Fretting wear characteristic tests of X2-GEN midgrid

The KEPCO Nuclear Fuel Co. requested the fretting wear characteristic tests of a X2-GEN midgrid at high temperature and pressure distilled water. The following results were obtained for the fretting wear test. -Fretting wear tests at high temperature and pressure distilled water- Based on the result of the fretting wear tests of the X2-GEN and 17ACE7 1x1 mid-grid, X2-GEN mid-grid showed a slightly severe wear rather than 17ACE7 spring and dimple. Fretting wear mechanism as well as the circular trace of the fuel rod motion were attributed to this result. The fretting wear mechanisms at each mid-grid were influenced by each spring shape, that are depended on the different impacting behavior under a circular rod motion. Based on the impacting load cell and displacement signals, a work-rate is calculated at each springs and dimples in 1x1 cell. The evaluated wear coefficients of the work-rate model in X2GEN and 17ACE7 mid-grids are 2∼6 x 10-15 Pa-1 and about 1 x 10-15 Pa-1. Consequently, wear characteristics of each mid-grid shows a relatively smaller wear rate compared with other test conditions and nuclear components