Seismic analysis of ITER fourth PF (Poloidal Field Coil) feeder

The ITER feeder systems connect the ITER magnet systems located inside the main cryostat to the cryo-plant, power-supply and control system interfaces outside the cryostat. The main purpose of the feeders is to convey the cryogenic supply and electrical power to the coils as well as house the instrumentation wiring. The PF busbar which carries 52 kA current will suffer from high Lorentz force due to the background magnetic field inspired by the coils and the self-field between every pair of busbars. Except their mechanical strength and thermal insulation performance must be achieved, the dynamic mechanism on PF structure should be assessed. This paper presents the simulation and seismic analysis on ITER 4th PF feeder including the Coil Terminal Box and S-bend Box (CTB and SBB), the Cryostat Feed-through (CFT), the In-Cryostat-Feeder (ICF), especially for the ground supports and main outer-tube firstly. This analysis aims to study seismic resistance on system design under local seismograms with floor response spectrum, the structural response vibration mode and response duration results of displacement, membrane stress, and bending stress on structure under different directions actuating signals were obtained by using the single-seismic spectrum analysis and Dead Weight analysis respectively. Based on the simulative and analytical results, the system seismic resistance and the integrity of the support structure in the 4th PF feeder have been studied and the detail design confirmed.     

Numerical analysis of ITER fourth poloidal field (PF) coil feeder

The ITER poloidal field (PF) feeder busbar which carries 52 kA current will be subjected to high Lorentz force due to the background magnetic field aroused by the coils and the self-field between a pair of PF busbars. Peak magnetic force requires dense supports. But to minimize the heat load to the busbars as well as the cryo-pipes, fewer and thinner supports design is proposed, so a balance between mechanical strength and thermal insulation performance should be achieved. This paper presents the analysis on support system design for ITER 4th PF feeder including the S-bend box, the cryostat feed-through, the in-cryostat-feeder. An electric–magnetic coupled analysis aims to get real magnetic force load under the worst scenario, then the Lorentz force result is imported into the mechanical analysis, applied on the busbars, meanwhile the busbar supports, the containment duct, the gimbals, the separator plate and the cryo-pipes, the cold mass supports are contained in the finite element model to check the full system performance under Lorentz forces, earth gravity and thermal contract at 4.5 K. Based on the analytical results, the quantity and the spaces between busbar supports in the 4th PF feeder have been studied and the detail design optimized.     

Consideration and research of high voltage insulation strategy for ITER Feeder busbar joint

The ITER Feeder busbar joint is an important component which connects different sections of busbar which run from the high temperature superconducting current leads to the magnet terminals. High voltage insulated bus bar sections will be assembled onto the feeder support structure (called the containment duct), and the joints between sections will be made in situ. The high voltage insulation over the joint is the final step to complete the insulation of the whole bus bar system, and its quality is key to achieving the required electrical performance of the system. The final joint has a complex external configuration with an irregular structure in places, which makes it difficult for the application of the insulation. The limited access in the Feeder and the complex joint external structure make the implementation of the joint insulation hard to solve. The Feeder group at ASIPP has carried out significant R&D for the joint insulation, involving research on the selection of materials, the design of the insulation structure, the curing technology and the quality inspection method. After many rounds of manufacturing and testing, the insulation strategy for the Feeder joint will focus on the so-called “wet-winding” technology. Despite the fact that this process has some intrinsic disadvantages, it is more appropriate for the joint structure compared to other methods. The sub-suppliers to ASIPP have chosen this impregnation method for the feeder qualification activities based on guidance from ASIPP. This paper describes the research procedure of the ITER Feeder busbar joint insulation, summarizes the activities on the joint insulation structure design, describes the trials of the impregnation method, and describes the pre-qualification tests. Even for the preferable “wet-winding” process, some improvements have been applied due to recommendations from ITER IO experts. For example, both the use of a vacuum bag during the process and investigation using non-destructive tests (NDT) have been implemented.     

