The effect of pond radiation levels on the response of ultrasonic transducers containing a polymer piezoelectric layer

The AECL random coil seal is to be used as a Nuclear Safeguards seal to deter and detect tampering with nuclear material in store. To be effective the ultrasonic signature from the seal must remain constant and be different from that of other seals. One established factor in the variability in the ultrasonic response from the same seal over a period of time is the variability of the ultrasonic transducers used to interrogate the seal. A possible solution to the problems of transducer variability is to use transducers based on one of the polymer piezoelectric materials rather than the usual ceramic piezoelectrics. Transducers of this type have been shown to be less variable and, being of a broader bandwidth than the ceramic-based alternatives, their response is under the control of the transducer driving circuit. The polymer material polyvinyledene fluoride or PVdF is widely available and is considered here as an alternative. As a piezoelectric material it is less efficient than typical ceramics but this is of little importance in the seal application where signal-to-noise ratios are expected to be good. (author)