Journal Article Establishing rapid analysis of Pu isotopes in seawater to study the impact of Fukushima nuclear accident in the Northwest Pacific

Men, Wu  ,  Zheng, Jian  ,  Wang, Hai  ,  Ni, Youyi  ,  Aono, Tatsuo  ,  L Maxwell, Sherrod  ,  Tagami, Keiko  ,  Uchida, Shigeo  ,  Yamada, Masatoshi

Rapid determination of Pu isotopes in seawater has taken on great importance, especially after the Fukushima Dai-ichi Nuclear Power Plant (FDNPP) accident. In this study, a rapid method to determine Pu isotopes in seawater by sector field inductively coupled plasma mass spectrometry (SF-ICP-MS) including Fe(OH)2 primary co-precipitation, CaF2/LaF3 secondary co-precipitation and extraction chromatographic (TEVA, UTEVA, and DGA resins) separations, was developed. A high concentration efficiency of Pu isotopes via Fe(OH)2 co-precipitation (~100%) and a satisfactory high U decontamination factor of ~107 were achieved. The plutonium chemical recoveries for the entire method were 74-88% with the mean of 83±5%. This method can achieve a precision of less than 5% for both 240Pu/239Pu atom ratios and 239+240Pu activity concentrations when 15 L of seawater samples with the typical 239+240Pu activity of the Northwest Pacific are measured. The limit of detection (LOD) for both Pu isotopes was 0.08 fg/mL, which corresponded to 0.01 mBq/m3 for 239Pu and 0.05 mBq/m3 for 240Pu when a 15 L volume of seawater was analyzed. The analysis of plutonium in seawater using this new method takes only 12 hours. This method was applied to determine Pu isotopes in the seawater samples collected 446-1316 km off the FDNPP accident site in the Northwest Pacific in July of 2013. The obtained 239+240Pu activity concentrations of 1.23-1.95 mBq/m3 and the 240Pu/239Pu atom ratios of 0.203-0.262 suggested that there was no significant Pu contamination from the accident to the Northwest Pacific.

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