Study of Control rod worth in the TMSR

Control rod is a primary control part of emergency control and power regulation in nuclear reactor. The main application of it is to control fast change of the reactivity. The theoretical analysis for the worth of control rod is necessary in the stage of design. Based on design requirements, some results are calculated. Firstly, control rod worth with different density of neutron absorber is calculated by MCNP here. Secondly, the study of integral and differential control rod worth is presented in this paper while the control rod is inserted into reactor core and total worth of three rods with different positions are also calculated. Finally, the effect of the axial and radial neutron flux in reactor core which is caused by the control rods is simulated. The simulation results of the control rods meet design requirements for TMSR.

Thermal behavior of the HTR-10 under combined PLOFC and ATWS condition initiated by unscrammed control rod withdrawal

Two tests initiated by unscrammed control rod withdrawal were performed on the High Temperature GasCooled Reactor-Test Module(HTR-10) in November 2003 after the reactor achieved its full power, and the test conditions represented a typical transient scenario of modular high-temperature reactors(HTRs), called pressurized loss of forced cooling, and anticipated transient without scram.Based on the test parameters, the HTR-10 thermal behaviors under the test conditions were studied with the help of the system analysis code THERMIX. The combination of the test results and the investigation results makes the HTR-10 safety potential better understood. Key phenomena, such as the helium natural circulation and the temperature redistribution in the reactor, were revealed. As the safety feature of most significance, there is a large margin between the maximum fuel temperature and its safety limit in each test. Temperatures of thermocouples in different components were calculated by THERMIX and compared with the test values. The applicability of the code was verified by good agreement obtained from the comparison.

Minimizing torque ripple in a brushless DC motor with fuzzy logic: applied to control rod driving mechanism of MNSR

A permanent magnet BLDC(brushless direct current) motor is used to move the control rod of a miniature neutron source reactor(MNSR). The BLDC motor drive is modeled using MATLAB/SIMULINK. Two main parts of the modeling are the inverter switching and the current control. Current control with chopping used to minimize the torque ripple of the MNSR control rod drive. Fuzzy logic current control together with soft chopping control shows the best response of all the three strategies. The prototype drive mechanism has an ATmega32 controller and power MOSFET switches. The simulation results are compared with experimental drive mechanism.

Control Rod Calibration and Worth Calculation for Optimized Power Reactor 1000 (OPR-1000) Using Core Simulator OPR1000

Control rod is used to change the power in nuclear reactor.?Certainly, the core at any moment can be made subcritical condition and shut downs when occurring?to emergency instance in the core. The rod is grouped based?on their function and located at different places in the core where their feature is maximized.?Two methods of control rod calibration are the asymptotic period method and the rod-drop method, which were applied in this experiment. In the first method, the reactor is made supcritical by inserting the control rod to be calibrated a certain level. The rod drop method is to determine the subcritical;at the critical state, the rod to be calibrated is dropped into the core, and the resulting decay of neutron flux is observed and related to the reactivity. In this paper, the regulating rod will be calibrated according to the reactivity in OPR-1000 that corresponds to a certain control rod insert or withdraw, and the reactivity in power reactor depends?on the integral and differential control rod group too. The core simulator OPR1000 is used to test those methods.

On Line Measurement of Reactivity Worth of TRIGA Mark-II Research Reactor Control Rods

The reactivity worth measurement system for control rods of the TRIGA MARK-II research reactor of Bangladesh has been design and developed. The theory of the kinetic technique of measuring reactivity has been used by this measurement system. The system comprises of indigenous hardware and software for online acquisition of neutron flux signals from reactor console and then computes the reactivity worth accordingly. Here for the TRIGA MARK-II research reactor, the reactivity measurement system was implemented with a dedicated circuit assembly and a conventional personal computer. A high-level Visual Basic real-time programming has been developed for data acquisition, reactivity calculation, online display (numerically as well as graphically), saving data, etc. To measure reactivity worth of TRIGA reactor control rods the rod drop experimental technique has been adopted. The results of tests experiments, carried out with the rod drop method for measuring various reactivity worth of control rods have been presented in the paper. A comparison between this results with the results using period method and that of computation method, demonstrated that the response of this reactivity measurement system is fast enough to monitor and measure the safety-related reactivity and power excursions in the reactor.

