乏燃料运输容器中子屏蔽层等效导热性能研究

Effective Thermal Conductivity of Spent Fuel Transport Cask Neutron Shielding Layer

目的乏燃料组件运输容器具有防止临界、包容、屏蔽、导出衰变热等功能。为了更好地分析乏燃料运输容器中子屏蔽层的导热性能,针对某型号乏燃料组件运输容器开展中子屏蔽层等效导热性能研究。方法采用三维计算流体力学软件,分别分析了正常运输工况和事故工况下不同换热鳍片对中子屏蔽层轴向和径向等效导热系数和圆环内部温度的影响。结果采用导热性能良好的散热鳍片可以有效提升中子屏蔽层的导热能力;对于轴向和径向导热,采用铜鳍片时,等效导热系数约是采用碳钢鳍片时的6倍,是采用304不锈钢鳍片时的10~13倍;由于所研究的运输容器内径较小,通过面积加权平均法计算的等效导热系数高于数值计算方法,相对误差约为17%;不同散热鳍片情况下,火烧30 min后屏蔽材料内表面温度差异不大。结论分析结果对后续乏燃料运输容器设计和热工安全分析可提供指导。

The transport cask for spent fuel assemblies undertakes functions such as preventing criticality,containment,shielding,and removing decay heat.In order to better analyze the thermal conductivity of the neutron shielding layer of the spent fuel transport cask,the work aims to study the effective thermal conductivity of the neutron shielding layer for a certain type of spent fuel transport casks.The 3D computational fluid dynamics software was used,the effects of different heat transfer fins on the axial and radial effective thermal conductivity of the neutron shielding layer and the temperature of the inner ring surface under normal transportation and accident conditions were studied.The results showed that using heat transfer fins with bigger thermal conductivity could effectively increase the thermal conductivity of the neutron shielding layer.For axial and radial thermal conductivity,when using copper fins,the effective thermal conductivity was about 6 times that of using carbon steel fins and 10-13 times that of using 304 stainless steel fins.Due to the small inner diameter of the transportation cask studied in this paper,the effective thermal conductivity calculated by the area weighted mean method was higher than that of the numerical calculation method,with an error of about 17%.The average temperature differences of inner surfaces of the shielding layer with different heat transfer fins were not significant after 30 min fire.The result has a strong guiding significance for the design of spent fuel casks and the thermal safety analysis.