Fire Safety Science Digital Archive

We conducted a reliability analysis of the Mocho water-supply system for the Lawrence Livermore National Laboratory (LLNL) to determine if an adequate supply of water would be available in the event of a major fire. We used the digraph fault-tree approach for logic model generation. The initiating-enabling event interval reliability approach was used for a probabilistic evaluation of the Mocho system fault tree. In the event of a major fire, the Mocho system demand unavailability was calculated to be 3.6 x .0001. We identified 16 single-component failures that would cause failure of the control loop which monitors storage-tank level. These failures would go undetected by monitoring personnel at LLNL. Our recommended changes would provide a redundant measurement of the tank level, resulting in a decrease of the predicted system unavailability by about a factor of 50.