Reduced Basis Approaches in Time-Dependent Non-Coercive Settings for Modelling the Movement of Nuclear Reactor Control Rods

In this work,two approaches,based on the certified Reduced Basis method,have been developed for simulating the movement of nuclear reactor control rods,in time-dependent non-coercive settings featuring a 3D geometrical framework.In particular,in a first approach,a piece-wise affine transformation based on subdomains division has been implemented for modelling the movement of one control rod.In the second approach,a“staircase”strategy has been adopted for simulating themovement of all the three rods featured by the nuclear reactor chosen as case study.The neutron kinetics has been modelled according to the so-called multi-group neutron diffusion,which,in the present case,is a set of ten coupled parametrized parabolic equations(two energy groups for the neutron flux,and eight for the precursors).Both the reduced order models,developed according to the two approaches,provided a very good accuracy comparedwith high-fidelity results,assumed as“truth”solutions.At the same time,the computational speed-up in the Online phase,with respect to the fine“truth”finite element discretization,achievable by both the proposed approaches is at least of three orders of magnitude,allowing a real-time simulation of the rod movement and control.

Dynamic Programming Method to Optimize Control Rod Positions in NHR-200

A code. OPTROD. based on dynamic programming method is developed and utilized to optimize control rod positions throughout the fuel cycle of the 200 MW nuclear heating reactor (NHR-200). A fuel cycle is divided into many steps or stages. Optimization of the multistage process is solved iteratively in the forward direction throughout a fuel cycle. The dynamic programming method is much more efficient than the normal nonlinear programming method. Convergence is obtained even if poor initial control rod positions are given.

Optimization of spatial structure designs of control rod using Monte Carlo code RMC

Control rod is the most important approach to control reactivity in reactors,which is currently a cluster of pins filled with boron carbide(B4C).In this case,neutrons are captured in the outer region,and thus the inner absorber is inefficient.Moreover,the lifetime of the control rod is challenged due to the high reactivity worth loss resulted from the excessive degradation of B4C in the high flux area.In this work,some control rod designs are proposed with optimized spatial structures including the spatially mixed rod,radially moderated rod,and composite control rod with small-sized pins.The control rod worth and effective absorption cross section of these designs are computed using the Monte Carlo code RMC.A long-time depletion calculation is conducted to evaluate their burnup stability.For the spatially mixed rod,rare-earth absorbers are combined with B4C in spatial structure.Compared with the homogenous B4C rod,mixed designs ensure more sufficient reactivity worth in the lifetime of the reactor.The minimum reactivity loss at the end of the cycle is only 1.8%from the dysprosium titanate rod,while the loss for pure B4C rod is nearly 12%.For the radially moderated design,a doubled neutronic efficiency is achieved when the volume ratio of moderator equals approximately 0.3,while excessive moderating may lead to the failure of control rods.The control rod with small-sized pins processes an enhanced safety performance and saves the investment in absorbers.The rod worth can be further enhanced by introducing small moderator pins,and the reactivity loss caused by the reduction of absorbers is sustainable.

Control rod drive for high temperature gas cooled reactor

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PCTRAN Westinghouse AP1000 Power Control of Pressurized Water Reactor Using Simulink of MATLAB

This paper introduces the simulation, and controls using Simulink of MATLAB for PCTRAN (Personal Computer Transient Analysis) of the power control system (PWR) type pressurized water reactor of PWR WESTINGHOUSE AP1000. The power controller model produces mathematical model description in nonlinear relation form in Simulink of MATLAB which is an important and popular program used at most universities for education. The power controller is described by a block diagram in this paper and some details introduce to clearly understand the work function. The results of action control compared with the PCTRAN programme in modes of automatic and manual control.

