1. Karasawa, H., Izumi, M., Suzuki, T., Nagai, S., Tamura, M. and Fujimori, S. (2000): Developme nt of Under-Sodium Three-dimensional Visual Inspection Technique using Matrix-arrayed Ultrasonic Transducer. J our. of Nucl. Sci. Technol., 37(9), 767-779.