The Fukushima-Daiichi nuclear power station accident in East Japan in 2011 released radioactive cesium (r-Cs) into the surrounding environment. In addition to the major contamination of soil and vegetation, surrounding concrete structures have also been contaminated. Understanding the contamination characteristics is important for the decontamination or disposal of offsite and onsite concrete structures. However, r-Cs contamination of actual concrete has not been extensively investigated. In this paper, the r-Cs contamination characteristics of actual concrete are introduced on the basis of several field surveys and analysis of concrete samples taken from actual contaminated structures in the Fukushima prefecture. As no dissolution to water was detected, the surface contamination was safely removed by water-jet abrasion. However, in KCl solution, significant dissolution of r-Cs was detected. A contamination depth analysis was performed by quantitative r-Cs concentration mapping based on β-ray radiography using imaging plates. In many cases, such as roadside gutter cover plates, r-Cs was located on the surface without significant penetration into the concrete. However, in cases such as degraded concrete, deeper penetration up to several millimeters deep was observed. In cracked concrete, the r-Cs penetrated at least 10 cm, with the contamination level decreasing one order of magnitude in the first 1 cm.

中文翻译：

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福岛第一核电站事故后混凝土放射性铯污染现场调查

2011 年在日本东部发生的福岛第一核电站事故向周围环境释放了放射性铯 (r-Cs)。除了土壤和植被受到严重污染外，周围的混凝土结构也受到了污染。了解污染特征对于场外和现场混凝土结构的净化或处置非常重要。然而，实际混凝土的 r-Cs 污染尚未得到广泛研究。在本文中，在对福岛县实际污染结构中的混凝土样品进行多次实地调查和分析的基础上，介绍了实际混凝土的 r-Cs 污染特性。由于未检测到溶解于水，因此通过水射流磨损安全地去除了表面污染物。然而，在 KCl 溶液中，检测到 r-Cs 的显着溶解。污染深度分析是通过使用成像板基于 β 射线照相的定量 r-Cs 浓度映射进行的。在许多情况下，例如路边排水沟盖板，r-Cs 位于表面上，而没有明显渗透到混凝土中。然而，在退化混凝土等情况下，观察到更深的渗透可达几毫米。在开裂的混凝土中，r-Cs 穿透了至少 10 厘米，污染水平在前 1 厘米内下降了一个数量级。r-Cs 位于表面上，没有明显渗透到混凝土中。然而，在退化混凝土等情况下，观察到更深的渗透可达几毫米。在开裂的混凝土中，r-Cs 渗透至少 10 厘米，污染水平在前 1 厘米内下降了一个数量级。r-Cs 位于表面上，没有明显渗透到混凝土中。然而，在退化混凝土等情况下，观察到更深的渗透可达几毫米。在开裂的混凝土中，r-Cs 渗透至少 10 厘米，污染水平在前 1 厘米内下降了一个数量级。