Computer program for tracing the ultrasonic rays within material has been developed to simulate the process of defect detection within weld in primary pressure boundary made of stainless steel. The program simulates through transmission and reflection technique in crack detection of austenitic stainless steel, and also ultrasonic beam propagation through multi-media including stainless steel cladding interface. As a special technique to detect cracks within weld, the use of electromagnetic acoustic transducer was tried to generate horizontally polarized shear wave. Althogh the first aim of the use of EMAT was to evaluate signal evaluation from weld, it was not directly achieved successfully. Instead, complete signal acquisition was done for base metal SUS 304 and carbon steel SA 508. Based on the analytical solution for the eddy current phenomena, the integral model that could be applied to arbitrary shaped defect has been suggested. The computer program with the integral model has been developed. The result of computer simulation for the case of artificial defects in the calibration standard tube was compared with experimental data. (Author).