Analysis of an Extreme Scenario in the Vacuum Vessel in KTX

The Vacuum Vessel(VV) system is a vital component of Keda Torus for experiment(KTX).Various accidental scenarios might occur on the VV.In this report,an extreme scenario is assumed and studied:plasma accidental termination during the flat-top stage.Numerical simulations based on finite element are performed as the major tool for analyses.The detailed distributions of eddy and the reaction forces on VV are extracted,and the total eddy current and the maximum reaction force due to electromagnetic load are figured out.In addition,according to the results,the VV can be approximately regarded as a centrally symmetric structure,even though its ports distribution is asymmetric.     

CFETR真空室超压保护系统管道设计与优化

真空室超压保护系统(VVPSS—Vacuum Vessel Pressure Suppression System)是中国聚变工程实验堆(CFETR—China Fusion Engineering Test Reactor)中重要的安全系统之一,它目的是预防在泄漏事故下,真空室和相关组件可能产生的过压损害。本文简述了VVPSS的总体设计和管道优化。主要介绍了VVPSS各个部件之间的联系和作用,初步得到管线布局;利用有限元分析软件对两种管路方案进行流体分析比较,得出对流体流动影响最小的方案;对是否能通过增加支路数目来减小爆破片的直径做出了初步探究,为核聚变装置中真空室超压保护系统的设计提供一定的参考依据。     

CFETR真空室超压保护系统管道设计与优化

真空室超压保护系统(VVPSS—Vacuum Vessel Pressure Suppression System)是中国聚变工程实验堆(CFETR—China Fusion Engineering Test Reactor)中重要的安全系统之一,它目的是预防在泄漏事故下,真空室和相关组件可能产生的过压损害。本文简述了VVPSS的总体设计和管道优化。主要介绍了VVPSS各个部件之间的联系和作用,初步得到管线布局;利用有限元分析软件对两种管路方案进行流体分析比较,得出对流体流动影响最小的方案;对是否能通过增加支路数目来减小爆破片的直径做出了初步探究,为核聚变装置中真空室超压保护系统的设计提供一定的参考依据。     

Design and Structural Analysis of Support Structure for ITER Vacuum Vessel

The International Thermonuclear Experimental Reactor (ITER) vacuum vessel (VV) is a safety component confining radioactive materials such as tritium and activated dust. An independent VV support structure with multiple flexible plates located at the bottom of VV lower port is proposed as a new concept, which is deferent from the current design, i.e., the VV support is directly connected to the toroidal coils (TF coils). This independent concept has two advantages comparing to the current one: (1) thermal load due to the temperature deference between VV and TF coils becomes lower and (2) the TF coils are categorized as non-safety components because of its independence from VV. Stress Analyses have been performed to assess the integrity of the VV support structure using a precisely modeled VV structure. As a result, (1) the maximum displacement of the VV corresponding to the relative displacement between VV and TF coils is found to be 15 mm, much less than the current design clearance of 100 mm, and (2) the stresses of the whole VV system including VV support are estimated to be less than the allowable ones defined by ASME Section III Subsection NF, respectively. Based on these assessments, the feasibility of the proposed independent VV support has been verified as a VV support.     

The Design of the Plasma Control System in KTX

KTX(Keda Torus for eXperiment)is a new reversed field pinch device.The KTX plasma control system(PCS)can provide real-time,stable,flexible plasma control which is designed by ASIPP(Institute of Plasma Physics,Chinese Academy of Sciences),based on the Linux cluster system and EPICS(Experimental Physics and Industrial Control System)framework,and developed from DIII-D(Doublet III-D)PCS.The control of the equilibrium field in KTX uses a PID(Proportional-Integral-Derivative)feedback controller.The control of the gas injection is an open loop control.The plasma control simulation system is one part of the plasma control system,which is used to test the plasma control algorithm if it is revised and updated.The KTX PCS has been successfully tested using HT-7(Hefei Torus 7)experiment data in simulation mode.In the next phase,an error field feedback control and KTX simulator will be added to the KTX PCS,and the KTX PCS will be applied in experiments in the future.     

