高放废物地质处置库热学分析的参数敏感性研究

Parameter sensitivity study in the thermal analysis of the geological disposal repository of high-level waste in China

应用FLAC3D软件建立高放废物地质处置库热学分析的简化计算模型,选择影响处置库温度场的包括材料热学参数、几何参数以及时间参数在内的16个关键参数,以膨润土内表面峰值温度(该物理量是高放废物地质处置库热学设计计算中作为温度准则的物理量)为参数敏感性分析的目标物理量,通过热学计算开展参数敏感性分析。在参数敏感性分析中,将参数敏感程度划分为高、中、低三等。分析表明:4个参数(膨润土导热系数、膨润土厚度、围岩导热系数、高放废物中间贮存时间)为高敏感度参数,2个参数(散热材料厚度、回填材料厚度)为中度敏感性参数,其它10个参数(高放玻璃固化废物体、外包装容器、散热材料、回填材料的导热系数与比热,以及膨润土与围岩的比热)为低敏感度参数。通过分析可以得到如下结论:在设计高放废物地质处置库时,对膨润土及围岩导热系数的测试应力求准确,对测试结果数据认真分析,确保为设计计算提供合理的输入参数;在确保膨润土满足工艺要求功能的前提下,宜尽量减小膨润土的厚度;按照本文热学分析模型初步估算,我国高放废物至少需要中间贮存20 a以上。

A simplified thermal model of geological disposal repository of high-level waste( HLW) in China is generated by the numerical code FLAC3 D. Sixteen key parameters having impact on the temperature field of geological disposal repository,including thermal,geometric and time parameters,are carefully selected. Peak temperature of inner surface of the bentonite,which is related to the temperature criterion for thermal design calculation of the geological disposal repository of HLW,is treated as the object temperature in the parameter sensitivity analysis. In the analysis,sensitivity degree is classified as three categories: high,medium and low. The research reveals that: 1) the following four parameters are of high sensitivity degree: conductivity of the bentonite; thickness of the bentonite; conductivity of the host rock; interim storage time of HLW. 2) thickness of heat spreader and backfill material are of intermediate sensitivity degree. 3) The rest ten parameters are of low sensitivity degree: thermal conductivity and specific heat of vitrified HLW,overpack,heat spread,backfill material,and specific heat of bentonite and host rock. Some conclusions are drawn from the analysis: in the design of geological disposal repository of HLW,accurate conductivity of bentonite and host rock should be obtained,the test results must be carefully treated to ensure the appropriate input in the design calculation; the thickness of bentonite may be reduced under the circumstances that the bentonite performs well in the engineered barrier system; more than 20 years of the interim storage time of HLW in China is estimated based on the simplified thermal model.