Human Error Rate Research Articles

인적행위개선 포스터 개발과 활용

As many as 111 reactor trips have occurred for recent 5 years('01~'05), and 26 cases of them have occurred due to human error. The trend of human error rate didn't decrease in 2004, so KHNP started to make efforts to decrease human errors. In 2006 KHNP bench marked excellent foreign nuclear power plants and introduced human error prevention tools. In addition, KHNP created as many as 40 posters for human performance improvement. The posters are based on the about 500 real incident reports collected through K-HPES from 1995. The incident reports were reinterpreted in view of human error preventive tools for the poster. This paper explains design of the posters and their application.

Evaluation of Multi-sensory Feedback on the Usability of a Virtual Assembly Environment

Virtual assembly environment (VAE) technology has the great potential for benefiting the manufacturing applications in industry. Usability is an important aspect of the VAE. This paper presents the usability evaluation of a developed multi-sensory VAE. The evaluation is conducted by using its three attributes: (a) efficiency of use; (b) user satisfaction; and (c) reliability. These are addressed by using task completion times (TCTs), questionnaires, and human performance error rates (HPERs), respectively. A peg-in-a-hole and a Sener electronic box assembly task have been used to perform the experiments, using sixteen participants. The outcomes showed that the introduction of 3D auditory and/or visual feedback could improve the usability. They also indicated that the integrated feedback (visual plus auditory) offered better usability than either feedback used in isolation. Most participants preferred the integrated feedback to either feedback (visual or auditory) or no feedback. The participants’ comments demonstrated that nonrealistic or inappropriate feedback had negative effects on the usability, and easily made them feel frustrated. The possible reasons behind the outcomes are also analysed.

Realistic human error rates for process hazard analyses

While human error has long been recognized as a contributor to process incidents, Process Hazard Analysis (PHA) teams often struggle to agree on the frequency at which human errors might occur. This difficulty in reaching a consensus can be due to the varied backgrounds and experiences of team members, as well as the degree to which they believe human error is inevitable as opposed to simply being a reason for discipline. A process that combines research-based, quantitative estimates of human error rates with plant experience and intuition is proposed for use during qualitative PHAs. Use of these quantitative estimates within a qualitative PHA is described, along with one facility's successful implementation of this process. © 2007 American Institute of Chemical Engineers Process Saf Prog, 2007.

An update of the probabilistic safety assessment of the Radiation Monitor Calibration Laboratory of a Brazilian nuclear power station

In 2001, a probabilistic safety assessment of the Radiation Monitor Calibration Laboratory of a Brazilian nuclear power station was performed to estimate its radiological risk. Owing to the lack of data, many conservative assumptions were considered. The purpose of this paper is to obtain the updated laboratory radiological risk. A human reliability analysis of the procedure for calibrating the monitors was performed by applying the Technique for Human Error Rate Prediction (THERP) methodology. For facing the lack of failure data, the Bayesian approach was used for the calculation of the irradiator failure probability. The exponential distribution was used to model the failure times of the electronic dosimeters. The radiological risk was obtained through an event tree, in which all relevant scenarios were considered. Although more accident scenarios were considered in the analysis, like external events, the approach was by no means conservative, and a radiological risk about one order of magnitude smaller was obtained.

Evaluation of Auditory and Visual Feedback on Task Performance in a Virtual Assembly Environment

This paper presents the creation of an assembly simulation environment with multisensory feedback (auditory and visual), and the evaluation of the effects of auditory and visual feedback on the task performance in the context of assembly simulation in a virtual environment (VE). This VE experimental system platform brings together complex technologies such as constraint-based assembly simulation, optical motion tracking technology, and real time 3D sound generation technology around a virtual reality workbench and a common software platform. A peg-in-a-hole and a Sener electronic box assembly task have been used as the task cases to conduct the human factor experiment, using sixteen participants. Both objective performance data (i.e., task completion time, TCT; and human performance error rate, HPER) and subjective opinions (i.e., questionnaires) on the utilization of auditory and visual feedback in a virtual assembly environment (VAE) have been gathered from the experiment. Results showed that the introduction of auditory and/or visual feedback into VAE did improve the assembly task performance. They also indicated that integrated feedback (auditory plus visual) offered better assembly task performance than either feedback used in isolation. Most participants preferred integrated feedback to either individual feedback (auditory or visual) or no feedback. The participants' comments demonstrated that nonrealistic or inappropriate feedback had a negative effect on the task performance, and easily made them frustrated.

