Abstract
The half-life of 243Am has been measured by an absolute and a relative method, i.e. by determining the specific activity of 243Am and the specific activity ratio with 241Am. A mixed 241,243Am reference material was produced and certified for its americium mass content and its isotope amount ratios. The characterisation of the mass content of 243Am was established by isotope dilution mass spectrometry using an 241Am spike, produced from highly enriched 241Pu material. The isotope amount ratios n(241Am)/n(243Am) and n(242mAm)/n(243Am) were measured by thermal ionisation mass spectrometry. Activity measurements were performed by alpha-particle counting at a defined solid angle, as well as high-resolution alpha-particle spectrometry. From the 243Am/241Am activity and isotopic amount ratios, a value of 16.988 (24) was derived for the 243Am/241Am half-life ratio. Using a value of 432.6 (6) a for the 241Am half-life, the corresponding 243Am half-life value, 7349 (15) a, is in good agreement with the result obtained from the absolute method, 7342 (14) a. The mean value, 7345 (14) a, agrees well with data from literature and lowers the relative standard uncertainty to 0.2%.
Highlights
The decay constant λ establishes the link between the number of atoms N of a particular radionuclide in a sample and their expected radioactive decay rate A, i.e. λ = A/N [1]
The value of λ-or inversely the half-life T1/2 = ln(2)/λ-is invariable in space and time, in spite of recent claims of variability in decay rate measurements erroneously ascribed to solar influences [2,3,4,5,6,7,8,9,10,11]
Accurate values for the decay constant or half-life of trans-uranium nuclides are required for accounting of nuclear material, assay of targets used in nuclear physics experiments, and characterisation of isotopic mixtures for radioanalytical purposes
Summary
Whereas mass spectrometry is the most accurate measurement method to determine isotope ratios in nuclear material, relative. Journal of Radioanalytical and Nuclear Chemistry (2020) 326:1785–1793 of an 243Am reference material for the quantification of Am in an unknown sample by isotope dilution mass spectrometry (IDMS) [16,17,18,19]. This responds to a pressing need in the fields of nuclear safeguards and security, nuclear forensics, and accountability in the nuclear fuel cycle [20, 21]. All uncertainty values in this work pertain to the standard uncertainty
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