Study On Damage And Failure Of Nuclear Power Plant Containment Caused By Main Pipe Swing

With the rapid development of China’s economy,higher demands are being placed on energy supply,and nuclear energy,as a clean and efficient energy source,can effectively solve the energy problems faced by China.To develop nuclear energy,it is necessary to ensure the safety of nuclear power plants.To prevent the leakage of radioactive materials,the nuclear power plant has set up three layers of protection.The first layer of protection is the nuclear fuel rod cladding,made of zirconium alloy;The second protection is pressure vessels,ensuring that radioactive substances do not leak on a large scale;The third line of defense is the nuclear power plant containment,which is the last line of defense to prevent nuclear leakage.The main pipeline inside the containment of a nuclear power plant is highly likely to rupture due to long-term service under high temperature and pressure conditions.The main pipeline may shake under the action of jet force,which may cause serious damage to the containment.The containment is the last barrier to prevent nuclear leakage.Therefore,the research on the damage and destruction of the main pipeline’s impact on the containment of nuclear power plants is of great significance for the design of pipeline anti impact limiting components and ensuring the safety of nuclear power plants.Based on this,this article takes the unit of the "Hualong No.1" nuclear power plant as the research object to conduct a study on the damage and damage of the main pipeline to the safety shell of the nuclear power plant caused by the impact of the main pipeline.The general laws of the main pipeline’s displacement rupture at the junction with the steam generator,the intersection elbow between the horizontal pipeline and the vertical pipeline,and the last elbow inside the safety shell,as well as the three different pipeline pressure swing,are analyzed and obtained;Further established a finite element model for the impact of the main pipeline on the containment vessel,and analyzed the impact failure morphology,displacement time history curve,and pipeline impact force time history curve of the main pipeline under three impact velocities,four impact positions,and four pipeline lengths.The work carried out in this article and the conclusions obtained are as follows:(1)A finite element model was established for the impact of pipelines on reinforced concrete slabs.Through comparison with experiments,the failure modes of pipelines,steel mesh,and concrete at three different speeds,as well as the excavation depth of reinforced concrete slabs,were mainly compared,verifying the reliability of numerical simulation.(2)A finite element model was established for the shaking of the main pipeline under jet load,and numerical calculations were conducted for the shaking of the main pipeline at three break locations and under three jet loads.The velocity of the main pipeline hitting the containment vessel was obtained,and the relationship between the break location,jet load,pipeline kinetic energy,and pipeline internal energy was obtained;At the same fracture position,the larger the injection load on the pipeline,the more work the injection force does,the higher the proportion of energy converted into kinetic energy,and the smaller the proportion of internal energy;Under the same injection load,at the break connected to the steam generator,the injection force does the most work,the kinetic energy of the pipeline is the highest,and the impact velocity of the pipeline is the highest;At the elbow break where the horizontal pipeline intersects with the vertical pipeline,the spraying force does the least work,but the proportion converted into pipeline kinetic energy is the highest,and the proportion converted into pipeline internal energy is the smallest.(3)A finite element model was established for the impact of the main pipeline on the safety shell of a nuclear power plant.The impact of the main pipeline on the safety shell was conducted at three break positions,four impact positions,and four pipeline lengths.The effects of the pipeline impact position,pipeline length,and other factors on the impact force time history curve,displacement time history curve,and safety shell failure morphology of the main pipeline were obtained;And it was found that the main pipeline had the most severe damage to the safety shell under the break at the connection with the steam generator,and the impact position was between the two vertical ribs.