Table of Content

15 June 2023, Volume 43 Issue 2

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Nuclear Fusion Engineering

Cu-Mn based solid solution brazing alloys for Cu and CuCrZr brazing and the joint structures 

XU Ri-sheng , ZHU Jie , GUO Feng , WEI Ming-yu , QIANG Jian-bing , WANG Ying-min , WANG Jian-bao , LIAN You-yun , FENG Fan , LIU Xiang

2023, 43(2):  125-131.  DOI: 10.16568/j.0254-6086.202302001

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 In order to solve the metallurgical connection problem between CFC and CuCrZr alloy, a series of solid solution brazing alloys with the nominal compositions of Cu₆₂Mn_37-xGaxCr_0.5Si_0.5(x=0~10, at.%) were designed by taking Cu₆₂Mn₃₈(at.%) as the basic composition, Ga with a low melting point as the major alloying element and Cr and Si the minor alloying elements. The brazing alloys in foil form of 100μm thick were made by arc melting, suction casting and subsequent cold rolling. The brazing alloy of Cu₆₂Mn₃₁Ga₆Cr_0.5Si_0.5 was employed to joint oxygen-free copper (OFC) and CuCrZr alloy at different brazing temperatures of 875~900℃ and holding times of 15~25min. The melting behavior of the brazing alloys was examined by thermal analysis, and their structures were identified by X-ray diffraction. The microstructure, composition and mechanical properties of joints were studied by means of optical microscopy, scanning electron microscopy, electron probe and mechanical properties tensile equipment, respectively. The results show that defect-free OFC/CuCrZr joints were obtained at a brazing temperature of 880℃ along with a holding time of 25min. The main bonding seam of the joints consists of a Cu solid solution matrix, in which small amount of nano Cr₃Si particles are unevenly and discontinuously embedded. In room temperature tensile test, the OFC/CuCrZr joint exhibited an tensile strength of 215MPa，a plastic strain of ~40%, and a tough fracture mode. The Cu₆₂Mn₃₁Ga₆Cr_0.5Si_0.5 brazing material associated with the specific brazing technique has been used to joint the carbon fiber composite and CuCrZr alloy in the fabrication of HL-2M divertor. 

Fe-based amorphous filler alloys for brazing tungsten and low-activation steels and the joint microstructures 

WEI Ming-yu , WANG Jian-bao , Jitendar Kumar , QIANG Jian-bing , WANG Ying-ming , LIU Tian-zhi , FENG Fan , LIAN You-yun , LIU Xiang

2023, 43(2):  132-139.  DOI: 10.16568/j.0254-6086.202302002

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For the joining of W and CLF-1 RAFM steel, a series of Fe-based amorphous filler alloys consisting of low-activation constituent elements, namely, Fe-B-Si, Fe-B-Si-Sn, Fe-B-Si-Cr-(Sn), Fe-B-Si-P-(Cr, Sn), Fe-B-Si-Mn-(Ga, Sn) and Fe-B-Si-(Cr, Mn, Ga, Ta, Sn), have been designed and made into amorphous alloys in foil form by means of rapid melt quenching. The microstructures of the W/CLF-1 RAFM steel joints were comparatively studied. X-ray diffraction was performed to identify the phases formed in the foil alloys and in the main bonding seams. The melting temperature and the liquid-phase line temperature of the amorphous foil alloys were examined by differential thermal analysis. The morphology and element mapping for the bonding seams were carried out using optical metallography and electron probe microanalysis respectively. The results show that with the Fe-B-Si, Fe-B-Si-Cr and Fe-B-Si-Mn-Sn amorphous filler alloys, W/CLF-1 joints with perfect structure integrity were fabricated. In the bonding seams, α-Fe solid solution phase is formed as the substrate phase with the first two sorts of filler alloys, and a martensite substrate phase is obtained in the latter case. The high B-content in these Fe-based amorphous alloys impels the FeWB, FeW₂B₂ and Fe3B types of intermetallic phases to alloying formation in the bonding seams, which effectively blocks the fast diffusion of W to the substrate of low activation steel during high temperature brazing. These new low-activation filler alloys are promising materials for jointing W and RAFMs and for the property assessment of joints. 

