Standardization of 243Am

Published

May 2, 2026

Author(s)

Madeleine Bodine, Lizbeth Laureano-Perez, Ronald Colle, Justin Wilde, Ryan Fitzgerald, Leticia Pibida, Jerome LaRosa, Adam Pearce, Richard Essex, Denis Bergeron

Abstract

Americium's longest-lived isotope, americium-243, has a half-life of 7367(23) years. It decays into neptunium-239 through alpha decay. Americium has a few practical uses: as a monitor for radioactive contamination and as a tracer for radiochemical processes. An 243Am solution was standardized by 4 liquid scintillation (LS) spectrometry with two commercial LS counters. The beta detection efficiencies for the 243Am daughter (239Np) were calculated for the CIEMAT/NIST efficiency tracing (CNET) and the triple-to-double coincidence ratio (TDCR) methods using a modified MICELLE2 code and accounting for contributions from the delayed (T1/2 = 193 ns) γ-ray emission from an excited state of 239Pu. Five confirmatory measurements of the activity were performed by 1) LS counting comparative measurements against the previous version of this standard SRM 4332e, which was standardized in 2008 by CIEMAT/NIST efficiency tracing using 3H as the detection efficiency monitor; 2) live-timed anticoincidence (LTAC) measurements; 3) triple-to-double coincidence ratio counting; 4) gamma spectrometry with high resolution HPGe detectors; and 5) decay energy spectrometry (DES) using transition edge sensors. Alpha spectrometry found a combined activity of 239, 240Pu of 0.087(2) Bq·g-1. The activity ratio of 241Am/243Am was obtained by alpha spectrometry, gamma-ray spectrometry, mass spectrometry, and DES, with an average value of 0.00168(3). Mass spectrometry was also used to obtain values for 239Pu, 240Pu and 241Pu impurities.

Citation

Applied Radiation and Isotopes

Volume

235

Pub Type

Journals

Download Paper

https://doi.org/10.1016/j.apradiso.2026.112674

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Keywords

anticoincidence, americium-243, CNET, TDCR, gamma-ray spectrometry, DES, liquid scintillation, TDCR, LTAC, Mass Spectrometry

Citation

Bodine, M. , Laureano-Perez, L. , Colle, R. , Wilde, J. , Fitzgerald, R. , Pibida, L. , LaRosa, J. , Pearce, A. , Essex, R. and Bergeron, D. (2026), Standardization of 243Am, Applied Radiation and Isotopes, [online], https://doi.org/10.1016/j.apradiso.2026.112674, https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=960500 (Accessed May 23, 2026)

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