Determination of the 229Th half-life

The paper describes the remeasurement of the half-life of Th-229 (ground state). The half-life was obtained by the measurement of amount content of Th-229 in the certified Th-229 radioactivity standard (SRM 4328C) from the National Institute of Standards and Technology. The measurement was performed by isotope dilution inductively coupled plasma mass spectrometry by using two independent standards for quantification. From the results the Th-229 half-life is determined to be 7917 years with an expanded uncertainty of 48 years using a coverage factor of k = 2. The methodology is traceable to the International System of Units, and the calculation complies with the recommendations of the Bureau International des Poids et Mesures for nuclear data evaluation.