The ω-factor approach for modeling the influence of organizational factors in probabilistic safety assessment

A model for assessing the influence of organizational factors on reliability of components and on operator performance is proposed for explicit inclusion of organizational factors in probabilistic safety assessment (PSA) of nuclear power plants. The structural and behavioral aspects of organization are modeled and factors directly influencing the quality of plant personnel in their interaction with plant hardware have been identified and their relationships with the elements of the organization model are considered. A modular structure of the organizational factors has been introduced which simplifies the quantification of the measure of their impact on workers´ performance. The result of this quantification is used to determine the amount of increase in equipment failure rate and human error probabilities due to organizational factors. In addition the nature of dependencies of events modeled in probabilistic safety assessment due to organizational factors is explored and a method for factoring these dependencies is proposed