ITER极向场线圈维修过程及照射剂量虚拟仿真

根据国际热核聚变实验堆ITER设计标准,ITER极向场线圈(PF Coils)的人工检测和连接维修任务的制定,需要开展维修方案的预评估,验证当前核设计方案的合理性和可行性。基于ITER组织提供的辐射场数据和工程模型,在核与辐射安全仿真系统SuperMC/VisualDose2.3的支持下,开展了ITER PF4维修过程的工人职业照射剂量仿真分析,包括维修过程的虚拟漫游仿真、器官剂量实时评估、累积剂量评估和人员操作过程的虚拟培训仿真。仿真结果显示,根据现有ITER核设计方案,ITER停堆106 s后人员进入低温室开展ITER PF4检修工作所受到的累积剂量为2.19mSv,为ITER核设计分析人员提供了参考。     

ITER环向场和极向场线圈导体PA中引用标准及存在问题分析

基于我国与国际热核聚变实验堆(ITER)组织签署的环向场(TF)线圈和极向场(PF)线圈导体采购安排协议(PA)的技术内容,介绍TF线圈导体PA和PF线圈导体PA中引用标准的总体情况,分析和总结这两个PA中引用标准存在的各种问题。     

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。     

ITER校正场线圈等效材料属性有限元分析

校正场线圈是ITER大型超导磁体系统的重要组成部分,其线圈体由多种材料组成且周期性排列,对其等效材料属性预测很重要。目前主要采用基于均匀化理论的有限元方法,但其处理过程复杂。本文提出了基于广义虎克定律的有限元方法,使求解过程更简便。分析对比两种方法,后一种方法处理过程更简单,结果更精确,所得结果为校正场线圈的结构分析和热分析提供了必要的参数。     

EAST核聚变实验装置中极向场线圈电流的确定

在EAST核聚变托卡马克实验装置中，无论是在设计阶段还是未来运行过程中，确定极向场线圈电流都是非常重要的。本文采用排列格林函数的方法，给出设计中固定边界计算和未来运行过程中反演计算两种条件下极向场线圈电流的确定方法,并在理论上证明了可行性，大大减少了计算时间。     

基于严格两步法的停堆剂量率计算程序的基准分析

基于蒙卡程序cosRMC的网格计数功能,开发了以严格两步法为核心的停堆剂量率计算程序,通过耦合粒子输运计算和活化分析计算,精确求解停堆剂量场。其中,采用ALARA程序开展活化分析计算,将程序应用于ITER诊断窗口计算基准题上,开展了充分的计算分析,并与其他严格两步法程序计算得到的停堆剂量率结果有较好的一致性。另外,由于聚变装置几何十分复杂,结构网格难以准确描述几何结构,往往一个网格包含多个栅元,此时网格的通量平均对停堆剂量率的精度会带来不好的影响,而非结构网格具有良好的几何适应性,因此,基于非结构网格对停堆剂量率程序作了进一步开发,并在基准题上开展计算分析,验证了程序基于非结构网格计算停堆剂量率的可靠性。     

HT—7U超导托卡马克极向场电源系统多变量解耦控制分析

本文针对ＨＴ－７Ｕ极向场电源系统负载线圈彼此耦合强,电源调试比较困难的情况,提出一种新型的电流解耦控制算法,使各线圈达到预期的电流波形。并通过计算机仿真的方法,证明了该算法的可行性与优越性。     

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.     

Assessment of ITER PF coil quality from magnetic measurements

A feasibility has been demonstrated for numerical reconstruction on the base of magnetic measurements for geometrical displacements or deformations occurred in the manufacture and assembly of magnet coils. For validation of the proposed approach the test results of reconstruction of possible misalignments and deviations of the ITER PF1 coil are presented.     

