The impact of computer-based procedures on team performance,communication, and situation awareness

In nuclear power plants, operating procedures are adopted to aid the operators in performing their tasks. With the evolution of computer hardware and software, the analog human-machine systems of the main control room in the nuclear power plant have been replaced with digital systems. Moreover, automated operations now outnumber manual operations. The purpose of this study was to evaluate the impact of computer-based procedures on the team performance, communication, and situation awareness of operators in the main control room. To achieve the purpose, a within-subjects experiment was designed and then a survey was conducted. The results showed that the teams had better objective performance and higher situation awareness when using computer-based procedures. In addition, the teams also had lower human error and lower communication rates when using computer-based procedures. This study proposes that computer-based procedures are advantageous to the operation of the systems of the main control rooms in nuclear power plants.Relevance to industryComputerized procedures system is one of the specific features for advanced nuclear power plant. This study explores and analyzes the team performance, communication, and situation awareness difference between paper-based, electronic, and computer-based procedures in detail. It may provide practical information for how to apply computer-based procedures to perform the tasks in the main control room of the advanced nuclear power plant.     

Development of distributed real-time simulators based on CORBA

The development of complex simulators with multiple simulation models running in a distributed way is a difficult task where communication plays a main role, particularly in cases where real-time constraints exist. This paper presents distributed simulators for nuclear power plants with communication based on Real-time CORBA, a middleware for real-time systems. The simulators are used to train power plant operators safely. They are based on a complex architecture of simulation models with real-time constraints involving many different applications that allow full scope simulation of the control room of a nuclear power plant. The use of Real-time CORBA in the simulators allows us to obtain platform and language independence, reusable components and the control of real-time properties.     

Team performance in process control: influences of interface design and staffing levels

A study performed at the OECD Halden Reactor Project compared the effects of interface design and staffing levels on various aspects of team performance. Teams of nuclear power plant operators participated in challenging simulator scenarios, working in either a simulated conventional plant, with a hard-control interface, or in a simulated advanced plant, with a computerized interface. Twoteam staffing levels, normal and minimum, were evaluated in each plant condition. All teams participated in the same five study conditions, lasting 1– 3 h each. Several measures assessed team performance: situation awareness, workload, rated team interactions, rated overall performance and objective performance. The findings revealed that combinations of interface design and staffing levels supported different aspects of performance. Larger crews consistently performed better than smaller crews in the conventional plant. In the advanced plant, both crew types performed equally well; however, smaller crews had better situation awareness than larger crews. In general, performance was better for crews using the advanced plant interface, but workload was higher. Workload also was consistently higher in the smaller crews than in the larger crews, regardless of interface type. Links between the performance measures were also noted.     

Team performance in process control: influences of interface design and staffing levels

A study performed at the OECD Halden Reactor Project compared the effects of interface design and staffing levels on various aspects of team performance. Teams of nuclear power plant operators participated in challenging simulator scenarios, working in either a simulated conventional plant, with a hard-control interface, or in a simulated advanced plant, with a computerized interface. Two-team staffing levels, normal and minimum, were evaluated in each plant condition. All teams participated in the same five study conditions, lasting 1-3 h each. Several measures assessed team performance: situation awareness, workload, rated team interactions, rated overall performance and objective performance. The findings revealed that combinations of interface design and staffing levels supported different aspects of performance. Larger crews consistently performed better than smaller crews in the conventional plant. In the advanced plant, both crew types performed equally well; however, smaller crews had better situation awareness than larger crews. In general, performance was better for crews using the advanced plant interface, but workload was higher. Workload also was consistently higher in the smaller crews than in the larger crews, regardless of interface type. Links between the performance measures were also noted.     

Error mode prediction

The study of accidents (‘human errors’) has been dominated by efforts to develop ‘error’ taxonomies and ‘error’ models that enable the retrospective identification of likely causes. In the field of Human Reliability Analysis (HRA) there is, however, a significant practical need for methods that can predict the occurrence of erroneous actions— qualitatively and quantitatively. The present experiment tested an approach for qualitative performance prediction based on the Cognitive Reliability and Error Analysis Method (CREAM). Predictions of possible erroneous actions were made for operators using different types of alarm systems. The data were collected as part of a large-scale experiment using professional nuclear power plant operators in a full scope simulator. The analysis showed that the predictions were correct in more than 70% of the cases, and also that the coverage of the predictions depended critically on the comprehensiveness of the preceding task analysis.     