Evaluation of the Impact of SAMG on the Level-2 PSA Results of a Pressurized Water Reactor

Probabilistic safety assessment (PSA) uses a systematic approach to estimate the reliability and risk of a nuclear power plant (NPP). Over the past few years, severe accident management guidance (SAMG), which delineates the mitigation actions of core melt accidents of an NPP, has been developed to support operators and staff in the technical support center in dealing with those misfortunes. It can be expected that the implementation of SAMG will lower the containment failure frequency and reduce the amount of radionuclides released to the environment during the accident. The plant studied is the Maanshan NPP of Taiwan Power Company, which employs a Westinghouse-designed three-loop pressurized water reactor (PWR) with large dry containment.The containment system event trees and containment phenomenological event trees of the Level-2 PSA model are modified to incorporate the new mitigation actions specified in SAMG. The HCR (Human Cognitive Reliability) and THERP (Technique for Human Error Rate Prediction) models are used to quantify the human error probability (HEP) of all the actions in the Level-2 PSA model. The MAAP4 (Module Accident Analysis Program version 4) code is used to perform thermohydraulic calculations to determine the demand time required in the HEP analysis.The results show that the frequency of most of the source term categories is reduced except the one in which both the reactor pressure vessel and containment are intact. The containment failure frequency is reduced by 14.8% after the implementation of SAMG. The frequency of containment early failure is reduced by 16.2%. Most of the reduction in the containment early failure frequency comes from the reduction in the induced steam generator tube rupture (STGR). The frequency of induced SGTR was reduced from 2.3 × 10–7/reactor·yr to 1.0 × 10–8/reactor·yr.

Human reliability: A key to improved quality in manufacturing

AbstractFor one to learn, one must make mistakes. Human error can be defined on the basis of the definition of quality. Because quality is influenced by human actions, the so‐called performance shaping factors have an important influence on the human error probability. Different methods have been developed to predict human error probability. One of the most established and detailed methods is THERP (technique for human error rate prediction), which was originally developed for application in the nuclear power industry. Here this method is applied to a simple example of manufacturing. Further experimental research in the area of commission will be reported, where methods of error prediction were also applied. In both cases, measures of improving human reliability can be derived. © 2005 Wiley Periodicals, Inc. Hum Factors Man 15: 353–368, 2005.

Optimal Reliability/Availability of Uncertain Systems via Multi-Objective Genetic Algorithms

The determination of optimal Surveillance Test Intervals (STI) is a matter of great importance in risk-informed applications, due both to the implications that maintenance actions have on the safety of the risky plants such as the nuclear ones, and to the important amount of resources invested in maintenance operations by the industrial organizations. The common approach to determining the optimal STI uses a simplified system-availability model relying on a set of parameters at the component level (failure rate, repair rate, frequency of failure on demand, human error rate, inspection duration, etc.), whose values are typically estimated on the basis of few, sparse data, and can suffer from appreciable uncertainties. Thus, the prediction of the system behavior on the basis of the parameters' best estimates is scarcely significant, if not accompanied by some measure of the associated uncertainty, such as the variance. This paper proposes a multi-objective optimization approach, based on genetic algorithms, which transparently and explicitly account for the uncertainties in the parameters. The objectives considered (the inverse of the s-expected system failure probability and the inverse of its variance), are such as to drive the genetic search toward solutions which are guaranteed to give optimal performance with high assurance. For validation purposes, a simple case study regarding the optimization of the layout of a pipeline is firstly presented. The procedure is then applied to a more complex system taken from literature, the Residual Heat Removal safety system of a Boiling Water Reactor, for determining the optimal STI of the system components. The approach provides the decision maker with a useful tool for determining those solutions which, besides being optimal with respect to the s-expected safety behavior, allow a high degree of assurance in the actual system performance.

