The Alignment and Assembly for EAST Tokamak Device

EAST （HT-7U） is a large fusion experimental device. It is a full superconducting tokamak with 1 MA of plasma current, 1000 s of plasma duration, high elongation and triangularity. It mainly consists of superconducting magnets of poloidal and toroidal field （PF ＆ TF）, vacuum vessel （VV）, thermal radiation shield （TRS） and cryostat vessel （CV）. The significant difficulty for assembly of EAST is tight installation tolerances, which are in the order of several tenth of a millimeter. In particular, the alignment of plasma facing components to the magnetic axis of the device is less than ±0.5 mm. At present, a reasonable assembly process of EAST has been defined, and based on it, the alignment method for EAST, including the survey control network, the location of the main components in different directions, the magnetic axis determination and the accurate positioning of the plasma facing components inside of the vacuum vessel and so on, has been defined by using the sophisticated optical metrology system （SOMS）. This paper describes the assembly procedure of EAST and the installation tolerances associated with the main components. Meanwhile, how to establish the assembly survey control network, magnetic axis determination methods, are introduced in detail.     

Design Study of Top Lid with Clamp Structure in JT-60SA Cryostat

JT-60SA is a fully superconducting coil tokamak upgraded from the JT-60U. This paper focused on the integrity of the top lid of cryostat in JT-60SA. The design requirement for the cryostat in normal operations is to achieve vacuum insulation of 10 3 Pa, and the top flange of the top lid is lightly welded onto its body flange. The weld is tensile-loaded by bending deformation of the top lid due to vacuum pressure of external 0.1 MPa. This weld integrity is evaluated with tensile-load reduction, which results in clamp reinforcement. The structural integrity of the top lid is validated.     

A Lower Rigid Support Structure for the HT—7U Vacuum Vessel

Vacuum vessel of the HT-7U is a fully welded toroidal structure with a noncircularcross-section nested in the bore of the TF coils. According to the requirement of the physicsdesign, sixteen horizontal ports on outboard mid-plane and thirty-two vertical ports on the topand bottom are designed for diagnostics, plasma heating, current driving, vacuum pumping andgas puffing. Bellows on these port necks are used for flexible components to absorb the relativedisplacement in radial and vertical directions due to external load, thermal expansion or contrac-tion and assembly tolerance, and also used for isolation of mechanical vibration. For the supportsystem of vacuum vessel it should be not only strong enough to withstand forces acting on thevessel interior components and the vessel itself due to the dead weight and electromagnetic inter-actions during plasma disruption, but also sufficiently flexible to be suited to thermal expansionduring baking. In order to solve this contradiction a new kind of low rigid s     

Electromagnetic and Stress Analyses of the ITER Equatorial Thermal Shield

The ITER equatorial thermal shield is located inside the cryostat and outside the vacuum vessel, and its purpose is to provide a thermal shield from hot components to the superconducting magnets. Electromagnetic analysis of the equatorial thermal shield was performed using the ANSYS code, because electromagnetic load was one of the main loads. The 40 sector finite element model was established including the vacuum vessel, equatorial thermal shield, and superconducting magnets. The main purpose of this analysis was to investigate the eddy current and electromagnetic force in the equatorial thermal shield during plasma disruption. Stress analysis was implemented under the electromagnetic load. The results show that the equatorial thermal shield can accommodate the calculated electromagnetic loads.     

Linear Buckling Analysis of the HT-7U Vacuum Vessel

1. IntroductionHT-7U superconducting Tokamak, as a nationalproject, is an advanced steady-state plasma exper-imental device to be built in 2Oo3. Now all kindsof engineering design have been begun. The vac-uum vessel is one of the key parts for HT-7U de- vice, which can provide not only a clean and ultra-high vacuum env1ronment in the operatlon of plasmafor the production quilibrium and heating of thelasma, but also reliable supporting structure andvarious channels for a series of equipme…     

Structural Analysis of the ITER VV Lower Port Region

A structural analysis of the International Thermonuclear Experimental Reactor （ITER） vacuum vessel＇s lower port region was presented by means of a finite element analysis method. The purpose is to evaluate the stress and displacement level on this structure under various combinations of five designed loads, including the gravity of the vacuum vessel, seismic loads, electromagnetic loads, and possible pressure loads to ensure structural safety. The cyclic symmetry finite element model of this structure was developed by using ANSYS code. The re- sults showed that the maximum stress does not exceed the allowable value for any of the load combinations according to ASME code and the nine vacuum vessel （VV） supports have the ability to sustain the entire VV and in vessel-components and withstand load combinations under both normal as well as off-normal operation conditions. Stress mainly concentrates on the connecting region of the VV support and lower port stub extension.     

