多模式机械补偿运行特性研究

经济、灵活及高自动化的运行控制策略是先进核电厂的设计目标之一。为适应这一发展趋势,近年来国际上提出了机械补偿运行控制的设计理念。机械补偿是一种主要通过控制棒的移动补偿堆芯反应性变化和控制轴向功率分布的先进控制策略。本文分别在基本负荷、负荷跟踪及启动/再启动运行模式下对机械补偿运行特性进行了研究。研究表明：机械补偿能自动实现堆芯的有效控制,并使功率峰因子保持在较低水平,是一种灵活、有效、经济的运行控制策略。此外,针对机械补偿运行对核电厂设计的影响进行了初步分析。     

CNP600堆芯调峰运行时轴向功率偏差影响因素及控制策略研究

随着我国能源的发展,核电将面临着越来越多的调峰运行压力,如采用CNP600堆型的海南昌江核电站,轴向功率偏差ΔI是调峰运行中堆芯功率控制的难点之一。针对CNP600堆芯,分析了慢化剂温度、控制棒棒位、可溶硼浓度等参数对ΔI的影响规律。以此为基础,采用程序模拟了CNP600 3种可能的调峰运行方案,提出了ΔI的控制策略,给出了功率变化过程中ΔI的具体控制方案。研究结果可为CNP600堆芯调峰运行时的堆芯ΔI的控制提供技术支持。     

利用Pu—238添加燃料代替可溶硼控制反应性的运行策略

在无可溶硼（SBF）压水堆堆芯中，引入了用Pu-238添加燃料控制反应性和功率分布的新概念。在SBF堆芯中，尽管不可避免地广泛使用可燃毒物和控制棒控制反应性，但是在堆芯功率分布控制方面存在着相当大的难度。因此，实际的SBF运行还要等待很长时间。在此项工作中，已经确认，通过引入Pu-238添加燃料可以大大地抑制剩余反应性。与从早期的600MWe SBF堆芯设计工作所获得的结果相比较，使用Pu-238添加燃料的600MWe无可溶硼压水堆（SBF PWR）堆芯概念设计使堆芯反应得到了很好控制。尤其是，借助于本研究研制的简单的轴向区域图，利用Pu-238的浓缩区域成功地进行了轴向功率形状的控制。并且，在1300MWe SBF PWR堆芯设计中也试用了Pu-238添加燃料，在这种堆型中，如果可溶硼控制不可用，与较小型反应堆比较起来，其功率分布控制要更困难。结果表明，即使在大型压水堆中，不使用可溶硼也可以成功地控制堆芯反应性和功率分布。因此，在SBF堆芯设计中，一个控制问题难点，可以通过引入新燃料概念得以很好地缓解。进一步预计本研究引入的Pu-238添加燃料、简单的轴向区域图和控制运行策略将直接用于 实际的SBF堆芯设计。     

MOX燃料在CANDU重水堆中应用可行性的研究

针对CANFLEX组件装载MOX燃料在CANDU重水堆中的应用进行了时均和瞬态验证计算。计算结果表明,最大通道功率和最大棒束功率均未超过限值。勿需对堆芯结构和运行模式做重大改变即可完成从天然铀堆芯向MOX堆芯的过渡。提出了应用MOX燃料的PWR／CANDU联合燃料循环策略。估算表明,秦山三期CANDU堆采用先进PWR／CANDU联合燃料循环,将使燃耗提高到13900MW·d／t(U);相对于PWR和CANDU堆各自独立的燃料循环,每年节省天然铀资源180t,减少乏燃料处置量约128t。     

AP1000核电厂堆芯寿期延长研究

在AP1000核电厂寿期末,维持满功率运行所需的临界硼浓度已经达到约7×10-6。为实现寿期末核电厂满功率运行,必须采取堆芯寿期延长措施。在基准工况下通过控制汽轮机调节阀开度和降低反应堆冷却剂平均温度引入正反应性,可使核电厂满功率多运行17 d。此外,对慢化剂温度系数和高压给水加热器的关闭列数进行敏感性分析,结果表明,慢化剂温度系数越负,反应堆平均温度降温速率越小,堆芯预期寿期越长。在2种敏感性工况下核电厂寿期末分别可满功率多运行约12 d和54 d。     

177燃料组件堆芯反应堆机械补偿控制策略研究

177燃料组件堆芯反应堆通常采用G模式运行,负荷跟踪期间需要调整堆芯硼浓度。受硼回收系统能力限制,仅在85%寿期内具备负荷跟踪能力。为改善177燃料组件堆芯反应堆负荷跟踪能力,扩大可进行负荷跟踪的寿期范围,基于177燃料组件堆芯进行了机械补偿控制策略的研究。设计了不同控制棒组布置方案,从控制棒组价值、对功率峰的影响、负荷跟踪过程中控制能力等方面进行了分析。基于优化的控制棒组布置方案和机械补偿控制策略,进行了全寿期基负荷运行、90%寿期末日负荷循环负荷跟踪以及启动过程模拟。结果表明,在适当的控制棒组布置方案下,177燃料组件堆芯可实施机械补偿控制策略,负荷跟踪能力达到了国际先进水平。      

