Numéro : 2030 - Year : 1987
Perturbations encountered in ultrasonic testing of PWR vessel because of the effect of the cladding
Y. BEURDELEY, Responsable du programme PISC à l'Etablissement des Constructions et Armes Navales d' INDRET
This statement presents one of the parametric studies of the international PISC II programme (Programme for the Inspection of Steel Components) This study is intended to explain the
difficulties encountered by teams of ultrasonic testing in inspecting the weld seams in PWR Pressure Vessels from clad side.
Regular tests must be performed at various stages of the life of these reactors .Several technics are used such as ultrasonic testing or radiography. Ultrasonic testing is often the only technic that can be used on account of the access, the presence of radioactivity , the shape of the weld or the type of the searched defects These ultrasonic testing are usually performed automatically.
Normal and angle probes with longitudinal or shear waves are used. Their frequency is l or 2 MHz. The angle between the sound beam and the normal to the surface is 45°, 60° or 70°. Focusing probes may be used with good results but in some cases, especially when the access is not good enough , one has to perform the test with manual probes.
Operators have known for a long time that clad surfaces induce perturbations of sound beams. Local attenuations of acoustic pressure and distortion of sound beams are the most important perturbations which may induce mistakes in detecting and sizing defects.
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