국부좌굴에 영향을 미치는 셀 구조물의 기하학적 불균일성에 대한 평가

The nuclear fuel assembly is consisted of one top/bottom nozzle, about 240 fuel rods, and approximately 10 spacer girds in the case of 16 by 16. The spacer grid plays important function of preventing impact failure by seismic and LOCA blowdown forces and supporting the fuel rods vertically. There are many mechanical and structural performance tests for spacer grid such as the performance of the grid spring, fuel rod vibration, fretting wear resistance, and the impact strength. A pendulum impact tester has been used to evaluate the impact characteristics such as impact velocity, critical strength and duration time. In the grid structure, there are two types of cell, one is fuel rod cell and the other is guide tube cell. In the impact test, the local buckling usually occurred around guide tube cell. Therefore, the effect of geometrical non-uniformity of the guide tube cell for local buckling has been investigated by considering guide tube cell configuration using the commercial FE code.