Error mode prediction

The study of accidents ('human errors') has been dominated by efforts to develop 'error' taxonomies and 'error' models that enable the retrospective identification of likely causes. In the field of Human Reliability Analysis (HRA) there is, however, a significant practical need for methods that can predict the occurrence of erroneous actions--qualitatively and quantitatively. The present experiment tested an approach for qualitative performance prediction based on the Cognitive Reliability and Error Analysis Method (CREAM). Predictions of possible erroneous actions were made for operators using different types of alarm systems. The data were collected as part of a large-scale experiment using professional nuclear power plant operators in a full scope simulator. The analysis showed that the predictions were correct in more than 70% of the cases, and also that the coverage of the predictions depended critically on the comprehensiveness of the preceding task analysis.     

Nuclear power plant communications in normative and actual practice: A field study of control room operators' communications

The safety and availability of sociotechnical critical systems still relies on human operators, both through human reliability and human ability to handle adequately unexpected events. In this article, the authors focus on ergonomic field studies of nuclear power plant control room operator activities, and more specifically on the analysis of communications within control room crews. They show how operators use vague and porous verbal exchanges to produce continuous, redundant, and diverse interactions to successfully construct and maintain individual and mutual awareness, which is paramount to achieve system stability and safety. Such continuous interactions enable the operators to prevent, detect, and reverse system errors or flaws by anticipation or regulation. This study helps in providing cues for the design of more workable systems for human cooperation in nuclear power plant operation. © 2007 Wiley Periodicals, Inc. Hum Factors Man 17: 43–78, 2007.     

针对DES加密算法的DPA攻击仿真平台

研究分析数据加密算法DES的特点,采用差分功耗分析(DPA)攻击方式进行密钥破解,针对DES算法实现一种差分功耗分析攻击仿真平台。该仿真平台具有精度高、模拟速度快等特点,其理论基础为集成电路中门电路在实现加密算法时的物理特性、功耗模型及数据功耗相关性。在该平台上针对DES加密系统,采用基于汉明距离的差分功耗攻击实现仿真模拟,成功破解了DES加密算法的密钥,从而给DES加密算法理论研究者提供了有益的基础和参考。     

Safety implications of cultural and cognitive issues in nuclear power plant operation

This research project was designed to investigate cultural and cognitive issues related to the work of nuclear power plant operators during their time on the job in the control room and during simulator training (emergency situations), in order to show how these issues impact on plant safety. The modeling of the operators work deals with the use of operational procedures, the constant changes in the focus of attention and the dynamics of the conflicting activities. The paper focuses on the relationships between the courses of action of the different operators and the constraints imposed by their working environment. It shows that the safety implications of the control room operators' cognitive and cultural issues go far beyond the formal organizational constructs usually implied. Our findings indicate that the competence required for the operators are concerned with developing the possibility of constructing situation awareness, managing conflicts, gaps and time problems created by ongoing task procedures, and dealing with distractions, developing skills for collaborative work.     

基于RELAP5的沸水堆机理模型建立与仿真

核电厂高精度、实时、动态仿真要求有准确的反应堆热工水力以及控制系统等模型,它除用于电厂安全分析、操纵员培训等,还可用于控制系统参数优化、实际仪表控制系统验证等方面。为了研究在核电站控制系统问题上引入智能控制和优化算法的可行性,利用热工水力软件RELAP5,以沸水堆核电站为例,对沸水堆的堆芯系统和主给水系统进行了建模,并在稳态和暂态工况下进行了仿真验证。仿真结果与电站的实际数据基本一致,表明了基于RELAP5程序所建立的沸水堆热工水力模型的正确性。     

Human factors approach for evaluation and redesign of human–system interfaces of a nuclear power plant simulator

Nuclear power production is a safety-critical process where ultimate execution of process change decisions lie with the operators. Thus it is important to provide the best possible decision support through effective supervisory control operator interfaces. This requires a human factors/ergonomics approach in the modernization of analog instrumentation and control systems of the existing nuclear power plants. In this article, we describe how this approach is being used for modernization of the ANGRA I power plant. Using a cognitive task analysis (CTA) approach, we observed operators working on an advanced control room of a nuclear power plant digital simulator and noted several opportunities for improvement in the human/system interfaces related to the graphics design, alarm systems and procedure integration. A redesigned prototype was constructed as an alternative to the current simulator and hardcopy procedure manuals. The design improves upon the graphical layout of system information and provides better integration of procedures, automation and alarm systems. The design was validated by expert opinion and a scenario-based comparison.

