Americium-241 analysis for plutonium age dating purposes at the Environmental Sampling Laboratory, IAEA

Bujak, R.*; 佐藤 義行; Katona, R.*; Konegger-Kappel, S.*; Koepf, A.*; Boulyga, S.*; Kilburn, M.*

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The environmental sampling program of the International Atomic Energy Agency serves to assess the completeness of State's declaration of the nuclear fuel cycle. Nuclear signatures that are collected on cotton swipes bear valuable information that help to draw safeguards conclusions. There is an increasing need to provide information on the age of Pu material by measuring Pu-241 and its daughter isotope Am-241, hence the Environmental Sample Laboratory (ESL) is extending its analytical capabilities to determine Am-241 down to the fg level. Since the goal of the work was to apply the new procedure to very small quantities of Pu and Am, and also to explore the limitations associated with chemical sample preparation and mass spectrometric analysis, test materials were prepared with 6 - 12 fg Am-241 and 0.6 - 1.2 fg Pu-241. All tested methods satisfactorily removed the REE to below one ppb. The calculated age of the CRM 137 agreed with the consensus value within uncertainties, whereas the expanded uncertainty (k=2) of the age varied between 4 and 4.5 years due to the very low amounts of Am and Pu analyzed.