Guidance on Radiochronometry

Williams, Ross W.¹  Gaffney, Amy M.¹  Kristo, Michael J.¹ 

[1]Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)

DOI  :  10.2172/1321436
RP-ID  :  LLNL-TR--701379
PID  :  OSTI ID: 1321436

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来源: SciTech Connect

【 摘 要 】

Radiochronometry is the measurement of radioactive materials and their decay products to determine the ???age??? of the material. It differs from the practice of geochronology in that the materials (samples) are man-made, and in that the timespan of interest is confined to the nuclear era, i.e., since the discovery of fission in 1939. In radiochronometry, the ???age??? of the material ideally records the time when the sample was manufactured, or produced in the final form that is analyzed in the laboratory. It is an important predictive signature in a nuclear forensic investigation which can help in the attribution to a source. The calculation of this ???age??? can only be made if a model is invoked that allows simplification of the parent radionuclide to daughter isotope decay equation. The simplification required for this model is that the parent was purified completely from all traces of its daughter product at the time of sample preparation. Then, this ???age??? should be described as the ???model age??? from which a ???model date??? in the past can then be calculated. For this model date to represent the date of sample preparation, two other assumptions are required to be true. The first is that the material has remained a closed system since that time (i.e., that there has been no loss or gain of either parent or daughter), and the second is that the analyses are accurate.