Generally, the inside of a fuel subassembly of sodium cooled fast reactor (SFR) has complex geometry and this complexity makes it difficult to conduct computational fluid dynamics (CFD) utilizing cyclic boundary condition in a radial direction. However, present work has created a new modeling method which enables us to model only one rod with one wire (1-rod model) to represent periodically installed rods with wires, like an actual fuel subassembly. The axial geometry of the 1-rod model has one wire pitch length and has two extra buffer zones to reduce the influence of inlet and outlet boundary conditions. Since this 1-rod model requires low calculation load to represent flow field of a center rod in the fuel subassembly, the model allows the choice of increased number of mesh in both radial and axial directions. With this 1-rod model, three-dimensional (3D) thermal hydraulic simulation has been conducted to evaluate a peak local temperature caused by contact of a wire with the fuel rod cladding. As the coefficient of wire contact effect, the simulation obtained a value of 2.4, which means peak coefficient of fuel cladding temperature.

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