Effect of impact frequency on the wear behavior of spring-supported tubes in room and high temperature distilled water

Sliding and impact/sliding wear tests have been performed in order to evaluate the wear properties of nuclear fuel rods in room and high temperature distilled water. In this study, tests have been conducted at a normal load of 10 N, sliding amplitudes of 10-100 μm and four impacting frequencies of 0, 5, 10 and 30 Hz by using a spacer grid spring of fuel assemblies. The results indicated that the wear volume of the fuel rods is rapidly increased with an increasing impact frequency and slip amplitude. This is mainly concerned with the behavior of the generated wear particles on the worn surfaces, which is affected by the impacting frequency of the spring specimen. Based on the observations of the worn area, the wear particles in the room temperature water remained in the contact surfaces below 10 Hz of an impact frequency even though the water fluctuation at the contact surfaces due to the impact motion was expected to easily remove the wear particles. However, the wear volume was decreased by increasing the test temperature. This seems to be closely related to the changed properties of the spring stiffness in the high temperature water and the formation of the load-bearing layers rather than the changed material properties on the worn surface. Based on the present results, the detailed mechanisms of the wear particle behavior according to the test conditions were investigated and the relationship between the spring characteristics and the wear behaviors in high temperature distilled water is discussed.