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Ground state spontaneous fission half-lives from thorium to fermium

Description: Measurements of the half-lives for spontaneous fission of the nuclidic ground states of elements from thorium to fermium have been compiled and evaluated. Recommended values are presented. An attempt has been made to distinguish between spontaneous fission and heavy ion emission. Spontaneously fissioning isomers have not been considered here. The difference between even-even nuclides and odd-even, even-odd and odd-odd nuclides are discussed. 3 tabs.
Date: January 1, 1988
Creator: Holden, N.E.
Partner: UNT Libraries Government Documents Department

Half-lives for selected actinides and long-lived radionuclides

Description: 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., ..cap 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.
Date: January 1, 1988
Creator: Holden, N.E.
Partner: UNT Libraries Government Documents Department

Characterization of consistent NDA (nondestructive assay) standards

Description: By combining calorimetry and traditional analytical methods five sets of unique NDA standards were characterized for the Savannah River Plant (SRP) of E.I. Du Pont de Nemours, Inc. The calorimetry measurements make it possible to nondestructively verify the homogeneity of the plutonia stock and to assure that the analytical aliquots were representative of the parent material. Two assay values were determined by calorimetric assay. When the isotopic composition was determined by mass spectroscopy and alpha pulse height analysis, the agreement between Pu content by calorimetry and controlled potential coulometry was within 0.06% for all five isotopic compositions. When nondestructive, gamma-ray isotopic techniques were used to assay the 1500 gram standards the agreement was within 0.1% for all five materials. The new half-lives and specific power recommended in the latest revision of ANSI N15.22-1987, Calibration Techniques for the Calorimetric Assay of Plutonium Bearing Solids were used for all computations. The standards were certified for plutonium content, isotopic composition, and thermal power. The mass of the standards varied from 20 to 1500 grams with /sup 240/Pu compositions ranging from 3 to 15 percent. 7 tabs.
Date: January 1, 1988
Creator: Rodenburg, W.W.; Novak, E.F. & Seiler, R.J.
Partner: UNT Libraries Government Documents Department