Thermal Safety Numerical Simulation And Analysis Of Horizontal Spent Fuel Dry Storage

With the increase of nuclear power installed capacity in China,it is estimated that by 2020,the installed capacity of nuclear power in the Mainland will reach 90 million kilowatts.It is estimated that the accumulated spent fuel from nuclear power plants will reach 7,000 tons or more in 2020.Among them,Qinshan,Tianwan,The 404 Company Limited.,China National Nuclear Corporation and Lingao and other nuclear power plant spent fuel pools were full or nearly full in 2019.Due to the lag of China's post-processing capacity,insufficient fuel transportation capacity and shortage of storage facilities,it is of great significance to study the design of intermediate storage solutions for spent fuel for passing through review and solving this problem.After comparison between wet storage and dry storage system,the dry storage of concrete modules has advantages of modular storage,low operating cost,less radioactive waste,and stronger ability to resist accidents.This paper first describes the process flow and related regulatory standards for horizontal dry storage.The NUHOMS horizontal spent fuel dry storage system introduced in China is optimized and improved.The dry storage system has three main equipments,namely Horizontal(Concrete)Storage Modules(hereinafter referred as HSM),Transfer Cask(hereinafter referred as TC)and Dry Shield Canister(hereinafter referred as DSC).Equipments that has been optimized and improved are DSC and TC.In this paper,the thermal safety analysis of the three major equipments under normal,off-normal,accident storage conditions and vertical loading and accident transfer conditions is carried out to verify that the three major equipments meet relevant regulatory standards.By comparing with the ORANO safety analysis report,the rationality of the modeling and calculation results is demonstrated.Finally,the process parameters demonstration and analysis were carried out for key designs and working conditions,and reasonable optimization suggestions were proposed.Using CFD to simulate the storage conditions of NUHOMS HSM.The results show that the temperature of concrete and components in HSM under normal and accident conditions does not exceed the regulatory standards limits,which correspons to the criteria of thermal safety.The main difference between the results of the HSM in ORANO report is that the component temperature in HSM and DSC surface is low under normal,off-normal and accidental ambient temperature conditions,especially the temperature of the concrete material.This temperature difference is more obvious when the vent is completely blocked for 40 hours.This is because the ORANO analysis report assumes that the concrete module is exposed to the sun for a long time,and it is not consistent with actual situation of spent fuel dry storage sites in the plant.Since the transfer process is a process with many complicated conditions and complex conditions,this paper focuses on the thermal analysis of vertical loading and the water loss accident in the water jacket,which is considered as most serious accident and bounded other accident conditions.The ANSYS simulation analysis shows that the temperature field of each component of the TC under vertical loading conditions and accident conditions does not exceed the standard limit.Since the improved TC has better radiation shielding effect than the NUHOMS TC,the heat dissipation effect is slightly worse.Subsequent TC should increase the number of vertical support plates for water jackets or fill a gas with better thermal conductivity to improve heat dissipation.In this paper,CFD analysis simulates the temperature of fuel assemblies and other components in DSC under storage and transfer conditions.The basic settings include: the surface temperature of the fuel tank obtained from the HSM and the TC as the wall boundary condition of the detailed model of DSC;the heat generation curve of the fuel assembly adopts a piecewise function to enclose the actual power curve;the equivalent physical parameters of the fuel assembly are obtained by FLUENT's porous medium model simulation.The analysis shows that the temperature of the fuel cladding does not exceed the maximum temperature of 570 ? under accident conditions;the temperature of other components does not exceed the allowable temperature limit of the material of each component.On this basis,combined with the four set of spent fuel loading program in the nuclear power plant,the thermal performance of DSC has evaluated in these cases.The improved DSC have better heat dissipation than the NUHOMS DSC.The simulation of improved DSC provides theoretical guidance for the development and use of more new materials and the design of integrated fuelbasket.