Development of high-sensitivity ultrasonic techniques for in-service inspection of nuclear reactors. Annual report, 1 October 1976--30 September 1977

During the period covered by this report, an ultrasensitive ultrasonic system, incorporating real-time signal averaging, pulse compression, dynamic focusing, and transducer matching, has been developed. The system was shown to be capable of penetrating highly-attenuating material, such as austenitic steel, and of detecting reflections in the presence of strong background signals due to grain scattering