Structure Design And Strength Analysis Of ITER Bellows

The International Thermonuclear Fusion Experimental Reactor(ITER)is a superconducting Tokamak experimental device planned to produce large-scale nuclear fusion reactions.The bellows between the vacuum vessel port and the cryostat port are called Duct Bellows,Used to connect the vacuum vessel and cryostat.The bellows between the cryostat port and the building wall of the ITER device are called Cell Bellows and are used to connect cryostat to external buildings.The bellows in the ITER device are mainly used to absorb the relative displacement generated between the vacuum vessel and the cryostat during the operation of the device to maintain the stability of the device.During normal operation,it may face various complicated working conditions,such as extreme working conditions such as earthquakes,baking,and vertical displacement events,which may cause deformation and even large displacements of the vacuum vessel and cryostat.Therefore,the bellows structure Safety directly affects whether the vacuum vessel can work safely.This paper studies the upper duct bellows between the vacuum vessel and the cryostat.The static strength and fatigue strength are checked by EJMA standard calculation stress and finite element analysis software to evaluate the rationality of the design.The analysis results provide a theoretical basis and technical guarantee for the engineering design and manufacturing of the bellows in the ITER device,and provide theoretical parameters for the testing of prototype parts,which play an active role in the smooth completion of the project.The main contents of the paper are:1)Introduce the basic structure of the vacuum vessel and cryostat in the ITER device,and explain the important role of the bellows in the device.2)According to the design requirements of the ITER device for bellows,the geometric model of the upper duct bellows is established through CATIA.Through the EJMA standard calculation,the film stress and bending stress of the convolution under different working conditions are obtained,and the structural design of the convolution is evaluated to meet the design requirements.3)Establish a finite element analysis model and optimize the finite element model.Optimize the contact mode between the parts,mesh the finite element model and perform mesh independence analysis,and select the most suitable mesh element size.4)The static strength assessment of the upper duct bellows is carried out.The stresses of the convolution,flanges and intermediate duct are analyzed under different working conditions.The film stress and bending stress are obtained through stress linearization.For the stress assessment of the welding zone,the stress value is calculated according to the RCC-MR standard to ensure compliance with the design standard.For the fatigue life assessment of upper duct bellows,the stress size of the bellows under Class I and Class II conditions is analyzed,and the calculated cycle times are compared with the design standard.The fatigue strength meets the design standard.