HALF-LIFE OF PU-242

The half-life of Pu242 was measured relative to the half-lives of Pu239 and Pu238 in two independent sets of experiments. Synthetic mixtures were prepared using enriched isotopes of Pu238, Pu239, and Pu242. The α activity ratios in these mixtures were determined by α spectrometry on electrodeposited sources using a silicon surface barrier detector while the atom ratios were obtained by mass spectrometry. The α activity ratios and the atom ratios were so chosen that these could be measured with a high precision and accuracy. A half-life value of (3.742±0.024) × 105 yr is obtained using the half-life of Pu239 as 24110 yr. The value obtained using the half-life of Pu238 as 87.74 yr is (3.766±0.025) × 105 yr. The average of these two independent sets of experiments leads to a half-life value of Pu242 as (3.754±0.025) × 105 yr. 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 discrepancy existing in the earlier published values for the half-life of Pu242 determined relative to the half-lives of Pu239 and Pu238 is resolved. RADIOACTIVITY Pu242 half-life, relative to the half-life of Pu239; measured: Pu239/Pu242 α activity ratio by α spectrometry, Pu239/Pu242 atom ratio by mass spectrometry; relative to the half-life of Pu238; measured Pu238/Pu242 α activity ratio by α spectrometry, Pu238/Pu242 atom ratio by mass spectrometry. © 1979 The American Physical Society.