A comparison of alpha and gamma spectrometry for environmental natural radioactivity surveys

• Published in: Applied radiation and isotopes Vol. 66; no. 2; pp. 215 - 222
• Main Authors: Saïdou, Bochud, François, Laedermann, Jean-Pascal, Kwato Njock, M.G., Froidevaux, Pascal
• Format: Journal Article
• Language: English
• Published: England Elsevier Ltd 01.02.2008
• Subjects: Levenberg–Marquardt algorithm; Multiplet deconvolution; Z-score; α-particle spectrometry; γ-ray spectrometry; χ2-tests; α-particle spectrometry; γ-ray spectrometry; Z-score; Levenberg–Marquardt algorithm; χ 2-tests; Multiplet deconvolution
• ISSN: 0969-8043; 1872-9800
• DOI: 10.1016/j.apradiso.2007.07.034

An α-spectrometry, using automated borate fusion and sequential extraction and exchange chromatography, was used to determine the uranium and thorium based on environmental radioactivity of 20 soil samples. The same set of the samples was analysed using γ-spectrometry with an HPGe detector. The two data sets were checked for coherence using Z-score and χ 2 statistical tests. We show that γ-spectrometry is a valid alternative to time-consuming α-spectrometry for the determination of natural uranium and thorium activity in soil (activity range: 12.5–58.2 Bq/kg). The measured activities were compared with the theoretical activities to ensure secular equilibrium in the 238U and 232Th series. For 226Ra, a special study was made on deconvolution of the 186 keV multiplet with the Levenberg–Marquardt algorithm. Finally, the combined use of Z-score and χ 2-tests was found to be a powerful tool for comparing the results obtained with two different methods.