Optimal design and analysis of the supporting structure for EAST eight-pairs current lead tank

WANG Kai-song , DOU Cheng-long , DU Shuang-song , XU Wei-wei , XI Wei-bin

2023, 43(2):  140-144.  DOI: 10.16568/j.0254-6086.202302003

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With the technical upgrade of the EAST high-temperature superconducting current lead, the support structure in the current lead tank was redesigned optimally, its structural stability analysis was carried out, and finally the optimal design scenario was determined according to the analysis results. The optimized design of the current lead canister is tested, and its result shows that the support structure can better ensure the safety and stability of the current lead. 

Development and application of a cutting and dismantling device for nuclear facility decommissioning based on laminar flow plasma

ZHANG Feng, PAN Guang-wei, ZHAO Yan-hong, YUE Jun

2023, 43(2):  145-149.  DOI: 10.16568/j.0254-6086.202302004

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A non-transfer-arc plasma cutting and dismantling device was developed for the remote cutting and dismantling operation on the large components during the decommissioning of nuclear facilities. This cutting device adopts laminar flow plasma technology, of which the effective cutting arc length can be more than 200mm and the cutting thickness towards steel can reach 150mm through the modification of the plasma generator, the power supply and the control system. This cutting technique successfully lengthens the cutting arc, reduces the amount of the blind spots, enhances the stability of the cutting arc, and enlarges the cutting thickness, all of which usually occur in those traditional plasma cutting devices. The application of this technology is expected to change the existing cutting and dismantling mode applied in the process of nuclear facility decommissioning.

Radioactive leakage analysis in LOCA accident for helium cooling divertor loop of CFETR 

HU Bo, HUANG Wen-yu, ZHOU Bing, WANG Xiao-yu, WANG Yan-ling, LU Yong, ZHANG Long, LIU Kuan-cheng

2023, 43(2):  150-155.  DOI: 10.16568/j.0254-6086.202302005

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 Based on the conceptual design of the CFETR helium cooled divertor loop, the calculation model of accident is established, and the Ex-vessel LOCA accident and both In-vessel & Ex-vessel LOCA accidents are simulated to evaluate consequences of the radioactive leakage. The results show that: In Ex-vessel LOCA accident, the pressure of the room in which the pipes are located rises in a small margin due to the leakage of the helium coolant, and the helium leakage is underneath the acceptable value; During the both Ex-vessel & In-vessel LOCA accidents, the gas would flow reversely from the room to the vacuum vessel while the isolation valves are not considered. While the isolation valves are added, the leakage to both the room and the vacuum vessel meets the acceptance criteria. In the meantime, the tritium leakage at the accident operating mode is estimated based on the calculation results. The results verify the safety of the preliminary design and provide data for following design process.

Experimental study of arc induced on tungsten surface in the EAST edge plasma

WANG Bao-guo, , ZHU Da-huan , DING Rui , MU Lei , LI Chang-jun , CHEN Jun-ling

2023, 43(2):  156-160.  DOI: 10.16568/j.0254-6086.202302006

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Arc induced triggering on tungsten samples with different surface properties and structures was studied in EAST using Material and Plasma Evaluation System (MAPES). The effect of depositions on arc triggering is studied using several kinds of coatings on tungsten and the fuzz structure is generated on tungsten surface by He⁺ plasma in ICP irradiation system. The results show that only the tungsten surface with the fuzz structure successfully triggers arcs, which proves that the fuzz structure on tungsten surface is more conducive to ignite arcs than coated tungsten, even far away from the SOL. There are two kinds of arcs on the tungsten fuzz structure, small arc trace and deep arc crater, in which the crater produced by stronger arcs will splash liquid droplets that are important sources of impurity and dust in plasma. The diameter and depth of the crater are about 3μm and 0.7μm, respectively. Some small holes and nanostructures are formed in the center of the arc crater, and the molten droplets around them have similar structures. 

