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

摘要

Soil samples at different depths (0-2,5-7 and 10-12 cm) were collected fromj Village, about 20 km south of Fukushima Daiichi Nuclear Power Plant (FNPP) to determine their radionuclide specific activities and activity ratios. The concentrations and activity ratios of 131I, m m 137Cs and 129mTe were obtained, but only trace amounts of 95Nb, 11OmAg and 140La were detected which were too low to provide accurate concentrations. Radionuclides such as 95Zr,103' 106Ru and 140Ba 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 1311/137Cs, 134Cs/137Cs, 135Cs/137Cs and i29mTe/i37Cs were 55, 0.90, 0.22 and 4.0 (corrected to March 11, 2011) in the 0-2 cm soil samples of April 20 and 28, 2011.