广义预测控制在堆芯变功率控制中的应用

针对不同功率水平下稳态中子密度造成的堆芯功率模型非线性问题,将广义预测控制（GPC）应用于堆芯功率控制,实现变工况条件下堆芯功率的自动控制。本文首先基于零功率堆芯模型和温度反馈模型建立堆芯功率模型,基于该模型阶次设计预测时域,并根据系统输入输出数据在GPC校正环节通过带遗忘因子的最小二乘法在线辨识不同功率水平下的模型参数。为验证控制器的鲁棒性,在满功率平稳运行时加入反应性扰动。基于MATLAB平台对控制器的性能进行仿真验证。结果表明,本文所设计的GPC在堆芯变工况运行时能使输出功率快速、准确地跟踪设定值,并能在线辨识不同功率水平的堆芯模型参数,具备一定的抗干扰能力。      

首循环含钆堆芯控制模式改进研究

在MODE-G控制模式的基础上,针对首循环含钆堆芯轴向功率分布的显著特点,对堆芯控制模式进行了改进。通过松弛轴向偏移控制策略(RAOC)将轴向偏移(AO)控制在一个带状区域内;应用改进后的控制模式对首循环含钆堆芯典型燃耗步进行了负荷跟踪模拟;并针对控制模式的改进特点,选择弹棒事故进行了初步事故中子学参数评价。结果表明,改进后的堆芯控制模式相对于MODE-G控制模式能更有效地加强对堆芯轴向功率分布的控制。     

秦山核电厂压水堆堆芯功率分布分析

本文简要地讨论了堆芯功率分布分析的目的和意义。详细地分析了影响核电厂压水堆堆芯功率分布的因素,研究了展平功率分布的各种方法。最后得到30万千瓦的秦山电厂堆芯的核功率不均匀系数F_(qq)~N=2.50的核焓升因子F_(△H)~N=1.58。并与国外相近规模核电站PWR的设计功率分布作了比较。     

基于PAnySimu的PWR核电站堆芯建模与仿真研究

基于PAnySimu仿真支撑系统对PWR核电站一回路堆芯部分进行建模与仿真分析.通过研究分析岭澳二期3/4号机组堆芯实际结构,将其分为功率计算、堆芯传递计算、控制棒引起的反应性、反应性反馈、毒物计算五个模型.在此基础上,分析堆芯中子通量,考虑控制棒位置、燃料和慢化剂温度、氙和钐中毒、硼浓度等因素对中子通量的影响.利用P...     

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。     

压水堆棒控系统动力熔断器烧毁原因分析及维修策略改进

对某核电厂反应堆棒控系统动力熔断器烧毁事件进行根本原因分析。通过对反应堆棒控系统原理和熔断器所在电路的分析,结合熔断器熔断特性和可控硅导通与关断特性,实测数据验证动力熔断器烧毁根本原因是可控硅性能异常导致相邻两相电压短路,相间短路造成两相动力熔断器瞬间熔断。并给出反应堆棒控系统维修策略改进建议。     

液态熔盐堆堆芯功率内模控制器设计与仿真

内模控制是一种基于过程数学模型进行控制器设计的新型控制策略,具有结构简单、设计直观、无需精确的数学模型、在线调整参数少等优点。为探索内模控制在反应堆控制领域中的应用,以熔盐实验堆堆芯功率控制为例,通过建立熔盐实验堆一回路系统线性化模型,采用内模控制技术,结合粒子群优化算法设计堆芯功率内模控制器。并基于MATLAB/Simulink建立熔盐实验堆一回路仿真系统,开展熔盐实验堆堆芯阶跃反应性扰动下的功率控制研究。结果表明,所设计的堆芯功率内模控制器可很好地控制堆芯功率,实现系统的快速稳定。     

核电厂反应堆功率数字冗余控制系统及其可靠性

针对核电厂反应堆功率控制系统连续运行时间长、可靠性和安全性要求高的特点,提出了一种全新的基于双CPU冗余、电源冗余和ControlNet现场总线网络冗余控制的实现方案,对原有的反应堆功率模拟控制系统进行数字化改造设计,实现反应堆功率的可靠控制.通过对系统的主要可靠性指标进行定量计算和分析,评估了系统的可靠性和可用性.     

Design and optimization of fuzzy-PID controller for the nuclear reactor power control

This paper introduces a fuzzy proportional-integral-derivative (fuzzy-PID) control strategy, and applies it to the nuclear reactor power control system. At the fuzzy-PID control strategy, the fuzzy logic controller (FLC) is exploited to extend the finite sets of PID gains to the possible combinations of PID gains in stable region and the genetic algorithm to improve the ‘extending’ precision through quadratic optimization for the membership function (MF) of the FLC. Thus the FLC tunes the gains of PID controller to adapt the model changing with the power. The fuzzy-PID has been designed and simulated to control the reactor power. The simulation results show the favorable performance of the fuzzy-PID controller.     