控制杆-强制旋转对圆柱涡激振动的抑制作用研究

为实现圆柱涡激振动的高效抑制,本文基于控制杆-强制旋转组合结构讨论圆柱涡激振动的抑制问题。对低雷诺数下的圆柱涡激振动进行数值模拟研究,对比分析不同控制杆数量和圆柱转速比下的流场特性、振动响应和流体力响应等。结果表明:与裸圆柱相比,控制杆具有一定的涡激振动抑制效果;对于三、五控制杆,通过调节转速比,可以实现最高98%的圆柱振幅抑制(对三控制杆,转速比为0.4~0.6;对五控制杆,转速比为0~0.2);圆柱振幅抑制与圆柱减阻区间相同;对于四、六控制杆,旋转对振幅抑制的影响较小;主圆柱表面的漩涡脱落和漩涡的合并会引起流体力系数的高幅波动,导致圆柱高振幅响应;没有漩涡合并和圆柱表面脱涡不明显时,流体力系数则无明显波动,圆柱振幅也显著降低。

Fluid Flow Past a Circular Cylinder with Tandem Rod and Staggered Rod at Low Reynolds Number

The flow past a primary cylinder with one tandem control rod and one staggered control rod is simulated in this paper through solving the Navier-Stokes equations. Two examples are simulated to validate the model, and the results matched well with those of previous researches. The Reynolds number based on the diameter of the primary cylinder is 500. The diameter ratio between the control rod and the primary cylinder （d/D） is 0.25. It was found that the effect of the combination of one upstream tandem control rod and one staggered control rod on the hydrodynamics of the primary cylinder is a linear superposition of the effect of a corresponding single control rod, and the effect of the upstream tandem control rod is dominant at larger spacing ratios such as G/D=2. For the combination of a downstream tandem control rod and a staggered control rod, the effect of the control rods is different from that of the corresponding single control rod in the region of 0.2〈G/D〈0.5 ＆ 30°〈a〈120° and 0.9〈G/D〈1.4 ＆ 30°〈a〈50°, where the additional effect is obvious. In this case, the effect of the downstream tandem control rod is dominant at small spacing ratios （such as G/D=0.1）. At moderate spacing ratios such as G/D=0.4, the effects of the tandem control rod and the staggered control rod are comparable in both cases.

农用推杆电机行程控制算法研究

研究实现了一种农用推杆电机的低成本行程控制算法。该算法基于霍尔计数原理,通过给普通农用推杆电机加装2个霍尔传感器使得电机运行时输出2路方波信号来实现。电机运行时每转一圈会触发霍尔传感器输出一个脉冲信号,2路信号具有90°的相位差,通过2路信号的相位关系可判断出电机的正反转状态并据此对脉冲信号进行加数计数或减数计数,算法根据用户设置的行程百分比、霍尔计数值以及全行程霍尔计数总值实现电机行程的自动控制。该算法具有行程控制稳定可靠、实现成本低、适用于农业高湿多尘环境等优点,可应用于设施农业和大田农业中相关设备的现场自动控制以及基于农业物联网的远程精准控制。

长寿期小型棒控压水堆控制棒方案研究

小型棒控压水堆舍弃了可溶硼,并高度依赖控制棒与可燃毒物棒控制堆芯的反应性。为研究控制棒对堆芯关键性能的影响,本文以核动力破冰船用KLT-40模型为对象,以轴向功率偏移、堆芯寿期、燃料利用率与径向功率峰因子为指标,开展长寿期小型棒控压水堆控制棒布置与动作策略设计分析。首先,基于OpenMC程序开发带棒燃耗程序;其次,比较堆芯带控制棒与无控制棒运行时的堆芯寿期等指标;最后,分析不同动作策略对轴向功率偏移等指标的影响。结果表明:控制棒将堆芯寿期从590 EFPDs(等效满功率天,Effective full power days)延长至650~698 EFPDs;低价值棒组优先动作策略使轴向功率偏移程度由−0.69与+0.80分别下降至−0.29与+0.52。因此,要准确计算长寿期压水堆寿期必须采用带控制棒燃耗计算策略,并且通过合理的动作策略能够有效减小控制棒带来的轴向功率偏移。

Controlling chaos based on a novel intelligent integral terminal sliding mode control in a rod-type plasma torch