KTX反场箍缩装置纵场线圈结构设计与电磁分析

KTX反场箍缩装置的主要参数介于RFX装置与MST装置之间。反场箍缩的外加纵场需跟随等离子体电流的演化而变化,同时由于RFP中的磁面对于外部特别是等离子体边界处的径向磁场较敏感,所以需外部线圈的磁场更加精细,这对于线圈的磁场分布、误差场以及波纹度等的设计提出了更高的要求。根据KTX物理目标参数要求,提出矩形和楔形截面纵场磁体线圈设计方案,借助有限元软件和程序分析了其电磁场空间分布和结构受力大小。结果表明,6.4°楔形截面方案相比矩形截面方案在控制误差场方面更具有可行性。     

Design of the poloidal field system for KTX

The design of the poloidal field (PF) system includes the ohmic heating field system and the equilibrium (EQ) field system, and is the basis for the design of a magnetic confinement fusion device. A coupling between the poloidal and plasma currents, especially the eddy current in the stabilizing shell, yields design difficulties. The effects of the eddy current in the stabilizing shell on the poloidal magnetic field also cannot be ignored. A new PF system design is thus proposed. By using a low-μ material (μ=0.001, ε=1) instead of a conductive shell, an electromagnetic model is established that can provide a continuous eddy current distribution on the conductive shell. In this model, a 3D time-domain problem with shells translates into a 2D magnetostatic problem, and the accuracy of the calculation is improved. Based on these current distributions, we design the PF system and analyze how the EQ coils and conductive shell affect the plasma EQ when the plasma ramps up. To meet the mainframe design requirements and achieve an efficient power-supply design, the position and connection of the poloidal coils are optimized further.     

Preliminary Design of GDC System for KTX Device

KeDa Torus for eXperiment (KTX) is a reversed field pinch magnetic confinement fusion research device whose main parameters are between in the RFX and MST. The base vacuum of KTX is 1 × 10^?6 Pa. Six sets of turbomolecular pumps parallel installed in the six horizontal ports which served as the main pumping system for KTX and the diameters of the ports are 0.15 m. Before plasma discharge, glow discharge cleaning (GDC) system is applied to clean C, O and hydrocarbon impurity on the vacuum vessel (VV) surfaces of KTX. An inflation system and residual gas analyzer system are designed to supply the working gas and monitoring the effect of GDC respectively. According to the GDC experiment practice, the working gas pressure of the KTX GDC system is designed as 0.3 Pa, with average current density of 0.15 A/m². Two sets of the GDC probes are installed in KTX horizontal ports symmetrically with interval angle of 180º and the input current of each anode is 1.6 A. According to the current density distribution, the centre of the VV cross section is the superior working area for GDC anode, a screw-nut pairs with the cooperation of bellows can transfer the anode from its storage position to its working position, and the stroke of the screw-nut pairs is 0.5 m. Based on the temperature rise calculation, the maximum equilibrium temperature of the anode during glow discharge is about 275 °C (under 200 °C baking). The thermal stresses caused by the temperature distribution on the anode’s components especially in the vacuum brazing areas are inspected during GDC process. All the simulation results show that the structure and base material of the KTX GDC anode can work normally without additional active cooling system.     

ITER Vacuum Vessel design and construction

After implementing a few design modifications (referred to as the “Modified Reference Design”) in 2009, the Vacuum Vessel (VV) design had been stabilized. The VV design is being finalized, including interface components such as support rails and feedthroughs for the in-vessel coils. It is necessary to make adjustments to the locations of the blanket supports and manifolds to accommodate design modifications to the in-vessel coils. The VV support design is also being finalized considering a structural simplification. Design of the in-wall shielding (IWS) has progressed, considering the assembly methods and the required tolerances. The detailed layout of ferritic steel plates and borated steel plates was optimized based on the toroidal field ripple analysis. A dynamic test on the inter-modular key to support the blanket modules was performed to measure the dynamic amplification factor (DAF). An R&D program has started to select and qualify the welding and cutting processes for the port flange lip seal. The ITER VV material 316 L(N) IG was already qualified and the Modified Reference Design was approved by the Agreed Notified Body (ANB) in accordance with the Nuclear Pressure Equipment Order procedure.     

Design of a Wedge-Shaped Toroidal Field Winding for KTX Device

The KTX device is a reversed field pinch(RFP)device currently under construction.Its maximum plasma current is designed as 1 MA with a discharge time longer than 100 ms.Its major radius is 1.4 m and its minor radius is 0.55 m.One of the most important problems in the magnet system design is how to reduce the TF magnetic field ripple and error field.A new wedgeshaped TF coil is put forward for the KTX device and its electromagnetic properties are compared with those of rectangular-shaped TF coils.The error field Bn/Btof wedge-shaped TF coils with6.4 degrees is about 6%as compared with 8%in the case of a rectangular-shaped TF coil.Besides,the wedge-shaped TF coils have a lower magnetic field ripple at the edge of the plasma region,which is smaller than 7.5%at R=1.83 m and 2%at R=1.07 m.This means that the tokamak operation mode may be feasible for this device when the plasma area becomes smaller,because the maximum ripple in the plasma area of the tokamak model is always required to be smaller than 0.4%.Detailed analysis of the results shows that the structure of the wedged-shape TF coil is reliable.It can serve as a reference for TF coil design of small aspect ratio RFPs or similar torus devices.     