炭鉱の保安計測システムの信頼性とリスク検知効果に関する研究

Inflammable gas concentration monitoring is an important part of centralized monitoring system in coalmine. That assists safety mining operation without gas explosion or gas combustion in deeper gassy coal faces in Japanese coal mines. Experiencing serious inflammable gas related disasters, a lot of efforts had been paid on researches and developments of inflammable gas measurement systems. Considerable financial resources distributed to the installation of inflammable gas measurement system in underground coalmines. However, as Japanese mine safety management system has not employed probabilistic evaluation, the total effect of the measurement system and reliability had not been evaluated before.Therefore, the question about excess of shortage of safety measure had caused. To derive the answer to the question, the authors investigated inflammable gas measurement system of a Japanese coalmine, and analyzed its reliability, especially in instantaneous failure rates.The authors developed Fault Tree about gas explosion or combustion accidents in relation with detection failure of inflammable gases. Then, we identified failures of the measurement system using Failure Modes and Effective Analysis format.The authors collected failure frequency rates data by site measurements, interviews about error frequency, and questionnaires about humane errors.As the result of those surveys and analysis, the authors obtained the following data; yearly drift error value and error rates of automatic inflammable gas alarms (detectors), error rates of the whole automatic methane detection system, human error rates of portable interferometer type methane detectors. Based on the data, the authors calculated the total instantaneous failure rates of whole automatic methane detection system. Then compare the present system with '60th and '80th system and discussed about potential surplus rule and over safety measurement devices installation in mines.

A multiobjective genetic algorithm approach to the optimization of the technical specifications of a nuclear safety system

Abstract Systems, structures, and components of Nuclear Power Plants are subject to Technical Specifications (TSs) that establish operational limitations and maintenance and test requirements with the objective of keeping the risk associated to the plant within the limits imposed by the regulatory agencies. Recently, in an effort to improve the competitiveness of nuclear energy in a deregulated market, modifications to maintenance policies and TSs are being considered within a risk-informed viewpoint, which judges the effectiveness of a TS, e.g. a particular maintenance policy, with respect to its implications on the safety and economics of the system operation. In this regard, a recent policy statement of the US Nuclear Regulatory Commission declares appropriate the use of Probabilistic Risk Assessment models to evaluate the effects on the system of a particular TS. These models rely on a set of parameters at the component level (failure rates, repair rates, frequencies of failure on demand, human error rates, inspection durations, and others) whose values are typically affected by uncertainties. Thus, the estimate of the system performance parameters corresponding to a given TS value must be supported by some measure of the associated uncertainty. In this paper we propose an approach, based on the effective coupling of genetic algorithms and Monte Carlo simulation, for the multiobjective optimization of the TSs of nuclear safety systems. The method transparently and explicitly accounts for the uncertainties in the model parameters by attempting to minimize both the expected value of the system unavailability and its associated variance. The costs of the alternative TSs solutions are included as constraints in the optimization. An application to the Reactor Protection Instrumentation System of a Pressurized Water Reactor is demonstrated.

391. PWR総合ディジタル化システム向け中央制御盤の標準化開発と検証

The design targets of main control boards of nuclear power plants are as follows. (1) To make a good working environment where operators can operate plants easily. (2) To reduce the work load and operators human error. To this end, Mitsubishi group and Japanese PWR utilities have been improving main control boards design for next PWR plants with full digital instrumentation and control system. The main control boards consist of a soft operation console and a large display panel. According to our evaluation, the work load and human error rate of the new main control boards are reduced much compared with the latest plants.In this study, in order to establish the standard specification of the advanced main control boards, validation test of mock-up for the actual plant, from 1998 to 2001, the dynamic operator verification linked with a simulator had been executed, as well as operational know-how is being collected, and detailed standardization is executed.

