【作者】 张波；

【导师】 王乃华；

【作者基本信息】 山东大学 ， 动力工程及工程热物理， 2017， 硕士

【摘要】 核电产业的快速发展,产生了大量的乏燃料,乏燃料的有效储存对核电厂的运行有着关键的影响。目前已经提出的非能动干式储存技术已被证明是一种更加灵活、安全和经济的储存方式,具有很大的应用前景与研究价值。本文采取数值模拟的研究方法,对典型的混凝土干式储存罐体结构HI-STORM系统进行传热方面的研究,主要的研究内容与结果有:(1)针对该储存罐体组成结构的特点,为合理简化其几何模型,本文提出把结构复杂的乏燃料组件进行等效多孔介质化的方法;针对传统传热模型存在的局限性,为建立更加准确的数值模型,本文提出同时考虑辐射传热和自然循环对流对该干式储存系统衰变余热排除的影响。(2)对乏燃料组件进行流动特性的研究:用ANSYS Fluent CFD软件选用标准κ-ε湍流模型,成功模拟出氦气在格架单元内的流动,得出氦气横截面上的速度分布,发现速度分布与实际经验吻合;拟合压降与速度的关系式,获得等效多孔介质区域的流动阻力公式,包括粘性阻力系数和惯性阻力系数。(3)对乏燃料组件进行传热特性的研究:建立二维对称结构,选用离散坐标(DO)热辐射模型,模拟乏燃料组件在横截面上的温度分布,结果表明,随着温度的升高,辐射传热对乏燃料组件内部的温度分布和传热的影响逐渐增大,且格架壁面温度较衰变热量对最高温度和有效导热系数的影响要大;拟合出等效多孔介质区域的径向有效导热系数与温度的关系式;对于轴向的有效导热系数,本文用面积加权平均的方法获得。(4)对乏燃料干式储存系统进行传热方面的研究:建立1/8三维对称结构,应用模拟得出的等效多孔介质的参数,采用DO热辐射模型和κ-ωSST湍流模型,成功模拟出该干式储存系统的传热机理;得到该系统温度的轴向和径向分布,包括MPC密闭容器、金属格架和混凝土防护层等固体部件的温度分布,同时得到氦气和空气的温度场、速度场和压力场;本文模拟得出的乏燃料最高温度为280℃,低于允许的储存温度。更多还原

【Abstract】 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 κ-ω 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 κ-ω 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.更多还原