ITER用极向场线圈导体短样分流温度测试

ITER用极向场（PF）线圈CICC导体短样是用西部超导材料科技有限公司提供的NbTi超导股线绕制完成,该股线在不同温度下的临界电流测试性能稳定,符合绕制导体的要求。对PF导体短样在SULTAN实验室进行了测试,经电磁循环通电前后,分流温度无较大改变,导体性能稳定。在考虑了导体自场作用的情况下,导体在5T、50kA运行环境下的分流温度为6.33K,满足ITER规定的要求。     

国际热核聚变实验堆过渡馈线设计与分析

国际热核聚变实验堆（InternationalThermonuclearExperimentalReactor，简称ITER）采用超导馈线系统传输磁体线圈所需电流、冷却液及数据信号等。本文介绍了馈线系统中过渡馈线的设计，并通过有限元法对设计结构进行全面校核和应力分析，为结构的进一步研制提供了理论依据。     

Hotspot temperature calculation and quench analysis on ITER busbar

This paper describes the analysis of ITER feeder busbar, the hotspot temperature of busbar is calculated by classical method in the case of 0%, 50%, 75% and 100% extra copper (copper strands). The quench behavior of busbar is simulated by 1-D Gandalf code, and the MQE (minimum quench energy) is estimated in classical method as initial external heat in Gandalf input file. The temperature and the normal length of conductor are analyzed in the case of 0%, 50% and 100% extra copper and no helium. By hotspot temperature, conductor temperature and normal length are contrasted in different extra copper cases, it is shown that the extra copper play an important role in quench protecting.     

Safety of fusion magnets: Model experiments to high current arcs at ITER busbars and feeder lines

Electric arcs moving along the power cables (the so-called busbars) of the toroidal field (TF) coils of ITER may reach and penetrate the cryostat wall. Model experiments with the VACARC (VACuum ARC) device were initiated to investigate the propagation and destruction mechanisms of busbar arcs in small scale. These experiments are intended to support the development and validation of a numerical model. The present setup simulates the fact that the busbar is contained by an inner and an outer feeder tube which absorb radiated energy and will be in contact with hot metal melt from the busbar. The tubes may also direct the hot plasma jet flow of the arc as long as they are intact. Experiments at scaled values for tube diameter, wall thickness and expected power density suggest serious damage to the inner feeder tube by the arc. This asks for further investigations that include the outer tube, too. The extent of damage to the tube samples depends on arc power, as expected. At high currents an additional luminous effect takes place, which is attributed to a reaction of oxygen and hydrogen probably set free from the dissociation of the insulation resin by the heat of the arc.     

Updating the design of the feeder components for the ITER magnet system

The ITER superconducting magnet system generates an average heat load of 23 kW at 4 K to the cryoplant, from nuclear and thermal radiation, conduction and electromagnetic heating, and requires current supplies 10–68 kA to 48 individual coils. The helium flow to remove this heat, consisting of supercritical helium at pressures up to 1.0 MPa and temperature between 4.3 and 4.7 K, is distributed to the coils and structures through 30 separate feeder lines. The feeders also contain the electrical supplies to the coil, helium supply pipes and the instrumentation lines, and are integrated with the current lead transitions to room temperature. The components consist of the in-cryostat feeders, the cryostat feedthroughs and the coil terminal boxes (CTBs). This paper discusses the functional requirements on the feeder system and presents the latest design concept and parameters of the feeder components.     

Busbar arcs at large fusion magnets: Conductor to feeder tube arcing model experiments with the LONGARC device

Electric arcs moving along the power cables (the so-called busbars) of the toroidal field (TF) coils of ITER may reach and penetrate the cryostat wall. Model experiments with the new LONGARC device continue the VACARC (VACuum ARC) experiments that were initiated to investigate the propagation and destruction mechanisms of busbar arcs in small scale [1]. The experiments are intended to support the development and validation of a numerical model. LONGARC overcomes the space limitations inside VACARC and allows also for advanced 1:3 (vs. ITER full scale) model setups. The LONGARC device and first results are presented below.     

