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Determination of the activity and half-life of Th.

07:00 EST 7th December 2018 | BioPortfolio

Summary of "Determination of the activity and half-life of Th."

Liquid scintillation samples with Th were prepared a few hours after the separation of the progeny. During the measurements, Th and its daughters are not in radioactive equilibrium. The counting efficiencies of the individual radionuclides of the decay chain differ from each other and the activity of an individual progeny relative to the activity of Th varies with time. Hence, the overall counting efficiency varies with time as well. The counting efficiency ε of Th and its progeny was determined by means of the CIEMAT/NIST efficiency tracing method. The free parameter is derived from the quench-indicating parameter, SQP(E), and from H tracer measurements. This makes it possible to compute the efficiency ε as a function of time. The individual efficiencies of all progeny are to be combined, taking correction factors and activity ratios into account. Thereby, a new, time-dependent correction, namely for the decay during the measurements, is applied. With this method, activity results are obtained that are stable over a long period of time. A least-squares method yields the time of the chemical separation as well as the Th half-life, which was also obtained by means of measurements in an ionization chamber. The weighted mean of the two methods (CIEMAT/NIST efficiency tracing and measurements in ionization chambers) was found to be T = 18.681(9) d.

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Name: Applied radiation and isotopes : including data, instrumentation and methods for use in agriculture, industry and medicine
ISSN: 1872-9800
Pages: 12-18

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