The lateral flow structures in a subchannel geometry were carefully examined in an enlarged 5 x 5 rod bundle array by using a two-color LDA system. The detailed measurement data of lateral velocities in subchannels have been obtained as fabricating the rod bundle array 2.6 times larger than the real bundle size. Two types of flow deflectors were selected for the test: a conventional split-type mixing vane and a swirl- type vane that had been designed to enhance the swirling flow in a subchannel. Experiments were performed in a cold test loop facility at KAERI. The experimental conditions were normal pressure (1.5 bar) and temperature (35 degrees C). The average axial velocity was maintained at 1.5 m/s and was equivalent to Re = 50,000. From the experimental results, specific flow characteristics for each vane types were observed.