Computerized Procedure System Research Articles

Transitioning Nuclear Power Plant Main Control Room From Paper Based Procedures to Computer Based Procedures

The United States (U.S.) has 99 operating Nuclear Power Plants (NPPs). The majority of these were designed and commissioned in the 1970s and 1980s. Plants are modernizing their control systems and main control rooms to be able to continue operating past their original 40-year license agreements. U.S. NPP main control rooms are migrating towards hybrid controls with both digital and analog systems. Digital upgrades, while costly, provide improved reliability, reduced maintenance cost, and the potential for fewer unplanned outages and fewer human errors. U.S. utilities have been slow to embrace computerized procedure system (CBP) research, even though CBPs demonstrate clear operational and human factors benefits. Most of the CBP research has been oriented to new reactor designs or full digital control rooms and is not applicable to the piecemeal modernization approach favored by U.S. plants. Research is needed to examine how CBPs impact operations in hybrid control rooms, and how current paper based procedures can be efficiently migrated to computerized platforms. Work is underway to develop tools and perform the obligatory research needed to design and validate CBPs for modernized U.S. nuclear control rooms.

How does a change in the control room design affect diagnostic strategies in nuclear power plants?

Recently, main control rooms have been considerably changed by modern computer techniques. Some of the features that distinguish digital control rooms from conventional, analog rooms in nuclear power plants include advanced alarm systems, graphic information display systems, computerized procedure systems, and soft control. These features can bring changes in operator tasks, changing the characteristics of tasks or creating new tasks for operators. It is especially expected that these features may bring out changes in the operator's diagnostic tasks and strategies in a digital control room as compared with an analog control room. This study investigates the differences in the operator's diagnostic tasks and strategies in analog and digital control rooms. This study also attempts to evaluate how new systems in a digital control room affect diagnostic strategies. Three different approaches, which are complementary, are used to identify diagnostic strategies in the digital control room and in the analog control room: (1) observation in the simulator, (2) interview with operators, and (3) a literature review. The results show that the digital control room introduces new diagnosis strategies compared with the analog control room while also changing the characteristics of the strategies, mostly by gaining more support from the computerized system.

Operator’s cognitive, communicative and operative activities based workload measurement of advanced main control room

An advanced man–machine interface system (MMIS) with a computer-based procedure system and high-tech control/alarm system is installed in the advanced main control room (MCR) of a nuclear power plant. Accordingly, though the task of the operators has been changed a great deal, owing to a lack of appropriate guidelines on the role allocation or communication method of the operators, operators should follow the operating strategies of conventional MCR and the problem of an unbalanced workload for each operator can be raised. Thus, it is necessary to enhance the operation capability and improve the plant safety by developing guidelines on the role definition and communication of operators in an advanced MCR. To resolve this problem, however, a method for measuring the workload according to the work execution of the operators is needed, but an applicable method is not available. In this research, we propose a COgnitive, Communicative and Operational Activities measurement approach (COCOA) to measure and evaluate the workload of operators in an advanced MCR. This paper presents the taxonomy for additional operation activities of the operators to use the computerized procedures and soft control added to an advanced MCR, which enables an integrated measurement of the operator workload in various dimensions of cognition, communication, and operation. To check the applicability of COCOA, we evaluated the operator workload of an advanced MCR of a reference power plant through simulation training experiments. As a result, the amount of high workload of the shift supervisor (SS) was observed in relation to the computerized procedure system newly introduced into the environment of an advanced MCR, and the overall increase in the workload was also observed owing to the screen operation for the soft control of MMIS. On the basis of these observations, it is necessary to reestablish the role and communication method of MCR operators suitable to the new operational environment and changed work, and develop appropriate operating guidelines.

Design-related influencing factors of the computerized procedure system for inclusion into human reliability analysis of the advanced control room

This paper presents major design factors of the computerized procedure system (CPS) by task characteristics/requirements, with individual relative weight evaluated by the analytic hierarchy process (AHP) technique, for inclusion into human reliability analysis (HRA) of the advanced control rooms. Task characteristics/requirements of an individual procedural step are classified into four categories according to the dynamic characteristics of an emergency situation: (1) a single-static step, (2) a single-dynamic and single-checking step, (3) a single-dynamic and continuous-monitoring step, and (4) a multiple-dynamic and continuous-monitoring step. According to the importance ranking evaluation by the AHP technique, ‘clearness of the instruction for taking action’, ‘clearness of the instruction and its structure for rule interpretation’, and ‘adequate provision of requisite information’ were rated as of being higher importance for all the task classifications. Importance of ‘adequacy of the monitoring function’ and ‘adequacy of representation of the dynamic link or relationship between procedural steps’ is dependent upon task characteristics. The result of the present study gives a valuable insight on which design factors of the CPS should be incorporated, with relative importance or weight between design factors, into HRA of the advanced control rooms.

