Oliver Sträter

Assessment of human reliability based on evaluation of plant experience: requirements and implementation

A major problem in assessment of human failures in probabilistic safety assessment is the lack of empirical data needed for human reliability analysis (HRA). This problem is aggravated by the fact that different HRA methods use different parameters for the assessment and that HRA is currently enforced to provide data and methods for assessment of human reliability in new technical environments such as computerized control rooms, in accident management situations, or in low-power and shut down situations. Plant experience is one source to deal with this problem. In this paper, a method is presented that describes how plant experience about human failures and human performance may be used to support the process of analyzing and assessing human reliability. Based on considerations of requirements of HRA, a method is presented first which is able to describe and analyze human interactions that were observed within events. Implementation of the approach as a database application is outlined. Second, the main results of the application of the method to 165 boiling water reactor events are presented. Observed influencing factors on human performance are discussed; estimates for probabilities are calculated and compared with the data tables of the THERP handbook. An outline is given for using the presented method for the analysis of cognitive errors or organizational aspects.

Considerations on the elements of quantifying human reliability

Abstract This paper attempts to provide a contribution for the discussion of what the term ‘data’ means and how the qualitative perspective can be linked with the quantitative one. It will argue that the terms ‘quantitative data’ and ‘qualitative data’ are not distinct but a continuum that spans over the entire spectrum of the expertise that has to be involved in the HRA process. It elaborates the rational behind any human reliability quantification figure and suggests a scientific way forward to better data for human reliability assessment.

Human-centered modeling in human reliability analysis: some trends based on case studies

As an informal working group of researchers from France, Germany and The Netherlands created in 1993, the EARTH association is investigating significant subjects in the field of human reliability analysis (HRA). Our initial review of cases from nuclear operating experience showed that decision-based unrequired actions (DUA) contribute to risk significantly on the one hand. On the other hand, our evaluation of current HRA methods showed that these methods do not cover such actions adequately. Especially, practice-oriented guidelines for their predictive identification are lacking. We assumed that a basic cause for such difficulties was that these methods actually use a limited representation of the stimulus-organism-response (SOR) paradigm. We proposed a human-centered model, which better highlights the active role of the operators and the importance of their culture, attitudes and goals. This orientation was encouraged by our review of current HRA research activities. We therefore decided to envisage progress by identifying cognitive tendencies in the context of operating and simulator experience. For this purpose, advanced approaches for retrospective event analysis were discussed. Some orientations for improvements were proposed. By analyzing cases, various cognitive tendencies were identified, together with useful information about their context. Some of them match psychological findings already published in the literature, some of them are not covered adequately by the literature that we reviewed. Finally, this exploratory study shows that contextual and case-illustrated findings about cognitive tendencies provide useful help for the predictive identification of DUA in HRA. More research should be carried out to complement our findings and elaborate more detailed and systematic guidelines for using them in HRA studies.

On the way to assess errors of commission

Abstract In January 2002, the OECD-NEA (Organization for the Economic Cooperation and Development, Nuclear Energy Agency) Working Group Risk (WGRISK) held a workshop at on Human Reliability data needs and potential solutions. The workshop was initiated to exchange the possibilities to proceed in the area of assessing errors of commission, those interventions of operators that are not required from the system point of view and aggravate the scenario evolution. A common sense in the research on errors of commission is that the respective HRA methods require a more profound database than the classical HRA methods. This paper summarizes the discussion of the workshop. It discusses the various data sources and their use in HRA, the problems that make it difficult to get appropriate data for HRA, and possible approaches to overcome this bottleneck in HRA.

Human reliability analysis: data issues and errors of commission

These areas are related to the issue of errors of commission (EOC), i.e. those human actions, which are not required from the system point of view and aggravate the scenario evolution. Errors of commission are also strongly linked to organizational factors of safety, because the decision processes underlying the human actions are often due to organizational misconceptions. Assessing errors of commission and organizational issues increases the importance of valid and reliable HRA data regarding these issues, from the qualitative as well as the quantitative side. Qualitative HRA data are needed in order to support the modeling of appropriate HRA models and search schemes. Quantitative data are needed then to enable quantification within a PSA framework. This special issue of Reliability Engineering and System Safety attempts to summarize the spectrum of approaches and recent achievements in research and development of HRA methods for errors of commission. As rich as the issue itself is the content of this special issue. A range of issues in the assessment of EOCs is covered:

