An extensive survey of computer-based systems that apply different approaches for faults diagnostics and identifications in nuclear power plants (NPPs) was presented. In the light of reviewed material, the classification criteria were developed. The classification of computational techniques (class of computing devices, class of programming languages, and simulation programs) was discussed. The classification of theoretical aspects applied (brief aspects, and detailed aspects) in computer-based diagnostic systems were established. The classification of metholology applied (symbolic reasoning methodology, event-based methodology, and function-based methodology) in the diagnostic systems was also depicted. In the end, the personal comments on the reviewed material, and scope of the study were described.