Distribution of 137Cs on components in urban area four years after the Fukushima Dai-ichi Nuclear Power Plant accident

Distribution of 137Cs on components in urban areas such as roofs and roads is crucial for evaluating the behavior of radiocesium and ambient dose rates in the area. This study evaluated relative 137Cs inventories, which are defined as the relative values of 137Cs inventory on each component to that on a nearby permeable plane field, for 11 buildings in the evacuation zone about four years after the Fukushima Dai-ichi Nuclear Power Plant accident. The average relative inventory of paved ground accounted for 0.18 of that on permeable plane fields. Other components showed small average values of less than 0.1, indicating rapid removal of radiocesium from urban areas even without decontamination. The differences in the relative inventories on roads and roofs with those in the case of Europe suggest that human activity and component materials largely affect the reduction of radiocesium in urban area.