Semi-quantitative analysis of leaf surface contamination by radioactivity from the Fukushima Daiichi nuclear power plant accident using HPGe and imaging plate |
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Authors: | Etsuko Furuta |
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Institution: | 1. Graduate School of Humanities and Sciences, Ochanomizu University, 2-1-1 Otsuka, Bunkyo-ku, Tokyo, 112-8610, Japan
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Abstract: | After the nuclear power plant accident at Fukushima Daiichi on 11 March 2011, green-leaves from trees, dead-leaves and grass on ground were collected from March to June 2011 in Japan. Radioactive concentrations were measured by a high purity germanium detector. Five radionuclides including 129mTe, 132Te, 131I, 134Cs and 137Cs were detected. The fission product concentration of the dead-leaves was higher than those of the green-leaves in many cases. The highest concentration observed was found on the dead-leaves collected at Iwaki, 60 km far from Fukushima Daiichi. A total activity of 2,000 Bq g?1 was measured for all 5 radionuclides. Clear images of radioactivity of the highly contaminated leaves were obtained with an imaging plate (IP) after <24 h exposure time without using a shielded box. The photostimulated luminescence values (PSL) of leaves arranged on half size of IP were roughly in proportion to their activities except for the low activity samples. Semi-quantitative analysis was possible by using PSL values with a large region of interest of half size of IP, because the radioactivity released in the case of the nuclear power plant accident was uniform in the early days. |
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