Thermal Resistance between Hexagonally Arrayed Channels

A new power-flattening method has been proposed for boiling water reactors (BWRs) which have an axially skewed power distribution caused by the void fraction distribution. In present BWRs, the skewed power distribution is avoided by using shallow control rods and/or axially distributed gadolinia fuel bundles. These means are effective for the axial power shape control, but perturb the self-power-flattening effect due to fuel burnup. The power-flattening method proposed here extensively utilizes this effect in the equilibrium cycle core. Based on this method, a new BWR core design and operating strategy, the WNS core concept, has been realized for reactor operation with no shallow control rod insertion and no fuel bundle shuffling. Studies of the WNS core has shown that the proposed power-flattening method has the potential to improve capacity factors, increase operating thermal margins and simplify reactor operations in comparison with current BWR cores.     

A cascade control strategy for a space nuclear reactor system

This work presents a linear feedback control for the space nuclear reactor power system TOPAZ II. The point-kinetics approximation with six-delayed-neutron-group is used to represent the neutron field dynamics. A favorable choice of input control variables is demostrated, which leads to a cascade control configuration with two classical either PI or P controllers. The strategy is based on linearizing-like feedback control endowed with a modeling error estimator via a reduced order-observer. The effectiveness of the control law to the tracking of a given thermal power profile in the start-up regime and the tracking of a given electric power profile in the operation regime are illustrated via numerical simulations.     

Neutronics analysis of megawatt-class gas-cooled space nuclear reactor design

ABSTRACT

Neutronics analysis was conducted for a proposed megawatt-class gas cooled space nuclear reactor design. The reactor design has a high operating temperature of up to 1500 K. Annular UO₂ fuel rods were used to reduce the central temperature of the fuel. The thermal power is 2.3 MWt and is converted into electric power by a direct Brayton cycle. The control rods were arranged in different configurations and were analyzed in order to evaluate the influence on the reactor design in different scenarios. The calculation results reveal that the control rods arrangements have influences on the begin-of-life (BOL) excess reactivity and the shutdown reactivity. The distribution of control rods affects the neutron economy and leakage in the fuel region, consequently affecting the reactivity. It is also known that the reactivity in flooding scenarios are not sensitive to different control rod arrangements. Meanwhile, according to calculation results, the proposed reactor design has enough shutdown reactivity margin which will allow for flexible control strategy. Further analysis is still needed for more detailed and accurate parameters of the reactor design.     

Improvement of core control strategy for CPR1000: Load follow without boron adjustment

This paper presents the study of load follow operations without boron adjustment for CPR1000. To enable the CPR1000 to perform load follow maneuvers without changing soluble boron concentration, the worth of Rod Cluster Control Assemblies (RCCAs) are reconfigured with their amount and location unchanged according to the reactivity variations during the load follow transient. To ensure the real-time ability of the reactor core, the target axial offset (AO) during load follow operations is set to the same value with that in based load, and the Delta-I is maintained within the special trapezoidal shaped target band around its target value.For the simulation of the reactor core, the time-dependent one-dimensional two group diffusion equations with the reactivity feedback of moderator temperature, Doppler and xenon–iodine are used. The transverse buckling is adjusted at each time interval so that the one-dimensional model can match the average characteristics of the three-dimensional reactor core accurately. To show the superiority of the improved core control strategy for CPR1000 reactor, the load follow results employing the purposed boron-adjustment free control strategy are compared to those obtained with the typical MODE-G control strategy. It has been demonstrated by the simulation results that the load follow capability of CPR1000 reactor is greatly improved due to the elimination of boron concentration adjustments during load change transients. Full load follow capability of the reactor has been extended from the initial 80% of cycle life to more than 90% of cycle life. Thus, the boron adjustment free improvement on the MODE-G core control strategy is feasible for CPR1000, which can improve the economical performance of the plant and simplify the operational process during power maneuvers.     

基于NSGA-Ⅱ算法的核反应堆功率LQG控制器设计

反应堆功率控制系统的设计与核电厂的安全性和经济性息息相关。为提高其功率控制性能,本研究以某压水堆核电厂为研究对象,建立了其非线性动态数学模型,推导了其状态空间模型;采用线性二次型高斯（LQG）最优控制方法,设计了堆芯功率控制器;进一步基于遗传算法NSGA-Ⅱ对LQR权重系数进行了多目标优化;将本文所设计的控制器与传统PID控制器进行了典型工况的仿真对比。结果表明,与传统PID控制器相比,基于NSGA-Ⅱ方法优化的LQG控制器不但响应快速、控制精度高、稳定性好,而且具有良好的鲁棒性,能获得更优越的堆芯功率控制效果。