Plant specific fire PSA considering measures taken to lower fire hazard and improved core damage frequency in a model plant

Fire PSA is a probabilistic analysis of fire events and their potential impact on the nuclear safety of a plant. Using probabilistic models, fire PSA takes into account the possibility of a fire at various plant locations (zones); the detection and suppression of the fire; the effect of the fire on safety related cables and equipment; the possibility of damage to these cables & equipments and assessment of the impact on plant safety. Understanding of different zone details such as physical geometry of the zone, distribution and layout of the equipment, spatial distance between different fire loads, arrangement of fire alarm system, arrangement of fire fight system and the provision for fire barriers to mitigate fire from further growth is essential for a good and complete fire PSA. Fire events are generally common cause events, and may cause the failure of multiple systems or components required to maintain the plant in a safe state, that would otherwise be considered to be independent of each other, required to maintain the plant in a safe state. The progression of a fire event from its initiation to severe core damage is very complex, with a very high correlation on the types of components and their physical proximity to each other. The PSA of fire events starts with the identification of the basic cause of the fire event, and then examines the impact of the IE on the systems that maintain the plant in a safe state. This identifies the systems that could be lost as a result of the fire and the probability with which they may be lost. This information is used to conjunction with modified internal event PSA system models, in order to quantify the plant damage Severe Core Damage Frequency (SCDF). The present paper discusses the plant specific study of FIRE HAZARD, defences taken at the plant level which lowers the fire hazard and it´s final impact on the CDF (Core Damage Freq.) calculated through FIRE PSA.