Natural variation of ambient dose rate in the air of Izu-Oshima Island after the Fukushima Daiichi Nuclear Power Plant accident
Abstract
The ambient dose rate in air and radioactivity concentration in soil samples collected on Izu-Oshima Island were observed in 2012, 2013 and 2014, i.e. 1, 2 and 3 years after the severe accident at the Fukushima Daiichi Nuclear Power Plant. A car-borne survey for the ambient dose rate in air was carried out for the entire island. Soil samples were collected for the radioactivity concentration measurements from 22 points. The ambient dose rates in air were 36 nGy h−1 in 2012, 34 nGy h−1 in 2013 and 29 nGy h−1 in 2014. The corresponding radioactivity concentrations in those years for 134Cs were 53, 39 and 29 Bq kg−1 and for 137Cs, 87, 73 and 75 Bq kg−1. All the values have decreased every year.
分别对2012年2013和2014年也就是辅导事故的后123年，对空气的环境剂量率和突然样品的比活度数据进行了收集。地点为日本的Izu-Oshima 岛，使用车载巡测了全岛的环境剂量率，土壤样品则选择了22个点进行了比活度测量。空气中的环境剂量率竟然才只有几十个纳，比我国的本底还低，说明空气中的污染已经很轻微了或者说完全没有了，不过土壤中的Cs-134和Cs-137还是有一些浓度的，说明了长寿命的还是存在的，尤其是Cs-137，30多年的半衰期，但是数据总体显示，两种核素的浓度每年都在减少，这个其实不说也知道的。