Experimental analysis on the influence of contact condition in fuel fretting wear

During reactor operation, the change in the characteristic of spacer grid springs and dimples results in the decrease of fuel rod supporting force. Since the supporting force affects fuel fretting wear, it is necessary to investigate the influence of the force. This paper is concerned with the experimental investigation of that, to this end, the supporting force (i.e., contacting force) was varied as 5 N and 0 N, and the gap of 0.1 mm was also simulated in the experiment. Shape, depth and volume of wear found on the fuel rod specimen were examined for the analysis. Total wear volume evaluated was separated with respect to the shape of the contact contour of spring/dimple, the stiffness and the slip direction to examine those effect in detail. As results, the slip regime depends on the contour shape even though the property of fuel rod vibration is the same, and the wear volume increases considerably when the gap exists. It is also found that wear becomes much severe in the case of the contact with spring and the axial slip rather than with dimple and transverse slip, respectively