核电厂严重事故工况下氢气浓度监测装置研制

研究解决了电化学测氢气浓度传感器中电极涂覆、结构设计等关键技术问题,设计制造了严重事故工况下氢气浓度在线监测装置样机,开展了不同压力、温度、氢气浓度条件下测试试验,正常工况下的性能测试试验和环境适应性试验。结果表明研制的氢气浓度监测装置具有选择性强、能实现在线监测、响应时间快、测量范围宽、测量精度高等特点,可用于我国的“华龙一号”（HPR1000）和大型先进压水堆（CAP1400）核电厂严重事故工况下氢气浓度在线监测。      

Application of a chronoamperometric measurement to the on-line monitoring of a lithium metal reduction for uranium oxide

Both a potentiometric and a chronoamperometric electrochemical technique have been applied in an attempt to develop an efficient method for an on-line monitoring of a lithium metal reduction process of uranium oxides at a high-temperature in a molten salt medium. As a result of this study, it was concluded that the chronoamperometric method provided a simple and effective way for a direct on-line monitoring measurement of a lithium metal reduction process of uranium oxides at 650 °C by the measuring electrical currents dependency on a variation of the reduction time for the reaction. A potentiometric method, by adopting a homemade oxide ion selective electrode made of ZrO₂ stabilized by a Y₂O₃ doping, however, was found to be inappropriate for an on-line monitoring of the reduction reaction of uranium oxide in the presence of lithium metal due to an abnormal behavior of the adopted electrodes. The observed experimental results were discussed in detail by comparing them with previously published experimental data.     

燃料破损在线探测系统在核电厂的应用与分析

国内两台核电机组分别安装了1套由中国原子能科学研究院研制的燃料破损在线探测系统（FDDS）。通过FDDS对两台核电机组发生燃料破损时的连续监测和分析,表明FDDS在核电厂一回路放射性核素活度浓度在线测量及燃料破损监测中发挥了良好的作用,弥补了化学取样分析方法的不足。     

华龙一号LPD在线监测系统误差分析

核电厂采用线功率密度（LPD）在线监测系统对电站运行的实测参数在线计算并显示堆芯线功率密度,能够准确、及时地描述堆芯状态,提高核电厂运行的安全性和经济性。LPD在线监测系统报警限值的设定,需要考虑在线监测系统的总体误差,并留有一定裕量。通过研究华龙一号LPD在线监测系统的总体不确定度的分析方法,将系统的各部分误差通过统计方法综合起来,得到系统的总体误差限值。结果表明,华龙一号采用的LPD在线监测系统误差满足工程要求。      

正电子致电离截面实验中束流强度的在线测量

本文采用HPGe探测器实时收集了正电子碰撞厚Ti靶伴随产生的湮灭光子,并结合HPGe探测器对放置在碰撞点处²²Na标准源产生的511 keV湮灭光子的探测效率刻度值,得到了8~9.5 keV正电子引起Ti原子内壳层电离截面实验中正电子束流强度的实时测量结果。结果表明,在实验测量的38 h内,基于²²Na标准源慢正电子束流装置产生的正电子束流强度不稳定,随时间的变化有着不同程度的衰减,且存在小幅度波动现象。因此,低能正电子致原子内壳层电离截面实验中应采用在线法获取慢正电子束流强度。     

核电厂放射性液态流出物总γ放射性浓度控制值估算

核电厂放射性液态流出物排放监测包括源项监测、排放前取样监测和排放过程中的实时在线监测,其中源项监测和在线监测都是测量液态流出物的总γ放射性浓度,而不是活度浓度。本文针对新颁布实施的国家标准《核动力厂环境辐射防护规定》和《核电厂放射性液态流出物排放技术要求》所规定的滨海核电厂除氚和碳-14外其他放射性核素的活度浓度限值,通过理论分析和实验测量,建立了一种通过核电厂放射性液态流出物活度浓度估算总γ放射性浓度的方法,并结合秦山第二核电厂1号和2号机组放射性液态流出物中核素组成比例,确定了1号和2号机组放射性液态流出物排放的总γ放射性浓度控制值。     

