磁悬浮式控制棒驱动机构静水转向性能研究

在中国先进研究堆(CARR)调试阶段,发现其控制棒驱动机构在转向过程中存在驱动线圈与控制棒运动不同步的现象。为掌握控制棒驱动机构的转向性能参数,在静水条件下进行了控制棒驱动机构转向性能测试试验。试验表明:驱动线圈与控制棒运动不同步是磁悬浮式控制棒驱动机构的固有特性;棒位、棒速和驱动线圈通电电流大小等因素对静水条件下转向性能影响不大,且四组驱动机构静水条件下转向性能具有一致性。     

中国先进研究堆控制棒驱动机构动态反向性能研究

在中国先进研究堆(CARR)调试试验期间,发现控制棒驱动机构在反向过程中存在驱动线圈与控制棒运动不同步的现象。为掌握控制棒驱动机构的反向性能参数,在主冷却剂系统运行条件下进行了控制棒驱动机构动态反向性能测试试验。试验数据和分析结果表明:驱动线圈与控制棒运动不同步是磁悬浮式控制棒驱动机构固有特性;棒位、棒速和驱动线圈通电电流大小等因素对动态条件下反向性能影响不大,且4组驱动机构动态条件下反向性能具有一致性;动态反向性能优于静态,是由控制棒驱动机构电磁力分布决定的。     

多编码棒三态码电感控制棒位置指示系统

提出了一种结构简单、工作可靠、测量精度高的控制棒位置指示系统——多编码棒三态码电感控制棒位置指示系统。该系统探测器由K个测量线圈、一个补偿线圈和K根编码棒组成,每根编码棒均由若干段强导磁材料、若干段弱导磁材料与数段非导磁材料按规律间隔分布构成。当K根编码棒随控制棒在K个测量线圈中央轴向运动时,导致线圈的感抗发生变化,线圈输入的交变恒流信号在测量线圈上产生随感抗发生变化的电压信号。对信号进行适当的处理,可获得表征棒位的三态码。详细地介绍了该系统探测器的编码原理与硬件结构。结论表明：它比现役压水堆使用的线圈编码棒位指示系统性能优越,完全满足供热堆的棒位测量要求。     

应力腐蚀裂纹涡流检测信号的处理及形状重构

在核电站热交换管道、压力容器等关键设备结构的无损评价中,裂纹型缺陷形状的确定非常重要.采用一种小波分析方法对采集的应力腐蚀裂纹涡流检测信号进行了预处理,减少了噪声及非缺陷信号,并提取了缺陷信号特征,然后采用神经网络方法对裂纹形状进行了重构.结果表明,该方法具有快速、精确的优点.但在数据生成及训练网络时需要花费一定的时间.另外,由于神经网络方法不能重构裂纹电导率的分布情况,因此不能保证所重构裂纹的可靠性.但从涡流检测实用性的角度出发,在不考虑多裂纹等复杂情况下,神经网络方法可以用来重构自然裂纹.     

控制棒驱动机构电流响应特性分析

控制棒驱动机构的提升与下插动作需要钩爪部件与3个电磁线圈配合完成,对线圈电流的动态响应过程要求较为严格。采用Simulink软件搭建控制棒驱动机构棒控系统与线圈部件的等效回路,计算分析控制棒驱动机构线圈电阻、电感、端电压等因素对线圈电流响应时间的影响;采用电磁分析软件MAGNET对移动线圈中电流的变化过程进行仿真分析。最终得到控制棒驱动机构线圈电流响应时间与线圈端电压、线圈等效电感、电阻以及棒控回路形式的关系。     

基于钒探测器补偿的轴向偏移控制设计

机械补偿控制是基于控制棒调节反应堆功率并进行轴向功率偏移控制的先进技术,频繁移动的控制棒对传统堆外校准后的轴向功率偏差测量精度有较大的负面影响,采用能给出准确堆内功率分布的钒基自给能探测器的信号可对其进行校正。为补偿钒探测器较长的响应时间,设计了超前/滞后控制器,提出了用补偿后的信号对堆外测量得到的轴向功率偏差信号进行修正的方法。仿真结果表明,该方法能有效应对控制棒移动对轴向偏移控制的影响,可提高控制精度。对该方法的安全相关影响、可实施性及性能分析表明,其具有较高的实用价值。     

模块式小型堆控制棒驱动机构风冷性能热态试验

采用1:1轴向比例模拟实堆运行环境,开展模块式小型堆(ACP100)控制棒驱动机构(CRDM)的风冷性能热态试验。测定了正常运行时不同冷却风速下各线圈平衡温度、线圈断风后温度变化及电气性能,获得了驱动机构的最小风速、允许断风时间、极限断风性能等关键参数,为ACP100的驱动机构通风冷却系统设计和实堆运行提供重要的参考。     

