Static Structural Analysis of 3D Loading Frame for ITER Gravity Support Prototype

The importance of static structural analysis for the 3D loading frame of the ITER gravity support prototype was described. The finite element model was established based on ANSYS Workbench. The forces applied on the 3D loading frame were analyzed. The static structural analyses of 3D loading frames under different working conditions were done with finite element method. Deformations, overall mean stresses and safety factors were then solved. Results show that the maximum total deformation, the y-direction maximum deformation, the maximum stress and the minimum safety factor for different working conditions meet the design requirements. The stress concentration region and the weakest part in the 3D loading frame were analyzed. The corresponding improved measures were presented.     

ITER重力支撑的制造设计、认证测试及关键技术研究

重力支撑（GS）作为国际热核聚变实验堆（ITER）磁体支撑系统的关键部件,不但要承受环向场超导磁体净重以及交变的电磁载荷,同时还需隔离来自杜瓦环的热量以维持环向场超导线圈的热稳定性。本文通过有限元分析和工程测试验证了GS结构设计的可靠性;通过换热分析和真空热交换效率测试验证了热锚连接结构的可靠性;通过全尺寸螺栓77 K疲劳测试验证了螺栓原型件的疲劳性能。在随后的制造过程中,使用液压拉伸器和研制的高精度螺栓伸长量测量装置对所有的螺栓进行了均匀、精确地紧固。真空正压氦检漏的测试结果证明了GS的泄漏率远低于ITER的要求。基于以上工程测试的结果,本文设计的GS的结构是可行的且能运用于ITER装置中。      

Design Study of Support for ITER ELM Coils

The support is an important part of ITER ELM coils. It should withstand the alternating electromagnetic (EM) force and thermal stresses. Based on the finite element method, 2D and 3D structures of the rigid and flexible support of ITER upper ELM coil in different loads are studied. Results show that the flexible support can reduce the stresses of the conductor and jacket. In the lower level of nuclear heat, two types of supports can be used in the quarter model. In the high level of nuclear heat, the flexible support is needed and 50 mm support is proposed for the quarter model. Considering the EM load, the rigid support has better performance than the flexible support. Therefore, reasonable support can be provided for ELM coil or similar coil according to the thermal expansion and EM load.     

A method for enabling real-time structural deformation in remote handling control system by utilizing offline simulation results and 3D model morphing

A full scale physical test facility, DTP2 (Divertor Test Platform 2) has been established in Finland for demonstrating and refining the Remote Handling (RH) equipment designs for ITER. The first prototype RH equipment at DTP2 is the Cassette Multifunctional Mover (CMM) equipped with Second Cassette End Effector (SCEE) delivered to DTP2 in October 2008. The purpose is to prove that CMM/SCEE prototype can be used successfully for the 2nd cassette RH operations. At the end of F4E grant “DTP2 test facility operation and upgrade preparation”, the RH operations of the 2nd cassette were successfully demonstrated to the representatives of Fusion For Energy (F4E).Due to its design, the CMM/SCEE robot has relatively large mechanical flexibilities when the robot carries the nine-ton-weighting 2nd Cassette on the 3.6-m long lever. This leads into a poor absolute accuracy and into the situation where the 3D model, which is used in the control system, does not reflect the actual deformed state of the CMM/SCEE robot. To improve the accuracy, the new method has been developed in order to handle the flexibilities within the control system's virtual environment. The effect of the load on the CMM/SCEE has been measured and minimized in the load compensation model, which is implemented in the control system software. The proposed method accounts for the structural deformations of the robot in the control system through the 3D model morphing by utilizing the finite element method (FEM) analysis for morph targets. This resulted in a considerable improvement of the CMM/SCEE absolute accuracy and the adequacy of the 3D model, which is crucially important in the RH applications, where the visual information of the controlled device in the surrounding environment is limited.     

ICRH ITER-like antenna tested on TS commissioning,electrical modeling and load resilience studies

A prototype of ICRF antenna based on the load-resilient electrical layout anticipated for ITER has been built at CEA-Cadarache. It consists of two toroidally adjacent resonant double loops (RDLs) based on the conjugate-T concept proposed for the ITER ICRF array. This prototype has been recently validated in Tore Supra plasmas exhibiting fast density perturbations in front of the antenna. This paper reports on the load resilience properties of the antenna prototype, as well as the RF modeling and the commissioning. Significant effort on modeling, coupled to an extensive low power campaign, has allowed characterization of the antenna in both vacuum and plasma loading conditions. Plasma load modelings computed with the code TOPICA – very helpful to set up the matching points on plasmas – are found to be in good agreement with the experimental results. The main studies focus on load resilience properties have been carried out in L-mode plasmas. Supersonic molecular beam injection (SMBI), able to launch a series of very short/dense gas jets at Mach number up to 5, was used to mimic the sudden increases of the antenna coupling provoked by ELMs. The results are found to be in good agreement with RF circuit calculations that include 3D modeling.     

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.     

