Application of liquid scintillation inclusion techniques for the simultaneous determination of alpha and beta activities in composite samples – A preliminary study

• Published in: Radiation measurements 2012-10, Vol.47 (10), p.936-946
• Main Authors: Bhade, S.P.D., Reddy, P.J., Babu, D.A.R., Sharma, D.N.
• Format: Article
• Language: English
• Subjects: Alpha rays; Automatic Efficiency Control (AEC); Beta; Calibration; Counting; Earth sciences; Earth, ocean, space; Exact sciences and technology; Geochronology; Gross alpha and beta activities; Inclusions; Isotope geochemistry. Geochronology; Knee point inclusion method; Knees; Liquid scintillation counting; Liquids
• ISSN: 1350-4487; 1879-0925
• DOI: 10.1016/j.radmeas.2012.07.003

Present work highlights liquid scintillation inclusion techniques as a tool for simultaneous determination of gross α and β activities in composite samples. This preliminary study comprises a preamble exercise to check whether Automatic Efficiency Control (AEC) and knee point inclusion techniques which are conventionally used for analysis of two β-emitting radio-nuclides in a mixture, can be implemented for quantification of gross α and β activities in composite samples. In inclusion techniques, two counting regions are set such that there are spill-up and spill-down of pulse events in each region from both types of radio-nuclides. AEC which is built-in feature in Packard Tri-Carb 2900 TR Liquid Scintillation Counter (LSC) provides automatic counting region adjustments for single and dual label samples according to the degree of quench present in sample. While knee point inclusion technique requires manual Lower Level (LL) and Upper Level (UL) discriminator setting to define two counting regions. In the present study, α/β spiked composite samples were treated as dual label samples with α and β radio-nuclides as two distinct entities contributing to the gross activities and analyzed employing AEC and knee point inclusion techniques. Instrument discriminator settings and regions of interest (ROI) were evaluated to determine optimum counting conditions for both the techniques. Three sets of pure alpha and pure beta standards simulating the activity concentrations of real samples in terms of α/β activity ratios were used to calibrate LSC. Calibration methodology for Packard Tri-Carb 2900 TR LSC with respect to the above measurements using 241Am, 36Cl and 90Sr/90Y calibration standards is explained in detail. The practicability and working performance of these techniques was checked by the validation trials with spiked synthetic samples covering range of α/β activity ratios from 1:1 to 1:50 and 50:1. Procedures have been tested by comparison with, established PSA technique and repeatability has been evaluated. ► Liquid scintillation inclusion techniques were implemented for determination of gross α and β activities. ► The practicability and working performance of these techniques was checked. ► Procedures have been tested by comparison with established PSA technique.