软件补偿自编码棒位指示系统

目前,压水堆核电站普遍采用线圈编码式棒位指示系统测量其控制棒位置,而在此基础上发展发展的自编码数字式棒位指示系统的探测器与前述系统的探测器均需补偿线圈来实现差动输出,从而提高输出信号的信噪比。本研究提出并从理论上证明后者可取消专设的补偿线圈而采用软件补偿,并据此设计了软件补偿自编码棒位探测器。该方案进一步简化了棒位指示系统的探测器结构,使其线圈数量少,轴向长度缩短,结构简单的优点得以在２００ＭＷ供     

数字模拟棒位探测器的研究

提出了一种结构简单、工作可靠、测量精度较高的控制棒棒位探测器－－数字模拟棒位探测器。该探测器由两个反饶串接的长电感线圈，两个短电感编码线圈与一根编码芯棒组成，其中，编码芯棒由一段导磁衔铁与一段非导磁材料组成。当编码芯棒在线圈中央轴向运行时，初级线圈上输入的交变励磁信号必在次级线圈上产生交变的感应信号，通过接收这些线圈的输出信号并进行处理从而判断控制棒在堆内的运行位置。实验结果表明：本数字模拟棒位探     

中国实验快堆控制棒驱动机构抗震鉴定试验

池式钠冷快堆的控制棒驱动机构具有细长、结构非线性和多激励点等特征,因此其抗地震性能鉴定问题一直受到世界发展快堆国家的重视。介绍了在竖井式多点激励地震台上所完成的对中国实验快堆(简称CEFR)控制棒驱动机构的抗震鉴定试验。试验结果表明,该型控制棒驱动机构的功能完好性和结构完整性满足设防地震下的规范要求。     

A case study on detection and sizing of defects in steam generator tubes using eddy current testing

Eddy current testing (ECT) method is widely used to detect various types of defects occurring in nuclear steam generator tubes. Therefore, the reliability of its detection and sizing accuracy for defects should be validated. For this purpose, two tubes with defect signals were pulled from an operating steam generator and destructively examined. The defect type was a circumferential crack for one tube and an intergranular attack (IGA) for the other tube. The plus point coil probe showed a better capability to detect and size both a circumferential crack and a volumetric IGA than pancake and bobbin coil probe. The destructive results are correlated with the ECT results obtained during the in-service inspection.     

Secondary side corrosion in steam generator tubes: lessons learned in France from the in-service inspection results

Non-destructive testing (NDT) has proved to be very important in the maintenance of steam generator tubing. This is particularly true in the case of secondary side corrosion, because this type of degradation leads to various morphologies which are often complex (intergrranular attack) (IGA), intergranular stress corrosion cracking (IGSCC), or a mixture of both. Their detection and characterization by the usual NDT techniques have been achieved through numerous laboratory studies, which were conducted in order to determine the performance and limitations of NDT. Pulled tube examination in a hot laboratory was very valuable, for both NDT and fracture mechanics aspects. The eddy current bobbin coil probe, used for multipurpose inspection of tubes, allows the detection of IGA-SCC at the tube support plate elevation. In France, the use of rotating probes is not required for that type of degradation, since the repair criterion is based on bobbin coil results only. The bobbin coil is also used for detection of IGSCC occurring in free spans, within sludge deposits. The eddy current rotating probe allows, in that case, characterization of main cracks. Concerning the outer diameter initiated circumferential cracks which occur at the top of the tube sheet, only the rotating probe is used. An ultrasonic (UT) inspection was performed several times, in order to obtain information on UT capabilities. The goal of tube inspection is obviously knowledge of the status of steam generators, but also to follow up degradations and to estimate their revolution, and to verify the beneficial effect of some corrective measures, e.g. boric acid injection.     

Evaluation of the electromagnetic characteristics of type 316L stainless steel welds from the viewpoint of eddy current inspections

This study evaluated the electromagnetic characteristics of austenitic stainless steel welds from the viewpoint of eddy current testing. Seven welded plate specimens, which were welded using JIS Z3221:2010 YS316L welding metals, were prepared. Two welding metals and several welding conditions were adopted to discuss the generality. The results of eddy current examination of the specimens using three different types of eddy current probes, that is, an absolute pancake probe, a differential plus-point probe, and a uniform eddy current probe, confirmed that the welds cause a large noise especially when the absolute pancake probe was used. The analysis of the signals through finite element simulations revealed that the magnetic property of the welds is not negligible from the viewpoint of eddy current testing. Complementary experiments were conducted using a vibrating sample magnetometer to validate the results.     

Modeling of eddy current probe response for steam generator tubes

Sample calculations were performed with a three-dimensional (3D) finite-element model to describe the response of an eddy current (EC) probe to defects in steam generator (SG) tubing. Such calculations could be very helpful in understanding and interpreting EC probe response to complex tube/defect geometries associated with the inservice inspection (ISI) of SG tubes. The governing field equations are in terms of coupled magnetic vector and electric scalar potentials in conducting media and of total or reduced scalar potentials in nonconducting regions. To establish the validity of the model, comparisons of the theoretical and experimental responses of an absolute bobbin probe are given for two types of calibration standard defects. Simulation results are also presented on the effect of ligament size in axial cracks on bobbin probe response.     