Numerical simulation on transport characteristics of tritium loaded thermomagnetic fluid in rectangular duct 

HAN Jia-jia , WANG Wei-hua , PU Wen-jing , JIANG Hai-yan , CHU De-lin , SHI Bo

2023, 43(2):  161-168.  DOI: 10.16568/j.0254-6086.202302007

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The transport process of tritium in the liquid metal blanket of fusion reactor is coupled with the flow and heat transfer process of MHD, resulting in the complex tritium transport characteristics in the strong magnetic field. Based on the developed MHD flow and heat transfer numerical simulation program, the flow and heat transfer characteristics of liquid metal MHD in a rectangular duct and its influence on tritium transport were numerically simulated. Firstly, the momentum conservation equation is solved and validated by the theoretical solution, and then coupled with the energy conservation equation, the liquid metal flow field distribution in the rectangular duct under the influence of temperature is obtained. On this basis, the tritium concentration distribution under the influence of strong magnetic field and high nuclear thermal gradient is numerically simulated, and the distribution characteristics of tritium concentration in the duct are obtained. The results shows that the flow and heat transfer of liquid metal in rectangular duct have significant effect on tritium transport. 

Numerical simulation and structure optimization of air intake for leak detection of manifold in gas injection system  

HAO Yu, HUANG Xiang-mei, LIU Xi-gang, LI Bo, LI Wei

2023, 43(2):  169-174.  DOI: 10.16568/j.0254-6086.202302008

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Based on the computational fluid dynamics analysis software ANSYS CFX, the gas flow of tritium monitoring branch in leak detection system of gas injection system (GIS) is simulated. It is found that the branch structure with half inches and 90 degrees cannot meet the demand of branch pipe air flow detection. Therefore, the structure is optimized by changing the angle between the bypass pipe and the main pipe or increasing the diameter of the branch pipe. The optimized results show that increasing the inner radius of the branch pipe to more than 6.9mm or reducing the included angle to less than 30° can make the leak detection pipeline meet the requirements of air inlet under various working conditions. 

Investigations on the MHD effect of liquid metals through an insulating circular pipe under large characteristic parameters

WANG Fan, ZHANG Xiu-jie, PAN Chuan-jie

2023, 43(2):  175-179.  DOI: 10.16568/j.0254-6086.202302009

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 The magnetohydrodynamics (MHD) effect of liquid metals is a key issue to be solved for liquid blankets of fusion reactors. In this study, the liquid metal MHD flow through an insulated circular pipe under large character parameters is investigated through experiments and numerical simulations, and then the results such as pressure drops and flow velocity distributions are provided. The experimental results indicate that MHD pressure drops increase linearly with the increase of external magnetic fields and average velocities, which are in good agreement with numerical and theoretical results. The characteristic of velocity distributions is that the velocity in Hartman layer changes sharply due to big velocity gradient. Based on the analysis of the experimental data about the pressure drop, a conclusion can be drawn that the laminar turbulent transition point of MHD flows through insulating pipes under strong magnetic fields is about Re/Ha=45. 

The research of millimeter wave TE10-TE11-HE11 mode converter 

CHEN Cheng, HUANG Mei, ZHANG Feng, WANG Chao

2023, 43(2):  180-184.  DOI: 10.16568/j.0254-6086.202302010

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This article designs a TE₁₀-TE₁₁-HE₁₁ mode converter with a central frequency of 105GHz and bandwidth 10GHz to build a low power measurement platform for the electron cyclotron resonance wave heating system (ECRH). Square-circle transition and gradient slot depth corrugated horn are used to achieve the related mode conversion. The simulation results show that the frequency range is 92~115GHz, the conversion efficiency of HE₁₁ mode produced by this mode converter is higher than 95% with Gaussian content.

Structure analysis and optimization of gas injection pipeline in tokamak 

YANG Yin, JIANG Tao, XIA Zhi-wei

2023, 43(2):  185-190.  DOI: 10.16568/j.0254-6086.202302011

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 Based on the finite element analysis method, in order to meet the relevant design criteria of ITER, the optimization design of the injection pipeline is carried out as an attempt for ITER gas injection system. The analysis results show that the pipeline flexibility is not effectively limited. Setting additional supports are needed on these positions with large deformation. The structure of the injection pipeline is optimized, and the analysis results show that there is no significant increase of secondary stresses while limiting the pipeline flexibility, and there is no plastic collapse, local failure and ratcheting. Meanwhile, the reaction force of pipeline is reduced by 33% on the auxiliary support. The structure optimization scheme is verified, and the reliability and safety of pipeline structure are improved. 