The performance test and analysis of ITER Main and Correction Busbar conductor

The first ITER Main Busbar (MBCN1) and Correction Busbar (CBCN1) conductor samples were manufactured in ASIPP and tested in the SULTAN facility. This paper introduces the sample manufacture, including strand, cabling, jacketing and sample preparation, and discusses the performance of MBCN1 and CBCN1 conductors. The testing results show that both samples have high T_cs, and meet the ITER requirement.Due to the ITER acceptance standard T_cs of MB conductor was changed to 6.7 K at 45.5 kA/3.9 T. The performance of MBCN1 conductor after cyclic load fits the ITER requirement, but the sample was only tested at 57 kA/2.75 T before cycling test. Using some hypothesis and equation to extrapolate the T_cs performance of MBCN1 conductor before cycling test, the result also fits the ITER requirement.For CBCN1 conductor, the central line of the central cooling spiral shifted about 1.3 mm during the cabling. The deviation causes an increase of the max self-field by about 0.005 T, which could not influence the CBCN1 conductor real T_cs performance at peak field.     

ITER Magnet Feeder:Design,Manufacturing and Integration

The International Thermonuclear Experimental Reactor(ITER) feeder procurement is now well underway.The feeder design has been improved by the feeder teams at the ITER Organization(IO) and the Institute of Plasma Physics,Chinese Academy of Sciences(ASIPP)in the last 2 years along with analyses and qualification activities.The feeder design is being progressively finalized.In addition,the preparation of qualification and manufacturing are well scheduled at ASIPP.This paper mainly presents the design,the overview of manufacturing and the status of integration on the ITER magnet feeders.     

Cryogenic mechanical testing of ITER prototype axial breaks

Within the superconducting magnet program for ITER, cryogenic components need to be tested to verify their design. Especially for the helium supply of the magnet system, feeders are needed integrating at the same time high voltage insulation to separate the inner magnet system electrically from the outer cryostat shell. Beside of high voltage and helium flow properties, these axial breaks will be exposed to a limited mechanical loading during operation of the magnet system. Therefore, mechanical tests needs to be performed at room temperature as well as at cryogenic temperature of 77 K.A possible breaker design was provided by Babcock Noell. To verify this design mechanically quasi-static and fatigue tests under bending, torsion and axial loading were done. Results on the performance of the prototypes are presented approving a superior mechanical quality.     

绕制预应力对MICE超导耦合磁体冷质量应力状态的影响

超导耦合螺线管磁体为μ介子离子化冷却实验装置(MICE)中的关键设备,其线圈内径1500mm,长度285mm,采用截面1.65mm×1.00mm的NbTi复合超导线,励磁到210A时,峰值磁场可达7.4T。在降温和励磁过程中,为减小导线窜动而导致失超,线圈绕制过程中需对导线和紧固带施加预应力。本文根据组合筒理论,得出了绕制过程中线圈和紧固带的预应力与冷质量内部应力分量的关系。采用有限元方法对线圈绕制、冷却和励磁3个连续过程进行动态仿真,分别分析了导线和紧固带绕制预应力的变化对冷质量内部各主要应力峰值的影响,得出线圈和紧固带绕制时满足磁体稳定性和结构安全的预应力优化结果,为MICE超导耦合磁体的研制及其他类似大直径、多层的超导螺线管磁体绕制提供理论依据。     

Performance evaluation and analysis of ITER poloidal field conductors

The performance evaluation and analysis of PF5 conductor of the ITER Project in China have been performed using the Gandalf code (Bottura [1]). This study focuses on the T_cs and MQE of PF5 conductor with Cu–non Cu ratio of 2.3 NbTi strands from WST. The PF5 conductor samples have been measured in SULTAN at CRPP for evaluating the performance successfully. The measurement results are also presented with the evaluation results in the paper. The evaluation results related to T_cs and MQE are agreed well with the measurement results. The simulation with Gandalf code can predict the performance of PF5 conductor effectively and provide the helpful method for ITER conductor design and analysis.     

Mechanical Analysis for ITER Lower CC Feeder

ITER correction coils (CCs) feeder is the important component of ITER feeder systems to supply the cryogens and electrical power for CCs. They should withstand the huge electromagnetic (EM) force and high thermal shrinkage. Considering the EM and thermal loads, mechanical analysis is performed to qualify the structural strength of the lower CC feeder. Results show that containment duct and cryopipe can meet the static criteria but busbar jacket cannot meet. It is proposed that more supports should be added at the corners for the busbar. Basically, the lower CC feeder design is valid and feasible.     

