NDTnet 1998 Aug, Vol.3 No.8

Abstract

The results of developing vibroacoustic and acoustic-emission piezoelectric transducers for leak detection systems ( hermetic nature testing) of primary tuned circuits in nuclear power plants (NPP) are presented. AP200 vibroacoustic transducer based on the three-layer ( piezoceramics - titanium - damper) sensitive element in the form of membrane rigidly frame fastened in the outside circuit has been chosen as the base model. The sensitive element center is provided with the fastened wave guide of high - strength ceramics, which transmits wave vibrations of the tested surface. The piezoelement providing a differential electric signal output is separated into two zones equal in areas, which are bounded by disk - and ring - shaped electrodes. AP200 transducer is capable of selecting waves having a crest - like periodic configurations Lamb and Rayleigh waves) out of the mechanical equipment noise caused by turbulent heat carrier motion, cavitation and boiling. When Lamb or Rayleigh waves propagate, electric signals form disk- and ring - shaped electrodes add together, and when body waves fall they are suppressed. There are given the results of comparison tests opf AP200 transducer and receivers of body and surface waves, which are based on piezoelements having a short cylinder form. The amplitude - frequency - responses of transducers are described. They have been measured using a metrological facility and bench - leak simulators having the water flow rate within 120 - 350 1/h and through holes lmm - 2.5mm in diameter.Detection of such leaks at an early stage of their evolution makes it possible to prevent global design - basis accidents resulting in an instant pipeline break.

At the same time there is presented a new method of calculating ultrasonic piezoelectric receiving transducers, which is based on the piezoelement electroelasticity analysis. In this case the sensitive element is in the volume stressed condition. The method allows design and arrangement parameters of sensors to be optimized with regard to input circuits of the amplifying - transducing instrumentation.

Abstract Source:
Book of Abstracts, 7th European Conference on Non-Destructive Testing, 26-29 May 1998, ISBN: 87-986898-0-00

Full-Text Source:
Proceedings of the 7th European Conference on Non-Destructive Testing, 26-29 May 1998, ISBN:

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