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*; ; ; ; Fukami, Akihiro*; *; Igawa, Kenichi*
PNC TN9410 91-175, 52 Pages, 1991/05
An acoustic detection method is one of the FBR reactor core malfunction detection methods, and is regarded as being promising. In this study, the preliminary experiment of boiling detection by acoustic method was conducted at JOYO to measure the acoustic signal level and to investigate the applicability of the acoustic method. The experiment was performed on June 13 and 14, 1990 during the 8th periodic inspection of JOYO. The results obtained though the experiment are as follows: (1)Sodium bubbling (boiling) induced by the electric heater was detected as the fluctuation of temperature single of the thermocouple attached to surface of the electric heater. (2)Bubbling single of the acoustic detector could not be identified cleary because of the high background noise caused by the primary main pump vibration, sodium flow in the reacter vessel and the electric supply in the containment vessel. (3)The correlation between the signal of the acoustic detector or the fluctuation of temperature signal of the thermocouple and the flow rate of the primary loops was not ascertained. It became clear through this study that the validity of the reactor core malfunction detction by acoustic method depend on the peculiar noise level in the reactor vessel, and the reduction of noise is the subject for a future study.
Shimoyama, Kazuhito; Kuroha, Mitsuo; *
PNC TN9410 87-014, 103 Pages, 1987/01
Acoustic type water leak detectors have promising potentiality in short detection time for minimising the extent of tube failure propagation caused by water leakage from a heat transfer tube of an LMFBR steam generator. Two different methods as follows were studied in this program : (1)The method to compare effective values between water leak sound and back ground noise using a single channel. (2)The method to detect and locate the leak using cross correlation signal processing of multi-channel. In the former one, it was estimated from acoustic signals obtained in the 50 MW Steam Generator Test Facility that the back ground noise levels of the Prototype and the Demonstration reactor were 0.0093G and 0.012G (G=gravity), respectively. The water leak rates equivalent to those back ground levels were evaluated as approximately 0.7 and 7 g/sec. In the latter one, first a detection and location software was developed in a off-line analysis, and secondly an on-line signal processing hardware was manufactured as a trial. In the off-line analysis, the influence of the internals on detection performance was examined by horizontal and vertical measurement. As the result, it revealed that back ground noise interfered the leak detection and location and that the potential depended on the leak positions even without noise. In the on-line analysis, leaks in a lower plenum were detectable with the same accuracy as the off-line analysis.