A Study on a Trend of Human Error Types Observed in a Simulated Computerized Nuclear Power Plant Control Room

Objective: The aim of this study is to investigate a trend of human error types observed in a series of verification and validation experiments for an Advanced Control Room(ACR) equipped with Lager Display Panel(LDP), Work Station Flat Panel Display(WS FPD), list type Alarm System(AS), Soft Control(SC) and Computerized Procedure System(CPS). Background: Operator behaviors in a fully computerized control room are quite different from those in a traditional hard-wired control room. Operators in an ACR all together monitor plant status and variables through their own interface system such as LDP and WS FPD, are notified of abnormal plant status through their own list type AS, control the plant through their own SC, and follow the structured procedure through their own CPS whereas operators in a traditional control room only separately do their duty directed by their supervisor. Especially the secondary task such as manipulating the user interface of ACR can be an extra burden to all the operators including the supervisor. Method: The Reason"s human error classification method was applied to operators" behavioral data collected from a series of verification and validation experiments where operators showed their plant operational behaviors under a couple of harsh scenarios using the ACR simulator. Results: As operators accustomed to the new ACR system, knowledge or rule based mistakes appearing frequently in the early series of experiments decreased drastically in the latest stage of the series. Slip and lapse types of errors were observed throughout the series of experiments. Conclusion: Education and training can be one of the most important factors for the operators accustomed to the traditional control room to be adapted to the new system and to run the ACR successfully. Application: The results of this study implied that knowledge or rule based mistakes can be reduced by training and education but that lapse type errors might be reduced only through innovative improvement in human-system interface design or teamwork culture design including a new leadership style suitable for ACR.

STATE TOKEN PETRI NET MODELING METHOD FOR FORMAL VERIFICATION OF COMPUTERIZED PROCEDURE INCLUDING OPERATOR'S INTERRUPTIONS OF PROCEDURE EXECUTION FLOW

The Computerized Procedure System (CPS) is one of the primary operating support systems in the digital Main Control Room. The CPS displays procedure on the computer screen in the form of a flow chart, and displays plant operating information along with procedure instructions. It also supports operator decision making by providing a system decision. A procedure flow should be correct and reliable, as an error would lead to operator misjudgment and inadequate control. In this paper we present a modeling for the CPS that enables formal verification based on Petri nets. The proposed State Token Petri Nets (STPN) also support modeling of a procedure flow that has various interruptions by the operator, according to the plant condition. STPN modeling is compared with Coloured Petri net when they are applied to Emergency Operating Computerized Procedure. A converting program for Computerized Procedure (CP) to STPN has been also developed. The formal verification and validation methods of CP with STPN increase the safety of a nuclear power plant and provide digital quality assurance means that are needed when the role and function of the CPS is increasing.

Assessing mental workload and situation awareness in the evaluation of computerized procedures in the main control room

Computerized procedure (CP) system has been developed in nuclear power plant (NPP) instrumentation and control (I&C) system. The system may include normal operating procedures (OPs), abnormal operating procedures (AOPs), alarm response procedures (ARPs), surveillance test procedures (STPs) and/or emergency operating procedures (EOPs). While there are many ways to evaluate computerized procedures design, the user's mental workload and situation awareness (SA) are particularly important considerations in the supervisory control of safety-critical systems. Users’ mental workload and situation awareness may be influenced by human factor issues relating to computerized procedures, e.g., level of automation, dealing with (partially) unavailable I&C, switching to back-up system (e.g., paper-based procedures). Some of the positive impacts of CPs on operator performance include the following: tasks can be performed more quickly; overall workload can be reduced; cognitive workload can be minimized; fewer errors may be made in transitioning through or between procedures. However, various challenges have also been identified with CP systems. These should be addressed in the design and implementation of CPs where they are applicable. For example, narrower “field of view” provided by CP systems than with paper-based procedures could reduce crew communications and crewmember awareness of the status and progress through the procedure. Based on a human factors experiment in which each participant monitored and controlled multiple simulated reactors, this study applied the NASA-TLX instrument for assessing mental workload. For the assessment of situation awareness (SA), the present research used the situational awareness rating technique (SART). In support of summarizing the results of user interface evaluation along multiple dimensions (e.g., workload, SA), we propose advantages for the CPs compared to the paper-based procedures.

