The Radioactive Waste Management Funding and Research Center(RWMC) in Japan has been conducting (research and development) for the disposal of radioactive waste since its establishment in 1976. More recently,RWMC has focused on important sociological and technical issues for geological disposal,such as monitoring,remote-handling and site investigation technology. Among these issues,the evaluation of gas migration from a repository is important for the development of more reliable safety assessments. This issue has been studied in a large scale in-situ experiment,the"gas migration test(GMT) in engineered barriers"at Nagra's Grimsel test site(GTS) in Switzerland. GMT has focused on issues related to waste-generated gas migration through the engineered barriers in a silo-type disposal. A reduced scale EBS(engineered barrier system) consisting of a concrete silo with a permeable gas vent and bentonite/sand buffer has been emplaced and instrumented in a specially constructed silo cavern at the GTS. The concrete silo was 2.5 m in height and 2.5 m in diameter and was located in an approximately 4 m diameter shaft excavated from the upper cavern. After saturation of the EBS and water permeability tests,gas was injected into the silo during two main injection periods. After the first gas injection,repeat water permeability tests were performed to identify changes in EBS performance. The second gas injection used a cocktail of gas tracers which were sampled from multiple points in the EBS and geosphere. Following the end of gas injection,the EBS was carefully excavated and characterized using a range of techniques.%自1976年以来,日本核废料管理基金会与研究中心(RWMC)一直在进行核废料处置的研究.最近,RWMC非常关注核废料处置库的监测、遥控以及现场勘查技术等重要的社会公众与技术问题.其中,处置库溢出气体是一项重要的安全可靠性评估项目.这项名为"工程屏障的气体渗透试验"(GMT)的研究是在瑞士Nagra的Grimsel现场实验室进行的.GMT集中研究在粮仓形的处置库中由核废料产生的气体在工程屏障中的渗透问题.在Grimsel现场,一个按比例缩小的工程屏障库由一个具有透气孔的混凝土仓和砂-膨润土缓冲材料组成,缓冲材料被放置在一个专门建造的洞室中.混凝土仓直径为2.5 m,高为2.5 m,放置在直径为4 m的从上到下开挖而成的竖井中.在工程屏障饱和及水渗透试验之后,气体分两个阶段被注入地窖中.气体第一次被注入之后,重复进行水渗透试验,以便观察工程屏障库的变化.第二次气体注入的时候,在工程屏障及岩石圈中采用一种可以多点取样的鸡尾酒气体跟踪器.在气体注入之后,小心挖掘出工程屏障库,然后用各种方法来进行鉴定,并采用实验室以及建模程序来进行现场的模拟研究.
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