Study On Mechanical Analysis Of CFETR CS Model Coil And The Design And Manufacturing Technology Of Helium Inlet And Outlet

The engineering goal of CFETR CS model coil is to design a model coil which can meet operational mode of CFETR CS coil by adopting model coil researched and manufactured with CS prototype conductor of CFTER.The highest field of model coil is 12T,and the conductor largest magnetic field change rate is 1.5T/S.The CS model coil consists of a hybrid magnet system with two Nb3Sn coils located in the high field and three NbTi coils located in the low field.The magnet system is compressed by a preload system.The CFETR model coil will be running in large current,high magnetic field and low temperature.The large electromagnetic force,preload force and thermal stress will produce greater stress and strain on the superconducting coil.The CFETR CS model coils are cooled by supercritical helium flow which can absorb heat load while flowing in the jacket to keep the cable's temperature at 4.5k and ensure the safe operation of the coil.Helium inlet is the most severe stress concentration area in the whole coil.In order to verify the feasibility and reliability of the design on engineering,the mechanical analyses and strength assessment were performed under the electromagnetic,thermal and preload loads,based on the 2D and 3D finite element models in ANSYS.For the R&D of helium inlet&outlet manufacturing,structural design,mechanical analyses,welding technology,helium hole milling and x-ray technique were carried out by theoretical analysis and relevant experiments.According to the engineering goal of CFETR CS model coil,the electromagnetic analysis of the 2D axisymmetric model of the coil was carried out based on ANSYS,and the electromagnetic design parameters were checked.Based on the mechanical analysis of the 2-d axisymmetric model,the mechanical evaluation of the jacket,insulation and G10 components under electromagnetic loads,all of which can meet the structural strength requirements.Based on the generalized Hooke's law,orthotropic smeared property used for CSMC winding pancake were calculated with one so-called 'unit cell' finite element model of the jacket and insulation and the calculation results of young's modulus,poisson ratio,shear modulus and thermal expansion coefficient can match the equivalent properties of ITER CS coil.According to the structure design and operation requirements of CS model coil,stress and strain of preload system were analyzed based on 3D FEA model under the electromagnetic,thermal and preload loads.Based on using the principle of stress linearization,the stress evaluation of preload system can meet the strength requirements.At the same time,the preload load of the single-root pretensioning rod is determined by this model.For insulation system,cross layer conductor,coil terminal lead and support,some 3D FEA models of local area were established to evaluate stress and strain of local area under different running condition.Based on using the principle of stress linearization,the stress evaluation of local area also can meet the strength requirements.According to the design requirements of helium inlets&outlets in CS model coil,the structure design was completed and optimized by statics evaluation based on the ANSYS.After a lot of research and experiments,the welding technology of helium inlets was determined,and the welding process evaluation process was described in detail.The mechanical properties of weld samples were tested in 4.5K.In addition,helium-hole processing technology was developed and related manufacturing equipment was developed.At last,the X-ray detection technology of helium inlet and outlet welds was developed.At present,relevant process research has been applied to the manufacture of helium inlets mock-up of CFETR CS model coil successfully.