模型预测控制在压水堆堆芯功率控制中的应用

在压水堆核电站中,堆芯功率的自动控制难以实现。将模型预测控制方法应用于压水堆堆芯,以实现堆芯功率的自动控制。堆芯功率自动控制模型的建立是以反应堆堆芯模型和模型预测模型为基础的。反应堆堆芯模型包括中子动力学模型、热工水力学模型和反应性模型,模型预测模型以状态空间形式表述。为评估所设计的基于状态空间的模型预测控制系统的性能,设计了堆芯功率控制仿真实验。模拟结果表明:所设计的控制方法能快速、准确地控制堆芯功率,跟踪负荷变化。     

基于RBF神经网络的压水堆堆芯三维功率分布方法研究

堆芯三维功率分布的实时监测对核电厂的安全高效运行和控制系统优化均有重大意义。本文利用堆外核测量系统及RBF神经网络构建了一个实时堆芯功率三维分布监测系统,以提高监测的实时性及减小三维功率分布的拟合误差。在300 MW压水堆核电厂全范围仿真机上进行了一系列仿真实验,结果表明,该监测系统能在燃料循环周期的一定燃耗范围内,实时呈现堆芯三维功率分布,并通过几种方法对模型的精度进行了有效改进。     

Application of Three Axial Offsets Trajectory Method for Load Follow Operation Control in PWRs

During load follow operation of PWRs, it is required to control the core power distribution and to reduce the amount of cost due to the usage of control devices such as boron adjustment and control rod. Since occurrence of xenon spatial distribution oscillation following the change of the reactor power can cause oscillation in the power distribution, one task in the core power distribution control is to suppress xenon oscillation as effectively as possible. A lot of studies have been done to solve the problem, some of which use complex mathematical treatments. On the other hand, the three axial offsets trajectory method, which uses a simple mathematical treatment based on two points reactor model, has been proved to be effective for xenon oscillation control. In this study, we examined the feasibility of application of the three axial offsets trajectory method in the load follow operation by comparing with conventional strategies such as boron priority control and control rods priority control. In order to increase the effectiveness of control means, we propose a new method that is constructed by considering the superiority of each control strategy.     

Sliding mode observer design for a PWR to estimate the xenon concentration & delayed neutrons precursor density based on the two point nuclear reactor model

One of the important operations in nuclear power plants is load-following in which imbalance of axial power distribution induces xenon oscillations. These oscillations must be maintained within acceptable limits otherwise the nuclear power plant could become unstable. Therefore, bounded xenon oscillation considered to be a constraint for the load-following operation. In other hands, precursors produce delayed neutrons which are most important in control of nuclear reactor, but xenon concentration & precursor density cannot be measured directly. In this paper, non-linear sliding mode observer which has the robust characteristics facing the parameters uncertainties and disturbances is proposed based on the two point nuclear reactor model to estimate the xenon concentration & delayed neutron precursor density of the Pressurized-Water Nuclear Reactor (PWR) using reactor power measurement. The stability analysis is given by means Lyapunov approach, thus the system is guaranteed to be stable within a large range. The employed method is easy to implement in practical applications. This estimation is done taking into account the effects of reactivity feedback due to temperature and xenon concentration. Simulation results clearly show that the sliding mode observer follows the actual system variables accurately and is satisfactory in the presence of the parameters uncertainties & disturbances.     

反应堆机组停堆检修后重返满功率运行的堆芯控制策略研究

核电站压水堆(PWR)在寿期末长时间停堆后重返满功率的运行过程中,堆芯控制存在困难,常常不能够安全快速地进入满功率运行。本文通过对影响堆芯控制的各种因素和物理过程进行分析,提出了一套基于临界点状态选择,在升功率期间采用提升功率控制棒和硼浓度稀释相结合的堆芯控制策略,并进行了实际验证。对重返临界点的选择和影响因素的分析直接影响后期操作,是堆芯控制策略的基础。策略对相同状况下的PWR堆芯控制有一定的指导意义。     

压水堆核电厂负荷跟踪建模与控制方法研究

压水堆核电厂负荷跟踪模式能够有效协调机组产能与电网需求,延长燃料的循环寿期,提高机组运行的经济性能。反应堆系统具有高度复杂、非线性、时变等特点。通过合理简化,建立了反应堆系统集总参数模型,设计了负荷跟踪控制策略。引入负荷阶跃变化扰动和线性变化扰动,对反应堆负荷跟踪控制系统特性进行仿真。结果表明,控制特性与实际基本一致,控制系统能够满足负荷跟踪性能要求。     

Load following control and global stability analysis for PWR core based on multi-model,LQG, IAGA and flexibility idea

The work is to design a nonlinear Pressurized Water Reactor (PWR) core load following control system and analyze the global stability of this system. On the basis of modeling a nonlinear PWR core, linearized models of the core at five power levels are chosen as local models of the core to substitute the nonlinear core model in the global range of power level. The combination control strategy of the Linear Quadratic Gaussian (LQG) control and the Proportional Integral Derivative (PID) control with an optimization process of Improved Adaptive Genetic Algorithm (IAGA) proposed is used to contrive a combined controller with the robustness of a core local model as a local controller of the nonlinear core. Based on the local models and local controllers, the flexibility idea of modeling and control is presented to design a decent controller of the nonlinear core at a random power level. A nonlinear core model and a flexibility controller at a random power level compose a core load following control subsystem. The combination of core load following control subsystems at all power levels is the core load following control system. The global stability theorem is deduced to define that the core load following control system is globally asymptotically stable within the whole range of power level. Finally, the core load following control system is simulated and the simulation results show that the control system is effective.     

