Direct activity measurement of pure beta-emitting radionuclides by the TDCR efficiency calculation technique

doi:10.1016/0168-9002(94)91771-X

Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment

Volume 339, Issues 1–2, 22 January 1994, Pages 14-20

https://doi.org/10.1016/0168-9002(94)91771-X Get rights and content

Abstract

The activities of a number of pure beta-emitting radionuclides have been directly determined by the triple-to-double coincidence ratio (TDCR) efficiency calculation technique. The nuclides were ³H, ¹⁴C, ⁶³Ni and ⁹⁹Tc, which were prepared in a variety of commercial liquid scintillation cocktails. The method enables the counting efficiency associated with a given source to be determined from just two observables: the double-tube and triple-tube counting rates. This information allows the source activity to be extracted irrespective of the chemical quenching state of the sample. There is no need for quench curves, extrapolation or efficiency tracing measurements.

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This paper reports on absolute activity measurements of iron-59 made at the National Metrology Institute of South Africa (NMISA) via 4π(LS)β–γ coincidence counting. The exercise formed part of an Asia Pacific Metrology Program (APMP) regional key comparison. Source data were analysed by the extrapolation technique for a number of gamma-ray window settings. In addition, a feasibility study was undertaken on a second technique; a non-extrapolation method based on a detection efficiency analysis. The reported activity concentration of the ⁵⁹Fe solution was determined with a relative uncertainty of 0.28% (k=1), the uncertainty being due mainly to the rate vs. efficiency fitting process. The result from the non-extrapolation method was lower than that given by extrapolation by 0.33%, within two standard deviations. Possible reasons for the small discrepancy are discussed.
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Citation Excerpt :
The triple-to-double coincidence ratio (TDCR) efficiency calculation and CIEMAT/NIST efficiency tracing (CNET) techniques both make use of a theoretical beta spectrum, whereas the 4π(LS)β–γ coincidence tracing method is independent of a knowledge of the beta spectral shape. The standardization of Tc-99 has been reported on previously by Calhoun et al. (1992), Coursey et al. (1984), Lucas (1998), Simpson and Meyer (1994) and Laureano-Perez et al. (2010). Mougeot et al. (2011) calculated the average energy of the beta spectrum from the beta endpoint energy (Emax=293.8 (14) keV) and the shape factor given above, to obtain Eave=94.6 (17) keV, based on the analytical approach developed by Gove and Martin (1971).
The NMISA participated in the international key comparison of the pure beta-emitter Technetium-99, CCRI(II)-K2.Tc-99. The comparison solution was standardized using three methods, namely the TDCR efficiency calculation method, the CIEMAT/NIST efficiency tracing method and the 4π(LS)β–γ coincidence tracing method with Co-60 as tracer. Excellent agreement between results obtained with the three methods confirmed the applicability of the beta spectral shape given by the latest (2011) DDEP evaluation of Tc-99 decay data, rather than the earlier (2004) evaluation.

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Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment

Abstract

References (15)

Appl. Radiat. Isot.

Appl. Radiat. Isot.

Appl. Radiat. Isot.

Int. J. Appl. Radiat. Isot.

Comp. Phys. Commun.

Trans. Am. Nucl. Soc.

Cited by (28)

Radionuclide standardization

Environmental liquid scintillation analysis

Liquid scintillation analysis: Principles and practice

Absolute standardizations of <sup>99m</sup>Tc and <sup>57</sup>Co by 4π electron-gamma liquid scintillation coincidence counting for SIRTI and SIR comparisons

Activity determination of <sup>59</sup>Fe by 4π beta-gamma counting using liquid scintillation in the beta channel

Standardization of Tc-99 by three liquid scintillation counting methods