基于DTW算法的参数缺失时的核动力系统故障诊断技术

由于核动力系统的在线监测参数在获取、传输过程中受到噪声的干扰,导致最终监测信号的随机缺失,对操纵员判断事故种类造成了较大的干扰。为此,提出了滑动时间窗口的动态时间弯曲故障诊断模型：构建在线实时监测参数的待测多元时间序列和已有的事故标准序列,将构建的待测多元时间序列采用滑动窗口去动态寻找标准序列中的最小累积距离,使用动态时间弯曲的算法计算待测序列或标准序列中监测参数缺失导致的序列不等长现象,通过最小累积距离得到待测时间序列的模式类别。结果表明：该方法从核动力系统事故发生的基本原理出发,对诊断结果具有较强的解释性和鲁棒性,同时可引入其他标准事故序列对模型进行拓展,该模型具有较强的拓展性。     

Diagnosis of the surface morphology of laser-ablated materials using the weighted- DCT approach in laser speckle interferometry for application to plasma facing materials

To implement on-line, real-time monitoring for the surface morphology of Plasma-Facing Materials (PFMs) in tokamak, we developed a Laser Speckle Interferometry measurement approach. A laser ablation method was used to simulate the erosion process during Plasma-Wall Interactions in a tokamak. In the present investigation, we evaluated the results of laser ablation morphology changes on the surface of Mo material reconstructed by four different approaches (Flood-fill, Quality-guided, Discrete Cosine Transform (DCT) and Weighted-DCT). The morphology results measured by the weighted-DCT approach are very close to the measurement results from confocal microscopy with an average error rate within 7%. It is verified that the weighted-DCT algorithm has high accuracy and can efficiently reduce the influence of noise pollution coming from laser ablation, which is used as a proxy for erosion from plasma wall interaction. Additionally, the CPU computer time has been shortened. This is of great significance for the real-time monitoring of PFMs’ morphology in the Experimental Advanced Superconducting Tokamak (EAST) in the future.     

On-line subcriticality measurement using a pulsed spallation neutron source

To investigate the applicability of the pulsed neutron source method using a pulsed spallation neutron source for an on-line subcriticality monitoring system of an accelerator-driven system, a subcritical experiment is conducted using the Kyoto University Critical Assembly in combination with the fixed-field alternating gradient accelerator. Reactivity values obtained from different traditional techniques, the area-ratio method and the α-fitting method, are discussed with respect to the applicability to on-line subcriticality monitoring. The results show that the area-ratio method robustly and accurately monitors subcriticality in shallow subcritical states with negative reactivity of up to a few dollars; however, this method faces problems with temporal fluctuations, spatial dispersion, and sensitivity to the proton-beam current with increasing depth of subcriticality. On the other hand, it is shown that the α-fitting method alleviates such problems in deep subcritical states. Moreover, a proposed fitting technique using the maximum-likelihood estimation method based on the Poisson distribution is robust enough to be applicable to on-line subcriticality monitoring for negative reactivity levels of up to roughly nine dollars.     

On-line monitoring applications in nuclear power plants

The nuclear power industry is working to reduce generation costs by adopting condition-based maintenance strategies and automating testing activities. These developments have stimulated great interest in on-line monitoring (OLM) technologies and new diagnostic and prognostic methods to anticipate, identify, and resolve equipment and process problems and ensure plant safety, efficiency, and immunity to accidents. This paper provides examples of these technologies with particular emphasis on eight key OLM applications: detecting sensing-line blockages, testing the response time of pressure transmitters, monitoring the calibration of pressure transmitters on-line, cross-calibrating temperature sensors in situ, assessing equipment condition, performing predictive maintenance of reactor internals, monitoring fluid flow, and extending the life of neutron detectors. These applications are discussed in the following sections. Emphasis is placed on the principles of a core OLM method - noise analysis - and the technical requirements for an integrated OLM system are summarized.     

