1. Introduction
Non-destructive testing (NDT) is a branch of engineering sciences
which has found application in almost all process and strategic
plants for the inspection of materials. Among several NDT
methods, ultrasonic testing is the most commonly and widely used
one in the industry. Time of flight diffraction (TOFD) technique is a
newly developed but well established ultrasonic testing technique
which has gained popularity in the recent past due to its greater
ability in detection, positioning and sizing of the defects. This technique
has been widely used in examination of thick wall welds
especially in nuclear power plants.
Austenitic Stainless steel has structural importance in nuclear
industry due to its excellent mechanical and chemical properties.
The weld region of austenitic stainless steel is highly anisotropic
because of the columnar grain structure. Ultrasonic waves interacting
with these grains result in high level scattering noise that may
mask the defect signals. Other contributions to the noise can be