Specific activity and activity ratios of radionuclides in soil collected about 20 km from the Fukushima Daiichi Nuclear Power Plant: Radionuclide release to the south and southwest

Abstract

Soil samples at different depths (0-2, 5-7 and 10-12cm) were collected from J Village, about 20km south of Fukushima Daiichi Nuclear Power Plant (FNPP) to determine their radionuclide specific activities and activity ratios. The concentrations and activity ratios of (131)I, (134, 136, 137)Cs and (129m)Te were obtained, but only trace amounts of (95)Nb, (110m)Ag and (140)La were detected which were too low to provide accurate concentrations. Radionuclides such as (95)Zr, (103, 106)Ru and (140)Ba that were found in Chernobyl fallout, were not found in these soil samples. This suggests that noble gasses and volatile radionuclides predominated in the releases from FNPP to the terrestrial environment. The average activity ratios of (131)I/(137)Cs, (134)Cs/(137)Cs, (136)Cs/(137)Cs and (129m)Te/(137)Cs were 55, 0.90, 0.22 and 4.0 (corrected to March 11, 2011) in the 0-2cm soil samples of April 20 and 28, 2011.