Theoretical Calculation and Kinematics Analysis of Double Seal Door for ITER Remote Handling Transfer Cask System

The moving direction of double seal door (DSD) of International Thermonuclear Experimental Reactor (ITER) remote handling transfer cask will change suddenly at the guide rail inflexion position (GRIP), where the force of hydraulic pole also will change significantly. The structure may damage and the system will possible be failed when the DSD moving through GRIP which is a mutant site. Based on special constitution, restriction conditions and working process of DSD, kinematics simulation and analysis were done by software ADAMS. The DSD moving equations were built based on the degree of freedom (DOF) of DSD mechanism system, and then the force of DSD moving were calculated in theoretical analyzing. By the above simulation and theoretical calculation the stress distribution of guide rail and hydraulic pole were obtained, at the same time optimization design of GRIP was confirmed according to the force analysis results. The above-mentioned analysis process and results not only provide technical data for the optimization design and the prototype manufacture of DSD, but also provide the examples and references of theoretical calculation and kinematics analysis for other important components of ITER.     

Lubricant coating of dowel for the ITER vacuum vessel gravity support

The ITER vacuum vessel gravity supports located in the lower level shall sustain loads in radial, toroidal and vertical directions. The hinge type VVGS consists of two hinges, upper and lower blocks and dowels. In order to develop the design concept and verify the structural integrity of the hinge system, the design analysis has been performed in detail. Inclination of 15° for the hinge based supporting system was introduced to provide centering force to make stable equilibrium state of the vacuum vessel. Due to this inclination the hinges are rotated by the radial expansion of the VV during operation and baking, respectively. If a dowel is seized in the hinge, the supporting system can be highly stressed due to the restrained displacement in the seized dowel. Therefore, solid lubricant coatings were suggested on dowels in order to avoid seizing in the sliding area. In this work, several sets of coupons were made with different coating materials to investigate the effect according to the selection of coating material. Also, a test facility was designed to cover the ITER relevant loading and boundary conditions, e.g. vacuum condition, temperature, contact pressure, cycles, etc. From those test results, the optimized coating method was found to avoid seizure of dowel in the ITER VVGS.     

Thermal–structural analysis of ITER triangular support for dominant load verification

The triangular support is located on the lower inner shell of vacuum vessel of ITER, which should be designed to withstand various loads such as nuclear heat, coolant pressure and so on. The appropriateness of its design is evaluated under the dominant load that could represent the most conservative condition among the design loads. In order to decide the dominant load, a valid method for thermal–structural analysis is firstly verified considering contradictory behaviors between heat and structural loads.In this paper, two approaches; one-way coupling and load combination, are introduced for thermal–structural analysis. The one-way coupling is a method generally used but has a limit to apply on contradictory conditions. The load combination could give a proper solution since it evaluates each load independently and then adds up each result linearly. Based on the results of each case, structural analysis for another load case, baking condition with incident, is conducted to find out which load is dominant for triangular support.Consequently, it is found that the baking condition is the dominant load for triangular support bracket. The proposed load combination method gives a physically reasonable solution which can be used as a reference for checking the validity of other thermal–structural analysis. It is expected that these results could be applied for manufacturing design of the triangular support under various load conditions.     

Study on the Flexible Support Legs for ITER Transfer Cask System

In fields of remote handing i.e. robot technology for fusion engineering reactor, such as ITER or the China fusion engineering test reactor, the flexible support legs are key components for their transfer cask system to adjust its position, joining to hot cell or tokamak ports for maintaining the fusion device. For ITER machine, each support leg should withstand maximum 50 tons load and adjust its height in 150 mm. Defect in original ITER design was presented. A new concept for the support legs was configured and its feasibility was proven. Detailed design and simulation was done for the new support leg with virtual prototype technology. Simulation results show that new support leg could not only meet all required function but also has merits of constant load during the tuning process with linear relation of control variable parameters, which is intended to be used for Tokamak reactors.     

Design assessment for manufacturability of supporting structures for IWS and ELM coil of ITER vacuum vessel

A vacuum vessel is one of the core facilities of ITER (International Thermonuclear Experimental Reactor) and basically all-welded structure. Korea is responsible for the procurement of sector 1 and 6 of the main vessel. Accordingly, the design review for the fabrication is in progress by ITER Korea and Hyundai Heavy Industries. Due to anticipated manufacturing problems such as the welding distortion, the design of some components of main vessel, IWS (In-Wall Shield) supporting rib and ELM (Edge Localized Mode) coil support, needs to be modified. To release the risk of welding distortion, the welding method called “bridge type” is suggested and the shape of weld joint is adjusted to secure the manufacturability of the issued components. The elastic and limit analyses with fatigue evaluation have been performed under the most critical loading condition to verify the structural integrity of modified design. Analysis results show that the proposed designs meet the design criteria of RCC-MR. The design deviation requests have been submitted to ITER Organization and ANB (Agreed Notified Body) for approval and their verification is currently in progress.     