Influence of Gap Distance on Vacuum Arc Characteristics of Cup Type AMF Electrode in Vacuum Interrupters

The greenhouse effect of SFe is a great concern today. The development of high voltage vacuum circuit breakers becomes more important. The vacuum circuit breaker has minimum pollution to the environment. The vacuum interrupter is the key part of a vacuum circuit breaker. The interrupting characteristics in vacuum and arc-controlling techniue are the main problems to be solved for a longer gap distance in developing high voltage vacuum interrupters. To understand the vacuum arc characteristics and provide effective technique to control vacuum arc in a long gap distance, the arc mode transition of a cup-type axial magnetic field electrode is observed by a high-speed charge coupled device （CGD） video camera under different gap distances while the arc voltage and arc current are recorded. The controlling ability of the axial magnetic field on vacuum arc obviously decreases when the gap distance is longer than 40 ram. The noise components and mean value of the arc voltage significantly increase. The effective method for controlling the vacuum arc characteristics is provided by long gap distances based on the test results. The test results can be used as a reference to develop high voltage and large capacity vacuum interrupters.     

Wall Recycling in Long Duration Discharges on the HT-7 Tokamak

The main efforts of HT-7 superconducting tokamak are directed to quasi-steady state discharges and relevant physics. Significant progress has been realized in obtaining high-performance discharges under a quasi-steady state in HT-7. The long pulse discharges have been obtained with duration up to more than one minute. Wall recycling has been studied in the long duration discharges in HT-7. The recycling coefficient R of each plasma increases with time. The uncontrolled density increase is accompanied by hydrogen and the impurity influx originating mainly from the limiter surface and the parts of the inner vessel. The edge recycling after boronization will also be discussed in this paper.     

Fusion Material Studies Relating to Safety in Russia in 2002

The paper is a summary of Russiau material studies performed in frames of activities aiming at substantiation of safety of the International Thermonuclear Experimental Reactor (ITER) after 2001. Subthreshold sputtering of tungsten by 5 eV deuterons was revealed at temperatures above 1150℃. Mechanism of globular films formation was further studied. Computations of tritium permeation into vacuum vessel coolant confirmed the acceptability of vacuum vessel cooling system for removal of the decay heat. The most dangerous accident with high-current arc in toroidal superconducting magnets able to burn out a bore up to 0.6 m in diameter in the cryostat vessel was determined. Radiochemical reprocessing of V-Cr-Ti alloy and its purification from activation products down to a contact dose rate of ∽10 μSv/h was developed.     

Feedback Control Systems on HT-7 Tokamak

1. IntroductionThe construction of HT－7 Tokamak is a 5－layerstructure, including a cryostat and a vacuum vessel, the screen of an outer and an inner copper shellwith a liquid nitrogen cooling, and a superconducting magnet with a forced flow of helium cooling.Theplasma is screened by two layers of copper with athickness of l.5 cm. [1] A simple structure is shownin Fig.1.For the vertical field being difficult to pass throllghthe double copper shells less than 400 ms, it is difficult for plas…     

Temperature Field and Thermal Stress Analysis of the HT-7U Vacuum Vessel

1.IntroductionHT-7UsuperconductingTokamakisanadvancedsteady-stateplasmaphysicsexperimentaldevice.ThedevicewillbebuiltattheinstituteofPlasmaPhysics,theChineseAcademyofSciencesintheyear2003.Itscessionistodevelopthescientific.basisandtechnologicbajsisforthefutureTokamakfusionreactorsandtostudyphysicalissuesonthesustenanceOfanon-burningplasmascenarioforthesteady-stateoperation.TheHT--7Uhasacapabilityforlongpulse(60-1000s)operation.Theprojecthasbeenapprovedandfundedasanationalmegscience-engin…     

Electrical Parameters of the Vacuum Vessel in HT-7U Tokamak

1. IntroductionThe time-t'arying currents in plasma and poloidalfield coils induce the eddy current on the vacuumvessel of tokamak- The magnetic field produced bythe eddy currents has an effect on the penetrationof poloidal field, the position and the shape of theplasma: t'.hich is related to the structure of the yao-uum vessel and the distribution of the eddy currentsThe level of the effect can be described by the electrical parameters of the vessel, being of very importance in the study Of t…     

Structural analysis of the JT-60SA cryostat vessel body

The JT-60SA cryostat is a stainless steel vacuum vessel (14 m diameter, 16 m height) which encloses the Tokamak providing the vacuum environment (10^?3 Pa) necessary to limit the transmission of thermal loads to the components at cryogenic temperature. It must withstand both external atmospheric pressure during normal operation and internal overpressure in case of an accident.The paper summarizes the structural analyses performed in order to validate the JT-60SA cryostat vessel body design. It comprises several analyses: a buckling analysis to demonstrate stability under the external pressure; an elastic and an elastic–plastic stress analysis according to ASME VIII rules, to evaluate resistance to plastic collapse including localized stress concentrations; and, finally, a detailed analysis with bolted fasteners in order to evaluate the behavior of the flanges, assuring the integrity of the vacuum sealing welds of the cryostat vessel body.     

