Official websites use .gov
A .gov website belongs to an official government organization in the United States.
Secure .gov websites use HTTPS
A lock (
) or https:// means you’ve safely connected to the .gov website. Share sensitive information only on official, secure websites.
Summary
A new Standard Reference Material (SRM) of 239Pu is being produced and calibrated. Plutonium-239 has a half-life of (24100 ± 11) years and decays to uranium-235 through alpha decay. Pu-239 is one of the primary fissile isotopes used in nuclear weapons.
Description
The certified massic activity for 239Pu was obtained by 4πα liquid scintillation (LS) spectrometry with two commercial LS counters. Confirmatory measurements were performed by LS counting comparative measurements against SRM 4330d, which was also standardized in 2009 by 4pa liquid scintillation (LS) spectrometry and alpha spectrometry. Determination by Decay Energy Spectrometry (DES) is being scheduled.
Alpha spectrometry and inductively coupled plasma mass spectrometry (ICP-MS) were used as secondary measurements to obtain the critical impurity assessment to correct the LS value. ICP-MS and isotope dilution were employed to quantify the 239Pu mass fraction against a high-purity 244Pu tracer. Additionally, isotopic composition measurements of un-spiked sample were used to obtain atom ratios n(240Pu)/n(239Pu), n(241Am+241Pu)/n(239Pu), and n(242Pu)/n(239Pu), which indirectly provide activity ratios A(240Pu)/A(239Pu) and A(242Pu)/A(239Pu).
Alpha spectrometry is a suitable technique for the 238Pu and 241Am activity measurements. Using 242Pu and 243Am as tracers, the sample was subjected to radiochemical separation of the Pu and Am fractions. However, alpha spectrometry is unable to resolve 239Pu from 240Pu. Thus, the Pu-containing fraction was measured to directly determine the combined 239+240Pu massic activity against the 242Pu tracer, where the 239Pu and 240Pu massic activities are deconvoluted from the ICP-MS atom ratio. The A(238Pu)/A(239+240Pu) ratio was measured directly. The Am-containing fraction was measured to determine the 241Am massic activity by alpha spectrometry against the 243Am tracer and confirmed by gamma spectrometry in a calibrated geometry. Finally, the A(241Pu)/A(239Pu) ratio can be approximated by a combined analysis of the alpha and mass spectrometry measurements.