γ辐射和高温对放射性废物水泥固化体强度的影响(英文)

Effect of Gamma Radiation and Elevated Temperatures on the Strength of Cementitious Barriers for Radwaste Disposal

为了处理高活性、放热性C级放射性废弃物,在比利时通常采用圆柱体混凝土"超级容器"作为基本途径。"超级容器"是合成的废弃物包,废弃物由碳钢包裹组成,碳钢被波特兰水泥制成的"缓冲器"包裹。自密实混凝土作为一种特殊类型的混凝土,正被考虑用来制备"缓冲器"。一旦"缓冲器"被浇筑并且硬化程度很高时,放射性废弃物就被包裹在"缓冲器"内,存在的缝隙可以采用新拌灌浆料填充(例如自密实砂浆)。用盖子将"超级容器"密封后应用于"超级容器"的混凝土层,即混凝土缓冲器、灌浆料及盖子在硬化期间(灌浆料)与硬化之后("缓冲器"与盖子)将暴露在废弃物热场与辐射场内。因此,需要解决2个主要的问题:1)γ射线(α与β射线被碳钢包裹层阻断,中子的影响可以忽略)对灌浆料硬化强度的影响;2)温度升高(从20℃升高到105℃)对硬化试件强度的影响。为了证实强度是否损失并确定强度损失后的主要机理,采用荧光显微镜,在砂浆或混凝土薄片的截面上直接分析毛细孔隙率。

During fabrication of the Supercontainer,the Belgian reference concept for the disposal of highly active,heat-emitting C-level waste assemblies,the different cementitious layers are exposed to external gamma radiation and heat attack.One special type of concrete is being considered for the buffer： a self-compacting concrete（SCC）.Once the buffer is cast and hardened sufficiently,the radwaste is emplaced inside the buffer layer of the supercontainer,and the remaining gap is filled by casting a fresh filler material（e.g.an SCC based mortar）.Afterwards the container is closed by fitting the lid.As a consequence,the concrete layers applied for the Su-percontainer,i.e.the concrete buffer,the filler and the lid,will be exposed to the heat-emitting radioactive waste during hardening（the filler material） and in a hardened state（the buffer and the lid）.Two main questions need to be answered： 1） What is the effect of gamma radiation（alpha radiation,beta radiation are blocked by the carbon steel overpack,the impact of the neutrons can be neglected） on the strength of the hardening filler material？ 2） What is the effect of elevated temperatures（between 20-105 ℃） on the strength of hardened samples？ Therefore a preliminary study is conducted to verify whether a possible strength loss can be noticed and to identify the main mechanisms behind the strength loss via fluorescence microscopy（directly linked to the capillary porosity） conducted on thin sections of the concrete or mortar samples.