Structural analysis of the JT-60SA cryostat base

Design and manufacturing of the JT-60SA cryostat is being performed by CIEMAT, according to the Broader Approach Agreement between Japan and the European Commission. Taking into account both the limitations of transport and the assembly sequence of JT60-SA, the cryostat is divided in two main parts, namely the cryostat base and the cryostat vessel body.The paper is focused on the structural analyses carried out by CIEMAT to evaluate the mechanical behavior of the JT-60SA cryostat base final design, since the cryostat vessel body will be designed and manufactured in a subsequent stage.The overall structural integrity of the cryostat base has been verified and confirmed utilizing the ‘limit analysis’ procedure defined in ASME code 2007 Section VIII, Div. 2. The study has been complemented by further finite element analyses that include the detail of the bolted fastenings, aimed to evaluate the mechanical behavior of the bolted joints themselves, as well as the stresses and deformations in the overall cryostat base structure.     

Overview of main-mechanical-components and critical manufacturing aspects of the Wendelstein 7-X cryostat

Wendelstein 7-X (W7-X) will be the world's largest superconducting helical advanced stellarator. This stellarator concept is deemed to be a desirable alternative for a future power plant like DEMO. The main advance of the static plasma is caused by the three dimensional shape of some of the main mechanical component inside the cryostat. The geometry of the plasma vessel is formed around the three dimensional shape of the plasma. The coils and their support structure are enclosed within the outer vessel. The space between the outer, the plasma vessel and the ports is called cryostat because the vacuum inside provides thermal insulation of the magnet system which is cooled down to 4 K. Due to the different thermal movements of both vessels and the support structure have to be supported separately. 10 cryo legs will bear the coil support structure. The plasma vessel supporting system is divided into two separate systems, allowing horizontal and vertical adjustments. This paper aims to give an overview of the main mechanical components of the cryostat. The authors delineate some disparate and special problems during the manufacturing of the components at the companies in Europe. It describes the current manufacturing and assembly.     

Design and assembly technology for the thermal insulation of the W7-X cryostat

The Max-Planck-Institut für Plasmaphysik in Greifswald is building up the stellarator fusion experiment Wendelstein 7-X (W7-X). To operate the superconducting magnet system the vacuum and the cold structures are protected by a thermal insulated cryostat. The plasma vessel forms the inner cryostat wall, the outer wall is realised by a thermal insulated outer vessel. In addition 254 thermal insulated ports are fed through the cryogenic vacuum to allow the access to the plasma vessel for heating systems, supply lines or plasma diagnostics.The thermal insulation is being manufactured and assembled by MAN Diesel & Turbo SE (Germany). It consists of a multi-layer insulation (MLI) made of aluminized Kapton with a silk like fibreglass spacer and a thermal shield covering the inner cryostat surfaces. The shield on the plasma vessel is made of fibreglass reinforced epoxy resin with integrated copper meshes. The outer vessel insulation is made of brass panels with an average size of 3.3 × 2.0 m². Cooling loops made of stainless steel are connected via copper strips to the brass panels. Especially the complex 3 D shape of the plasma vessel, the restricted space inside the cryostat and the consideration of the operational component movements influenced the design work heavily. The manufacturing and the assembly has to fulfil stringent geometrical tolerances e.g. for the outer vessel panels +3/?2 mm.     

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.     

核聚变装置HT-7U环境辐射剂量蒙特卡罗模拟计算与分析

在聚变评价数据库FENDL／2的基础上，采用三维蒙特卡罗输运程序MCNP／4C，对核聚变装置HT07U运行时的环境辐射剂量率进行了模拟计算及相关分析，着重研究了HT-7U硼水屏蔽层不同设计方案对环境剂量率的影响。计算结果表明，硼水层有效地减小了装置运行时周围环境的辐射剂量率，而浓缩硼水方案相对天然硼水方案，屏蔽效果提高不明显。同时本文也对聚变装置环境辐射剂量计算中的天空反(散)射效应进行了初步的研究，计算结果显示，当屏蔽大厅顶厚减至0．5m以下时，装置运行时大厅外辐射剂量分布呈现明显的阴影效应。