Mode-C运行与控制模式设计技术研究

本文基于运行与控制模式设计,结合核电厂的运行需求,针对国内压水堆核电厂以基负荷运行方式为主、负荷跟踪运行需求较少的特点,首次开展了与之适应的Mode-C运行与控制模式设计。通过控制策略设计、控制棒设置设计、核电厂运行方式设计、核电厂运行范围设计等设计步骤,研究Mode-C运行与控制模式的设计技术。结果表明：采用Mode-C模式的压水堆核电厂能根据负荷变化需求选择执行单变量自动控制模式或双变量自动控制模式,实现了设定的控制策略,Mode-C运行与控制模式的设计技术在反应堆物理专业方面是可行的。     

移动式堆芯中子注量率测量系统概述

堆芯中子注量率测量系统是压水堆核电站核测量系统的主要组成部分,用于测量反应堆堆芯的中子注量率水平,从而提供反应堆的功率分布情况。文章介绍了中核（北京）核仪器厂国产化的移动式堆芯中子注量率测量系统,并对测量系统的概况、系统组成、工作原理及功能等进行了描述。     

Fuel management optimization based on power profile by Cellular Automata

Fuel management in PWR nuclear reactors is comprised of a collection of principles and practices required for the planning, scheduling, refueling, and safe operation of nuclear power plants to minimize the total plant and system energy costs to the extent possible. Despite remarkable advancements in optimization procedures, inherent complexities in nuclear reactor structure and strong inter-dependency among the fundamental parameters of the core make it necessary to evaluate the most efficient arrangement of the core. Several patterns have been presented so far to determine the best configuration of fuels in the reactor core by emphasis on minimizing the local power peaking factor (P_q).     

CNP650压水堆不调硼负荷跟踪可行性研究

海南昌江核电厂等CNP650压水堆采用Mode-A控制模式,该模式采用黑体控制棒,有很好的基负荷运行能力,但负荷跟踪能力相对较差。而对一些具有小电网的国家或地区,负荷跟踪运行能力具有一定的市场需求。不调硼负荷跟踪通过棒控系统自动完成,大大减轻了操纵员负担;负荷跟踪过程基本不需要频繁地调硼操作,允许简化化学和容积控制系统设计,减少了废液处理成本。为此,在CNP650压水堆上进行了不调硼负荷跟踪研究。负荷跟踪过程主要有两个控制任务:一是反应性补偿;二是功率分布控制。根据不调硼负荷跟踪的控制任务,重新进行了控制棒的设计、分组和布置,设置两套独立控制的控制棒组(功率补偿棒组和轴向偏移控制棒组),分别用于堆芯反应性控制和轴向功率分布控制,以实现不调硼负荷跟踪。使用SCIENCE程序包进行典型的12h~3h~6h~3h、100%—50%—100%功率水平的日负荷循环计算来进行不调硼负荷跟踪分析。计算步骤为:进行三维堆芯模型计算;根据三维堆芯模型建立一维堆芯模型;在一维模型基础上,进行模拟计算。完成了海南昌江核电厂平衡循环寿期末典型的日负荷循环不调硼运行分析,模拟计算结果表明在CNP650压水堆上不调硼负荷跟踪运行模式是可行的。     

停机不停堆后的风险分析及其控制措施探讨

根据机组实际控制中的运行经验和模拟机教学经验,对压水堆核电机组满功率运行时,一旦由于故障,发生停机不停堆后,可能发生的现象和风险进行分析并提出相应的控制措施。     

Evaluation of Reactivity and Xe Behavior during Daily Load Following Operation

A boiling water reactor (BWR) has an excellent load following capability provided by a core flow control, which is used for changing a reactor power level and for compensating the subsequent Xe concentration change.

The core characteristics during load following operations are investigated in detail, using our reactor core simulator. Comparisons of changes of the Doppler reactivity, the void reactivity and the Xe reactivity during transients are performed. Also the features of Xe transient during load following operations are shown.

It has been shown that the core flow change required to compensate the Xe reactivity change produces much greater change of the void reactivity than that required for power level changes, and that the resulting local power change in the lower part of the core is greater than that in the upper part, because the Xe concentration change in the lower part is hardly compensated by the core flow control. Also the effects of power level changes, cycle patterns, and initial concentration of Xe and I on the Xe transient behavior have been investigated.     

