This paper presents conceptual design for a passive residual heat removal (PRHR) system of the pressure tube water reactor (PTWR) that is called thorium-based advanced nuclear energy system (TANES) as well. The passive PRHR system includes two nature circulation loops to transfer the reactor residual heat to the heat sink. The RETRAN02 code was used to calculate the ability of the passive PRHR system of TANES at the design-based accident of losing conventional and dependable electrical power under full power. The calculation gave the conclusion that the passive PRHR system can remove the reactor residual heat to the ultimate heat sink and keep the pressure of the coolant loop and the moderator loop less than the limitations. Some factors such as the elevation of the heat exchanger are also studied.