The amount of the tritium removed from the Wolsong NPPs after the WTRF operation start was simulated through the modeling of the tritium balance between the Wolsong NPPs and the WTRF. Five WTRF operating scenarios were proposed and the profiles of the tritium level depending on these scenarios were obtained from the simulation. It was predicted that about 9×1017 Bq/yr of tritium would be removed in the beginning of WTRF operation. However the tritium levels in the moderators will be steadily reduced and saturated less than 3×1011 Bq/kg in 2013, and then about 2×1017 Bq/yr of tritium will be removed from the Wolsong NPPs by the WTRF operation.