Research on Influence of Air Gap and Contact Thermal Resistance on Thermal Safety of Container for Spent Fuel Dry Transfer
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摘要: 结构壳体与铅层之间的间隙是转运容器向外排出衰变热的重要路径之一，2者之间的传热受到接触热阻的影响。在对转运容器热工安全评估的基础上，针对灌铅工艺中产生的铅层和结构壳体之间的接触热阻设定不同厚度的空气间隙，采用FLUENT软件进行了水平转运期间的瞬态数值模拟。结果表明，铅层和结构壳体之间的空气间隙层所产生的接触热阻致使2者之间产生显著的温差，温差随空气层厚度增加而变大，温差过大易导致铅层过热从而失去屏蔽安全功能；在转运容器的设计和制造中，灌铅工艺的优化应以缩小铅层和结构壳体间的间隙为目标，增强2层结构间的贴合度，以提高转运容器的热工安全性能。Abstract: The gap between the structural shell and the lead layer is one of the important paths for the transfer container to discharge decay heat, and the heat transfer between the two is affected by the contact thermal resistance. Based on the thermal safety assessment of the transfer container, the air gap with different thickness is set for the contact thermal resistance between the lead layer and the structural shell produced during the lead filling process, and the transient numerical simulation during horizontal transfer is carried out by using FLUENT software. The results show the contact thermal resistance generated by the air gap layer between the lead layer and the structural shell causes a significant temperature difference between the two. The temperature difference increases with the thickness of the air layer. Excessive temperature difference can easily cause the lead layer to overheat and lose the shielding safety function; In the design and manufacturing process of the transfer container, the optimization of the lead filling process shall aim to reduce the gap thickness between the lead layer and the structural shell, and enhance the fit degree between the two layers, so as to improve the thermal safety performance of the transfer container.
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图 2 无接触热阻时各部件温度变化曲线
Figure 2. Temperature Variation Curve of Each Structure without Contact Thermal Resistance
图 3 无空气层和3 mm空气层的DSC外壳温度变化对比图
Figure 3. Comparison Chart of DSC Shell Temperature Variation (Without Air Gap Layer VS with 3 mm Air Gap Layer)
图 4 无空气层和3 mm空气层的铅层和结构壳体温度变化对比图
Figure 4. Comparison Chart of Temperature Variation of Lead Layer and Structural Shell (Without Air Gap Layer VS with 3 mm Air Gap Layer) Gap
图 5 3 mm空气层下铅层与结构壳体的温度云图
Figure 5. Temperature Contours of Lead Layer and Structure Shell With 3 mm Air Gap Layer
图 6 1.5 mm空气层下铅层与结构壳体的温度云图
Figure 6. Temperature Contours of Lead Layer and Structure Shell with 1.5 mm Air Gap Layer
图 7 1 mm空气层下铅层与结构壳体的温度分布
Figure 7. Temperature Distribution of Lead Layer and Structure Shell with 1 mm Air Gap Layer
图 8 3、1.5、1 mm空气层厚度下DSC外壳、铅层和结构壳体的温度变化对比
Figure 8. Comparison of Temperature Variations of DSC Shell, Lead Layer and Structure Shell with 3 mm, 1.5 mm and 1 mm Air Gap Layers
图 9 DSC外壳、铅层和结构壳体在不同空气层厚度下的的温度变化对比
Figure 9. Comparison of the Temperature Variations of the DSC Shell, Lead Layer and the Structural Shell with Air Gap Layers in Different Thicknesses
表 1 不同热发射率下铅层和结构壳体的最高温度（3 mm空气层）
Table 1. Maximum Temperatures of Lead Layer and Structure Shell with 3 mm Air Gap Layer with Different Emissivities
参数 热发射率为0 热发射率为0.28 温差/K 铅层最高温度/K 423.23 423.21 +0.020 结构壳体最高温度/K 366.11 366.11 −0.002 
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表 2 不同空气层下铅层和结构壳体在最终状态下的最高温度
Table 2. Maximum Temperatures of Lead Layer and Structure Shell with Different Air Gap Layers in Final State
对比条件 最终状态
所用时间①/h铅层最高
温度/K结构壳体
最高温度/K两壁面
温差/K3 mm空气层 48.9 423.7 366.4 57.3 1.5 mm空气层 65.5 413.1 383.2 29.9 1 mm空气层 71.6 410.7 385.3 25.4 实际测量值 — 422.6 392.6 30.0 注：“—”—无此项
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表 3 顶盖覆盖板和底部屏蔽层的热流密度
Table 3. Heat Fluxs of Top Cover Plate and Bottom Shielding Layer
空气层 顶盖覆盖板热流
密度/（W·m−2）底部屏蔽层热流
密度/（W·m−2）3 mm空气层 3290.1 449.6 1.5 mm空气层 3138.2 436.2 1 mm空气层 3108.0 432.9
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表 4 顶盖覆盖板和底部屏蔽层的最高温度和安全限值
Table 4. Maximum Temperatures and Safety Limits of Top Cover Plate and Bottom Shielding Layer
对比条件 顶盖覆盖板最高温度/K 底部屏蔽层最高温度/K 3 mm空气层 359.75 350.46 1.5 mm空气层 359.09 349.07 1 mm空气层 359.01 348.73 长期操作安全限值 394.15 394.15
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