Condition monitoring methods applied to class 1e cables

Sandia National Laboratories is currently conducting long-term aging research on representative samples of nuclear power plant Class lE cables. The objectives of this program are to determine the suitability of these cables for extended life (beyond 40-year design basis) and to assess various cable condition monitoring (CM) techniques for predicting remaining cable life. The cables are being aged for long times at relatively mild exposure conditions with various CM techniques being employed during the aging process. Following the aging process, the cables will be exposed to a sequential accident profile consisting of high dose rate irradiation followed by a simulated design basis loss-of-coolant accident (LOCA) steam exposure.This paper covers two aspects of the research program: the laboratory measurements and on-line electrical measurement techniques that have been developed and are being performed and initial data that has been generated from the on-line measurements. The electrical measurement results presented include insulation resistance, polarization index, capacitance, and dissipation factor from a few of the cable samples tested.     

Implementation of an integrated on-line process surveillance and diagnostic system at the Halden reactor project: MOAS

MOAS is an integrated on-line process surveillance and diagnostic system that uses several different models for knowledge acquisition and diagnostic reasoning, such as goal-tree success-tree model, process monitor trees, and sensor failure diagnosis trees. Within these models, the knowledge of the process and its operation, including deep knowledge, like mass balance or controller algorithm, is incorporated. During an extensive review, made as part of the integrated diagnosis system project of the Halden reactor project, MOAS (Maryland Operator Advisory System) was identified as one of the most thorough systems developed thus far. MOAS encompasses diverse functional aspects that are required for an effective process disturbance management: (1) intelligent process monitoring and alarming, (2) on-line sensor data validation and sensor failure diagnosis, (3) on-line hardware (besides sensors) failure diagnosis, and (4) real-time corrective measure synthesis. The MOAS methodology was used for the NORS (Nokia Research Simulator) process at the Halden man-machine laboratory HAMMLAB of the OECD Halden reactor project. The performance tests of MOAS, implemented in G2 real-time expert system shell, show that MOAS successfully carries out its intended functions, i.e. quickly recognizing an occurring disturbance, correctly diagnosing its cause, and presenting advice on its control to the operator. The lessons learned and insights gained during the implementation and performance tests also are discussed.     

核电厂基于频带方差与能量算子的轴承故障诊断方法

对核电厂设备在线监测与诊断,有助于实时掌握其运行状况,预测可能发生的故障,从而提高核电厂的安全性与经济性。本工作针对核电厂旋转设备上常见的轴承缺损类故障展开研究,采用能量算子对轴承的振动信号进行包络解调,将故障特征频率从噪声与高频信号中发掘出来。为能够自动确定带通滤波器的中心频率,提出用频带方差作为相应的指标,该指标具有在共振频率处取得最大值的特性。利用实验数据验证本工作的可行性与有效性,结果表明本工作提出的方法可有效监测轴承状况并正确诊断出其相应的故障类型。     

线功率密度和DNBR保护在田湾核电站的应用

堆内核测量系统是田湾核电站反应堆监测、控制和诊断系统的重要组成部分,在机组正常运行和瞬态工况下实时计算和监测反应堆参数。首次在田湾核电站将燃料棒线功率密度和偏离泡核沸腾比(DNBR)信号作为对反应堆的在线保护信号,达到了反应堆安全和经济运行的目的。     

On-line monitoring of instrument channel performance in nuclear power plant using PEANO

On-Line monitoring evaluates instrument channel performance by assessing its consistency with other plant indications. Industry and EPRI experience at several plants has shown this overall approach to be very effective in identifying instrument channels that are exhibiting degrading or inconsistent performance characteristics “On-Line Monitoring of Instrument Channel Performance by EPRI (2000)”.

