||VARIABILITY OF RADIOCAESIUM INVENTORY IN FUKUSHIMA SOIL CORES FROM ONE SITE MEASURED AT DIFFERENT TIMES
Mishra, S. ,
Arae, H. ,
Sorimachi, A. ,
Hosoda, M. ,
Tokonami, S.ishikawa, T.
Radiation Protection Dosimetry
347 , 2015-11 , Oxford University Press
The Fukushima Daiichi Nuclear Power Plant (FDNPP) accident has resulted in the deposition of radioactive contamination of soils mainly by 134Cs and 137Cs. The contaminated areas are of a great concern since external radiation may lead to significant long-term doses to humans and animals. External dose rate above ground will decrease with physical decay of the radionuclides and as they migrate deeper into the soil with time. In the present study, depth profiles of Cs radioisotopes have been studied at dif- ferent times over a period of 1 y. Radiocaesium inventories for 134Cs and 137Cs down to a depth of 10 cm at the four measurement times varied from 2.09 to 4.14 MBq m22 with coefficient of variation (CV): 27.4 %, n 5 4 and from 2.13 to 4.23 MBq m22 with CV: 27.3 %, n 5 4, respectively. The activity ratio for 134Cs/137Cs decreased from 0.62 to 0.46 during 1 y of measurement i.e. July 2012 to June 2013. However, the ratio with decay correction (15 March 2011) was found to be constant ∼1, indicating con- tamination from FDNPP origin. In order to understand the radiocaesium distribution in soil profile, physico-chemical character- isation of soil has been carried out.