Experimental Research On Sodium Columnar Fire Combustion And Suppression In Sodium-cooled Fast Reactor

The sodium-cooled fast reactor(SFR)has excellent safety and economy properties,therefore it is recommended as one of the generation IV advanced reactors.Liquid sodium is used as a coolant in the SFR for its excellent thermophysical properties.However,liquid sodium has a high chemical reactivity,which would burn and lead a sodium fire accident when leaked and exposed to air.In the present design,particularly the pool-style SFR,the leaked liquid sodium would flow downward in a columnar flow because of the limitation of the thermal isolation materials wrapped round the liquid sodium pipes,which could lead a sodium columnar fire.In this thesis,an experimental research on sodium columnar fire combustion and suppression was conducted.The present research contained a series of sodium columnar combustion experiments by the sodium fire combustion system.And the suppression experiments executed by the sodium fire suppression system was conducted based on the combustion experiments.The experiment phenomenon and data including the temperature,pressure and heat release rate were recorded by the data acquisition system.The experiment phenomenon and data were analyzed by means of dividing the combustion process into different phases and comparing the data in different zones.The results shows that,the sodium columnar fire combustion could divided into the sodium columnar combustion phase and the pool combustion phase by the end of the liquid sodium spray.In the sodium columnar combustion phase,a spray angle would formed for the breakup of liquid sodium spray under the nozzle,which divided the combustion vessel into the burnt zone and the unburnt zone.In the burnt zone the sodium from the breakup may adhere and burn on or near the surface of the thermocouples of the measuring points tree,therefore the temperatures in the burnt zone would increase sharply and reach quite high.While the temperatures in the unburnt zone would increase smoothly and could not reach as high as those in the burnt zone.There was not large temperature difference in the burnt zone or in the unburnt zone,but the maximum temperature differences went large at the boundary between the burnt zone and the unburnt zone.The liquid sodium would burn as a pool fire when drop into the sodium collection plate in the pool combustion phase.A large-scale poolcombustion would arise with the heat accumulation from the oxidization of the liquid sodium,which caused temperature rising rapidly in the sodium collection plate.In the late period of the pool combustion phase,the burn faded slowly and therefore the sodium collection plate cooled down tardily,and the temperature field would went uniform.During the process of the pool combustion phase,the combustion center could move occasionally.In the sodium fire suppression experiments,the extinguishment agent affected the combustion process more or less.However,the sodium pool combustion was just suppressed in some degree and the large-scale pool combustion was delayed,but not put out completely.The pool combustion arose again finally after the pool gathered enough heat.The extinguishment agent did not influence the maximum temperature of the measuring points in the sodium collection plate,but the temperature may be cooled down by the extinguishment agent.The research is promising to evaluate the liquid sodium combustion characteristics,and to provide technical reference for the sodium fire protection.