Basic Metrology: Recent Primary SRM Standardizations

Summary

Following is a tabulation of the primary standardizations of Radioactivity SRMs performed over the past decade.

Description

SRM No.	Radionuclide	Reference Date	Method Used	Relative expanded uncertainty (k = 2)	References
4332f	Americium-243	8 March 2024	The certified massic activity for 243Am was obtained by 4pab LS spectrometry with two commercial LS counters. The beta detection efficiencies for the 243Am daughter 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, using two different LS measurement systems (with varying operating systems) and two different LS cocktail compositions, and by gamma – ray spectrometry.	1.3 %
4324c	Uranium-232	31 October 2022	The certified massic activity for 232U was obtained by 4pab 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. Confirmatory measurements were performed by LS counting comparative measurements against SRM 4324b, using two different LS measurement systems (with varying operating systems) and two different LS cocktail compositions, and by gamma – ray spectrometry.	0.86 %
4328d	Thorium-229	14 July 2022	The certified massic activity for 229Th was obtained by 4paβ LS counting by comparative measurements against SRM 4328c using two different LS measurement systems (with varying operating systems) and two different LS cocktail compositions. Solution homogeneity measurements were made with a NaI(Tl) well counter.	1.0 %	Colle, R. , Laureano-Perez, L. and DiGiorgio, M. (2023), Preparation and Standardization of 229Th SRM 4328d, Special Publication (NIST SP), National Institute of Standards and Technology, Gaithersburg, MD, https://doi.org/ 10.6028/NIST.SP.260-235
4239a	Strontium-90	25 December 2019	The certified massic activity for 90Sr in radioactive equilibrium with 90Y was obtained by 4πß liquid scintillation (LS) spectrometry with two commercial LS counters.	0.30 %
4338b	Plutonium-240	27 August 2019	The certified massic activity for 240Pu was obtained by 4πα liquid scintillation (LS) counting using three different LS measurement systems	1.1 %
4329a	Curium-243	15 May 2019	The certified massic activity for 243Cm was obtained by 4πα liquid scintillation (LS) counting using three different LS measurement systems Confirmatory measurement was performed by gamma-ray spectrometry	0.56 %
4322d	Americium-241	1 March 2019	The certified massic activity for 241Am was determined by 4πα liquid scintillation (LS) counting using two different LS measurement systems.	0.32 %
4251d	Barium-133	13 July 2018	The certified massic activity for 133Ba was obtained by 4π (e, X) - γ(NaI) live-timed anti-coincidence (LTAC) counting. Confirmatory measurements: (i) 4παβ liquid scintillation (LS) spectrometry; (ii) LS-based 4παβ triple-to-double coincidence ratio (TDCR) method; (iii) 4πγ ionization chamber measurements using NIST chamber “A”; and (iv) HPGe γ-ray spectrometry	1.2 %
4334j	Plutonium-242	9 August 2017	The certified massic activity for 242Pu was obtained by 4πα liquid scintillation (LS) spectrometry with two commercial LS counters.	0.51 %
4321d	Natural Uranium	15 March 2017	Quantitative dissolution of a uranium (normal) metal assay and isotopic standard (CRM 112-A) with conversion to massic activity values using assumed half-lifes of 234U, 235U and 238U. The uranium assay for CRM 112-A was determined by coulometry. The certified isotopic atom fractions were determined by mass spectrometry. Solution homogeneity measurements were made with a NaI(Tl) well counter. Confirmatory measurements for total massic activity and 234U and 238U isotopic massic activity were performed by 4παβ liquid scintillation counting and by isotope dilution alpha spectrometry, respectively.	238U: 0.25 % 235U: 0.31 % 234U: 0.52 %	Natural Uranium Radioactivity Solution Standard: SRM 4321d R. Collé, L. Laureano-Perez, S. Nour, J.J. La Rosa, B.E. Zimmerman, L. Pibida, D.E. Bergeron. J Res Natl Inst Stan (2017) 122:44.
4323c	Plutonium-238	11 October 2016	The certified massic activity was determined by 4πα liquid scintillation (LS) spectrometry with two LS commercial counters	0.50 %
4927g	Hydrogen-3	1 May 2015	The certified massic activity was determined by relative liquid scintillation (LS) counting with two LS commercial Confirmatory measurements of both SRM 4927F and SRM 4927g were performed by triple-to-double coincidence ratio (TDCR) measurements.	0.96 %	Comparison of tritiated-water standards by liquid scintillation for calibration of a new Standard Reference Materials R. Collé, L. Laureano-Perez, D.E. Bergeron Applied Radiation and Isotopes 112 (2016) 38–49
4222d	Carbon-14-n-hexadecane	10 September 2014	The certified value was based on Triple-to-Double Coincidence Ratio (TDCR) measurements with the beta spectrum calculated using the shape factor limit given by Alimonti et al., 1998]. The liquid scintillation (LS) detection efficiency was calculated using the MICELLE2 code. Confirmatory measurements were done by 4παβ LS spectrometry with two commercial LS counters. The LS detection efficiency was also calculated using the MICELLE2 code for CIEMAT/NIST efficiency tracing,	0.96 %	Comparison of C-14 liquid scintillation counting at NIST and NRC Canada, Bergeron, D., Galea, R., Laureano-Perez, L., and Zimmerman, B. Applied Radiation and Isotopes, Volume 109, March 2016, Pages 30-35.
4949d	Iodine-129	01 January 2014	The 129I massic activity was measured by live-timed 4παβ(LS) - γ(NaI) anticoincidence counting (LTAC) with a single-PMT liquid scintillation (LS) detector for the beta channel and a NaI(Tl) well detector for the gamma channel. Confirmatory measurements were done by triple-to-double coincidence ratio (TDCR) and gamma-ray spectrometry.	1.08 %