Development Of Buoyant Jet Models For Application Under Accident Condition In Small Containments

In recent years,the small modular reactor(SMR)power plant attracts increasingly attention to the world,especially the developing countries.SMRs possess various advantages such as low initial investment,short construction period,high security,multiple purpose and so on.Small reactor nuclear power plant s,if built in China,can deal with problems about electric power supply for islands or remote area and be used for heat supply of urban area or sea water desalination.As the last barrier of the nuclear power plant(NPP),the containment should receive special concentration on the post-accident analysis.As for the large dry containment,such as AP1000,the release of steam after the loss of coolant accident(LOCA)or main seam line break accident(MSLB)would harm the cooling of the containment.A lot of research has been carried out on that.Based on the thermal stratification theory,the one-dimensional code BMIX++ developed at University of California,Berkley can be used to calculate the temperature distribution in the post-accident containment.Due to the large free volume,the break-induced jet occupy relatively small space.Therefore,the jet body can be ignored in the accident analysis of large dry containment.However,the small containment for a SMR possesses small free volume and compact equipment lay-out.Some safety-related facilities might be exposed in the jet body.In that case,the steam jet with high temperature and pressure will surely harm the normal operation of these devices.Therefore,predictions of temperature and velocity of the break-induced jet are necessary.A one-dimensional hot-air to cold-air jet integral model was firstly established in this work.Based on the air jet model,in additional with previous research result,a 1D steam-to-cold air jet model was completed.Related experimental study and CFD simulations were also carried to validate the current model.The results of the integral model are coincident with the experimental data and the CFD simulations.The current 1D model showed apparently advantage on the calculating time compared with the 3D CFD simulation.Both calculating and experimental result showed that the temperature and velocity of the released gas decreased rapidly in the jet flow and then maintained a low value.The large entrainment of ambient cold air may explain the quick decay of the jet temperature and velocity.The modeling and experimental results could offer certain suggestion on the equipment lay-out in the area where break accident may easily happen.