Probabilistic assessment of fire related events in CWPH (Pilot study)

As a part of Fire PSA for KAPS, a pilot study has been taken up identifying CWPH as the important zone vulnerable to fire. As the CWPH houses pumps belonging to all important cooling (APWC, FFW, NAHPPW, NALPW, etc.) of both the units, a single fire leads to failure of multiple safety/safety support system cooling affecting the safety of the plant. The objective of this study is as follows: Familiarising with the various published Fire-PSA study, comparing and finalisation of the computer code amongst various codes available with DAE, identifying and sequencing different activities involved for carrying out Fire PSA, i.e. Zoning and Sub-Zoning of Fire Source Area, Fire vulnerability of System and Component surrounding Fire Source, etc., finalization of report format and documentation. Computer Code FDS is used to carry out Fire Hazard Analysis. FDS is the latest state-of the-art software package extensively used for Fire Hazard Analysis. It develops a 3D scenario for any given fire giving credit to actual physical location of fire load and ventilation. It gives the time dependent of any fire in a specific zone crediting the time required by operator to take necessary preventive action which helps in quantifying the probability of error for any particular operator's for PSA study. To identify the most vulnerable sub-zone in CWPH, a walk down was organized and physical location of each load; their separation, fire barrier, ventilator in the room, arrangement of fire protection/fighting system, localized operator's room were reviewed. Fire in the middle diesel tank with pump is considered as initiating event in the sub-zone of CWPH. The Event Tree for this initiating event for CWPH was developed. Event Tree end states are identified as large fire i.e. fire which is failed to be detected by both means, i.e. early and late and failure in fighting by both means i.e. early and late. (author)