Fracture Simulation Study On Passive Shutdown Device With High Temperature Shearing Trigger Absorber Ball

In the face of the widespread global climate change and a serious shortage of resources crisis,nuclear energy with the advantages of safe,clean,and high efficient has become a new direction and hotspot in international energy investment.The molten salt reactor is one of the six alternative heap types of the fourth generation advanced nuclear energy system.Owing to its good economy,high inherent safety,anti-nuclear proliferation and many other advantages,the molten salt reactor has good application and development prospect in the field of nuclear system.The passive shutdown system is an important safety guarantee for nuclear energy systems under accident conditions,which is related to the lifeline of molten salt reactor and even the nuclear power development.On the basis of Chinese Academy of Sciences pilot technology-thoriumbased molten salt reactor nuclear energy system,and combined with 10 MW solid fuel thorium-based molten salt reactor project,this paper studies and designs the passive shutdown device for the thorium-based molten salt reactor to ensure and enhance the safety of thorium-based molten salt reactor nuclear energy system.In this paper,the development history of molten salt reactor and the research status of passive shutdown device is reviewed.By comparing the existing water reactor,fast reactor,gas-cooled reactor and other reactor-type of passive shutdown device,a new type of the passive shutdown device with high temperature shearing trigger absorber ball is proposed to improve the safe shutdown capacity of thorium-based molten salt reactor in the emergency conditions.Based on the proposed high-temperature shearing trigger absorption ball passive shutdown device,thermal stress fracture simulation is a very comprehensive problem.In this paper,the basic theory of thermal stress analysis and the fracture mechanics are introduced and explained,which lays a theoretical foundation for the fracture simulation of the high temperature shear trigger device.According to the characteristics of ASME standard materials,Inconel 625 alloy,whose the mechanical properties steep drop from 650? to 700? is selected to design the thin-wall baffle as the high temperature shearing trigger structure with the reference of design parameters of 10 MW solid fuel thorium-based molten salt reactor.At last,the steady state and transient fault fracture simulation of the two dimensional structure are carried out by Abaqus software at different temperatures under accident conditions.The simulation results show that the thin-wall baffle cracks within 4s~10s when the set temperature exceeds 650? and continues rising.While it will not fracture under the non-accident condition when the temperature rises to 670? and then reduces immediately.The high temperature shearing trigger structure can reliably fracture to trigger the passive shutdown system under the emergency condition,further enhance the safety of thorium-based molten salt reactor,and provides important theoretical and engineering reference for the future.