Engineering Design Research On Divertor For Tokamak Fusion Reactor

China Fusion Engineering Test Reactor(CFETR)is an experimental device of magnetic confinement tokamak fusion reactor that is being designed and developed in China,and the divertor is its important plasma facing components(PFCs).The basic function of the divertor is to remove heat and impurities.For the CFETR device that carries out research on high fusion power,the design of the divertor faces greater challenges:higher requirements for heat removal capacity(peak heat flux of 20 MW/m2),higher mechanical requirements(electromagnetic forces up to several hundred thousand N caused by halo current,electromagnetic torque up to KN·m magnitude,and the combination of multiple loads),requirements for low activation under strong neutron flux radiation,requirements for remote handling(RH)maintenance and lightweight,and a new type of the divertor that can improve the tritium breeding ratio(TBR)of the device.The CFETR device proposes a Divertor-blanket hybrid integrated structure to improve the TBR.The Divertor eliminates the cassette support and adopts a separate design.The lower space is occupied by the breeding blanket,and each target is connected with the breeding blanket respectively.Compared with the integrated Divertor with a cassette support,its advantages are as follows:first,it increases the volume and number of the breeding blankets on the premise of meeting the basic requirements of the divertor,and effectively improves TBR.The second advantage is that the separate design of the divertor can realize separate RH maintenance of each target,reduce RH maintenance load and improve RH maintenance efficiency.The third advantage is that the targets of the divertor adopt flat plasma facing units(PFUs),which are simple in structure and have the ability to eliminate heat load of 20 MW/m~2.Based on the engineering challenges above faced by the divertor and the advantages of the Divertor-blanket hybrid integrated structure,the engineering design and research of the divertor for the tokamak fusion reactor was carried out relying on the CFETR device:1)According to the geometric configuration of the Divertor-blanket hybrid integrated structure in the plasma physical simulation,the structural design of the divertor was completed using low activation materials,which met the requirements of low activation under strong neutron flux radiation,the requirements of RH maintenance of the front of the target,and the requirements of particle discharge with a total effective air extraction flow of 250 Pa·m~3/s.Neutronics analysis shows that the TBR of the CFETR device has been increased to 1.1567 and meets the tritium self-sustaining requirements.2)According to the operation parameters of the CFETR device(fusion power P=1.5 GW,plasma center magnetic field strength B_T=6.5 T and plasma current I_P=14 MA),the thermal load(plasma thermal load and neutron deposition nuclear heat),electromagnetic load(Halo current electromagnetic force and eddy current electromagnetic torque)and experimental test load(liquid pressurization and nitrogen baking)of the divertor were studied.3)According to the above load study,the simulated working conditions of the divertor are summarized and relevant analysis is completed,including thermal-hydraulic analysis and structural analysis.Thermal-hydraulic analysis shows that the cooling system of each target of the divertor meets the requirements of thermal hydraulic parameters,and has the heat transfer performance of eliminating the steady-state peak heat flux of 20 MW/m~2.The structural analysis shows that the mechanical properties of each target of the divertor meet the requirements.