Evaluation of the Environmental Gamma-ray Dose Rate by Skyshine Analysis During the Maintenance of an Activated TFC in ITER

Gamma-ray exposure dose rates at the ITER site boundary were estimated for the cases of removal of a failed activated Toroidal Field (TF) coil from the torus and removal of a failed activated TF coil together with a sector of the activated Vacuum Vessel (VV). Skyshine analyses were performed using the two-dimensional SN radiation transport code, DOT3.5. The exposure gamma-ray dose rates on the ground at the site boundary (presently assumed to be 1 km from the ITER building), were calculated to be 1.1 and 84 Sv/year for removal of the TF coil without and with a VV sector, respectively. The dose rate level for the latter case is close to the tentative radiation limit of 100 Sv/year so an additional 14 cm of concrete is required in the ITER building roof to satisfy the criterion for a safety factor often for the site boundary dose rate.     

Production and installation study of the ITER PF4 in-pit feeder

The PF4 in-pit feeder includes the In-Cryostat-Feeder (ICF) and Cryostat-Feed-Through (CFT), with busbars being their key components. The relative positions of the busbar terminal joints are measured by using a laser tracker and adjusted by positioning tools. The busbars are not fixed on the separate plate until the position errors meet the manufacture tolerances. The CFT has a 2.38° penetration angle relative to the ground and will be installed firstly. The position of the connection interface between the CFT and its lifting tool is analyzed, and to reduce the total deformation and keep the assembly precision of the joints the straight part of the CFT needs to be supported. The ICF has the most critical assembly operation space, as it must be installed on its temporary support in a temporary position. After the PF4 coil has been installed the ICF will be moved to its final position. To guarantee the 30 mm safety assembly clearance provided by ITER, the collision analysis of the ICF is performed, which demonstrates that the assembly procedures are feasible.     

Shut-Down Dose Rate analysis for ITER Diagnostic Equatorial and Upper Ports

The Shut-Down Dose Rate (SDDR) is an important criterion of radiation safety for the personnel access for maintenance operations in ITER ports after the cessation of the D-T 14 MeV neutron fusion source. Therefore, the problem of the SDDR calculations attracts the attention of fusion neutronics community because SDDR in such a large and geometrically complicated fusion device as the ITER tokamak is challenging to compute. This challenge has been faced and overcome by applying dedicated methodological approaches explained in this paper. The results of the SDDR analysis allowed us to propose several design solutions for improvement of the radiation shielding of the ITER Generic Diagnostic Equatorial and Upper Port Plugs (EPP and UPP). The SDDR analysis was focused on the interspace area located between the ITER bioshield and port plugs where the personnel access is envisaged at ∼12 days after the ITER shut-down. By this analysis the radiation streaming pathways and dominant sources of decay radiation were revealed and the methods to mitigate the streaming and subsequent activation were found. The optimization of the port shielding was targeted on minimization of the SDDR in the interspace area following the ALARA principle and taking into account the feasibility to implement proposed shielding options with the actual hardware. Among them, wrapping the EPP walls with the B₄C tiles improves the EPP shielding performance. While void around the ELM/in-vessel coils and blanket manifolds leads to the performance reduction. The SDDR inside the Generic UPP interspace depends mainly on the environment (blanket, manifolds, and gaps).     

Mechanical analysis of the PF1 feeder for ITER

The ITER experimental device contains very powerful superconducting magnets operated at cryogenic temperatures to generate and control the deuterium–tritium plasma for thermo-nuclear fusion. The function of the feeders is to convey the cryogenic supply and electrical power through the warm-cold barrier to ITER magnets. Due to the complexity of the structure and working conditions, a global mechanical analysis is required to have simulation information to check the structural reliability of the design. Electromagnetic force analysis of PF1 feeder for further mechanical analysis was calculated under the worst scenarios with the maximum working current in every coil. Mechanical analysis model was built using the finite element software ANSYS. The structural performance of the PF1 feeder was analyzed. The numerical simulation results show that the design of the PF1 feeder is feasible.