Fuel tube spacer-pad spot-weld quality estimation using guided ultrasonic waves

TLDR: In this paper, a real-time ultrasonic system for spot weld quality monitoring for the fuel tube, potentially allows for the elimination of expensive destructive testing, reduce the amount of time-consuming off-line ultrasonic inspections and ensure quality and reliability during operation.

Abstract: A guided wave technique for quality analysis of the spot weld spacer pad on the Pressurized Heavy Water Reactor (PHWR) fuel tubes using the strength of signal energy that is reflected from the welds is discussed here. The development of a real-time ultrasonic system for spot weld quality monitoring for the fuel tube, potentially allows for the elimination of expensive destructive testing, reduce the amount of time-consuming off-line ultrasonic inspections and ensures quality and reliability during operation. Due to the rather small spot size of these welds (less than 2 mm in diameter), the current methods such as ultrasonic scanning were found to be difficult to implement, particularly under production conditions Hence, a guided wave method was explored in this work that has the potential to be implemented in the welding. A fixture was developed in order to generate L (0, 1) mode in the wall of the tube and travelling along the length of the tube. Couplant was not used and instead uniform pressure was applied to ensure the coupling of the wave into the tube. The experimentally obtained guided wave reflected signals were correlated destructive assays. The main goal of such testing systems is to reduce operational time and provide reliable means of quality inspection.