An Initiating Event is a postulated trigger event that creates a disturbance in the plant and calls for a reactor trip or power reduction. The event has a potential to lead to an accident sequence depending on the successful operation or failure of the various mitigating systems. An internal initiating event is one of such trigger events mainly caused by random component failures from within the plant systems. Internal Initiating Events are usually classified as Transients, LOCAs and Special Initiators.
For each of the initiating events identified, the plant response is determined and modelled in terms of sequence of events that lead either to a successful state or to a core damage state depending on success or failure of safety and support systems (typically using event tree concept). System failure modes and unavailabilities are modelled by using fault tree concept which is a top down approach identifying all the combinations of component / logic failures / maintenance unavailabilities that result in overall system unavailability.
Our consultants have extensive experience in development of full-scope PSA models for various clients covering initiating event analysis, accident sequence progression, system fault tree development, data analysis & parameter estimation, common cause failure analysis, human reliability analysis, quantification, sensitivity and uncertainty analyses.
