Investigation On Ultimate Pressure And Seismic Bearing Performance Of Steel Containment In Nuclear Power Plant

Nuclear power has been favored by more and more countries in recent years due to its nonpolluting,low-cost,and high-efficiency advantages,and has become one of the important energy sources for sustainable supply worldwide.However,when the nuclear power plant is destroyed by an accident,a large amount of radioactive materials will be produced,posing a huge threat to the safety of people’s lives and property.Therefore,as the last barrier to ensure the safe operation of nuclear power,the containment has played a vital role.In the event of an accident,cracks may occur in the weak location of the containment,which will invalidate the protection of the containment and cause nuclear leakage.Therefore,predicting the ultimate bearing capacity of the containment under extreme environments and determining the location of the damage are of great significance to nuclear safety.This paper takes a CAP1400 steel containment as the research object,uses ABAQUS finite element software to study the ultimate bearing performance and failure mode of the steel containment under accidental overpressure,and analyzes the seismic performance to determine the weak location of the containment.The research results can provide a certain reference for the safe operation of nuclear power.The main contents and conclusions are as follows:(1)The material performance parameters were obtained through mechanical experiments,and the finite element model of the steel containment was established.The method of gradually increasing internal pressure is used to analyze the containment under different internal pressures,and explore the ultimate bearing capacity and failure mode of the containment.The results show that when the internal pressure is the design internal pressure,the stress at the inner wall connecting the containment and the foundation is the largest,but the yield strength is not exceeded,and the containment is in the elastic range without damage.When the internal pressure reaches 1.5 times the design internal pressure,the yield strength is reached locally,it begins to enter the elastoplastic stage,and the plastic area increases as the internal pressure gradually increases.When the internal pressure reaches 2.5 times the design internal pressure,the equivalent plastic strain exceeds the limit value of the material and the deformation is suddenly enlarged,the containment enters a dangerous state.(2)Three actual seismic waves with different seismic intensities are selected,and the seismic intensity is gradually increased by the incremental dynamic time history analysis method to analyze the seismic performance of the containment.The results show that as the seismic intensity increases,the seismic response of the containment becomes more intense.Nuclear power plants should be built in areas with seismic intensity less than 8 degrees for greater safety.Under the action of three types of ground motions,the relative displacement at the bottom of the containment has changed suddenly,indicating that the weak location of the structure is near the bottom.Under the action of the set ultimate seismic strength,the maximum stress of the containment appears at the bottom of the structure and is lower than the yield strength of the steel,indicating that the containment has no plastic behavior and failure.It also has good seismic performance when it is affected by strong earthquakes.(3)By considering the extreme conditions that the containment may face(including the simultaneous action of pressure and earthquake),the pressure and earthquake are regarded as two variables,and the influence of pressure and earthquake on the performance of the containment is studied by quantitative methods.The results show that with the increase of internal pressure,the stress change of the containment by the earthquake decreases;with the increase of the input seismic intensity,the distribution of stress and equivalent plastic strain of the containment changes.The influence becomes more obvious especially when the material yields.At the same time,the distribution of the acceleration and displacement responses of the containment changes because of the existence of internal pressure under the action of ground motions.And with the increase of the input seismic intensity,the displacement difference with different internal pressures becomes more obvious,so the earthquake accelerates the speed of the containment damage.