Half-life of 238Pu

The half-life of 238Pu has been determined by the relative activity method considering 239Pu as a reference isotope. Five synthetic mixtures were prepared by using solutions of 238Pu and 239Pu isotopes. The α activity ratios and the atom ratios in these mixtures were kept close to unity by employing the double dilution technique so that these ratios could be measured with high precision and accuracy. The activity ratios were determined by α spectrometry on electrodeposited sources using a silicon surface barrier detector and the atom ratios were obtained by mass spectrometry. A value of 87.98+-0.51 y was obtained for the half-life of 238Pu using the half-life of 239Pu as 24110 y. The uncertainty specified on the value is a combination of one standard deviation on the average value and the error evaluated from estimates on various error components. (author)