Status of European manufacture of Toroidal Field conductor and strand for JT-60SA project

In the framework of the JT-60SA project, part of the Broader Approach (BA) agreement, EURATOM provides to Japan, the Toroidal Field (TF) magnet system, consisting of 18 superconducting coils. The procurement of the conductor for the TF coils is managed by Fusion for Energy, acting as EU representative in the BA agreement. The TF conductor procurement is split into two contracts, one dedicated to the production of Niobium Titanium (NbTi) and Cu strand and the other to TF conductor production through strand cabling and cable jacketing operations.The TF conductor is a rectangular-shaped cable-in-conduit conductor formed by 486 (0.81 mm diameter) strands (2/3 NbTi–1/3 Cu) wrapped in a stainless steel foil and embedded into a stainless steel jacket.The 18 TF coils require (including spares) 115 ‘Unit Lengths’ (UL) of such conductor, each 240 m long for a total of about 28 km. Correspondingly about 10,000 km for NbTi and 5000 km for Cu strand are produced.The Japanese company Furukawa Electric Co. (FEC) is in charge of TF strand manufacture while the Italian company Italian Consortium for Applied Superconductivity (ICAS) is in charge of cabling and jacketing of TF conductor ULs. In the paper, we provide information on the production stages presently achieved in TF strand and conductor contracts.     

Design Evolution and Analysis of the ITER Cryostat Support System

The cryostat is a vacuum tight container enveloping the entire basic systems of the ITER tokamak machine,including a vacuum vessel,a superconducting magnet and thermal shield etc.It is evacuated to a pressure of 10~(-4)Pa to limit the heat transfer via gas conduction and convection to the cryogenically cooled components.Another important function of cryostat is to support all the loads from the tokamak to the concrete floor of the pit by its support system during different operational regimes and accident scenarios.This paper briefly presents the design evolution and associated analysis of the cryostat support system and the structural interface with the building.     

ITER校正场磁体馈线结构分析

基于ANSYS对ITER校正场磁体馈线的结构进行了分析。根据馈线结构特点,对有限元模型进行了简化。通过电磁分析,获取了超导母线的电磁力,研究了电磁力与超导母线支撑间距的关系,并根据结果提出了推荐的支撑间距。在进行馈线模型结构分析时,电磁力按支反力的形式施加,并施加不同的载荷工况,获取了不同工况下馈线的应力及变形数据。分析结果显示馈线结构设计是合适的,满足设计应力准则要求。     

超导电流传输线导体等效弹性模量的预测

国际热核聚变实验堆（ITER）超导电流传输线导体的内部电缆体由超导股线和纯铜股线经多级绞缆后复合而成,相对柔软。在传统复合材料理论的基础上,对ITER超导电流传输线导体等效弹性模量进行理论预测：预测一,只考虑电缆体外的不锈钢导管、双绝缘和双屏蔽层;预测二,忽略柔性电缆体的影响,但考虑其内部氦管;预测三,假设电缆体呈各向同性,弹性模量取1～10GPa;预测四,利用均匀化理论分析电缆体的等效弹性模量,复合材料损伤理论分析超导电缆与中心氦管之间、电缆复合体和不锈钢导管之间界面情况。预测值与参考实验值进行比较证实,预测四较符合实际情况,电缆体对整个超导电流传输线导体等效弹性模量的影响较小。     

Structural analysis and optimization of the break-out & feeder of the ITER lower vertical stabilization coil

Break-out & feeder is an essential component connecting the ITER lower vertical stabilization (VS) coil to the outside power source. It plays the role of interface between the in-vessel and out-vessel devices and has large influence on the coil performance. Due to the special location of the ITER lower VS coil, the break-out & feeder has to endure severe in-vessel environment such as high temperature, strong magnetic field and neutron irradiation. High temperature and restricted cooling paths can easily make the break-out under high thermal stress. While square crossing with the Tokamak toroidal magnetic field will result in large Lorentz forces in the feeders. Structural analysis of the break-out & feeder shows overlarge thermal stress concentrating in the coil spine where the conductors lead out. The primary stresses in the feeders are also extremely high. Moreover, there is difference in loading in comparison with the coil main body, which is designed to be mainly in compression and with relaxed crack growth issues, the break-out & feeder is not so compressive and will endure large tensile stress in work. Therefore, relieving the high stresses is important for its design. According to the results of further analysis, structure optimizations such as using block structures in the break-out and modifying the feeder supports are proved with good effect.