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。     

Manufacturing preparations for the European Vacuum Vessel Sector for ITER

The contract for the seven European Sectors of the ITER Vacuum Vessel, which has very tight tolerances and high density of welding, was placed at the end of 2010 with AMW, a consortium of three companies. The start-up of the engineering, including R&D, design and analysis activities of this large and complex contract, one of the largest placed by F4E, the European Domestic Agency for ITER, is described. The statutory and regulatory requirements of ITER Organization and the French Nuclear Safety regulations have made the design development subject to rigorous controls. AMW was able to make use of the previous extensive R&D and prototype work carried out during the past 9 years, especially in relation to advanced welding and inspection techniques. The paper describes the manufacturing methodology with the focus on controlling distortion with predictions by analysis, avoiding use of welded-on jigs, and making use of low heat input narrow-gap welding with electron beam welding as far as possible and narrow-gap TIG when not. Further R&D and more than ten significant mock-ups are described. All these preparations will help to assure the successful manufacture of this critical path item of ITER.     

ITER中国液态锂铅实验包层模块设计研究与实验策略

在广泛调研和深入分析国际聚变堆包层发展状况的基础上,根据液态锂铅包层一般特点和中国发展的系列液态锂铅包层概念设计,提出了一个具有演示氦气单冷却剂和氦气/锂铅双冷却剂包层技术的双功能包层模块实验系统方案,对其性能进行了分析研究,作为中国向ITER实验包层工作组(TBWG)提交的液态包层实验模块最终设计描述文件的内容框架。总结了该工作主要内容,包括基本设计思想和方案描述、性能分析概况、对辅助系统的要求和实验策略与关键技术等。     

A study of the influence of electron beam welding sequences on the ITER vacuum vessel prototype VATS

This paper presents a detailed finite element simulation of the welds of the prototype Vessel Advanced Technology Segment (VATS) by electron-beam welding. The flexible support housings are reinforcing cylinders of the pressure boundary of the ITER vacuum vessel. They connect inner and outer shells. Eight different simulation sequences were carried out to explain the different mechanisms that drive the distortion process during welding and to lead to an optimum sequence which minimizes the final distortions. The simulations were used to guide the manufacture of the final sequence of the VATS.     

Development of ITER divertor Thomson scattering support structure design on the basis of engineering analyses

The support structure for divertor Thomson scattering equipment – the front diagnostic rack, which actually plays plugging role of the divertor port, should be designed to sustain the severe ITER conditions. Meeting the requirements of multifield analyses (which often contradict each other) results in an iterative design process. A number of design variants based on engineering analyses results were developed in 2011–2012. We study here the close to the final design of the diagnostic rack for consistency to electromagnetic, thermal and seismic loads. The specific ITER environment imposes a restricted list of materials and requires a careful design of optical elements to accommodate their thermal expansion. Special attention is focused on the mirror deformed shape under operating loading conditions and its effect on optical system performance, which is vital for all optical systems with mirrors specially designed for the ITER.     

Design analysis of the hinge support for the ITER vacuum vessel

In order to verify design feasibility and structural integrity of a hinge type support for the ITER VV support system, the design analysis has been performed in detail, which includes heat transfer, elastic stress and limit analyses. The structural analyses were performed to confirm the transfer of forces through the supporting structure and to determine the maximum allowable loads according to the RCC-MR. From the heat transfer analysis for VV baking stage, total heat flow into the support was obtained to confirm the thermal heat flux into the cryostat under baking condition. In addition, the design modification was also discussed to enhance the structural performance of the supporting system.     

Thermo-hydraulic and structural analysis for finger-based concept of ITER blanket first wall

The blanket first wall is one of the main plasma facing components in ITER tokamak. The finger-typed first wall was proposed through the current design progress by ITER organization. In this concept, each first wall module is composed of a beam and twenty fingers. The main function of the first wall is to remove efficiently the high heat flux loading from the fusion plasma during its operation. Therefore, the thermal and structural performance should be investigated for the proposed finger-based design concept of first wall. The various case studies were performed for a unit finger model considering different loading conditions. The finite element model was made for a half of a module using symmetric boundary conditions to reduce the computational effort. The thermo-hydraulic analysis was performed to obtain the pressure drop and temperature profiles. Then the structural analysis was carried out using the maximum temperature distribution obtained in thermo-hydraulic analysis. Finally, the transient thermo-hydraulic analysis was performed for the generic first wall module to obtain the temperature evolution history considering cyclic heat flux loading with nuclear heating. After that, the thermo-mechanical analysis was performed at the time step when the maximum temperature gradient was occurred. Also, the stress analysis was performed for the component with a finger and a beam to check the residual stress of the component after thermal shrinkage assembly.     

Paschen testing of ITER prototype cryogenic axial breaks

Axial insulation breaks are needed in forced cooled cryogenic high voltage devices for the separation of the high voltage area from the grounded pipe system. The ITER cryogenic axial breaks will be surrounded by good vacuum in case of normal operation but also under vacuum breakdown conditions sufficient dielectric strength is required for a reliable fast discharge of the coil system. A Paschen tight design of the ITER prototype breaks enables high voltage operation independent on the outer vacuum or gas conditions. Consecutively two pretested ITER prototype breaks were integrated in the insulation system of a Paschen test unit and high voltage tested. Two different ways to perform the Paschen testing were used for both breaks. The preparation of the breaks and the test setup are described and the test results are given.