UO2/BeO界面热阻及其对燃料导热系数的影响
UO2/BeO interfacial thermal resistance and its effect on fuel thermal conductivity
摘要：
采用扩散失配模型（DMM）计算了UO 2/BeO界面热阻（ITR），研究了界面热阻对UO 2-BeO热导率的影响。DMM预测的ITR约为10-9 m2 K/W。利用该ITR，通过理论模型计算了UO_2-BeO的热导率，并与实验数据进行了比较。结果表明，DMM预测适用于UO 2与分散BeO之间的界面，而不适用于UO 2与连续BeO之间的界面。如果要使含连续BeO的UO_2的热导率与实验数据相符合，则其ITR应在10 ~（-6）~ 10 ~（-5）m ~ 2K/W的数量级。因此，DMM认为UO_2和BeO之间的振动失配是UO_2/弥散BeO界面热流衰减的主要机制，而不是UO_2/连续BeO界面热流衰减的主要机制。此外，它被发现，ITR的存在导致的UO 2的热导率分散BeO的BeO尺寸的依赖性。随着BeO尺寸的减小，UO 2-BeO的热导率降低。当BeO尺寸小于临界值时，UO 2-BeO热导率变得甚至小于UO 2热导率。对于含有连续BeO的UO 2，热导率随被BeO包围的UO 2颗粒尺寸的减小而减小，但不一定小于UO 2热导率。在临界温度下，UO 2-BeO体系的热导率始终大于UO 2的热导率。在临界温度以上，只有当UO 2颗粒尺寸足够大时，UO 2-BeO体系的热导率才大于UO 2的热导率。导出了通过掺杂BeO实现UO 2热导率有针对性提高的条件。这些条件可用于设计和优化BeO的分布、含量、尺寸和UO 2颗粒的尺寸。
英文摘要：
UO2/BeO interfacial thermal resistance (ITR) is calculated by diffuse mismatch model (DMM) and the effects of ITR on UO2-BeO thermal conductivity are investigated. ITR predicted by DMM is on the order of 10-9 m2K/W. Using this ITR, UO2-BeO thermal conductivities are calculated by theoretical models and compared with experimental data. The results indicate that DMM prediction is applicable to the interface between UO2 and dispersed BeO, while not applicable to the interface between UO2 and continuous BeO. If the thermal conductivity of UO2 containing continuous BeO was to be in agreement with experimental data, its ITR should be on the order of 10-6 - 10-5 m2K/W. Therefore, the vibrational mismatch between UO2 and BeO considered by DMM is the major mechanism for attenuating the heat flux through UO2/dispersed-BeO interface, but not for UO2/continuous-BeO interface. Furthermore, it is found that the presence of ITR leads to the dependence of the thermal conductivity of UO2 containing dispersed BeO on BeO size. With the decrease in BeO size, UO2-BeO thermal conductivity decreases. When BeO size is smaller than a critical value, UO2-BeO thermal conductivity becomes even smaller than UO2 thermal conductivity. For UO2 containing continuous BeO, the thermal conductivity decreases with the decrease in the size of UO2 granule surrounded by BeO, but not necessarily smaller than UO2 thermal conductivity. Under a critical temperature, UO2-BeO thermal conductivity is always larger than UO2 thermal conductivity. Above the critical temperature, UO2-BeO thermal conductivity is larger than UO2 thermal conductivity only when UO2 granule size is large enough. The conditions for achieving the targeted enhancement of UO2 thermal conductivity by doping with BeO are derived. These conditions can be used to design and optimize the distribution, content, size of BeO, and the size of UO2 granule.
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