Quality Evaluations of the Fuel Bundle Welds and Brazed Joints by Acoustic Microscopy

Abstract

For more than 20 years, the quality control of the end-cap, end-plates welds and of the brazed appendage joints is made by destructive methods (metallographic examinations or mechanical tests) on specimens sampled from production. Having a very limited statistics, these destructive methods are useful only to indicate "trends" of the production quality, not for detecting infrequent single defect events. It is recognized that nondestructive examination techniques are required to achieve sufficient evidence of the production quality. at a statistically significant sampling rate. For this reason, the INR-Ultraacoustics R and D Lab has develop a family of equipments for high resolution ultrasonic imaging, at performances close to the Acoustic Microscopy domain. The paper make a presentation of the examination methods and of the experimental results obtained on characteristic welds and brazed joints samples. Detailed off-line evaluations of the C-scan and B-scan ultrasonic images are made and comparative analyses with metallography are performed. Also, in the case of end-cap welds. numerical stress analysis are made, in order to establish the influence of flaws on the weld strength.