兰州大学机构库 >土木工程与力学学院
高放废物缓冲砌块导热性能研究
Alternative TitleStudy on thermal conductivity of compacted bentonite block as HLW buffer
赵秉正
Thesis Advisor张虎元
2017-04-30
Degree Grantor兰州大学
Place of Conferral兰州
Degree Name硕士
Keyword高放废物 地质处置 缓冲砌块 膨润土-砂混合物 导热性能
Abstract

缓冲砌块作为高放废物地质处置库中重要的屏障,需要有良好的导热性能。将高庙子(GMZ)膨润土和标准石英砂混合,采用半自动化液压机压制大型缓冲砌块,测试含水率、干密度与其导热性能的关系,并在此基础上探讨缓冲砌块导热性能均匀性检验方法和导热系数预测模型的适用性。

研究发现,随含水率和干密度的增大,缓冲砌块导热系数极值(最大值、最小值)和平均值都显著增大,大致呈线性关系;且平均值均大于IAEA推荐的导热系数下限值0.8W/m∙K,满足推荐要求。导热系数的最大相对误差随着含水率和干密度的增大逐渐减小,即缓冲砌块导热系数趋于均匀,且含水率增大时趋势更明显。随含水率和干密度的增大,热扩散系数的极值和平均值都总体呈增大趋势,基本呈非线性。随含水率和干密度的增大,质量比热容的极值和平均值变化不显著,基本呈平稳趋势。

缓冲砌块导热系数在R、Q、Z三个方向上具有良好的各向同性。采用t检验法对缓冲砌块导热系数进行均匀性检验,与实测结果相同,证明t检验法今后可以用来检验缓冲砌块导热系数的均匀性。

经导热系数实测值验证,Johansen模型能够较准确地预测缓冲砌块的导热系数,其偏差在±10%以内,吻合度较高。采用该预测模型对初始干密度为1.50g/cm3~1.90g/cm3,水化愈合之后的缓冲砌体结构导热系数进行了预测。结果表明,缓冲砌体结构导热系数随其初始干密度的增大而增大;且接缝处理组的导热系数明显大于刚性拼接组的导热系数,随着初始干密度的增大,这种趋势更加明显。研究认为,水化愈合之后的缓冲砌体结构的导热系数范围为1.5~2.2W/m·K,此量值可供处置结构多场耦合计算参考。

Other Abstract

Satisfactory thermal conductivity property is essential to buffer block as high-level radioactive waste (HLW) barrier. By using semi-automatic pressing apparatus, buffer blocks with the mixtures of GMZ bentonite and standard quartz sand were prepared to study the effect of water content and dry density on the thermal performance of buffer block and so to evaluate the uniformity of thermal performance and the feasibility of predicting model.

Test results show that: the mean value and extreme values (both maximum and minimum) of thermal conductivity of buffer blocks increase linearly with increase in water contents and dry densities. The mean value of thermal conductivity satisfies the requirement, which is more than 0.8 W/m∙K recommended by IAEA. The maximal relative errors of thermal conductivity decrease as water contents and dry densities increase. It means that thermal conductivity of buffer blocks tends to be homogeneous, especially at a more dense and wet condition. The mean value and extreme values of thermal diffusion coefficient increase nonlinearly as water contents and dry densities increase. No obvious change was found on mean value and extreme values of mass specific heat capacity for blocks with water contents and dry densities increase.

The thermal conductivity of buffer blocks exhibits a good homogeneity in the directions along R, Q and Z axis. Test results are in agreement with results of t test in statistics, and that proves t test can be successfully used to check the thermal conductivity data of buffer blocks in the future.

Data analysis shows that Johansen model can predict thermal conductivity of buffer block with an error less than ±10% compared with the experimental values. Johansen model was used to a supposed barrier, which is to be constructed with blocks whether the block joints are sealed or not in case that contact with water to predict the thermal conductivity of buffer blocks of 1.50g/cm3~1.90g/cm3 in dry densities. The results show that the thermal conductivity of “practical” buffer block barrier increase as initial dry densities increase and the sealed situation has a better thermal conductivity than that of the un-sealed situation. This tendency is much more obvious as initial dry densities increase. Generally, the values of thermal conductivity are among 1.5~2.2W/m·K, which is a good reference for multi-field coupling simulation of depository barrier.

URL查看原文
Language中文
Document Type学位论文
Identifierhttps://ir.lzu.edu.cn/handle/262010/226439
Collection土木工程与力学学院
Recommended Citation
GB/T 7714
赵秉正. 高放废物缓冲砌块导热性能研究[D]. 兰州. 兰州大学,2017.
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