Direct quantitative gross aB-measurements of environmental water contaminated with nuclides from the uranium, thorium and actinium decay series and semi-qualitative identification of nuclides concerned.

Abstract

Naturally occurring radioactive materials (NORMs) in environmental samples are of crucial importance in the case of radiological impact studies in any environmental compartment. For this reason, valuable information is needed for the determination of NORMs in environmental samples and this requires accurate measurement techniques. This information can be obtained from liquid scintillation counter (LSC) by fast screening of contaminated water samples with NORMs. However, direct determination of these nuclides via LSC is far from straight forward since LSC can only quantitatively determine total alp-activity. In addition, identification of a-P emitters with the LSC method requires an exact determination of the peak position or end-point energy. This requires energy calibration under various quenching conditions. The a-energy calibration is a correlation of a-energy and the channel peak position of the spectrum. The appearance of quenching in the sample affects not only counting efficiency but the a-β discrimination as well. LSC allows the measurement of both a- and P-activities and in some cases an indication can be obtained of the a-energy, although the resolution of a-spectra is much poorer than that attained by semi-conductors. In this investigation we evaluated the potential of a low-background liquid scintillation system with advanced spectrometry capabilities, the Quantulus 1220™, to be used directly for the determination of the gross a- and Naturally occurring radioactive materials (NORMs) in environmental samples are of crucial importance in the case of radiological impact studies in any environmental compartment. For this reason, valuable information is needed for the determination of NORMs in environmental samples and this requires accurate measurement techniques. This information can be obtained from liquid scintillation counter (LSC) by fast screening of contaminated water samples with NORMs. However, direct determination of these nuclides via LSC is far from straight forward since LSC can only quantitatively determine total a/β-activity. In addition, identification of a-β emitters with the LSC method requires an exact determination of the peak position or end-point energy. This requires energy calibration under various quenching conditions. The a-energy calibration is a correlation of a-energy and the channel peak position of the spectrum. The appearance of quenching in the sample affects not only counting efficiency but the a-β discrimination as well. LSC allows the measurement of both a- and β-activities and in some cases an indication can be obtained of the a-energy, although the resolution of a-spectra is much poorer than that attained by semi-conductors. In this investigation we evaluated the potential of a low-background liquid scintillation system with advanced spectrometry capabilities, the Quantulus 1220™, to be used directly for the determination of the gross a- and β-activities and the identification of the most likely nuclides that contribute to the activity of NORM-nuclides in environmental water. Although element specific radiochemical separations followed by a-spectrometry are still the better option the method developed offers an attractive and cost-effective alternative.-activities and the identification of the most likely nuclides that contribute to the activity of NORM-nuclides in environmental water. Although element specific radiochemical separations followed by a-spectrometry are still the better option the method developed offers an attractive and cost-effective alternative.