Reaching environmental levels of 244 Pu by accelerator mass spectrometry at the Centro Nacional de Aceleradores

Pu (T = 81 My) is the longest-lived, most minor, and the most understudied Pu isotope. The anthropogenic production of Pu is linked to nuclear detonations. Reported Pu/ Pu atom ratios in environmental samples range from below 10 to above 10 . This work discusses the performance of the 1 MV Accelerator Mass Spectrometry system at the Centro Nacional de Aceleradores (CNA, Seville, Spain) to analyse Pu at environmental levels. The presence of Th traces in the Pu sample limits the sensitivity of the technique through the formation of the diatomic trication ( Th C) , of mass 244 u, which must be suppressed by adjusting the stripper gas pressure. A Pu background of 0.0075 fg (2 × 10 at) is demonstrated for samples that have undergone a chemical treatment. The reliability of the technique is proved through the analysis of three reference sediments provided by the International Atomic Energy Agency (IAEA-412, IAEA-465, IAEA-385). Pu results are complemented with Pu, Pu, Pu and U and their relative isotopic abundances are discussed.