High temperature gallium orthophosphate transducers for NDT and monitoring purposes in nuclear power plants

There is a need for ultrasonic transducers to operate at temperatures up to 580°C for NDT and monitoring purposes in nuclear power plants. One of the key aspects of designing such transducers using high temperature (HT) piezoelectric single crystal material gallium orthophosphate - GaPO4 has been studied: ultrasonic performance of this piezoelectric material at HT as a function of time. An experimental setup was used where two thickness extension mode GaPO4 plates operating at frequency of 2.17 MHz were bonded to a carbon steel block using HT silver adhesive and these were placed in an electric furnace. HT wiring led from the piezoelectric plates through an opening in the furnace outside to an ultrasonic testing device. The ultrasonic measurements show that GaPO4 works as a functional ultrasonic transducer generating and receiving ultrasound at the temperature of 580°C for 13 consecutive days when HT corrosion of carbon steel block occurred leading to failure of the experiment. From the aspect of HT operation of this piezoelectric material, the results are very encouraging for proceeding with development of ultrasonic transducers using GaPO4 for application in nuclear power plants