Reliability analysis of Diesel Generator power supply system of Prototype Fast Breeder Reactor

The unavailability of Diesel Generator power supply system has been evaluated using Fault tree method with ISOGRAPH reliability software and is found to be 4.75E−3 for 2/4 (DG success) and 1.47E−3 for 1/4 (DG success). Common cause failures contribute significantly to the unavailability of the system. Statistical analysis indicates that the DG unavailability is uncertain by Error Factor 4.4 (90% confidence bound) for 2 out of 4 DG system (system success) and by Error Factor 4.1 (90% confidence bound) for 1 out of 4 DG system (system success). Support systems namely Safety related service water system, Fuel oil system and circuit breaker control power supply dependency have been modeled. Results of importance analysis and sensitivity study are used to identify significant contributors to unavailability. DG fails to run, DG fails to run due to CCF and DG maintenance out of service is identified as dominant and important contributors of DG unavailability. Uncertainty analysis has been carried out through Monte Carlo simulations.