In this study, the system thermal-hydraulic code LOCUST is applied to simulate reflood heat transfer experiments conducted in the RBHT facility, and the effect of spacer grids are considered. The calculation results of LOCUST are compared with experimental data and the calculations of RELAP5 4.0. The results show that both LOCUST and RELAP5 4.0 are capable of predicting the reflood behaviors at a satisfactory level. Besides, the calculations of cladding temperature and heat transfer coefficient are generally in good agreement with experimental data. When spacer grids are introduced, PCT calculated by RELAP5 4.0 and LOCUST are 1178K and 1201K, respectively. However, the calculations without spacer girds are 1184K and 1206K, respectively. The comparison reveals that a decrease of around 5K in the PCT occurs due to spacer grids.