Research On Manufacturing Technology Of High Heat Flux Components Of Fusion Reactor Divertor

The purpose of developing fusion reactors is to convert fusion energy into electricity that can be used directly by humans.As one of the key components of a magnetic confinement fusion reactor,the main function of the divertor is to remove impurities,heat and helium ash.The high heat flux component of the divertor interacts directly with the plasmas,and the service environment is very harsh.It needs to withstand the comprehensive impact of strong particle flows such as plasma and high heat fluxes and electromagnetic forces.In addition,the 14 MeV high-energy neutrons generated by the fusion reaction can cause severe damage to the divertor materials.Therefore,the high heat flux components of the divertor must be made of materials with low neutron activation characteristics,as well as the ability to withstand plasma bombardment,discharge large amounts of heat timely and efficiently,and withstand electromagnetic loads.Its successful development requires the use of appropriate plasma facing materials(PFM),heat sink materials and structural materials.For this purpose,two material combinations are selected for the preparation of the high heat flux components of the divertor,namely,W/Cu/CuCrZr/316 L,which is currently selected for ITER and most fusion devices,and KW/Cu/ODS-Cu/RAFM,which is more suitable for the fusion reactor environment.In this paper,first,numerical simulation is used to analyze whether the two high heat flux components can meet the operational requirements of the divertor,and the results verify the rationality of the material and structure design.Then,the bonding methods and fabrication routes of the dissimilar materials in the two components are investigated,analyzed and evaluated.Finally,the feasible fabrication routes and schemes of the high heat flux components of the divertor with two different material combinations were screened out.The fabrication process of the high heat flux components of the flat-type W/Cu/CuCrZr/316 L divertor is divided into three steps.First,W and the interlayer Cu are connected to form a W/Cu tile,then CuCrZr and 316 L are joined to form a composite heat sink,and finally the W/Cu tile and the composite heat sink are connected to form a divertor mockup.In this paper,W/Cu is connected by"casting+hot isostatic pressing(HIP)" and"casting+vacuum hot pressing(VHP)" methods;CuCrZr/316 L is connected by explosive welding;Cu/CuCrZr is connected by HIP and vacuum brazing.The results of ultrasonic nondestructive test(UT),shear test and microscopic examination show that the interfaces of W/Cu,CuCrZr/316 L and Cu/CuCrZr are well connected.Then,according to different W/Cu and Cu/CuCrZr process combinations,the W/C u/CuCrZr/3 16 L divertor high heat flux component was prepared by three fabrication routes.route 1:"casting+HIP’+explosive welding+HIP",route 2:"casting+HIP’+explosive welding+vacuum brazing",route 3:"casting+VHP’+explosive welding+vacuum brazing".Subsequently,through the systematic high heat flux tests and result analysis,the better fabrication route for preparing W/Cu/CuCrZr/316 L is selected.After 350 cycles of 20 MW/m2 for the mockup prepared by route 1,the surface temperature of W increased significantly,and the temperature rise exceeded 20%of the initial temperature,which is not within the acceptable range of the fatigue test.Therefore,the experiment is terminated.After the experiment,UT results show that there has large area defects at the Cu/CuCrZr interface.The mockups prepared by route 2 and route 3 have successfully withstood 1000 cycles of 20 MW/m2.After the test,the interface of the mockup has no obvious damage,and the heat transfer performance remains stable.The surface temperature of mockup W prepared by route 3 is about 106℃(12.8%)lower than that of route 2.The above results show that the performance of the divertor mockup prepared by route 3 is relatively better,that is,using"casting+VHP" method to connect W/Cu,explosive welding to connect CuCrZr/316 L,and vacuum brazing to connect Cu/CuCrZr.The fabrication process of the high heat flux components of the flat-type KW/Cu/ODS-Cu/RAFM divertor is first carried out in China.The fabrication process is divided into three steps:firstly,KW and interlayer Cu are connected into KW/Cu tiles,then,ODS-Cu and RAFM are connected to form a composite heat sink,and finally,KW/Cu tiles and composite heat sink are connected to form a divertor mockup.In this paper,KW/Cu is connected by"casting+hot isostatic pressing(HIP)"method;ODSCu/RAFM is connected by explosive welding;Cu/ODS-Cu is connected by HIP and vacuum brazing.The brazing filler is Cu-8Sn-5Ti.The brazing temperature,holding time and other process parameters are optimized to realize the reliable connection between Cu and ODS-Cu.The results of UT,shear test and microscopic examination show that the interfaces of KW/Cu,ODS-Cu/RAFM and Cu/ODS-Cu are well combined.Then,according to different Cu/ODS-Cu process combinations,the high heat flux component of KW/Cu/ODS-Cu/RAFM divertor is prepared by two fabrication routes,route 1:”’casting+HIP’+explosive welding+HIP",route 2:"’casting+HIP’+explosive welding+vacuum brazing".Subsequently,through the systematic high heat flux tests and result analysis,the better fabrication route for preparing KW/Cu/ODS-Cu/RAFM is selected.After 400 thermal cycles of 20 MW/m2 for the mockup prepared by route 1,the surface temperature of KW increased significantly,and the temperature rise exceeded 20%of the initial temperature,which is not within the acceptable range of the fatigue tests.After the tests,UT results show that there has large area defects at the KW/Cu interface.The mockup prepared in route 2 has successfully withstand 1000 thermal fatigue tests of 20 MW/m2.After the test,the interface of the mockup has no obvious damage and the heat transfer performance remains stable.The above results show that the performance of the divertor mockup prepared by route 2 is relatively better,that is,using"casting+HIP" method to connect KW/Cu,explosive welding to connect ODS-Cu/RAFM,and the vacuum brazing to connect Cu/ODS-Cu.The high heat flux components of the divertor prepared by this route have strong neutron irradiation resistance.Through the research work in this paper,the fabrication routes of the high heat flux components of the flat-type W/Cu/CuCrZr/316 L and KW/Cu/ODS-Cu/RAFM divertor are screened out.The divertor mockup that can maintain various performances after 1000 cycles of 20 MW/m2 thermal fatigue tests was successfully prepared,which verified the reliability of the divertor structure and fabrication routes,and can provide useful data reference and technical support for the development of future fusion reactors.