[en] Experience with maintenance and diagnostics at Angra 1 is described including the following issues: predictive maintenance program at Angra 1 NPP; Angra 1 predictive maintenance master list; maintenance evolution at Angra 1 NPP; MOVs evaluation program

[en] The aim of the Technical Committee Meeting (TCM) was to review developed systems and methods in diagnostics in the scope of their impacts and importance to the safety of Nuclear Power Plants. Papers presented on TCM came from different sources, from developers, from manufacturers, from licensing authorities and from NPP personal. They reflect up to date status in the given subject. Participants of TCM formulated three working groups to elaborate different questions which were raised during the discussions. Their results are reflected in the three chapter titles of the given material. Annex 1 to this document contains presentations made at the Technical Committee Meeting. Refs, figs, tabs

[en] The experience of the Russian EDO ''Gidropress'' of using diagnostic systems for WWER type reactor NPPs and problems with implementation are discussed in the presentation. 3 refs, 5 figs

[en] The ''Frequency Plan'' worked out for the Czech Power System specifies a set of preventive measures along with the set of the frequency ranges. This problem was solved in details for the Dukovany nuclear power plant. The design changes under preparation support a reliable as well as safe operation in the island-operation mode until a full restoration of the whole power system. The design modifications are based on the following three main innovations: An incorporation of the FREA 16 frequency relay into the protection circuits; large modifications in turbine control loops; installation of software routine for the operator to support the island operation mode. The capability of the island operation has been demanded by relevant regulations both for the operating units and for that under construction. The capability can be tested under the transition to houseloads, as well as through the direct simulation of abnormal grid conditions. 1 fig

[en] Monitoring of a power plant is one of the essential tasks during operation and the computer-based implementations are nowadays seemingly quite mature. However, presently these are still not satisfactory enough to meet the high standards to the licensing requirements and they are mostly not truly integrated to the plant's design-based monitoring system. This is basically due to the robustness problem as the majority of the methods are not robust enough for the monitoring of the safety parameter set in a plant or intelligent supervision. Therefore, a supervisory monitoring system (SMS) in a plant is necessary to supervise the monitoring tasks: determining the objectives to be obtained and finding the means to support them. SMS deals with the changing plant status and the coordination of the information flow among the monitoring subunits. By means of these robustness and consistency in monitoring is achieved. The paper will give the guidelines of knowledge and data management techniques in a framework of robust comprehensive and coordinated monitoring which is presented as supervisory monitoring. Such a high level monitoring serves for consistent and immediate actions in fault situations while this particularly has vital importance in preventing imminent severe accidents next to the issues of recognition of the monitoring procedures for licensing and enhanced plant safety. (author). 8 refs, 5 figs

[en] In this paper our aim is to give very short introduction on different types of well selected noise diagnostics methods and then mentioning their occurrence in WWER reactors we analyze what impact they might have to operational safety and for ageing (which also affects on safety of the installations). We do not deny, that one of our main aim is to call the attention of management staff of NPP, which deals with safety, safety culture, maintenance and operation proving, that such methods and system can give not only benefit to economy but also impact on safety of nuclear installations. 14 refs, 6 figs

[en] The modern diagnostic systems for loose parts, vibration and leakage monitoring of Siemens marked improvements in signal detection, ease of operation, and the display of information. The paper gives an overview on: Loose parts monitoring system KUeS '95 - a computer-based system. The knowledge and experience about loose parts detection incorporated into this system can be characterized as ''intelligence''. Vibration monitoring system SUeS '95 - a fully automated system for early detection of changes in the vibration patterns of the reactor coolant system components and reactor pressure vessel internals. Leak detection system FLUeS - a system that detects even small leaks in steam-carrying components and very accurately determines their location. Leaks are detected on the moisture distribution in a sample air column into which the escaping steam locally diffuses. All systems described represent the latest state of technology. Nevertheless a considerable amount of operational experience can be reported. (author). 5 refs, 10 figs

[en] Safety assessment of the primary system and its components with respect to their mechanical integrity is increasingly supported by acoustic signature analysis during power operation of the plants. Acoustic signals of Loose Parts Monitoring System sensors are continuously monitored by dedicated digital systems for signal bursts associated with metallic impacts. Several years of ISTec/GRS experience and the practical use of its digital systems MEDEA and RAMSES have shown that acoustic monitoring is very successful for detecting component failures at an early stage. Advanced powerful tools for classification and acoustic evaluation of burst signals have recently been realized. The paper presents diagnosis experiences of BWR's and PWR's safety assessment. (author). 7 refs, 8 figs

[en] For realization of leak detection of input pipelines and output pipelines of RBMK reactor the method, based on detection and control of acoustic leak signals, was designed. In this report the review of methods of processing and analysis of acoustic noise is submitted. These methods were included in the software of the leak detection system and are used for the decision of the following problems: leak detection by method of sound pressure level in conditions of powerful background noise and strong attenuation of a signal; detection of a small leak in early stage by high-sensitivity correlation method; determination of a point of a sound source in conditions of strong reflection of a signal by a correlation method and sound pressure method; evaluation of leak size by the analysis of a sound level and point of a sound source. The work of considered techniques is illustrated on an example of test results of a fragment of the leak detection system. This test was executed on a Leningrad NPP, operated at power levels of 460, 700, 890 and 1000 MWe. 16 figs

[en] HUmidity MOnitoring System (HUMOS) has been developed and designed to detect the presence of leak in selected primary circuit high energy pipelines and components that are evaluated from the point of view of Leak Before Break (LBB) requirements. It also requires to apply technical tools for detection and identification of coolant leaks from primary circuit and components of PWRs reactors. Safety significant of leaks depend on: leak source (location); leak rate, and leak duration. Therefore to detect and monitor coolant leaks in to the containment atmosphere during reactor operation is one of important safety measures. As potential leak sources flange connection in the upper head region of WWER reactors can be considered. HUMOS does not rely on the release of radioactivity to detect leaks but rather the relies on detection of moisture in the air resulting from a primary boundary leak. Because HUMOS relies on moisture and temperature detection, leaks can be detected without requiring the reactor to be critical. Therefore leaks can be detected during integrity pressure tests and any other mode of operation provided the reactor ventilation system is operating and primary circuit and components are pressurized. 3 figs