Overview of Recent KFKI AEKI Activities in the Field of Plant Surveillance and Diagnostics

Abstract

Application of noise diagnostics techniques for the regular surveillance of the four VVER-440/213 type reactors of the Paks NPP (Hungary) has long time traditions at KFKI AEKI. In the eighties (shortly after the commissioning of the four units) the AEKI has designed, manufactured, installed and utilised a reactor noise diagnostics system (PDR, see [5]), which was capable of measuring a limited number of selected in-core or ex-core detectors simultaneously. Later the PDR system was modified to incorporate new services (e.g., acoustic leakage detection and vibration monitoring), this new version was installed at Units 3–4 of the Paks NPP in 1993 (CARD, see [6]). However, an important limitation still existed: the number of available in-core input signals for noise diagnostics was limited by the cumbersome hardware coupling. This problem was eliminated by the installation of a new signal coupling system connected to the VERONA core monitoring system [3]. This noise signal coupling system offers the possibility to connect any in-core signal group (arbitrary selected from 252 SPN detectors, 210 assembly outlet thermocouples, etc.) to the noise analysis system through well-conditioned data channels, passing AC and DC signal components alike. The actual number of signals depends on the hardware used for primary noise signal processing (e.g., for A/D conversion), routinely 18 or 32 signals are handled simultaneously by the present noise analysis system. This powerful in-core noise signal coupling system is in use still today, regular measurements are performed by two noise analysis configurations: one system is devoted to Units 1–2, while the other is used for Units 3–4. Actually the hardware components and software modules of these configurations can be considered as a mixture of those originating from the CARD system [6] and the JEDI system [7]. The JEDI was an ambitious project conducted by KFKI AEKI in the mid-nineties: the basic aim of the project was to build a system incorporating most of the proven noise analysis and signal validation methods in a unified shell. However, only the prototype of the system was developed, its application in the NPP was only partly realised.