Fabrication and installation of equilibrium field coils for the JT-60SA

Recently, fabrication of the first superconducting coil in JT-60SA tokamak (EF4 coil) was finished. EF4 coil has ten double pancake (DP) coils. All DP coils were stacked up to form the winding pack. In order to check the manufacturing error of DP coils, their circularities (in-plane ellipticities) were evaluated for all DP coils. Positions of conductors for each DP coil were measured before curing process. Error bars of the current centers, which were used for the index for DP coil's circularity, ranged between 1.1 and 2.5 mm. During stacking the DP coils, the positions of these coils were optimized in order to cancel the error of circulation of the winding pack. As the result, the manufacturing error of the radial current center was achieved 0.6 mm for the winding pack. This value was an order of magnitude smaller than the required manufacturing error of EF4 coil.     

Surry steam generator - examination & evaluation

This report summarizes research conducted during the fourth year of the five year Steam Generator Group Project. During this period the project conducted numerous nondestructive examination (NDE) round robin inspections of the original Surry 2A steam generator. They included data acquisition/analysis and analysis-only round robins using multifrequency bobbin coil eddy current tests. In addition, the generator was nondestructively examined by alternate or advanced techniques including ultrasonics, optical fiber, profilometry and special eddy current instrumentation. The round robin interpretation data were compared. To validate the NDE results and for tube integrity testing, a selection of tubing samples, determined to be representative of the generator, was designated for removal. Initial sample removals from the generator included three sections of tube sheet, two sections of support plate and encompassed tubes, and a number of straight and U-bend tubing sections. Metallographic examination of these sections was initiated. Details of significant results are presented in the following paper.     

Finite Element Analyses and Instrumentation Layout for Single Coil Testing of TF Coils in HT-7U

The HT-7U tokamak is a magnetically-confined full superconducting fusion device, consisting of superconducting toroidal field (TF) coils and superconducting poloidal field (PF) coils. These coils are wound with cable-in-conductor (CICC) which is based on UNK NbTi wires made in Russian '. A single D-shaped toroidal field magnet coil will be tested for large and expensive magnets systems before assembling them in the toroidal configuration. This paper describes the layout of the instrumentation for a superconducting test facility based on the results of a finite element modeling of the single coil of toroidal magnetic field (TF) coils in HT-7U tokamak device. At the same time, the design of coil support structure in the test facility is particularly discussed in some detail.     

Development of ITER sector assembly tools and mock-up

ITER sector assembly tools are customized tools for final integration of nine 40° sectors sub-assembled at assembly building and ex-vessel components. These tools include a central column, radial beams and their supports, assembly tools for poloidal field (PF) coils, and pre-compression ring (PCR) assembly tools and so on. The central column was designed to have sufficient strength to support nine 40° sectors and adjustment function of toroidal field coil (TFC). The PF assembly tools were designed also to support temporarily PF5 and 6 coils during sectors assembly duration, and to assembly PF coils to designated position with synchronized lifting and adjustment functions. Synchronized system applied to hydraulic cylinders of TF inner adjustment device and PF coil assembly tools is the key function to make highly precise assembly at final positioning. Hence, mock-ups were fabricated and tested to verify synchronized system of TF inner adjustment device and PF assembly tools. As results of tests, synchronized system operated by solenoid valves and linear sensors was verified to have high-resolution for final assembly of TFC and PF coils.     

Products of research and development in NDT

The Nondestructive Ultrasonic Testing and Evaluation is directed to describe flaws microstructure, structure residual stress, reliability or quality insurance. An overview is given on the scientific background, interpretation capability based upon mathematic-numerical models, new design of equipments and demonstrated at components containing relevant flaws. Emphasis is laid upon SNR-improvement in the UT of austenitic weldings. Examples are shown using the backscattering technique with linear polarized shear waves. Stress measurements are performed with electromagnetic ultrasonic probes (EMAT). The surface inspection with magnetic imaging of the eddy current field or the multi-frequency eddy current methods are described. The possibilities of detection, classification and reconstruction of flaws are demonstrated in the time- and frequency domain with the satellite pulse echo technique, focal probes and the synthetic aperture methods like ALOK, Phased Array, Holography and SAFT.     

Steam generator mock-up for assessment of inservice inspection technology

A steam generator mock-up has been assembled for round-robin (RR) studies of the effectiveness of currently practiced inservice inspection technology for detection of current-day flaws. The mock-up will also be used to evaluate emerging inspection technologies. The 3.66 m (12 ft)-tall mock-up contains 400 tube openings, each consisting of nine test sections that can be used to simulate current-day field-induced flaws and artifacts. Included in the mock-up are simulations of tube support plate (TSP) intersections and the tube sheet (TS). Cracks are present at the TSP, TS, and in the free span sections of the mock-up. For initial evaluation of the RR results, various eddy current methods, as well as multivariate models for data analysis techniques are being used to estimate the depth and length of defects in the mock-up. To ensure that the RR is carried out with procedures as close as possible to those implemented in the field, input was obtained from industry experts on the protocol and procedures to be used for the exercise. One initial assembly of the mock-up with a limited number of flaws and artifact has been completed and tested. A second completed configuration with additional flaw and artifacts simulations will be used for the round robin.