On-Line monitoring of instrument channels provides information about the condition of the monitored channels through accurate, more frequent monitoring of each channel's performance over time. This type of performance monitoring is a methodology that offers an alternate approach to traditional time-directed calibration. On-line monitoring of these channels can provide an assessment of instrument performance and provide a basis for determining when adjustments are necessary. Elimination or reduction of unnecessary field calibrations can reduce associated labor costs, reduce personnel radiation exposure and reduce the potential for miss-calibration.

PEANO “A Neuro-Fuzzy Model Applied to Full Range Signal Validation of PWR Nuclear Power Plant Data by Fantoni (2000)” is a system for on-line calibration monitoring developed in the years 1995–2000 at the Institutt for energiteknikk (IFE), Norway, which makes use of Artificial Intelligence techniques for its purpose. The system has been tested successfully in Europe in off-line tests with EDF (France), Tecnatom (Spain) and ENEA (Italy). PEANO is currently installed and used for on-line monitoring at the HBWR reactor in Halden. This paper describes the results of performance tests on PEANO with real data from a US PWR plant, in the framework of a co-operation among IFE, EPRI and Edan Engineering, to evaluate the potentials of PEANO for future installations in US nuclear plants.     

Structural Material Anomaly Detection System Using Water Chemistry Data

The concept of an advanced water chemistry diagnosis system for detection of anomalies and preventive maintenance of system components is proposed and put into a concrete form. Using the analogy to a medical inspection system, analyses of water chemistry change will make it possible to detect symptoms of anomalies in system components.

Then, correlations between water chemistry change and anomaly occurrence in the components of the BWR primary cooling system are analyzed theoretically. These fragmentary correlations are organized and reduced to an algorithm for the on-line diagnosis system using on-line monitoring data, pH and conductivity. By using actual plant data, the on-line diagnosis model system is verified to be applicable for early and automatic finding of the anomaly cause and for timely supply of much diagnostic information to plant operators.     

On-line reconstruction of in-core power distribution by harmonics expansion method

Fixed in-core detectors are most suitable in real-time response to in-core power distributions in pressurized water reactors (PWRs). In this paper, a harmonics expansion method is used to reconstruct the in-core power distribution of a PWR on-line. In this method, the in-core power distribution is expanded by the harmonics of one reference case. The expansion coefficients are calculated using signals provided by fixed in-core detectors. To conserve computing time and improve reconstruction precision, a harmonics data library containing the harmonics of different reference cases is constructed. Upon reconstruction of the in-core power distribution on-line, the two closest reference cases are searched from the harmonics data library to produce expanded harmonics by interpolation. The Unit 1 reactor of DayaBay Nuclear Power Plant (DayaBay NPP) in China is considered for verification. The maximum relative error between the measurement and reconstruction results is less than 5.5%, and the computing time is about 0.53 s for a single reconstruction, indicating that this method is suitable for the on-line monitoring of PWRs.     

核反应堆故障早期检测和在线状态监测方法

即将颁布的核行业标准《核电厂反应堆堆内构件的振动监测》(简称标准)对早期监测反应堆压力容器堆内构件蜕化的方法、故障检测仪表和监测程序提出了要求,适用于以中子波动信号和反应堆压力容器振动信号为基础的堆内构件和一回路部件的动态特性的监测。本文强调了标准所包含的核电站新型仪表控制系统的监测方法。新系统不同于传统的监测系统,它的主要目的是早期故障检测．以便向电厂操纵员和检查维修人员提供有用的状态信息。     

An on-line method to monitor bwr core stability based on an autocorrelation method

An on-line monitoring method is introduced for BWR core stability. The method utilizes only autocorrelation values for two delay time intervals. Its simplicity makes it suitable for an on-line monitor. Accuracy of the core decay ratio calculated by the method improves as the core condition approaches instability. The error in the decay ratio for regional limit cycle oscillations is 0.2% when calculated from local signals in the most unstable region, and 4% when calculated from core averaged signals.