Half-Lives for Selected Actinides and Long-Lived Radionuclides.

摘要

Long-lived actinide nuclides are of interest for their use in nuclear reactors, for nuclear reactor burnup studies in waste management, and for safeguard applications, e.g., alpha counting is used to determine the amount of material present. Some long-lived radionuclides are of interest for their use in determining geological ages using various dating methods, and in calculating the cosmic-ray exposure ages of meteorites. Recommended values are presented for both the total half-life and for the spontaneous fission half-life of /sup 232-236,238/U, of /sup 236,238-242,244/Pu, of /sup 241,242m,243/Am, and of /sup 242-248,250/Cm. Problems with the presentation of uncertainties are discussed. The impact of the revised sup 14 C half-life on the carbon dating technique and various sup 14 C ages is discussed. The possible primordial occurrence of sup 92 Nb is now definitely ruled out. Based on examination of the sup 26 Al half-life, the calculated value for the cosmic-ray exposure age of meteorites remains too high compared to the age calculated using other radionuclide half-life values. sup 204 Pb, which was once thought to be radioactive, is shown to be stable. 37 refs., 5 tabs. (ERA citation 13:047630)