Research on EAST-NBI experimental data analysis system based on neural networks 

LIU Zhi-min , WANG Jin-xin , ZHAO Yuan-zhe , XIE Ya-hong , XIE Yuan-lai

2023, 43(2):  191-198.  DOI: 10.16568/j.0254-6086.202302012

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The mismatch of the operation parameters of the NBI(neutral beam injection) ion source of the nuclear fusion experimental device will lead to the instability of the plasma in the ion source, and maybe cause breakdown in the ion source, which will limit the long pulse and high power operation of the NBI. To stabilize the plasma in the ion source, data from multiple campaigns of experiments along with a prior information obtained from a predictive plasma model are used. For the problem of poor accuracy of the existing key-values extraction algorithms for experimental data, the OPTICS (Ordering Point To Identify the Cluster Structure) algorithm is used to improve the accuracy of the experimental data extraction, and provide a reference for the failure analysis during the experimental operation. A method based on Self-Organizing feature Map (SOM) and Back Propagation (BP) neural network is adopted. By training historical data, the pulse width of the NBI ion source beam extraction process is estimated under given parameters to adjust the operating parameters. 

Installation and bench test of CO2 dispersive interferometers based on inductively coupled plasma source 

LI Meng-ge, ZHANG Shou-biao , LI Wei-ming , LIU Hai-qing , ZHANG Yao , JIE Yin-xian , LIAN Hui

2023, 43(2):  199-203.  DOI: 10.16568/j.0254-6086.202302013

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A CO₂ dispersion interferometer for horizontal single-channel measurement without a damping system has been successfully installed on an inductively coupled plasma (ICP) source to measure the chord-integrated electron density of the plasma and compared with the data of HCN interferometer. The results of the instrument prove the feasibility of the CO₂ dispersion interferometer. 

Plasma Physics

Fast ion D_α diagnostic and simulations in the HL-2A tokamak

HOU Yu-mei , ZHOU Hang-yu , CHEN Wei , HAO Bao-long , LIU Yi , SHI Zhong-bing , XU Ming , DUAN Xu-ru

2023, 43(2):  204-211.  DOI: 10.16568/j.0254-6086.202302014

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The fast ion D_α (FIDA) diagnostic in the HL-2A tokamak is introduced in this paper. The fast ion distribution in phase space is obtained by analyzing FIDA spectra with FIDASIM and TRANSP. A theoretical fast ion population calculated by the TRANSP code is input for the FIDASIM code. The collision-radiation model is solved by the FIDASIM code to obtain the theoretical FIDA spectrum. The comparative analysis of experimental and simulation results shows that the simulated FIDA spectrum evolution is consistent with the experimental result, therefore the fast ion distribution calculated by the TRANSP code is verified. 

Improvement of Stark broadening algorithm based on wavelet transform

ZHANG Zhi-tao, DING Fang , LUO Yu, CHEN Xia-hua, YE Da-wei, ZHANG Qing, HU Zhen-hua , LUO Guang-nan

2023, 43(2):  212-218.  DOI: 10.16568/j.0254-6086.202302015

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To improve the accuracy of the calculation of plasma electron density by Stark broadening, based on the wavelet threshold denoising processing method for EAST divertor deuterium spectral signals and using the signal-to-noise ratio (SNR) and root mean square error (RMSE) as the evaluation basis for the filtering effect, the optimal wavelet basis db4 is determined by comparison, and the optimal wavelet decomposition is 4 layers. The adaptive threshold parameter is calculated according to the noise estimation to reconstruct the signal, and the denoised data is applied to the analysis process of the plasma density calculated by the Stark broadening algorithm. The results show that the wavelet hard threshold denoising can effectively improve the signal-to-noise ratio of the spectral signal, reduce the root mean square error, and eliminate the noise in the spectral signal while retaining the useful spectral detail feature information to the greatest extent, which is beneficial to the spectral data modeling effect, and the more accurate plasma electron density is obtained.  