压水堆堆芯非线性系统的全局稳定性分析

判定压水堆堆芯非线性系统的全局稳定性是待解决的问题。建立了压水堆堆芯非线性系统,利用微小摄动方法求取其线性化模型。依据基于平衡流型的堆芯非线性测度在功率水平域内的分布情况,选择7个功率水平处的线性化模型作为堆芯局部模型,以局部模型组合来近似替代堆芯非线性系统。利用Lyapunov稳定性理论,分析堆芯非线性系统全局稳定性。计算结果表明：压水堆堆芯非线性系统是全局渐进稳定的;在判定堆芯系统全局稳定性时,这种非线性系统的建模方法是有效可行的。     

压水堆上腔室流场的实验研究

ＰＷＲ作为核电发展的主要堆型，在全世界范围内得到了广泛的应用，也是我国的主要发展堆型。但是对关系到反应堆安全运行的、直接作用在控制棒导向筒上的上腔室流场的分析研究，长期以来由于紊流流动机制的复杂性和上腔室中控制棒导向筒组件布置的密集性，这方面的研究一直没有深入下去。在压水堆运行期间，作用在上腔室构件上的作用力与冷却剂的流动特性有很大的关系，通过模拟实验弄清上腔室的流速分布，对了解作用在控制棒上的水力载荷，以及控制棒能否按指令在导向筒内自由升降和快速下插具有十分重要的意义。本文在３００ＭＷｅ核电站ＰＷＲ上腔室１：４可视化模拟体中，以水为介质进行了上腔室流场的可视化实验研究。采用激光多普勒测速仪（ＬＤＶ）和Ｎ－Ｊ型应变片式测速仪测得了上腔室模拟体中的流速，并用归一化的数据处理方法，显示了整个流场的流速分布规律，找出了整个流速的最大区和最大值。从而为控制棒导向筒的结构力学分析和ＰＷＲ上腔室的数值模拟分析提供实验依据。     

基于BP神经网络的堆芯三维功率重构方法研究

堆芯功率分布包含了堆芯内的大量信息，由于在反应堆运行过程中无法直接测量堆芯内所有位置的功率，因此需通过其他方法得到堆芯三维功率分布的情况。本文以秦山一期工程为对象，利用堆外中子探测器在不同棒位和不同功率下的计数及BP神经网络对堆芯三维功率分布进行重构计算，并利用REMARK程序对该计算结果进行验证。结果表明，该功率重构方法能在反应堆运行的50%～100%功率范围内，较好地呈现堆芯三维功率分布。     

用于压水堆负荷跟踪运行的硼浓度模糊控制系统

对压水堆负荷跟踪运行进行了研究，提示将一种三维模糊控制系统应用于硼浓度自动调节的设计方案，在设计中，将核电站全范围模拟机的数学模型移植到微机上作为控制对象，对硼浓度模糊控制系统进行仿真实验的结果证实，该模糊控制方法不仅可行，而且效果良好。     

固态燃料熔盐堆自适应功率控制器设计及分析

钍基熔盐堆核能系统(Thorium-based Molten Salt Reactor,TMSR)是中国科学院首批启动实施的战略性先导科技专项,旨在研发第四代反应堆核能系统。固态燃料钍基熔盐实验堆(The Solid Fuel Thorium-based Molten Salt Experimental Reactor,TMSR-SF1)是一个10 MW热功率的氟盐冷却球床堆,目前已经完成方案设计和初步工程设计。功率控制系统是反应堆一个关键控制系统,实现反应堆正常启动、功率运行和正常停堆功能,对保证反应堆安全和稳定运行起着极其重要的作用。根据TMSR-SF1运行控制要求,结合自适应控制理论,基于Lyapunov稳定性理论设计了一种TMSR-SF1模型参考自适应功率控制器。基于TMSR仿真平台,使用MATLAB/Simulink建立了自适应功率控制系统模型,并开展了控制器特性分析。结果表明,自适应功率控制器具备良好的负荷跟随能力,抗干扰能力强、稳定性好、可靠性高,能够满足TMSR-SF1功率控制的要求,确保堆芯的输出功率与功率设定值相匹配。     

Core Design and Operating Strategies for Better Daily Load Following Performance in BWR Cores

New core design and operating strategies have been proposed for daily load following of an improved BWR core with large power swing.

The core concepts were based on the WNS core which uses an axially two-zoned enrichment fuel. One principal design strategy utilized was to reduce power in the lower portion of the core by adjusting a division point of the axially two-zoned enrichment fuel. One operating strategy introduced is for controlling Xe distributions. This method, coupled with a direct power distribution control by control rods, could decrease the xenon induced power change in the lower part of core.

The BWR core designed and operated under the new strategies was shown to meet the daily load demand with large power swing: 1-h reduction in power from 100 to 50%; 8-h hold at 50% power; 1-h increase in power from 50 to 100%; and 14-h hold at 100% power.     

核电厂严重事故下卸压对氢气产生的影响分析

研究了1000MWe压水堆核电厂在典型的高压严重事故序列下卸压对氢气产生的影响。分析结果表明,开启1列、2列和3列卸压阀进行一回路卸压均会在堆芯熔化进程的3个阶段导致氢气产生率的明显增大：1）堆芯温度1500～2100K;2）堆芯温度2500～2800K;3）从形成由硬壳包容的熔融池（2800K）到熔融物向压力容器下封头下落。开启卸压阀的列数越多,氢气产生率的增大越明显。