Research On Added Mass Model In Fluid-Structure Interaction Of Spent Fuel Storage Rack

With the development of nuclear power in China,the amount of spent fuel unloaded from nuclear power plants is increasing,and the storage capacity of spent fuel in our country is far from meeting the requirements.Many spent fuels are temporarily stored in the storage pools in the reactors of nuclear power plants.In order to increase the spent fuel storage capacity of nuclear power plants,the power plant has taken measures to expand the capacity of spent fuel storage,such as retrofitting spent fuel storage racks or increasing the number of racks to achieve spent fuel intensive storage.At the same time,in order to realize the localization of spent fuel storage racks,it is necessary to design and improve the spent fuel storage racks of large advanced pressurized water reactor nuclear power plants.In reactor storage,spent fuel storage racks provide storage space for spent fuel components unloaded from the core.Its critical safety,structural integrity,and radioactive containment are of great significance for the continuous,stable,and safe operation of nuclear power plants.In order to obtain better seismic performance,the bottom of the spent fuel storage rack of AP1000 and CAP 1400 adopts a free-style structure without bolt connection:it is directly placed on the bottom surface of the spent fuel pool,and no fixed measures are set at the bottom and side.Because the free-style rack structure is highly non-linear,under seismic load,fuel components in the spent fuel storage chamber may shake back and forth,and the supporting feet of the spent fuel storage rack may also be raised,causing an impact on the surrounding rack.Therefore,in the seismic analysis of the rack,the effects of non-linear effects such as the collision between adjacent spent fuel storage racks,the slip of a single rack,sloshing,dumping,and torsion need to be considered.In particular,the effects of fluid-structure interaction need to be fully considered.The current research on the fluid-structure interaction effect of the spent fuel storage rack is mainly focuses on simplifying the rack into a regular shape,and then apply the classic theoretical formula to calculate its additional mass.However,the correctness of the fluid-structure interaction formula cannot be verified.Insufficient assumptions may lead to the destruction of the structural integrity of the racks under seismic conditions.A few experimental studies have also simplified the model structure,resulting in that the results cannot truly reflect the fluid-structure interaction parameters of rack,so it is necessary to conduct a numerical simulation study of the complete rack model.Based on the previous research,this paper fully considers the added mass of the interaction between the moving rack,any rack in the whole pool and the wall of the pool.Numerical simulation is performed on all the racks arranged in the spent fuel storage pool,and finally the added mass matrix of the whole pool rack is obtained.The elements in the full mass added mass matrix obtained in this paper can be directly used as input parameters for ANSYS finite element structural dynamic analysis.The added mass matrix of any two racks required in the MATRIX27 mass matrix unit in ANSYS can be extracted from it,but the process is complicated.This method reduces the parameter extraction time and guarantees the accuracy of the results.In this paper,the Matlab program is developed to extract the added mass matrix between any two racks from the added mass matrix of the whole pool,making the results more suitable for the mass matrix input in the seismic calculation of the rack.