Analysis of acoustic leak signals for enhancing sensitivity of control due to the creation of effective diagnostic indicators

Acoustic leak control systems (for instance, SAKT) are used at present for controlling leak tightness of equipment and pipelines, as well as for detecting in timely manner coolant leaks from the primary cooling circuit of nuclear reactor installations (NRI) during operation of power unit on different power levels in the modes of normal operation and during disturbances of normal operation. Time averaged dispersion of acoustic signal is used as the main diagnostic indicator for detecting leaks in these systems. Sensitivity of this indicator is determined by the exceedance by the signal of the preset threshold value which is defined in accordance with the background. Here, background values of acoustic signal depend on the operational modes of the equipment and do not allow in many cases determining coolant leak during early stages of leak development. New approach to the formation of diagnostic indicators for detecting loss of sealing in the circuit during early stage of development of coolant leak is suggested. Methodology for obtaining diagnostic indicators is based on the processing in different frequency bands of acoustic signal accompanying coolant leakage from the pipeline using the method of principal components. Efficiency of the developed methodology of coolant leak detection is illustrated by processing acoustic signals for experimental facility modeling coolant leakage in case of loss of sealing of the circuit. Even in the presence of significant acoustic background sensitivity of the method allows detecting leaks with significantly lower flow rates (up to five times smaller) than the conventional processing of acoustic signals. Implementation of the developed methodology will not require significant expenditures for upgrading already existing leak control systems operated at present on different NPPs.

Development of the Pump-Integrated Intermediate Heat Exchanger in Advanced Loop-Type Sodium-Cooled Fast Reactor for Demonstration

In the framework of generation IV international forum (GIF), safety design criteria (SDC) and safety design guideline (SDG) for the generation IV sodium-cooled fast reactors (SFRs) have been developed as part of the worldwide deployment of SFRs. Japan Atomic Energy Agency (JAEA) and the Mitsubishi FBR Systems, Inc. (MFBR) have been investigating design study of an advanced loop-type SFR to satisfy SDC in the feasibility study of SDG for SFR. In this study, the ability of the pump-integrated Intermediate Heat Exchanger (IHX) is evaluated as a safety measure for the advanced loop-type SFR. Furthermore, maintainability and reparability of the safety measures are taken into account for the advanced loop-type SFR design study. The pump-integrated IHX has been modified to satisfy these requirements. This paper describes the modifications to withstand severe earthquake, primary coolant leak and sodium-water reaction. Also, this paper includes evaluations of thermal transient, structural vibration with pump rotation and wear-out of IHX tubes for they have been adversely affected by the modifications.

Recording Oil's Vital Signs

This article focuses on efforts that are aimed at developing on-board systems to measure oil quality in real time or, at least, to base predictions on specific, observable conditions. A reliable means of monitoring the condition of engine oil will permit a new kind of just-in-time maintenance, and that, according to some forecasters, could save millions of quarts of oil a year. Although car companies schedule oil changes along conservative time frames, some experts say strictly schedule-based maintenance doesn't solve the problems of premature lubrication failure. The article also highlights that an on-board capacitive sensor developed by Kavlico assesses oil quality by measuring the oil's dielectric constant, which increases as molecules break down and additives deplete with use. It is stressed that a combination of measurements will present a truer picture of oil degradation than just one measurement. A combined approach of monitoring driving conditions and using sensors has been taken by DaimlerChrysler of Stuttgart, Germany. The company has developed a passenger car maintenance system, called Assyst, for Mercedes-Benz vehicles. The dielectric number can warn the driver that water is present in the sump or a coolant leak is occurring in the engine.