An integral terminal sliding mode controller is proposed in order to control chaos in a rod-type plasma torch system.In this method, a new sliding surface is defined based on a combination of the conventional sliding surface in terminal sliding mode control and a nonlinear function of the integral of the system states. It is assumed that the dynamics of a chaotic system are unknown and also the system is exposed to disturbance and unstructured uncertainty. To achieve a chattering-free and high-speed response for such an unknown system, an adaptive neuro-fuzzy inference system is utilized in the next step to approximate the unknown part of the nonlinear dynamics. Then, the proposed integral terminal sliding mode controller stabilizes the approximated system based on Lyapunov＇s stability theory. In addition, a Bee algorithm is used to select the coefficients of integral terminal sliding mode controller to improve the performance of the proposed method. Simulation results demonstrate the improvement in the response speed, chattering rejection, transient response,and robustness against uncertainties.

液力悬浮式控制棒落棒动力学特性研究

钠冷快堆中非能动停堆的控制棒下落规律和下落时间是控制棒设计的重要参数,是典型的水动力学问题。为解释钠冷快堆控制棒组件在落棒试验中的摆动和撞击现象,采用仿真软件动网格方法模拟研究了控制棒的下落过程,分析了影响控制棒下落规律的影响因素,提出了缓冲控制棒下落速度的方法,试验件落棒时间试验结果与数值模拟结果之间的误差为2.44%。主要结论:模拟发现控制下落过程出现晃动与偏心现象,降低控制棒重心可减缓晃动幅度;控制棒初始偏心及下落偏心对总体下落时间影响较小;缓冲杯底部小孔不影响缓冲效果,缓冲杯表面采用锯齿形沟槽结构可有效提高缓冲效果,锯齿形沟槽缓冲效果比矩形槽提高了47.2%。

基于振动信号的控制棒驱动机构滚轮早期故障诊断研究

针对现有研究未充分关注控制棒驱动机构(control rod drive mechanism,CRDM)的早期故障诊断问题、很难将故障特征定位至具体部件以及人工引入的故障样本与装备实际故障特征存在差异等不足,提出了一种基于振动信号的CRDM滚轮早期故障诊断方法:首先,利用寿命考核试验时机采集了某密封磁阻马达式CRDM的滚轮全寿命振动信号,基于经验模态分解(empirical mode decomposition,EMD)和Hilbert变换方法进行解调分析,获得与滚轮退化状态相关的模态成分;然后,采用时、频域分析方法获得了11个能够直接表征CRDM滚轮磨损状态的特征量,并根据退化趋势提取出与实际故障特征高度吻合的早期故障样本;最后,分别基于BP神经网络和支持向量机两种方法实现了CRDM滚轮早期故障的多特征智能诊断。结果表明:提取的滚轮早期磨损故障样本与实际运行过程保持了较好的一致性,证明所提CRDM滚轮早期故障诊断方法具有较强的工程应用价值。

基于一步法的重反射层反应堆启动物理试验控制棒价值校核计算研究

由于重反射层可减低中子泄漏从而提升中子经济性,因此某些大型先进压水堆采用重反射层减少临界尺寸来优化空间布局。由于重反射层与以往常用的围板水反射层差异较大,采用传统的两步法物理计算程序获得重反射层反应堆的精确中子学参数存在一定的难度,因此使用先进的一步法物理计算程序对重反射层反应堆启动物理试验控制棒价值展开了计算,计算结果表明,确定论一步法程序NECP-X计算结果与蒙特卡罗参考值吻合良好。

关于核电厂压力容器顶盖热套管磨损下沉导致控制棒卡涩问题的研究

热套管在国内被认为是控制棒驱动机构的部件之一,其吊挂在驱动机构密封壳底部,采用非固定式安装结构形式。欧美核工业界一般把热套管视为压力容器顶盖的内部构件之一,对控制棒驱动杆起导向作用,同时对顶盖贯穿件起保护作用。在冷却剂的流动冲击下,热套管会发生振动并与密封壳底部互相磨损,致使热套管下沉甚至断裂,从而可能会导致控制棒卡涩。此类问题对于我国M310及其改进型机组具有较高的反馈价值。本文将分析国内外核电厂压力容器顶盖热套管磨损下沉导致控制棒卡涩问题的研究现状、事件原因和维修策略,并提出合理建议。