ACTIVITY RATIO OF URANIUM IN FUKUSHIMA SOIL SAMPLES USING MULTI-COLLECTOR INDUCTIVELY COUPLED PLASMA MASS SPECTROMETRY

The Fukushima soils have been collected from Namie and Futaba areas for the radiocaesium and uranium isotope ratio studies. The Cs-137 activity concentration of soil samples ranged from 6 +/- 1 to 756 +/- 14 kBq/kg. The uranium isotope ratios are measured using multi collector inductively coupled plasma mass spectrometry. The activity ratio (U-234/U-238) of the Fukushima soils is calculated from the measured U-234/U-238 isotope ratio. Activity ratio varied from 0.98 to 1.02 which indicates that U-234 and U-238 are in secular equilibrium. The U-235/U-238 atomic ratio of the Fukushima soils did not show any heterogeneity compared with the natural terrestrial ratio even with high level of Cs-137 in soils.