混合型缓冲回填材料导热性能试验

Experimental study on thermal properties of the bentonite-sand mixed buffer backfill materials

为提高高放废物地质处置库中缓冲回填材料的导热性能,选用高庙子钙基膨润土和钠基膨润土为基础材料,添加不同比例的石英砂、石墨和沸石配置成混合型缓冲回填材料,运用瞬变平面热源法进行了不同含水率、不同干密度条件下导热系数的测试分析,并提出了混合型缓冲回填材料的建议配合比。结果表明,缓冲回填材料的导热性能随着含水率、干密度的增大而增大,各材料导热系数的大小排序为:石墨(M)>石英砂(S)>钠基膨润土(N)>钙基膨润土(G)>沸石(F)。石英砂和石墨作为添加剂可以极大地提高缓冲回填材料的导热性能,沸石对混合材料导热性影响不大,但其优良的吸附性与化学稳定性可为混合型缓冲回填材料其他性能提供保障。

In order to improve the thermal performance of the buffer backfill materials in the high-level radioactive waste geological repository,the Gaomiaozi sodium bentonite( N) and calcium bentonite( G) are selected as basic materials which are mixed with various proportions of quartz sand,graphite,and zeolite to form the mixed buffer backfill materials. Their thermal conductivities under conditions of various moisture contents and dry densities have been measured by using transient plane heat source method. The recommended mix ratio of the mixed buffer backfill material has been proposed in this paper. The test results show that the thermal conductivities of the buffer backfill materials are increased with the increase of their water contents and dry densities. The thermal conductivities of various materials are decreased in following order from graphite( M),quartz sand( S),sodium bentonite( N),calcium bentonite( G),to zeolite( F). The thermal conductivities of buffer backfill materials can be greatly improved with the addition of quartz sand and graphite as their additives. Zeolite has little effect on the thermal conductivities of the buffer backfill materials,but its excellent adsorption capacity and chemical stability can provide guarantee for other properties of the mixed buffer backfill materials.