Numerical simulation of ohmic discharge in J-TEXT iron core model 

ZHANG Shun , GUI Teng , YANG Jin-hong , CHEN Kai-jie , LU Ye , SONG Qiang , JIANG Zhong-he , WANG Wei-hua

2023, 43(2):  219-226.  DOI: 10.16568/j.0254-6086.202302016

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In order to simulate the discharge process of J-TEXT tokamak with iron core, the magnetic field characteristics of J-TEXT complete iron core model, J-TEXT plasma current wire model and J-TEXT simplified central solenoid model were analyzed by finite element analysis software, and the geometric parameters and current of the simplified central solenoid were determined. Then, the parameters of the finite length central solenoid were input into the TSC(tokamak simulation code) to simulate the ohmic discharge process of J-TEXT, and the ohmic discharge current, electron temperature, plasma density, plasma current and magnetic axis position were obtained. The simulation results were consistent with the experimental data, and an effective method for the simulation of tokamak with iron core was provided.

Zero-dimensional simulation of tokamak discharge startup by pure ohmic heating 

PENG Yan-li, ZHAO Shi-qiu, SHI Xiao-feng, DI Hao-ran

2023, 43(2):  227-231.  DOI: 10.16568/j.0254-6086.202302017

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A zero-dimension numerical model has been carried out to simulate ITER discharge. The time evolutions of plasma density, plasma current and electron temperature are calculated, as well as electron and ion energy losses. By analyzing the plasma parameters, it is found that for a given loop voltage, the initial gas pressure has an upper limit. The energy loss mechanisms during the startup process have also been analyzed. The electron equilibration and transport losses are dominant after the neutral has been fully ionized.

Preliminary simulation investigation of the energetic particle transport on CFETR 

YANG Wen-jun , GONG Xue-yu , GAO Xiang , LI Xiao-e

2023, 43(2):  232-237.  DOI: 10.16568/j.0254-6086.202302018

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In order to analyze the behavior of energetic particles on CFETR, the transport code ONETWO is used to investigate the fusion reaction and the transport phenomenon of energetic particles. Without the neutral beam injection (NBI), the density of energetic alpha particles gradually decreases with time. With the NBI, the alpha-particle density has an obvious drop. When the beam-ion energy increases while the NBI power is unchanged, the alpha-particle density has almost no change in other regions except for a certain decrease in the plasma center region. When the NBI power increases while the ion energy is unchanged, the alpha-particle density has an obvious drop in the central region of the plasma. 

Suppression neoclassical tearing mode instability at the initial stage by segmented electron cyclotron current drive 

YANG Zhen, WU Bin , CHEN Yu-qing

2023, 43(2):  238-242.  DOI: 10.16568/j.0254-6086.202302019

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Neoclassical tearing mode(NTM) instability will seriously affect the confinement performance of tokamak, which is an unavoidable MHD instability in all major tokamak devices. How to suppress the NTM instability has become one of the key issues of fusion research. It has been found that electron cyclotron wave current drive (ECCD) is one of the main methods to suppress NTM instability. Using the numerical simulation, the influence of the continuous ECCD on the development of neoclassical tear mode was studied by adding ECCD in the early stage of neoclassical tearing mode. The numerical results represent that a small ratio of continuous ECCD can reduce the growth rate of neoclassical tearing mode at early stage and improve the efficiency of later ECCD to suppress neoclassical tearing mode in the growth stage. 

1/2 dimensional integrated simulation of CFETR steady state operation scenario and analysis of the impact of impurity particle ratio 

WANG Jun , WANG Zhan-hui , SHI Yong-fu , LI Jing-chun

2023, 43(2):  243-248.  DOI: 10.16568/j.0254-6086.202302020

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 A 1GW fusion power reversed shear (RS) scenario is designed for CFETR steady state operation using the fast integrated modelling tool, METIS. This RS scenario is maintained by 40MW off-axis electron cyclotron current driving (ECCD) and 40 MW neutral beam current driving (NBCD). In this scenario, the steady safety factor profile has a minimal q, q_min=3.1 at ρ=0.52. Therefore, the dangerous m/n=3/2, 2/1, 5/3 NTM (neoclassical tearing mode) would be avoid. The influence of Argon atom fraction in plasma on the performance of this RS scenario is also analyzed.