Abstract: A system includes a processor and a memory system in communication with the processor. The memory system stores instructions that when executed by the processor result in the system being operable to access an event list that defines a plurality of events and a scenario list that defines a plurality of scenarios as routes through a tree structure that includes one or more of the events for each of the scenarios. The system is also operable to build a specific risk matrix that calculates a plurality of combined probabilities based on each pairing of an occurrence of each of the events in combination with each of the scenarios. The system is further operable to output a residual probability for each of the events based on a summation of the combined probabilities for each of the events.