;②the longitudinal angle between the crack surface and the inlet pipe is 10°;③ The angle between the crack surface and the longitudinal section of the inlet pipe is 30°.The results show that the stress intensity factor will change with the change of the included Angle.With the continuous expansion of the crack,the crack with an angle with the longitudinal section of the inlet pipe gradually tends to the crack without an Angle with the longitudinal section of the inlet pipe,and the crack expands according to type Ⅰ.