A critical review of methods and models for evaluating organizational factors in Human Reliability Analysis

• Performing shaping factors modify basic probabilities by linear factors.
• Organizational factors do not model all political, economical and normative aspects.
• Interactions between organizational factors are not linear.
• Organizational factors, error mechanisms and unsafe actions interact nonlinearly.
• FRAM and STAMP are promising approaches for treating organizational factors.

This work makes a critical evaluation of the deficiencies concerning human factors and evaluates the potential of quantitative techniques that have been proposed in the last decades, like THERP (Technique for Human Error Rate Prediction), CREAM (Cognitive Reliability and Error Analysis Method), and ATHEANA (A Technique for Human Event Analysis), to model organizational factors, including cognitive processes in humans and interactions among humans and groups. Two important models are discussed in this context: STAMP (Systems-Theoretic Accident Model and Process), based on system theory and FRAM (Functional Resonance Analysis Method), which aims at modeling the nonlinearities of socio-technical systems. These models, however, are not yet being used in risk analysis similarly to Probabilistic Safety Analyses for safety assessment of nuclear reactors. However, STAMP has been successfully used for retrospective analysis of events, which would allow an extension of these studies to prospective safety analysis.