An analysis of the interdependence between human actions in case of research reactors

To identify, evaluate and estimate the contribution of the human factor in case of research reactor operation, the Human Reliability Analysis (HRA) is used. An important step in HRA is the dependence level analysis between the human actions, a step in quantitative analysis of the human error probabilities. The dependence may occur between actions performed by the same person or between the actions performed by different persons (the situation in which the probability of failure (success) per action is different depending on whether a failure or success occurred for the other action). The necessary information was obtained from operating experience of research reactor TRIGA of INR Pitesti. The required data were obtained from generic databases. This analysis is realized through the following two methods: Standardized Plant Analysis Risk Human Reliability Analysis (SPAR-H) and Techniques for Human Error Rate Prediction (THERP), respectively. After performing this analysis the conditional human error probabilities (CHEP) and joint human error probabilities (JHEP) were estimated. The achieved sensitivity analyses determine human performance sensitivity for systematic variations of the dependence levels between human actions. The human error probabilities estimated in this paper are adequate values for integration both in HRA and in PSA performed for TRIGA reactor. Thus this analysis helps finding the impact of human factor upon system availability, reliability and safety and hence to establish the ways of reducing the likelihood of human errors. (authors)