Diagnosis systems in nuclear power plants developments and applications

With the progress in on-line digital data processing and the availability of powerful process computer systems a new dimension of plant monitoring has been opened. Besides introducing information presentation by color screens and its consequence for control room design, new types of condensed information has been made available by using the potential of computers, e.g. status surveillance, computerized operational manuals, success path monitoring. One of the important items necessary for these new systems are methodologies to recognize the deviations from normal operation or normal behaviour of components in an early stage. While on-line early failure detection in the beginning have been developed as separate systems (e.g. process disturbance analysis, vibration monitoring), it has been recognized later that they play a key role in plant monitoring and therefore have to be integrated in the plant information system. In this sense the paper deals with early disturbance and failure diagnosis and outlines developments and applications in German nuclear power plants, with emphasis on work performed at GRS and IST. Beginning with principles of an overall information concept, the methodologies and systems are treated in two main chapters: System/process diagnosis comprising system status surveillance and integrated disturbance analysis, considering also recent progress in developing a real-time on-line expert system, and early diagnosis of component failures or malfunctions comprising vibration diagnostics (passive systems and rotating machinery) and loose parts monitoring. In the appendix basic viewpoints on on-line real-time expert systems are given. (author). 16 refs, 13 figs