Determination of actinides in Pacific Ocean water by AMS with respect to the Fukushima accident

A chemical separation procedure for plutonium (Pu) and neptunium (Np) was developed using extraction chromatography to determine their amounts and isotopic ratios in sea water. ²⁴¹Am, which causes isobaric background on ²⁴¹Pu in mass-spectrometric measurements, was successfully separated from the Pu fraction by this method. Water samples which were spiked with ²⁴²Pu and ²³⁷Np or ²³⁹Np, respectively, were used for chemical yield determination. Chemical yields of Pu and Np, which were determined by alpha and gamma spectrometry at the Radiochemie Muenchen, of more than 85 % were obtained. The developed method was applied to analyze the amount of Pu and Np in the certified reference material, IAEA-443, by accelerator mass spectrometry (AMS) at the Maier-Leibnitz-Laboratory to check the applicability of the method. The amounts of ²⁴⁰Pu, ²⁴¹Pu and ²³⁷Np obtained in this study are in agreement with the literature values within the uncertainties. This method can be used for the analysis of Pu and Np in Pacific Ocean water samples collected after the Fukushima accident.