Relevance to industry

Human factors/ergonomics are not playing the role they deserve in the design of process control systems making them less controllable than they could be if human factors were adequately incorporated. The use of human factors approach in the design of process control systems throughout the industry presents many opportunities for improvements with regard to system effectiveness, efficiency, reliability and safety.     

核电厂高压电气断相故障仿真分析

核电厂高压电气断相故障,在实际电厂运行中主控室无法监测到。而现有分析仅仅是从电网设备角度分析,核电厂无法得到电网计算分析结果,是业内断相问题分析的空白。将电网断相计算分析模型与核电厂全范围模拟机系统模型集成在一起,能够从电网侧和核电厂工艺系统运行设备侧完整分析出断相后核电厂运行情况。将成熟的电网断相计算与模拟完善的模拟机软件通过接口开发,连接在一起进行多种电压等级断相故障测试是难题,通过三相电机模型开发,接口转换工具开发等处理,很好的解决了两种计算模型的接口问题,之后的断相测试结果,为核电站在断相故障发生后的快速反应提供了重要的依据。     

There is more to monitoring a nuclear power plant than meets the eye

A fundamental challenge in studying cognitive systems in context is how to move from the specific work setting studied to a more general understanding of distributed cognitive work and how to support it. We present a series of cognitive field studies that illustrate one response to this challenge. Our focus was on how nuclear power plant (NPP) operators monitor plant state during normal operating conditions. We studied operators at two NPPs with different control room interfaces. We identified strong consistencies with respect to factors that made monitoring difficult and the strategies that operators have developed to facilitate monitoring. We found that what makes monitoring difficult is not the need to identify subtle abnormal indications against a quiescent background, but rather the need to identify and pursue relevant findings against a noisy background. Operators devised proactive strategies to make important information more salient or reduce meaningless change, create new information, and off-load some cognitive processing onto the interface. These findings emphasize the active problem-solving nature of monitoring, and highlight the use of strategies for knowledge-driven monitoring and the proactive adaptation of the interface to support monitoring. Potential applications of this research include control room design for process control and alarm systems and user interfaces for complex systems.     

基于冗余TTCAN的核电站报警窗改进设计

鉴于推行核电设备国产化以及核电报警系统的升级改造需求,对核电报警系统空气闸门报警窗的通信模块进行了改进研究。考虑到核电站场景的高安全性需求,报警窗通信模块的改进设计采用了实时性高、可预测性好、抗干扰性强的基于时间触发的控制器局域网络(TTCAN)总线,并以报警窗为主节点,各报警采集模块为从节点。在分析了主流TTCAN冗余方式的基础上,提出一种新的TTCAN冗余方式,应用了带有双路总线控制器的微控制单元(MCU)以及双通道互相独立的传输架构,搭建了TTCAN冗余网络,并提出了相应的新型冗余管理策略。试验证明,采用新型冗余TTCAN通信方式的报警窗总线利用率高、数据传输速率快、数据传输稳定、误码率低,具有高实时性和高可靠性,是TTCAN总线应用于核电仪控系统和报警系统的一次积极尝试。     

Evaluation of operators' performance for automation design in the fully digital control room of nuclear power plants

Recent technical developments in computer hardware and software have meant that human–machine systems can be automated in many respects. If automation fails, however, human operators can have difficulty in recognizing the existence of a problem, identifying what has failed, and taking corrective action to remedy these out‐of‐the‐loop (OOTL) performance problems. Several studies have suggested that taxonomies of levels of automation (LOAs) and types of automation (TOAs) can be used to solve OOTL problems. This study examined the impact of LOAs in process control automation within the context of nuclear power plants (NPPs). A simulation experiment in an NPP is performed to validate this framework using an automatic mode and a semiautomatic mode. Mental demand is found to be significantly reduced under the automatic mode; however, participants felt frustrated with this LOA. Situation awareness is found to be similar in the two modes. The results of an end‐of‐experiment subjective rating reveal that participants were evenly divided between the two modes with respect to generating and selecting functions. It is therefore suggested that human operators be involved in generating and selecting functions under an automatic mode. © 2009 Wiley Periodicals, Inc.     