Systemic assessment of the effect of mental stress and strain on performance in a maritime ship-handling simulator

Abstract Two studies will be presented as part of a systemic approach for assessing performance in nautical simulators. A mixed-methods quasi-experimental field study (N=6) was conducted, aiming at discerning the systemic causes behind nautical students’ human errors during simulator exercises and to what extent these causes can be related to the layout of a new decision supporting display. Results indicate that all errors occur under the same kind of (demanding) man-machine interaction. Based on this, design requirements were proposed. The second study aims at exploring the impact of situation-related affective arousal on system safety. Anger- and frustration-like situations will be generated and the possible impact of these affect-laden situations on the risk- and error-related performance of simulator ship bridge crews assessed. The studies address different aspects of performance in complex environments and their modularity towards each other will be highlighted in the context of an overall systemic perspective.

Gesundes Führen für effiziente Organisationen der Zukunft

Die psychologischen Aspekte einer guten Fuhrung sind seit Jahrzehnten recht gut erforscht. Beispielsweise ist bekannt, dass der Entscheidungsspielraum ein wichtiges Kriterium fur Arbeitszufriedenheit und Produktivitat ist (z. B. Ulich 1994). Dennoch andert sich – trotz zahlreicher Seminare zum Fuhrungsverhalten, welche die derzeitigen Erkenntnisse zusammenfassen – in den Organisationen hinsichtlich der Fuhrungsqualitat nur wenig. Dies zeigt sich in einer Reihe von empirischen Befunden (Zusammenfassungen z. B. in Kromm und Frank 2009). Insbesondere weist der Gesundheitsreport des Bundesverbands der Betriebskrankenkassen seit 2009 mehr als 10 % der Arbeitsunfahigkeitstage von Mitarbeitern und Fuhrungskraften uber alle Berufssparten dem Aspekt schlechter Fuhrung zu. Krankheit ist jedoch nur die Spitze des Eisberges einer ineffizienten Organisation; ungesunde Fuhrung hat fur einen Betrieb hinsichtlich Motivation, Produktivitat und Qualitat bereits weitaus fruher Folgen. Vor diesem Hintergrund befasst sich der Artikel zunachst mit den kognitiven Grunden fur ineffiziente Fuhrung und der Verbindung von Fuhrung und Gesundheit. Er zeigt auf Basis dieser Zusammenhange ein kognitiv-emotionales Erklarungsmodell, warum wir als Menschen immer wieder in ungesundes Fuhrungsverhalten verfallen.

Responsibilities and Challenges of Human Reliability Assessment in the Regulatory Framework

Human Reliability Analysis (HRA) within the Probabilistic Safety Assessment (PSA) has a challenging role for ensuring the safe operation of complex systems in the future. The paper will discuss this role and the resulting responsibilities with emphasis on the responsibilities and roles of regulators.

Analysis of Dynamic Performance Data for the Assessment of Cognitive States: Results from Aviation, Assembly Tasks and Maritime Transportation

The rapid development and application of biometric recording devices has resulted in a plethora of human performance data in various industry settings. This article will demonstrate how the data generated by these recording devices can be used for inferring cognitive states in a variety of field settings and thus applied complementary to traditional data collection methods. The authors will present results from several studies demonstrating how data from portable motion and eye tracking devices can be used to assess three main aspects: the transition between safety-relevant cognitive coping strategies by pilots in aviation, the onset and time-based development of worker mental fatigue in assembly tasks and the time-based impact of situation-induced affective states on visual attention and decision-making in maritime transportation. Furthermore the paper outlines the underlying theoretical framework (the cognitive processing loop; Strater (2005) Cognition and safety: An integrated approach to systems design and assessment. Ashgate, Aldershot). The benefits of this kind of approach will be demonstrated by showing how work systems can be improved by providing a better fit between cognition and workplace design.

Safety Culture Assessment — Methods and Indicators, Results of a German Research Project

The method for development of practical criteria for safety culture assessment — based on event orientated safety culture assessment — is a promising approach in the current situation. The event orientated assessment of the root causes of real events is based on the assumption that events in a nuclear power plant are indicators for deficiencies in safety culture.