膨润土-砂混合物缓冲层热传导性试验研究

由于高放废物长期衰变放热,因此缓冲材料的热性能参数对处置库的稳定和安全运营具有重要意义。膨润土-砂混合物中石英砂的掺入可有效改善其热传导性能。本研究采用中粒石英砂作辅料,利用Hot Disk TPS2500s热常数分析仪对不同干密度、掺砂率和含水率试样进行测量,分析不同参数对导热性能的影响;采用自行设计的装置对按比例缩小后的试样进行不同热源温度下的热传导模拟试验,并对缓冲层热-力耦合过程进行数值模拟分析,得到了缓冲层温度、应力和位移的变化及分布情况,对比分析不同热源幅值对其分布影响的敏感程度。研究结果表明,导热系数随着干密度、掺砂率增大而增大,且含水率越高增幅越明显;热源温度越高,缓冲层温度、应力及位移的变化越大,且热-力耦合条件下,径向比轴向变化相对较大。热源温度较低时处置库更为稳定。

Study on Thermal Conductivity Test of Bentonite-sand Mixed Buffer Layer

Because of the long-term decay and heat release of high-level radioactive wastes, the thermal performance parameters of the buffer material are of great significance for the stable and safe operation of the disposal repository. The addition of quartz sand in bentonite - sand mixture can effectively improve its thermal conductivity. In this study, medium-grained quartz sand was used as auxiliary material, and Hot Disk TPS2500s thermal constant analyzer was used to measure samples with different dry densities, sand content and water content. The influence of different parameters on thermal conductivity was analyzed. A self-designed device was used to simulate the heat conduction test for samples of scaling reduction at different heat source temperatures, and thermal-mechanical coupling process of the buffer layer was simulated and analyzed. The variation and distribution of temperature, stress and displacement of the buffer layer were obtained, and the sensitivity of the influence of different heat source amplitude to its distribution was compared and analyzed. The results show that the thermal conductivity increases with the increase of dry density and sand content, and the higher the water content is, the more obvious the increase is. The higher the temperature of the heat source is, the greater the change of the temperature, stress and displacement of the buffer layer is. Under thermal-mechanical coupling, the radial variation is relatively larger than axial variation. The disposal repository is more stable when the heat source temperature is lower.