Integrated Facility Assessment Simulation, 20-R9728Printer Friendly Version
Inclusive Dates: 07/01/07 09/11/08
Background - For years, nuclear materials, chemical production and petroleum refining industries have performed assessments to identify hazards in these facilities and make them safe for workers and the surrounding public. Despite these efforts, unexpected events at times have led to accidents resulting in serious injuries, loss of life and catastrophic damage to the facilities. Post-accident investigations sometimes show that hazard assessments for these facilities inappropriately assume ideal worker or operator response in emergency situations such as "the operator will follow the procedures" or "the operator will be trained." When ideal responses are assumed, the potential consequences of adverse actions are assumed to no longer exist. More broadly, such assessments may not adequately account for human error among trained, experienced workers.
Approach - This research focused on developing a new Integrated Facility Assessment (IFA) approach that increases the realism of safety assessments and accounts for different ways in which human operators can perform their assigned tasks. In support of this research objective, an integrated approach, a simulated state-transition model, and an IFA prototype simulation based on SwRI®-developed composable behavior modeling techniques were developed for evaluation purposes. Researchers compared the results from this integrated approach, implemented using both a state-transition model and the IFA prototype simulation, to the results from a traditional assessment conducted as part of this project.
Accomplishments - The IFA approach was successfully developed and implemented using a simulated state-transition model developed in MATLAB®. This model bridged the gap between traditional assessments using event tree and fault tree analysis techniques and an IFA simulation of a facility. In particular, the model identified cases that highlight the advantages of the IFA approach over the traditional approach. Researchers used this model to assess variations in the quality of a maintenance program and found a significant increase in the frequency of an undesirable event when maintenance actions were missed even a small percentage of the time. The findings from the state-transition model highlight the importance of increasing realism in safety assessments to improve results, quantitatively compare the effects of the safety culture (or lack of) in industrial applications, and show how human errors can contribute to failure even in the best managed facilities.
Based on the hazards assessment analysis, an IFA prototype simulation was designed with a limited set of equipment and human behavior models to demonstrate the potential for this new approach. The prototype simulation models a generic, reconfigurable representation of a facility defined by specifying its workflow as a series of tasks with a set of probabilities of successful task completion and times to complete each task. The software simulation framework provides the capability to incorporate additional features and functionality for more advanced cause-and effect analysis in future studies.