Computational Method For The Added Mass Of Fluid Imposed On Spent Fuel Storage Racks Considering Three-dimensional Flow

Spent fuel is the fuel unloaded from the reactor,which is highly radioactive and has a certain thermal power,and needs to be stored safely in the spent fuel pool in the form of a storage rack.For the structural safety of the spent fuel,seismic analysis of the storage racks is required.In order to minimize the transfer of seismic loads,the spent fuel racks are not in fixed contact with the bottom of the pool,and the spent fuel racks are placed in a high-density arrangement in the spent fuel pool.This design leads to a strong fluid-structure interaction between the spent fuel rack and the pool,which is often characterized by the added mass in engineering.For the calculation of the added mass of the rack,the traditional method is to reduce the rack to a two-dimensional concentric square column for theoretical and simulation calculations,which has a high computational efficiency,but leads to excessive margins.In addition,due to the porous structure of the CAP 1400 spent fuel rack,there is a significant difference between the calculation of the added mass and that of the conventional rack,and the traditional simplified method is not applicable to the calculation of the added mass of the spent fuel rack of the CAP 1400.Considering the complex three-dimensional structure inside the CAP 1400 spent fuel rack and the influence of the three-dimensional flow of the fluid outside the rack on the added mass,a more accurate calculation method is needed.In this paper,the effect of the connection structure inside the spent fuel rack and the flow of fluid outside the rack on the added mass is investigated qualitatively by using experiments combined with numerical simulations,and the results show that the connection structure inside the rack increases the added mass of the spent fuel rack,and the three-dimensional flow of fluid outside the rack decreases the added mass of the spent fuel rack.Then,a method to calculate the added mass of the rack is proposed in this paper and validated by experimental data.The method takes into account the influence of the internal connection structure of the rack and the three-dimensional flow around the rack,which can calculate the added mass of the spent fuel rack more accurately and reduce the margin of calculation.Finally,this paper uses this new method combined with experimental data to quantitatively study the influencing factors of the added mass of the rack and proposes an equation containing four factors to calculate the added mass coefficient of the rack,revealing that the added mass coefficient shows the characteristics of a cubic function with the share of the connection piece to the height of the rack and an exponential function with the height of the fluid domain in the z-direction of the rack.