The half-life of U232 was determined by two independent methods: a specific activity method and a relative activity method involving the half-life of U233. In the specific activity method, the disintegration rate of U232 was determined by liquid scintillation counting as well as by proportional counting, and the number of atoms of U232 was determined by isotope dilution mass spectrometry. The radiochemical purity of the purified U232 was confirmed by spectrometry. A half-life value of 69.000.40 yr was obtained. In the relative activity method, synthetic mixtures were prepared using isotopes of U232 and U233. The activity ratios in these mixtures were determined by spectrometry and the atom ratios were obtained by mass spectrometry. The activity ratios and the atom ratios were such that these could be measured with a high precision and accuracy. A half-life value of 68.810.38 yr was obtained using the half-life of U233 as 1.592 × 105 yr. The average of these two independent determinations leads to a value of 68.900.39 yr for the half-life of U232. The uncertainty given on the values is a combination of the one standard deviation on the average value and the error evaluated from estimates on various error components. The values reported earlier are significantly higher as compared to the half-life value obtained in this work. RADIOACTIVITY U232 half-life, specific activity; measured: activity by liquid scintillation counter and proportional counter, uranium concentration by isotope dilution mass spectrometry; relative to the half-life of U233; measured: U232/U233 activity ratio by spectrometry, U232/U233 atom ratio by mass spectrometry. © 1979 The American Physical Society.
