Modeling of Passive Safety Thermosyphon Loops Cooling System for Nuclear Applications

Heat pipes are passive heat transfer devices, of long lives. Material and testing reactors (MTRs) have residual heat after shutdown. Usually MTRs have also spent fuel storage tanks to compromise heat that need to be removed. Gravity assisted two-phase closed heat-pipe loop (GTPHL) covered by removal of decay heat (or heat after shutdown) with evaporator and condenser lengths each 100 m helical coil shape with outer diameter 15 cm and 3 mm thickness as a passive cooling system for a nuclear spent fuel storage pool. This study proposes a completely passive cooling system using thermosyphon loop for cooling and dissipation of the residual heat of wet spent fuel storage by running as main or alternative cooling system. The design focuses on heat removal from the spent fuel storage tank of a research reactor. The model considers natural convection by air for the condenser part of the heat-pipe loop to confine the residual heat. A numerical simulation, using special design of GTPHLs, was used to investigate the thermal performance of the GTPHL. The effects of heat loads were analyzed. Demineralized water was used as the GTPHL working fluid. The atmospheric air was circulated around the condenser as a cooling system. The thermal performance of the GTPHL is evaluated at heat input ranging from 25 to 15 degree kW with filling ratio of the working fluid of 100%. The results show that a good thermal performance is obtained at high evaporator heat load obtained from nuclear spent fuel storage tank.