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 U-232 has been produced and calibrated. Uranium-232 is an isotope of uranium. It is a side product in a nuclear fuel cycle that uses, 232Th, as the fertile material. It has been cited as an obstacle to nuclear proliferation using 233U as the fissile material because the intense gamma radiation emitted by 208Tl (a daughter of 232U, produced relatively quickly) makes the 233U contaminated with it more difficult to handle.
Description
The certified massic activity for 232U was obtained by 4παβ LS spectrometry with two commercial LS counters. The beta detection efficiencies for the 232U daughters were calculated using the MICELLE2 code for the CIEMAT/NIST efficiency tracing (CNET) method with composition-matched LS cocktails of a 3H standard as the efficiency detection monitor. For 212Pb, 212Bi, and 208Tl, the beta detection efficiencies were obtained using the MICELLE2 code and the simplified decay scheme from Napoli, et al (2020) [Napoli et al, 2020]. All α emitters in the 232U decay chain were assumed to be detected with 100 % efficiency. The short-lived 212Po ((300 ± 2) x 10-9 s) daughter and its 212Bi parent were assumed to be detected with a combined efficiency of 100 %. Confirmatory measurements were performed by LS counting comparative measurements against SRM 4324b, which was standardized in 2002 by live‑timed anticoincidence counting, using two different LS measurement systems (with varying operating systems) and two different LS cocktail compositions, and by gamma-ray spectrometry. A re-standardization of 4324b by CNET as part of this work was in agreement with the decay corrected certified value by 0.66 %. Confirmatory values by LS comparative measurements and gamma-ray spectrometry were in agreement with the value obtained by CNET by 0.30 % and 0.84 %, respectively. The certified massic activity of 232U (in equilibrium with its progeny) in SRM 4324c, is (26.30 ± 0.23) Bq·g-1 at k = 2 as of 1200 EST, 31 October 2022.
Napoli, E.; Cessna, J.T; Fitzgerald, R.; Pibida, L.; Collé, R.; Laureano-Pérez, L.; Zimmerman, B.E.; Bergeron, D.E.; Primary Standardization of 224Ra Activity by Liquid Scintillation Counting, Appl. Radiat. Isotop., Vol. 155, pp. 108933 (2020).