The development and demonstration of integrated models for the evaluation of severe accident management strategies—SAMEM

This study is concerned with the further development of integrated models for the assessment of existing and potential severe accident management (SAM) measures. This paper provides a brief summary of these models, based on Probabilistic Safety Assessment (PSA) methods and the Risk Oriented Accident Analysis Methodology (ROAAM) approach, and their application to a number of case studies spanning both preventive and mitigative accident management regimes. In the course of this study it became evident that the starting point to guide the selection of methodology and any further improvement is the intended application. Accordingly, such features as the type and area of application and the confidence requirement are addressed in this project. The application of an integrated ROAAM approach led to the implementation, at the Loviisa NPP, of a hydrogen mitigation strategy, which requires substantial plant modifications. A revised level 2 PSA model was applied to the Sizewell B NPP to assess the feasibility of the in-vessel retention strategy. Similarly the application of PSA based models was extended to the Barseback and Ringhals 2 NPPs to improve the emergency operating procedures, notably actions related to manual operations. A human reliability analysis based on the Human Cognitive Reliability (HCR) and Technique For Human Error Rate (THERP) models was applied to a case study addressing secondary and primary bleed and feed procedures. Some aspects pertinent to the quantification of severe accident phenomena were further examined in this project. A comparison of the applications of PSA based approach and ROAAM to two severe accident issues, viz hydrogen combustion and in-vessel retention, was made. A general conclusion is that there is no requirement for further major development of the PSA and ROAAM methodologies in the modelling of SAM strategies for a variety of applications as far as the technical aspects are concerned. As is demonstrated in this project, the generic modelling framework was refined to enable a number of applications. Some recommendations have also been made regarding the applicability of these approaches to existing operating reactors and future reactors. The need for further research and development in the area of human reliability quantification was identified.

The human error rate assessment and optimizing system HEROS — a new procedure for evaluating and optimizing the man–machine interface in PSA

Abstract A new procedure allowing the probabilistic evaluation and optimization of the man–machine system is presented. This procedure and the resulting expert system HEROS, which is an acronym for Human Error Rate Assessment and Optimizing System, is based on the fuzzy set theory. Most of the well-known procedures employed for the probabilistic evaluation of human factors involve the use of vague linguistic statements on performance shaping factors to select and to modify basic human error probabilities from the associated databases. This implies a large portion of subjectivity. Vague statements are expressed here in terms of fuzzy numbers or intervals which allow mathematical operations to be performed on them. A model of the man–machine system is the basis of the procedure. A fuzzy rule-based expert system was derived from ergonomic and psychological studies. Hence, it does not rely on a database, whose transferability to situations different from its origin is questionable. In this way, subjective elements are eliminated to a large extent. HEROS facilitates the importance analysis for the evaluation of human factors, which is necessary for optimizing the man–machine system. HEROS is applied to the analysis of a simple diagnosis of task of the operating personnel in a nuclear power plant.

Trends in quality of anesthesia care associated with changing staffing patterns, productivity, and concurrency of case supervision in a teaching hospital.

