Study on the diagnostic system of nuclear power plants

When the accident experiences occurred so far in actual engineered system are analyzed, in most cases, first the symptom of abnormality appeared, and in the process of the development of this abnormality, the misjudgement and mishandling of operators arose, thus the abnormality developed into accident. The diagnostic techniques for nuclear power plants are those for detecting abnormality quickly and taking the appropriate countermeasures, and are rated as the software techniques for safety and reliability. To achieve the role, monitoring board, alarm system, safety protection system and so on are equipped in nuclear power plants, but also the jobs depending on skilled operators are many. The research concerning the diagnostic techniques for nuclear power plants has been made on the diagnosis using noise analysis, cause consequence tree (CCT) analysis, multi-variable analysis and condition presumption, and real time accident tracing simulators. These techniques are explained. The systems being developed for the application to nuclear power stations are composed of the diagnosis part analyzing observable signals and the man-machine interface transmitting the results of diagnosis to operators. (Kako, I.)