| Steam generator tube rupture(SGTR)accident is one of the most typical benchmark accidents in nuclear power plant,which not only causes the loss of primary coolant,but also leads to the release of radioactive iodine into the secondary side of steam generator.Due to the effect of mass force and concentration difference in the secondary side liquid phase,a part of elemental iodine will remain in the liquid phase,and the rest may enter the gas phase space with the uncondensed steam through the liquid phase and be released into the secondary loop or even the environment.Therefore,it is very important to accurately grasp the retention and release behavior of gaseous elemental iodine under SGTR accident condition for accident source term analysis.In this paper,the washing efficiency of elemental iodine and the equilibrium distribution behavior of elemental iodine in liquid phase under steam jet were studied.The effects of inundated depth,inlet pressure,evaporation rate and solution subcooling degree on the water washing efficiency of elemental iodine,and the effects of solution p H and absorption pressure on the equilibrium distribution of elemental iodine were analyzed.In addition,based on the jet hydraulics model,this paper constructed a calculation model of elemental iodine washing efficiency under jet conditions,and compared it with the experimental results.Through the experimental study on the washing efficiency of elemental iodine,it was found that increasing the inundate depth,decreasing the inlet pressure,decreasing the evaporation rate and increasing the subcooling degree of the solution were all conducive to the retention of elemental iodine in the liquid phase,which improved the washing retention efficiency of elemental iodine.Through the experimental study on the equilibrium allocation share of elemental iodine water washing retention,it was found that under the condition that the concentration of elemental iodine gas phase remained unchanged,the increase of solution p H and absorption environmental pressure was conducive to improving the total absorption of elemental iodine by the solution and the water washing allocation coefficient of elemental iodine.The relationship between the distribution coefficient and the absorption pressure and p H of solution is given.In addition,a calculation model of elemental iodine washing efficiency under jet flow was established.Through calculation,it is concluded that the absorption of iodine by droplet plays an absolute leading role in the process of gas-liquid two-phase mass transfer,and the mass transfer time has a great influence on the total mass transfer of iodine.Under the condition of lower inlet pressure and higher submergence depth,the calculated results are in good agreement with the experimental results. |
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