161Tb has potential applications in targeted radionuclide therapy and nuclear forensic science. However, the half-lives of 161Tb in previous studies show a discrepancy. In this study, 161Tb samples were produced by irradiating 160Gd2O3 with thermal neutron flux. A series of procedures were applied to extract a pure 161Tb solution and three solid samples were prepared. The half-life of 161Tb has been measured with a high-purity germanium (HPGe) detector. The time-dependency of the 161Tb activity was followed by assessing the count rate of their characteristic gamma-ray emissions at 48.9 keV and 74.6 keV over a period of 33-43 days. The experiment and uncertainty budget are discussed in detail. Different uncertainty propagation equations were applied for random uncertainties, medium-frequency deviations and potential systematic errors. The result for the 161Tb half-life of 6.967 (11) d was determined by the weighted mean of half-lives from three samples, which confirms that the half-life is longer than the of the current evaluated half-life of 6.89 (2) d. From all available quoted experimental values, a recommended half-life of 6.934 (14) d was determined by the power-moderated method (PMM). Based on recent four published half-life values, a half-life of 161Tb of 6.9582 (33) d was determined by the PMM analysis.
Keywords: (161)Tb; Gamma ray spectrometry; Half-life; Uncertainty budget.
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