Measurements of thorium and uranium daughters in radioenvironmental samples using γγ-coincidence spectrometry

Andrew Tillett; Larry Benninger; John Dermigny; Christian Iliadis

doi:10.1016/j.apradiso.2018.08.013

Measurements of thorium and uranium daughters in radioenvironmental samples using γγ-coincidence spectrometry

Appl Radiat Isot. 2018 Nov:141:24-32. doi: 10.1016/j.apradiso.2018.08.013. Epub 2018 Aug 23.

Authors

Andrew Tillett¹, Larry Benninger², John Dermigny³, Christian Iliadis⁴

Affiliations

¹ Department of Physics and Astronomy, The University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA.
² Department of Geological Sciences, The University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA.
³ Department of Physics and Astronomy, The University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA; Triangle Universities Nuclear Laboratory (TUNL), Durham, NC 27708, USA.
⁴ Department of Physics and Astronomy, The University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA; Triangle Universities Nuclear Laboratory (TUNL), Durham, NC 27708, USA. Electronic address: iliadis@unc.edu.

PMID: 30145529
DOI: 10.1016/j.apradiso.2018.08.013

Abstract

We present the performance of a γγ-coincidence spectrometer for measuring the activities of thorium and uranium daughters in environmental samples. The spectrometer consists of two NaI(Tl) detectors facing each other inside a low-background passive shield. We present coincidence gating schemes for achieving the best signal-to-noise ratios, coincidence detection efficiencies, background levels, and minimum detectable activities. The spectrometer is simulated using Geant4 to correct sample efficiencies for self-absorption effects. The device is used to measure thorium and uranium daughter activities in Brazil nuts, potting mix, and magazine paper. Our results for Brazil nuts agree with some, but not all, previous measurements. Thorium or uranium daughter activities have previously not been reported for commercial potting mix. For magazine paper, our measured activities are lower than most previously determined values.

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