Thermal Hydraulic Behavior Research On The Blanket Gas Within The Top Space Of Fast Reactor Main Vessel

Fast reactor main vessel is the class one equipment in nuclear safety,whose material is 316 stainless steel.According to the nuclear safety review,it is necessary to analyze whether the intensity and stiffness of equipment meet the design requirements or not.In order to do the intensity analysis,the temperature load top of the main vessel must be known.The construction of fast reactor main vessel's roof consists of large argon cavity,plug cock,part of biological shielding column,main pump and heat-exchangers as well as a small size air gap between plug cock and argon cavity.Therefore,it has an important significant to do a thermal hydraulic behavior research on blanket gas top of the main vessel for getting detailed temperature distribution.Because of the enormous structure of argon cavity,it's better to a numerical simulation rather than experiment.There are both large and small spaces differing in two orders of magnitudes simultaneously.Simplified simulation cannot get a detailed temperature distribution,leading to rather large errors in stress analysis.There are convective and radiation heat transfer in the argon cavity.However,the suitable radiation heat transfer model of the complex blanket gas within the top space of main vessel hasn't been put forward.Moreover,researchers do not know much about the thermal hydraulic characteristics inside the air gap.The degree of gap thickness affects mental layer temperature has no definite answer.Hence,detailed modeling of the blanket gas space within the top space of fast reactor main vessel is quiet necessary,which provides reference for above questions.First of all,this paper will use simplied model of CEFR to choose radiation heat transfer model for the fast reactor.Secondly,in order to solve the problem of concurrence of both large and small spaces,this paper drew grids of detailed model respectively.Thirdly,in order to analyze the influence of convective and radiation heat transfer to mental layer,the later calculation improves the surface temperature of biological shielding column whose effect of radiation heat transfer is strongest.At last,in order to study the effect of air gap thickness on the temperature of metal layer,this paper will do two more cases of Omm air gap and 90mm air gap in comparison with the situation of 30mm air gap.The result shows that DO radiation heat transfer model is more suitable to the calculation of thr top space tn the fast reactor.The analysis result of overall thermal hydraulic characteristics shows good symmetry.The flow pattern is natural circulation.The temperature difference of argon and stainless steel is 40-60?.Because of the strong radiation effect between biological shielding column and mental layer,the highest temperature outside the metal layer appears at the position of the hoist lug boss.After increasing the temperature of biological shielding column surface to 540?,it has little effect on the argon convection.But due to the impact of radiation heat transfer,temperature of metal layer gets higher on the contrary.Moreover,in such conservative circumstances,the highest temperature of mental layer is 387? lower than the creep temperature of 316 stainless steel.The air gap plays a good heat insulation role between the cock plug and argon gas cavity.At last,by comparing three calculations of 0/30/90 mm thicknesses air gap,the conclusion that 30mm air gap has the best heat insulation effect provides certain consultation for concept design in the practical engineering.