Modeling of computerized procedure execution with State Token Petri Net for formal verification of procedure flow

Computerized procedure system (CPS) is one of the primary operating support systems in the digital main control room (MCR) of a nuclear power plant. CPS displays the procedure at computer screen in the form of a flow chart and displays plant operating information along with procedure instructions. It also supports the operator to make a decision by providing system decision with logic. Most importantly, CPS guides the operator to follow a procedure flow that is predefined when the computerized procedure (CP) is written. A procedure flow should be correct and reliable, as error would lead to operator misjudgment and inadequate control. As such, the procedure flow should be verified before being applied to the MCR. In this article, we present a model of CPS that enables formal verification based on Petri nets. The proposed State Token Petri Net also supports modeling of a procedure flow that has various interruptions by the operator according to the plant condition.

Human Error Mode Identification for NPP Main Control Room Operations Using Soft Controls

The operation environment of main control rooms (MCRs) in modern nuclear power plants (NPPs) has considerably changed over the years. Advanced MCRs, which have been designed by adapting digital and computer technologies, have simplerinterfaces using large display panels, computerized displays, soft controls, computerized procedure systems, and so on. The actions for the NPP operations are performed using soft controls in advanced MCRs. Soft controls have different features from conventional controls. Operators need to navigate the screens to find indicators and controls and manipulate controls using a mouse, touch screens, and so on. Due to these different interfaces, different human errors should be considered in the human reliability analysis (HRA) for advanced MCRs. In this work, human errors that could occur during operation executions using soft controls were analyzed. This work classified the human errors in soft controls into six types, and the reasons that affect the occurrence of the human errors were also analyzed.

Development of a qualitative evaluation framework for performance shaping factors (PSFs) in advanced MCR HRA

Human reliability analysis (HRA) is performed as part of the probabilistic risk assessment to identify and quantify human actions and the associated impacts on structures, systems, and components of complex facilities. In performing HRA, conditions that influence human performance have been analyzed in terms of several context factors. These context factors, which are called performance shaping factors (PSFs) are used to adjust the basic human error probability (BHEP), and PSFs have been derived in various ways depending on the HRA methods used. As the design of instrumentation and control (I&C) systems for nuclear power plants (NPPs) is rapidly moving toward fully digital I&C, and modern computer techniques have been gradually introduced into the design of advanced main control room (MCR), computer-based human–system interfaces (HSIs), such as CRT-based displays, large display panels (LDPs), advanced information systems, soft control, and computerized procedure system (CPS) will be applied in advanced MCR. Environmental changes in MCR have some implications for PSFs, and they have an influence on when PSFs should be applied in HRA because different situations might induce different internal or external factors which can lead to human errors. In this study, PSFs for advanced MCR HRA are derived, and a new qualitative evaluation framework for these PSFs is suggested. First, PSFs from various HRA methods are collected, and these PSFs are further grouped into PSFs categories to be used in advanced MCR HRA. Second, human factor (HF) issues in advanced MCR are analyzed and derived to be used as an evaluation framework for PSFs.

Human Error Mode Identification for NPP Main Control Room Operations Using Soft Controls

The operation environment of main control rooms (MCRs) in modern nuclear power plants (NPPs) has considerably changed over the years. Advanced MCRs, which have been designed by adapting digital and computer technologies, have simplerinterfaces using large display panels, computerized displays, soft controls, computerized procedure systems, and so on. The actions for the NPP operations are performed using soft controls in advanced MCRs. Soft controls have different features from conventional controls. Operators need to navigate the screens to find indicators and controls and manipulate controls using a mouse, touch screens, and so on. Due to these different interfaces, different human errors should be considered in the human reliability analysis (HRA) for advanced MCRs. In this work, human errors that could occur during operation executions using soft controls were analyzed. This work classified the human errors in soft controls into six types, and the reasons that affect the occurrence of the human errors were also analyzed.

