Application of FMEA and FTA techniques for assessing the occurrence of LOCA in a TRIGA MARK I Reactor

Abstract

This study presents a framework merging failure mode and effect analysis (FMEA) and fault tree analysis (FTA) techniques to evaluate loss of coolant accident (LOCA) in the Brazilian Reactor TRIGA IPR-RI. At first, FMEA identified failure modes and prioritized risk management based on the risk priority number (RPN). Subsequently, FTA established logical relationships between these failure modes, revealing minimal cut sets. Results indicated that the path involving “loss of coolant from reactor tank” correlate to an externally caused leak, exhibiting a low probability and, consequently, a low RPN. On the other hand, the path involving “loss of coolant through primary circuit rupture without a pump shutdown” highlighted high RPN due to the lack of shutdown signals from the monitoring indicators. Finally, FTA unveiled that LOCA associates with a primary circuit rupture and the simultaneous failure of safety mechanisms, including ultimately human error.