Measurement of Pressure Loss in Tight Lattice Rod Bundle with Spacer Grid

KAERI (Korea Atomic Energy Research Institute) has been developing a dual-cooled annular fuel to increase a significant amount of the reactor power in OPR1000, an optimized PWR (Pressurized Water Reactor) in Korea. The dual-cooled annular fuel is simultaneously cooled by the water flow through the inner and the outer channels. To introduce the dual cooled fuel to OPR1000 is aimed at increasing the power of reactor by 20% as well as at reducing the fuel temperature by 30%, as compared to the conventional solid fuel without the change of reactor components. However, the pitch-to-diameter ratio of dual-cooled annular fuel assembly, one of the important geometrical parameters to determine the pressure drop, should be decreased in order to become the same array size and guide tube location as the solid fuel assembly. In such a case, the trend of pressure loss in the dual-cooled annular fuel assembly may be definitely different from that in the conventional solid fuel assembly due to the different pitch-to-diameter ratio. In this study, the 4x4 rod bundle having the pitch-to-diameter ratio of 1.08, which simulates the dual-cooled annular fuel assembly, is prepared with the plain and the split-vane spacer grids. Then, the friction factor in rod bundle and the pressure loss coefficients of spacer grids are preliminarily tested and reported