北山花岗岩岩屑-膨润土混合材料导热性能研究

高放废物地质处置库缓冲/回填材料的重要作用之一是传导和散失高放废物衰变热，在膨润土中添加石英砂、石墨、花岗岩岩屑等导热性能较好的添加剂是提高缓冲/回填材料导热性能的主要方法。选用北山花岗岩岩屑为添加剂，与高庙子钠基膨润土GMZ01组成混合材料，制备不同含水率、不同密度的试样。使用Hot Disk TPS2500s热常数分析仪测定样品的导热系数，分析其与花岗岩岩屑含量、干密度、饱和度等参数的关系，并运用多种混合物热传导模型分析预测导热系数。研究结果表明，花岗岩岩屑能够有效提高缓冲/回填材料的导热性能，混合材料的导热系数分别与其饱和度、气体体积存在线性关系；Maxwell方程能够较好预测北山花岗岩岩屑-膨润土混合材料的导热系数。

Thermal conductivity of mixtures of Beishan bentonite and crushed granite

One of the major functions of buffering or backfill material is to conduct and dissipate the heat generated by the high-level radioactive waste to the host rock. Sand, graphite and crushed granite rock can improve the thermal property of bentonite with relatively high thermal conductivity. In this paper, mixtures of crushed Beishan granite and GMZ01 bentonite with different dry densities and water contents were compacted, and Hot Disk TPS2500s Thermal Constants Analyzer was used to measure thermal conductivity of the mixtures. The experimental results were analyzed to observe the effects of granite content, dry density, degree of saturation on the thermal conductivity. Various theoretical models were adopted to predict the thermal conductivity of bentonite/crushed Beishan granite mixtures. It is found that the thermal conductivity of GMZ01 bentonite can be effectively improved by the addition of crushed Beishan granite. Linear correlations are observed between the thermal conductivity of bentonite/crushed Beishan granite mixtures and degree of saturation, and volumetric fraction of air, respectively. Maxwell’s equation provides the most satisfactory prediction for the thermal conductivity of bentonite/crushed Beishan granite mixtures.