| A new technique called Master Logic Diagram was developed for efficient reliability analysis of complex systems. A new model has also been developed to analyze a system's reliability directly from its topology. This model is combined with the Master Logic Diagram as the proposed approach for performing PRA level-1 analysis. We have used artificial intelligence technology to develop our approach. It has been shown that the proposed approach provides significant advancement over the conventional methods of reliability risk analysis.; There are several benefits from using the MLD concept and block diagram method for Level-1 PRAs: (1) It provides a way to modularize, in a hierarchical fashion, a complex plant by its systems. (2) With the proposed method, the analyst can concentrate on the interdependencies between the different systems only. (3) Using AI techniques, one can easily recognize a graphic description of a block diagram and calculate the system's availability directly from its topology. The HPSI system discussed in chapter 6, for example, can be entered and analyzed within 2 hours. The same calculation will require at least one week of effort by the conventional method (i.e., a fault tree analysis). (4) After an MLD is built, it can be used in routine plant analyses. That includes--checking the plant's status, finding the impact of routine maintenance, and redoing the PRAs after a plant modification. An IBM-PC AT version of MLD analysis, that requires at least 5 MB RAM extended memory, has been developed; it can generate 10,000 support system sequences and can calculate their frequencies within 30 minutes. This is a substantial improvement over conventional PRAs, where such analysis may take months to finish. (5) With the help of AI techniques, some simple model-based intelligent PRA analyses can be directly performed by the computer, for example, suggesting the recovery actions. |
