Preliminary Study on the Fretting Wear Reliability of an Annular Nuclear Fuel

Abstract

Recently, a dual-cooled fuel (i.e. annular fuel) which is compatible with current operating PWR plants has been proposed in order to increase both power densities and safety margins. Due to the design concept that is compatible with current PWR plants, however, when compared with a current solid nuclear fuel it shows a narrow gap between fuel rods and needs to modify spacer grid shapes and their positions. Because a flow-induced vibration by fast primary coolant is inevitable phenomenon, it is necessary to examine the fretting wear behavior between an annular fuel and designed spacer grids. In this study, fretting wear has been performed to evaluate the wear resistance of the annular fuel by using specially designed spring and dimple of spacer grids that have a cantilever type and a hemispherical shape, respectively. At the spring specimen with relatively small stiffness value, fretting wear was initiated at both end regions and then proceeded gradually to center region. Based on the test results, the fretting wear behavior of annular fuel was compared with the current solid nuclear fuel and a comparative factor of its reliability was proposed.