Simulation And Analysis Of Equivalent Parameters Of Spent Fuel Assembly

The rapidly growing nuclear power industry,which produces a large amount of spent fuel,has a critical impact on the operation of nuclear power plants.So,the spent fuel must be stored effectively.At present,the passive dry storage of spent fuel has been proven to be a more flexible,safe and economical storage method,which has a great application prospect and research value.In this paper,the numerical simulation method is used to study the heat transfer of the HI-STORM system,which is a typical concrete tank structure for spent fuel dry storage.The main research contents and results are as follows:(1)According to the characteristics of the structure of the concrete dry storage tank and in order to simplify the geometric model,this paper puts forward a method of equivalent porous media for the complex structure of spent fuel assembly.In view of the limitation of the traditional heat transfer model and in order to establish a more accurate numerical method,both the effects of radiation and natural convection heat transfer on the decay heat removal of the dry storage system are considered.(2)The flow characteristics of spent fuel assemblies were studied.By using ANSYS Fluent CFD software and the standard ?-? turbulence model,the flow of helium within the basket unit was successfully simulated and the velocity distribution in the cross section was obtained,which was found to be consistent with the practical experience.And then,the formula of flow resistance of the equivalent porous medium,including the coefficients of viscous resistance and inertia resistance,is obtained by fitting the relationship between pressure drop and velocity.(3)The heat transfer characteristics of the spent fuel assembly were studied.Based on the two dimensional symmetrical structure,the discrete coordinate(DO)thermal radiation model was used to simulate temperature distribution of the spent fuel assembly on the cross section.Results show that with the increase of temperature,the influence of radiation on the temperature distribution and heat transfer of the spent fuel assembly increases gradually and accordingly.It's also found that the influence of basket wall temperature on the effective thermal conductivity and maximum temperature of the spent fuel assembly is greater than that of decay heat.And then,a correlation formula between radial effective thermal conductivity and temperature of the equivalent porous media region is proposed.As for the axial effective thermal conductivity,it was calculated by using the area weighted average method according to the material of each solid component.(4)The heat transfer characteristics of the spent fuel dry storage system were studied.Based on the simulation results from the parameters of equivalent porous media and by constructing a 1/8 three-dimensional symmetrical structure model,the heat transfer mechanism of the dry storage system was successfully simulated by using the DO radiation model and the ?-? SST turbulence model.Then,the axial and radial temperature distribution of the system were obtained,including the solid components such as the MPC sealed canister,the metal basket and the concrete shield.The temperature field,velocity field and pressure field of helium and air were also obtained.The simulated maximum temperature of spent fuel is 280?,which is lower than the allowable storage temperature.