Design And Manufacturing Of The Flat-Tile Component With Hypervapotron Cooling Concept

The divertor is a key component in a fusion reactor that directly faces the huge thermal power from the fusion plasma,thus its capability to withstand high heat flux is essential for the stability and safety of the fusion devices.In order to further enhance the heat transfer capability of the component,a new type structure with inner rib was suggested basing on the hypervapotron structure of ITER(International Thermonuclear Experimental Reactor).Computational thermal fluid dynamic analysis was used to prove the rationality of the new structure.Then,a new one-step hot isostatic pressing(HIP)technique was developed to prepare W-Cu/CuCrZr/316L compound modules and mock-ups with the new inner rib were fabricated successfully.Finally,high heat flux test(HHFT)was carried out by an electron beam platform in order to evaluate the performances of the new mock-ups.Firstly,a new type structure with inner rib was suggested basing on the hypervapotron structure of ITER.Different from the traditional fin structure of ITER,the new design was changed to the cross-rib structure with longitudinal rib as the main structure and transverse rib as the supplement structure.In this new cross-rib component,the longitudinal rib could effectively increase the heat transfer area while greatly reduce the pressure drop of the fluid.Due to both ends of the longitudinal rib were directly connected with the component,it could effectively improve the mechanical strength of the component in the length direction,as a "reinforcing rib".On the other hand,the smaller transverse rib was favorable to remove bubbles which were produced by subcooled flow boiling near the wall surface.The internal dimensions of the new cross-rib structure were optimized with the single phase by the software of Fluent.The optimized height of the longitudinal rib was set to 4 mm and the width was set to 2 mm.The optimized height of the transverse rib was set to 1 mm and the width was set to 3 mm.Numerical simulations of the heat transfer with the subcooled flow boiling were carried out for investigating the distributions of the temperature field of the new type structure under different thermal hydraulic conditions.In addition,simulation results also showed that the new structure has the most excellent capability to remove thermal power by comparing the peak temperature of traditional ITER hypervapotron,monoblock structure and the new cross-rib structure under the same thermal hydraulic conditions.Secondly,a new one-step HIP technique was proposed and developed to prepare the W-Cu/CuCrZr/316L compound module.In the HIP process,both W-Cu/CuCrZr and CuCrZr/316L joints were connected simultaneously by diffusion bonding at 900 ℃.140 MPa for 2 h.Then for recovering the properties of CuCrZr alloy,heat treatment process was imposed on the HIPed module,including solution annealing at 900 ℃ for 1 h,water quench and aging treatment at 475 ℃ for 2 h.After that,nondestructive testing of ultrasonic was applied to the compound module and no defects were found at the bonding interfaces.SEM(Scanning Electron Microscope)results showed that the grain size of CuCrZr alloy met the ITER requirements.Besides,no microscopic crack was observed in the brittle material tungsten or at the interface of W/Cu joint,so it could be proved that the water quenching treatment did not cause any damage of tungsten or the W/Cu HIP joint.Tensile test was performed on the bonding interface of CuCrZr/316L joint at room temperature.Fracture took place in the CuCrZr alloy base,but not at the interface.Charpy impact test was also performed on the interface of CuCrZr/316L joint and the impact toughness value was about 104 ± 2 J/cm~2.The mechanical test results showed that the strength of the CuCrZr/316L joint was pretty high.Finally,two hypervapotron mock-ups with the new cross-rib structure were machined from the W-Cu/CuCrZr/316L compound module which was produced by the one-step HIP technique.The size of each mock-up was 116 mm×36 mm×20 mm.High heat flux test was carried out by an electron beam platform in order to evaluate the performances of the new design mock-ups.The hydraulic conditions were as follows:0.3 MPa of inlet pressure,20℃ of inlet temperature and approximately 3.7 m~3/h of water volume flow inside the module.The results of high heat flux test showed that the mock-ups successfully withstood thermal fatigue tests,including 80cycles at 10 MW/m~2 and 10 cycles at 15 MW/m~2 and 10 cycles at 20 MW/m~2.An infrared thermometer was used to monitor the surface temperature of the mock-ups in the experiment and it showed that the peak temperature of the mock-up surface was stable and no hot spot was appeared during the whole experiment.The peak temperature of the tungsten tile was 370℃,592℃ and 780℃ under the high heat flux of 10 MW/m~2,15 MW/m~2 and 20 MW/m~2,respectively.Macro-morphology analysis was done after the test,no melting and ablation phenomena were found on the mock-ups.All these confirmed that the new type mock-ups had good heat transfer capability and the design and preparation of the new structure was available.The results of simulation analysis and experimental test can be concluded as follows:The new cross-rib structure of longitudinal rib plus transverse rib can effectively enhance the capability of heat transfer of the flat-tile divertor.The W-Cu/CuCrZr/316L compound module can be successfully manufactured by one-step HIP technique and both the microstructure and properties of the W-Cu/CuCrZr/316L compound module were significantly optimized.The researches can provide technical support for the development and preparation of divertor of CFETR(China Fusion Engineering Test Reactor)and DEMO(Demonstration Fusion Reactor)in the future.