Determination of isotopic ratios of plutonium and uranium in soil samples by thermal ionization mass spectrometry

Isotopic ratios of plutonium and uranium in soil samples were investigated, in order to understand the level of contamination with plutonium and uranium released at the accident of Fukushima Daiichi nuclear power plant. At first, plutonium and uranium were recovered from the standard reference soil/sediment materials by extraction/ion-exchange chromatography, and their isotope compositions were analyzed by TIMS. By applying our analytical technique to soil samples obtained from Fukushima prefecture, a possibility of atmospheric release of nuclear fuel material during the accident of FDNPP was discussed. The contamination with uranium was under detection limit, while that with plutonium was observed.