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Nuclear Science User Facilities 74 Figure 4. Temperature-dependent performance of an AlN piezoelectric transducer. The transducers operated at their highest efficiencies at the design temperature. Figure 5. Temperature-dependent performance of the ZnO transducer. The transducer did not perform well at the design temperature however it recovered its original amplitude upon cooling. This indicates that the sensor will operate satisfactorily during reactor shutdown enabling us to measure performance degradation at those times. using fast Fourier transform FFT. The results of this analysis are shown in Figures 79. Figure 7 shows the pulse-echo amplitude measured from the survivingAlN sensor.The plot was normalized to the pre-irradiation ampli- tude.The pulse-echo amplitude varies by - 20 during irradiation. Figure 8 shows the pulse-echo ampli- tude measured from the BiT sensor. During the first cycle the pulse-echo amplitude decreased by approximately 65. Figure 9 shows the pulse-echo amplitude of the magnetostrictive trans- ducers.These plots were also normalized to the pre-irradiated pulse-echo ampli- tude.The transient behavior in these sensors seems to be less pronounced as the pulse-echo amplitude only varies by about - 10. To gauge the materials practical use in harsh radiation environments the selec- tion criteria of piezoelectric materials The in-pile use of ultrasonic transducers during irradiations at MITR is extremely important because they could provide more accurate higher-resolution data on the performance of candidate fuels and materials exposed to the harsh conditions of irradiation testing. for nondestructive evaluation NDE and material characterization were analyzed. PiezoelectricAlN was observed to be a viable candidate material.Test results on transducers based onAlN BiT Remendur and Galfenol operating in a nuclear reactor within a 40-day window at a fast-neutron flux of 4.05 1013 ncm2 and a gamma dose rate of 1 109 rhr were also evaluated. In each case clearA-Scan measurements were taken at the end of the power cycle. Remendur Galfenol andAlN seemed to maintain their initial transduction efficiencies.The pulse-echo amplitude of theAlN sensors varied by - 20 while that of the Remendur and Galfenol varied by 10. Conversely by the end of the first power cycle the BiT pulse-echo amplitude had decreased by 65. The data shows both piezoelectric and magnetostrictive transducers hold promise for use in high-neutron-flux environments. Each shows potential for improving reactor safety and furthering the understanding of the effects of radiation on materials by enabling researchers to monitor a materials structural health and NDE even in the