External Flow Field Analysis Of Passive Containment Cooling System

AP1000, which is designed by Westinghouse, is a kind of advanced passive PWRnuclear power technology. However, until now, some vital safety functions haven’t beenverified. So, research on AP1000passive safety system is one of the important missions for usto best digest, absorb these new technologies and further develop our own. The passivecontainment cooling system (PCCS) of AP1000provides an ultimate thermal trap for nuclearpower plant, which is the most effective protection for the integrity of the containment.What’s more, the containment is the last barrier to prevent radioactive substances fromreleasing into environment in design basis accident. Therefore, it is of great important todevote more efforts to research and innovate the technology of PCCS.The main principle of PCCS is condensation on the inside surface of the steelcontainment and evaporation, radiation and natural convection on the outside surface. Thetwo processes are coupled by conduction through the steel containment. In this paper, theexternal flow field of steel containment is studied and evaporation, radiation and naturalconvection are mainly taken into account.Simplified rectangular channel is usually applied in most of the existing research ofcontainment vessel, especially in research concerning radiation and natural convection, whichfailed to establish a complete geometric model. In this paper,1:10two-dimensional radiationand natural convection model and spray optimization model are established, and detailedcalculation analysis is also conducted.In this paper, GAMBIT is used to establish geometry model and grids, then advancedfluid analysis software—FLUENT is applied in numerical simulation. In radiation and naturalconvection model, the influence of channel width, airflow speed and blackness of wall surfaceon heat transfer is studied in this paper. Finally, pressure nephogram, temperature nephogram,velocity nephogram and the temperature distribution contours through the whole outsidesurface of the containment under different conditions are obtained, which provide a goodresearch direction for further optimization. In spray optimization model, an optimized designis proposed from generalized passive concept, in which, self-designed low-powerself-operated regulator valve is used to control spray water flow rate, and the surface temperature of containment is used to control the opening of the valve. Furthermore,FLUENT is used to simulate the optimization model. In this paper, user-defined function(UDF) is applied to simulate evaporation of surface water film because there is no matureevaporation model in FLUENT. This optimization not only can make up for the deficiencythat spray water flow is not enough during the earlier stage of accident, but also can ensurethe sustainability of water flow and improve the utilization of spray water.