Nuclear power plant designs are based on the defense-in-depth concept. Therefore, there are multiple paths to recover the plants in emergency situations even if some components are unavailable. A system that generates the optimal success path and supports the plant operator in emergency situations is developed based on integrated reliability rules, which are expressed by the unavailabilities of success paths. These rules include the probabilities of hardware failure and human error. The system can be operated in real time because the path sets are generated and stored in a data base in advance. Results of previous plant risk and system reliability analyses are incorporated. The system is tested for a typical auxiliary feedwater system. The concepts developed can be used as tools for operator training, emergency recovery, and severe accident management planning.

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