Half-life of 241Pu

The half-life of 241Pu was determined by studying the ingrowth of 241Am in two independent sets of experiments: (i) by α spectrometry taking 242Pu as well as 239Pu and 240Pu as reference isotopes, and (ii) by α proportional counting. In these experiments, separate synthetic mixtures, prepared by mixing different isotopes of plutonium, were used with an objective of obtaining periodically a desired change in the α activity ratio (as in α spectrometry) or in the total α activity (as in α proportional counting) and to measure this change with high precision and accuracy. In α spectrometry, from the 65 measurements carried out on five electrodeposited sources over a period of 574 days, a value of 14.37 +- 0.09 yr was obtained for the half-life of 241Pu. In the α proportional counting, from the 20 measurements carried out on five sources over a period of 704 days, a value of 14.50 +- 0.08 yr was obtained. The average of these two independent determinations leads to a value of 14.44 +- 0.06 yr for the half-life of 241Pu. The uncertainty quoted on the values is a combination of one standard deviation on the average value and the error evaluated from estimates on various error components. The half-life obtained in this work is in good agreement with the results reported earlier from this laboratory by α spectrometry, taking 239Pu and 240Pu as reference isotopes as well as with the preliminary results reported by other laboratories using different methods