膨润土-砂混合物缓冲层轴向热传导性研究

Study on axial thermal conductivity of bentonite-sand mixed buffer layers

膨润土-砂混合物作为高放废物处置库缓冲材料,在高放废物衰变释热作用下,其物理力学性能对处置库的稳定和安全性具有重要影响。本研究采用自行设计的装置,对按比例缩小后的不同干密度、含水率、掺砂率试样进行热传导模拟试验,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、应力和应变的变化及分布情况,重点分析了温度的影响。结果表明,增大试样干密度、含水率和掺砂率均可提高其导热性,应变也随之增大,应力受温度影响较早达到平衡;缓冲层靠近热源的位置温度、应力和应变最大,沿轴向方向递减,初始时刻变化明显。

Physical and mechanical properties of bentonite-sand mixtures have important influence on the stability and safety of a high level radioactive waste repository when they are used as buffer materials for high level radioactive waste repository,which may be affected by the decay heat released from high level radioactive wastes. Some heat conduction simulation tests for small samples with different dry density,water content,and sand content were carried out using a designed device in our study. The thermal-mechanical coupling process of buffer layer was simulated and analyzed,and variation and distribution of temperature,stress and strain of buffer layers were obtained with a focus on the influence of temperature. The results show that the increasing of dry density,water content and sand content can increase thermal conductivity and strain,stress is affected by temperature and reaches equilibrium earlier,and the temperature,stress and strain of buffer layer near heat source are the largest and decrease along the axial direction,with obvious change at the initial period.