Experimental Research On Heat Transfer Characteristic Of SMR's Passive Containment Cooling System

Compared to large reactor,small and medium sized reactors have a good safety design concept and the characteristics of structure simplification.The reactors have the advantages in special areas which can meet the requirements of medium and small power grid,municipal heating,industrial heating and sea water desalination.Containment building is one of the primary barriers for mitigating the consequences of a Loss of Coolant Accident(LOCA),and Main Steam Line Break(MSLB)accident.For avoiding the harm of nuclear emergency at most,the integrity of containment must be guaranteed.At present,some small and medium sized reactors adopt the scheme of PCCS and steel containment,such as Nuscale,ACP100.Except as inclusive equipment,the steel containment will play the role of heat transfer after LOCA or MSLB accident.With the rapid development of small reactor,the experimental study about thermal stratification and heat transfer process of small reactors' steel containment is important for its design and safety analysis.To study the thermal stratification and heat transfer caused by the plumes or buoyant jets in the small steel containment during the LOCA or MSLB accidents,experiments and numerical calculations are performed.Using steam as the working medium and measuring temperature experimentally,the experiments were conducted with various jet inlet flow rate,inlet height,inlet diameter and spray water flow rates to identify their influence on the thermal stratification phenomena and heat transfer of wall.Temperature and condensation water of inner wall were obtained in the experiments.Some work has been done by FLUENT,which has Euler multiphase flow model and evaporative condensation model,to compensate for experiment weaknesses and provide reference for nuclear proprietary program development of steel containment in future.By analyzing the experimental data,it is found that thermal stratification is common in the containment after the break accident.The temperature of the upper part of the containment is evenly mixed,and there is an obvious isothermal zone.The lower part of containment is a low temperature zone which has a certain temperature gradient.The effect of jet flow,inlet diameter and inlet height on the thermal stratification is mainly to change the isothermal zone thickness.Spraying flow holistic changes the space temperature of the containment.The containment heat flux is affected by the isothermal zone thickness and temperature.The thermal stratification of the containment is also found in the simulation results.Combined with the flow field in the shell,it is found that the gas velocity has a great influence on the thermal stratification.However,the calculation results show that the space temperature is higher and the temperature gradient of lower part is insignificant.