Computerized procedure system for the APR1400 simulator

The ShinKori Unit 3&4 which is the reference plant for APR1400 simulator plans to utilize various display devices and computerized Human Machine Interface (HMI) as well as many kinds of digitalized instrumentation and control. The operating crew will be given a lot of information on display devices in order to diagnose the system states and control devices. And with the limitations of paper-based procedure (PBP) including lack of interactive capabilities between the PBP and sophisticated systems, and the high volume and cost associated with paper manuals used in complex and technically demanding environments, the computerized procedure system (CPS) is developed as a part of computerized systems for APR1400 simulator. The developed CPS covers all operating procedures including normal, abnormal and emergency, and provides information through workstation consoles using flowchart and tree structure and also has automatic checking capabilities of step logic including continuously applied steps. The CPS consists of Procedure eXecution System (PXS), and Engineering System (ES) including procedure editor (PED) and Non-Integrated System Test System (NISTS). The PXS is the execution system for the procedure provided to the operators and has the following functions. 1) Display of the plant status information necessary for the instructions and executions for the procedure, 2) auto-check functions instead of manual monitoring based on the paper-based procedures, 3) detection and recovery functions of operators’ faults, 4) generation function of the LCP (Logged Computerized Procedure) to search the results of the procedure execution, 5) generation function of the Log Paper Procedure supporting the continued operation using the paper procedure when the CPS fails. The ES (Engineering System) is the environment provided to the writer and maintainer of the CP (Computerized Procedure), the application program loaded in the PXS. The CP is frequently revised in the plant, and related to the safety of the plant. Therefore, the CP is provided to secure the quality and convenience of the developed procedure. For the verification, among the implemented computerized procedures by using PED, a procedure for the LOCA (Loss-Of-Coolant Accident) is selected for testing the integrity of the CPS including communication between CPS and other systems for APR1400 simulator, which is proved to be well implemented. Currently, the implemented CPS is being used to the Preliminary Validation Phase II Test hosted by NETEC (Nuclear Environment TEChnology Institute) in Korea.

Modeling of a Dependence between Human Operators in Advanced Main Control Rooms

For the human reliability analysis of main control room (MCR) operations, not only parameters such as the given situation and capability of the operators but also the dependence between the actions of the operators should be considered because MCR operations are team operations. The dependence between operators might be more prevalent in an advanced MCR in which operators share the same information using a computerized monitoring system or a computerized procedure system. Therefore, this work focused on the computerized operation environment of advanced MCRs and proposed a model to consider the dependence representing the recovery possibility of an operator error by another operator. The proposed model estimates human error probability values by considering adjustment values for a situation and dependence values for operators during the same operation using independent event trees. This work can be used to quantitatively calculate a more reliable operation failure probability for an advanced MCR.

디지털 정보표시 환경의 지침 기반 평가 기술

The analog typed interface of main control room in nuclear power plant(NPP) is gradually being replaced to the one suitable for the digital environment. SKN 3,4 is currently developed in such a way to employ digitalized displays and controls such as computerized procedure system(CPS), large display panel(LDP), and Soft control. The main control room (MCR) of the SKN3, 4 was designed based on the human factors guidelines, which somehow lack of the confidence for the rapidly changing digital environment. Although the suitable review guidelines for the digitalized information displays was developed, the developed guidelines needs to extend to the one to apply for the total digital environment including task environment, hardware and workstation. In order to achieve the research objectives, tremendous guidelines and technical papers related to evaluation issues of digital environment has been collected, analyzed and transformed to electric database forms and then built on database management system to retrieve the appropriate issues for the practical usage of evaluators-in-field.

DESIGN REVIEW SUPPORTING SYSTEM FOR HMS WITH ADVANCED INFORMATION DISPLAYS

The analog typed interface of main control room in nuclear power plant (NPP) is gradually being replaced to the one suitable for the digital environment. SKN 3,4 Nuclear Power Plant is currently developed in such a way to employ digitalized displays and controls such as computerized procedure system(CPS), large display panel(LDP), and Soft control. The main control room (MCR) of the SKN3,4 was designed based on the human factors guidelines, which somehow lack of the confidence for the rapidly changing digital environment. The suitable review guideline for the digitalized information displays was developed with an extension to the total digital environment including task environment, hardware and workstation. For the guideline development, tremendous guidelines and technical papers related to evaluation issues of digital environment has been collected, analyzed and transformed to electric database forms and then built on database management system to retrieve the appropriate issues for the practical usage of evaluators-in-field.

An Evaluation of Computerized Procedure System in Nuclear Power Plant

This paper reports an observational study of a Computerized Procedure System (CPS) under development for an advanced main control room in Korea. The purpose of this study was to examine possible effects of using the CPS. The crew, a shift supervisor and two operators, admitted that the CPS reduced their mental workload and they thought the CPS was better than or as good as paper-based procedures. One significant effect was that the amount of communication between the shift supervisor and two board operators was reduced considerably.