ADAPTIVE NUCLEAR REACTOR CONTROL WITHOUT EXPLICIT IDENTIFICATION

Abstract

Adaptive control of a nulcear power plant, the parameters of which may vary slowly with time, is considered without requiring explicit identification. It is based on the use of a reference model representing the desired behavior of the system. Stability of the adaptive loop is guaranteed by Liapunov's second method. The scheme is applied to control the power level changes of the nuclear reactor and a two-level controller is designed using signal-synthesis adaptation. Extensive results of simulation using a realistic model of the reactor at the Douglas Point power station indicate that the performance of the scheme is satisfactory.     

The effects of heuristic rule training on operator performance in a simulated process control environment

In complex work environments, the occurrence of novel system states represents a particular challenge for the design of training. This article is concerned with the use of heuristic rules to prepare operators for the management of unfamiliar fault states. An experiment was carried out to examine the effects of heuristic rule training on operator performance and system management behaviour. Thirty-nine trainee operators from the chemical industry took part in the study. They were trained for 4 h on a PC-based simulation of a process control task. Operators in the experimental group received training on heuristic rules while operators in the control group did not. One week later the operators participated in a 70-min testing session. While the results showed that heuristic rules training led to better diagnostic performance, it was also associated with increased operator fatigue and impaired secondary task performance. The implications of the findings for using heuristic rule training are discussed.     

数据库技术在当代电厂仿真中的应用

社会发展对电力调节控制要求的不断提高促使电厂必须不断努力保证和提高集控人员的技能,这促进了电厂仿真技术的快速发展。而电厂仿真实现过程中大量信息数据的组织、存储和处理必须要有计算机数据库技术的支持。该文结合电厂先进建模方法以及仿真支撑平台构成的介绍阐述了计算机数据库技术在当代电厂仿真中的应用,尤其是C/S模式在电厂仿真领域中的应用。     

Feasibility of methods for early formative control room system evaluation

In a nuclear power plant, human factors evaluation is an important activity in the design of the control room system to ensure safe operation. The purpose of this study was to test the feasibility of methods for early formative evaluation of nuclear power plant control room systems, that is to say assessment of more general design decisions. Two methods were chosen for the assessment, scenario-based talkthrough and heuristic evaluation, and they were tested in three nuclear power plant control room system modification projects. The two methods were found useful and suitable for early formative evaluation. The combination of the methods makes it possible to take advantage of the strengths of both methods. Using guidelines focuses the evaluation on identifying typical design problems, while using a scenario-based use-focused approach allows identifying problems less typical and more unique for the specific design being evaluated. Doing the latter thoroughly result in a recourse-intensive evaluation, but this can be countered by trading some of the thoroughness for efficiency by using guidelines in the evaluation. Proposals for future work include improving the method combination by providing better support for adapting the implementation of the methods, as well as for the practical execution of the evaluation activity. Future work should also include further investigation of the method combination's usefulness, for example in other domains.     

Operators’ orientations to procedure guidance in NPP process control

Resilience in nuclear power plant (NPP) process control depends, among other things, on balance between operators’ autonomy in online decisions and pre-defined guidance for operations. Striking balance between these inherent demands of process control belongs to the strategic decisions by the management, but finally balancing takes place at the sharp end, by the operating personnel. We studied operators’ basic assumptions about the role of operating procedures in action. Conceptions of 62 control room operators at two Finnish NPPs were queried. Answers were classified into theory-based categories, i.e., interpretative, confirmative or reactive orientations. Orientation is an epistemic attitude to work that influences the process and content of sense making in situations that require action. In both NPPs, the confirmative orientation, emphasising the importance of acting according to rules, prevails, which corresponds to the expectations set by the organisations. It was also found that orientations reflect the operator roles and their demands: Among turbine operators, the interpretative orientation is significantly more prevalent than among the reactor operators as regards control of action. All operators consider interpretative orientation as a characteristic of a “good operator”. It is concluded that interpretative orientation represents an epistemic attitude to NPP operator work, in which autonomy based on operators’ professional competence and procedure usage is not seen opposite to each other, but intertwined into a practice. Identification interpretativeness as an epistemic attitude relevant in action extends the notion of “intelligent use of procedures” proposed earlier, by elaborating the inherent logic and ethos of operators’ procedure usage. It is recommended that appropriation of interpretative orientation should be actively supported as a means to facilitate resilience in NPP activity.