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Summary
A new Standard Reference Material (SRM) of Am-243 has been produced and calibrated. Americium's most stable isotope, americium-243, has a half-life of (7367 ± 23) years. It decays into neptunium-239 through alpha decay. Americium can be produced in kilogram quantities and has a few practical uses. It is used in smoke detectors and can be used as a portable source of gamma rays.
Description
The certified massic activity for 243Am was obtained by 4παβ LS spectrometry with two commercial LS counters. The beta detection efficiencies for the 243Am daughter (239Np) were calculated using the CN2003 code for the CIEMAT/NIST efficiency tracing (CNET) method with composition-matched LS cocktails of a 3H standard as the efficiency detection monitor. Confirmatory measurements were performed by LS counting comparative measurements against SRM 4332e, which was standardized in 2008 by CIEMAT/NIST Efficiency Tracing using 3H as the detection efficiency monitor, live-timed anticoincidence (LTAC) measurements; alpha spectrometry of electrodeposited sources; and by gamma spectrometry with high-resolution HPGe detectors. Confirmatory values by LS comparative measurements, LTAC, alpha spectrometry, and gamma-ray spectrometry agreed with the CNET certified value by -0.21 %, -0.21 %, -0.21 %, and -0.46 %, respectively. Triple-to-double coincidence (TDCR) was used to determine the counting rate ratio for R4332f/ R4332e. The ratio obtained by TDCR agreed with the ratio by LS to within -0.05%. The certified massic activity of 243Am (with the 241Am impurity correction) in SRM 4332f, is (48.18± 0.63) Bq·g-1 at k = 2 as of 1200 EST, 8 March 2024.
The ratio of alpha-emitting impurities 241Am/243Am = 0.00162 ± 0.00007 was obtained by alpha spectrometry. Based on gamma ray spectrometry 241Am/243Am = 0.0019 ± 0.0007. Mass spectrometry for (241Am+ 241Pu)/243Am agrees with alpha spectrometry 241Am/243Am ratio to +3.3 %.