A spacer grid is one of the primary components of the PWR nuclear fuel. Spacer grid maintains proper pitches between the fuel rods and enables the fuel rod to cool down by providing coolant flow path. However, when the nuclear fuel is subjected to an unexpected excessive load during shipping, handling, manufacturing and operating, it could lead to fuel failure such as spacer grid buckling and cladding tube deformation. The most limiting load acting on the spacer grid is the lateral impact load during seismic/loss-of-coolant accidents. Dynamic crush strength of the spacer grid greatly contributes to the nuclear fuel integrity throughout the fuel lifetime [1]. This buckling strength tends to become weak in end of life (EOL) condition. KEPCO NF (KNF) carried out dynamic crush tests of the spacer grid and analyzed its characteristics. Spacer grids were prepared with three groups that have different cell sizes according to beginning of life (BOL), EOL and enlarged EOL simulated conditions. In addition, two kinds of dynamic crush tests were performed. One is pendulum impact test that drops a hammer to the grid in a short time. And the other is hydraulic long-pulse test that pushes impact plate to the grid in longer time. These tests and analysis results were compared in each group and discussed to explore key factors for improving crush strength of the spacer grid. In this paper, the spacer grid manufactured by additive manufacturing (AM) technology [2] is also introduced to verify the buckling performance. AM is a method to make designed shape with metal powder and built-up technology that is different from conventional manufacturing. Through the study, it could be a good alterative solution that the new manufacturing method might be helpful to improve dynamic impact characteristics.

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