Study On Fatigue Life Prediction For Flat Target Of Divertor Under Electromagnetic And Thermal Coupling Condition

The divertor is one of the core components inside the tokamak device,and it is also the one closest to the plasma,which will face the test of complex and severe operating conditions.High thermal loads will result in large thermal stresses and deformations in the divertor,and also generate large electromagnetic loads acting on the divertor when a vertical displacement event or plasma disruption event occurs.This is a great test for the structure and material of the divertor.In this paper,the structure of the hypervapotron target is designed with reference to ITER,and the structure is optimized under thermal load.The safety performance evaluation of the divertor target under electromagnetic and thermal load is carried out,and the reliability fatigue life prediction model under electromagnetic and thermal operating conditions is established.In this paper,the principle of enhanced heat transfer of hypervapotron target is described.The Euler-Euler model coupled with RPI boiling model is used to carry out the simulation analysis of hypervapotron target,the heat transfer capacity of three fin structures under different cooling water flow rate and different heat flow density conditions are studied,and the optimization of fin-wall clearance parameters is carried out.Based on this,the fatigue life of the structure under steady-state thermal load was evaluated according to the local strain-life method,Neuber’s law and the fatigue life cycle curve of the material,and the ITER internal component design evaluation criteria were used.Ratchet failure analysis was performed on the heat exchanger components,and the results showed that the structure is not subject to ratchet failure.Based on this,the fatigue life of the structure was evaluated under steady-state thermal load based on the local strain-life method and Neuber’s law,and a ratchet failure analysis of the heat exchanger component was performed using the ITER internal component design criteria,which showed that the structure would not experience ratchet failure.Then,the generation mechanism of Halo current and eddy current is discussed in terms of vertical displacement and disruption conditions of plasma,and the values of electromagnetic force are obtained through simulation analysis and theoretical calculation.By simulating the real stress state in the impact process,the evolution transient dynamics of the hypervapotron structure was analyzed.The safety performance of the structure was evaluated according to the elastic and elastoplastic evaluation criteria of the internal component design criteria of the fusion device,which shows that the structure has high reliability.Finally,the fatigue life prediction model of the hypervapotron structure under electromagnetic and thermal coupling was established by multiple linear regression method.The life prediction model could be used to predict the life of the flat-type target structure.The reliability of the model was verified theoretically based on the parameter characteristics of the model.A fatigue life experimental scheme was also designed to modify the fatigue life model.In this paper,a complete system is established for the structural reliability and fatigue life analysis of the divertor under electromagnetic and thermal loads.The fatigue life model established can reasonably predict the fatigue life of the flat-type divertor in service.