Measurement of uranium isotope ratios in Fukushima-accident contaminated soil samples using multi collector inductively coupled plasma mass spectrometry.

In the present study, Cs and U activity concentrations, U/U activity ratio, and U/U isotope ratio were measured in fifteen soil samples collected from the exclusion zone around the Fukushima Daiichi Nuclear Power Station (FDNPS). The Cs activity concentrations of Fukushima-accident contaminated soil samples ranged from 29.9 to 4780 kBq kg with a mean of 2007 kBq kg. On the other hand, the U activity concentrations of these soil samples ranged from 5.2 to 22.4 Bq kg with a mean of 13.2 Bq kg. The activity ratios of U/U ranged from 0.973 to 1.023. The U/U isotope ratios of these exclusion zone soil samples varied from 0.007246 to 0.007260, and they were similar to the natural terrestrial ratio confirming the natural origin. Using isotope dilution technique, the U/Cs activity ratio was theoretically estimated for highly Cs contaminated soil samples from Fukushima exclusion zone ranged from 5.01 × 10 - 6.16 × 10 with a mean value of 2.51 × 10.