KTX反场箍缩装置主支撑结构设计与分析

KTX反场箍缩实验装置主支撑由柔性支撑和支撑平台组成,主要用来支撑真空室、导体壳和纵场线圈的重量。鉴于主支撑结构的重要性,通过有限元分析和理论分析相结合的方法对主支撑进行了强度分析和稳定性分析,给出了主支撑应力分布和变形情况及不同结构参数下的临界载荷。分析结果验证了主支撑结构的可行性,并为主支撑的后续优化设计提供理论依据。     

氚在真空贮存容器材料中的吸附和渗透行为

研究了贮存氚靶约4 a和20 a的两个316 L不锈钢真空贮存容器(以下简称贮存容器)及其垫片材料对氚的吸附行为,并对氚在贮存容器材料中的渗透速率进行了测量和分析。结果表明,贮存容器外表面氚污染为几十Bq/cm2,不锈钢与陶瓷中吸附的氚活度均为106Bq/g;热解吸至1 273 K过程中,材料中99%的氚释放出来;在解吸出的氚中,陶瓷中的HTO比例高于不锈钢;贮存温度对氚靶贮存容器的渗氚速率有较大影响,夏季约为冬季的4倍。上述结果提示,氚在贮存容器材料内表面吸附后,一部分会向晶格扩散并滞留下来;另一部分则透过材料向外环境渗透,其中温度是影响氚向外环境渗透的主要因素之一。     

CARR堆芯容器用辐照监督装置的设计优化

本文详细介绍了中国先进研究堆堆芯容器用辐照监督装置,通过物理计算及热工水力计算多种方案建模分析,对辐照监督装置的结构进行了优化设计,并完成施工设计。     

船用堆辐射屏蔽优化设计平台开发与验证

船用堆对核反应堆屏蔽设计提出了更高的要求,传统辐射屏蔽设计方法及设计软件已不能满足要求。为了得到更加精确的辐射屏蔽设计,本文基于开源的SALOME框架建立了一套集“几何建模-材料建模-屏蔽优化-结果可视化”功能为一体的船用堆辐射屏蔽多目标优化平台——MOSRT。MOSRT平台可实现屏蔽结构三维CAD实体建模、基于遗传算法的辐射屏蔽多目标优化以及屏蔽计算结果剂量场三维可视化。基于Savannah和MRX船用堆模型对MOSRT平台进行了辐射屏蔽优化验证,优化方案与初始方案相比,在剂量、质量、体积方面均得到了良好的优化效果,证明了MOSRT平台初步具备辐射屏蔽优化设计功能,可为船用堆工程及概念屏蔽设计提供辅助设计手段。      

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…     

Numerical Analysis on Neutron Shielding Structure of ITER Vacuum Vessel

The neutron shielding component of ITER （International Thermonuclear Experimental Reactor） vacuum vessel is a kind of structure resembling a wall in appearance. A FE （finite element） model is set up by using ANSYS code in terms of its structural features. Static analysis, thermal expansion analysis and dynamic analysis are performed. The static results show that the stress and displacement distribution are allowable, but the high stress appears in the junction between the upper and lower parts. The modal analysis indicates that the biggest deformation exists in the port area. Through modal superposition, the single-point response has been found with the lower rank frequency of the acceleration seismic response spectrum. But the deformation and the stress values are within the permissible limit. The analysis results would benefit the work in the next step and provide some reference for the implementation of the engineering plan in the future.     

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…     

Capability Assessment of the Equilibrium Field System in KTX

Radial equilibrium of the KTX plasma column is maintained by the vertical field which is produced by the equilibrium field coils.The equilibrium is also affected by the eddy current,which is generated by the coupling of copper shell,plasma and poloidal field coils.An equivalent circuit model is developed to analyze the dynamic performance of equilibrium field coils,without auxiliary power input to equilibrium field coils and passive conductors.Considering the coupling of poloidal field coils,copper shell and plasma,the evolution of spatial distribution of the eddy current density on the copper shell is estimated by finite element to analyze the effect of shell to balance.The simulation results show that the copper shell and equilibrium field coils can provide enough vertical field to balance 1 MA plasma current in phase 1 of a KTX discharge.Auxiliary power supply on the EQ coils is necessary to control the horizontal displacement of KTX due to the finite resistance effect of the shell.