Measurement of (90)Sr radioactivity in cesium hot particles originating from the Fukushima Nuclear Power Plant Accident

A method for the determination of (134+137)Cs and (90)Sr in cesium hot particles (Cs-HPs) originating from the Fukushima Daiichi Nuclear Power Plant accident has been developed. The method depends on a response function that is calculated by PHITS code and fitted to the beta-ray spectrum measured with a Si-detector. The (134+137)Cs radioactivity in the Cs-HPs was consistent with that measured by a Ge-detector, thus confirming the reliability of the method. The (90)Sr/(137)Cs ratios, which ranged from 0.001 to 0.0042, were consistent with a (90)Sr/(137)Cs inventory ratio for contaminated soil samples. That is, the extracted Cs-HPs contained (90)Sr in the same ratio as that for the (90)Sr/(137)Cs inventory ratio for the contaminated soils. The method is attractive in that the samples are unaltered, andthat no chemical separation techniques are required.