The authors used continuous quality improvement (CQI) program data to investigate trends in quality of anesthesia care associated with changing staffing patterns in a university hospital. The monthly proportion of cases performed by solo attending anesthesiologists versus attending-resident teams or attending-certified registered nurse anesthetist (CRNA) teams was used to measure staffing patterns. Anesthesia team productivity was measured as mean monthly surgical anesthesia hours billed per attending anesthesiologist per clinical day. Supervisory ratios (concurrency) were measured as mean monthly number of cases supervised concurrently by attending anesthesiologists. Quality of anesthesia care was measured as monthly rates of critical incidents, patient injury, escalation of care, operational inefficiencies, and human errors per 10,000 cases. Trends in quality at increasing productivity and concurrency levels from 1992 to 1997 were analyzed by the one-sided Jonckheere-Terpstra test. Productivity was positively correlated with concurrency (r = 0.838; P<0.001). Productivity levels ranged from 10 to 17 h per anesthesiologist per clinical day. Concurrency ranged from 1.6 to 2.2 cases per attending anesthesiologist. At higher productivity and concurrency levels, solo anesthesiologists conducted a smaller percentage of cases, and the proportion of cases with CRNA team members increased. The patient injury rate decreased with increased productivity levels (P = 0.002), whereas the critical incident rate increased (P = 0.001). Changes in operational inefficiency, escalation of care, and human error rates were not statistically significant (P = 0.072, 0.345, 0.320, respectively). Most aspects of quality of anesthesia care were apparently not effected by changing anesthesia team composition or increased productivity and concurrency. Only team performance was measured; the role of individuals (attending anesthesiologist, resident, or CRNA) in quality of care was not directly measured. Further research is needed to explain lower patient injury rates and increases in critical incident reporting at higher concurrency and productivity levels.

Instruction Effect on Human Error Reduction

Results of past research indicate that instruction is one of the human performance-shaping factors (Swain & Guttmann, 1983). This study investigated further how instructions interact with task types to affect human error rates. An experiment was conducted to study the interaction effect among 60 participants. The independent variables were instruction type (conceptual and procedural), task type (high and low inference), and participants' knowledge level. Results indicated that for high-inference tasks, high-knowledge participants using conceptual instructions made less errors than those using procedural instructions; for low-inference tasks, both high- and low-knowledge participants using procedural instructions made less errors than those using conceptual instructions.

The effect of group discussion on interrater reliability of structured peer review.

The effect of group discussion on interrater reliability of structured peer review.

Performance Comparison Of Two Methods For Human Reliability Analysis

This paper considers the different results obtained in qualifying the human error rate using two différent techniques: THERP (Technique for Human Error Rate Prediction) and De-BDA (Detailed Block Diagram Analysis). The effect of dependence between both tasks and persons is considered. The theoretical differences among the methods developed are such that it is difficult to predict the nature and range of variations that could be obtained in results, if these methods are applied to compute the performance of human actions. The question of applicability is discussed.

Some statistical characteristics of a repairable, standby, human and machine system

This paper presents a model for a two-unit s-identical system with one operating-unit (OU) online and the other, warm standby-unit (SU) human machine system. The failure rates for both the OU and SU (common-cause, human error and hardware failures) are constant, whereas the repair times are arbitrarily distributed for a failed system. Linear ordinary differential equations are used to obtain a general expression for system steady-state availability for failed system by taking the repair time distributions as Gamma. Generalized expressions for system reliability, and time-dependent availability are presented. Graphs demonstrate the impact of human error on system steady-state availability for various distributions, and some physical meaning is given. As time increases, the time-dependent availability decreases for exponential repair time distribution for different values of initial human error rate.

ESAP, an easy-to-use expert system for the systematic analysis of operator actions within the scope of probabilistic risk assessment

The assessment of operator actions within the scope of probabilistic risk analyses is an important task; however, it is connected with considerable uncertainties. The aim of the expert system ESAP (an easy-to-use expert system for the systematic analysis of operator actions within the scope of probabilistic risk assessment) is the reduction of those uncertainties caused by subjectivities in using the technique of human error rate prediction (THERP) methodology. The transformation of THERP using the expert system shell knowledge engineering environment (KEE) and the input logic are briefly described as well as the calculation of error probabilities using KEE rules. The advantages of ESAP and further developments are summarised.

Stochastic analysis of a general standby system with constant human error and arbitrary system repair rates

This paper presents a mathematical model for performing reliability and availability analyses of a general standby system with constant human error and common-cause failure rates. In addition, system repair times are assumed arbitrarily distributed. Markov and supplementary variable techniques were used to develop equations for the model. The method of linear ordinary differential equation is developed to obtain the general expressions of the steady state availability. The Laplace transform technique was used to obtain the system time-dependent availability, reliability and mean time to failure expressions.