Metal Chronometry for Pre-Detonation Nuclear Forensics Applications

The ability to determine the time since forming of seized nuclear material would provide crucial data to be used in its investigation. This paper examines the time dependent processes of diffusion; to include grain boundary diffusion, and discontinuous precipitation, and assess the utility of examination of impurity and alloying element concentration profiles, for use as a pre-detonation nuclear forensics tool for determining the age of a metal sample. Several examples provided illustrate the effects of time on both binary alloys and multi-component systems. This study draws parallels from studies of diffusion in mineral samples under geologic time and proposes modifications to that approach in order to determine the time since a metal sample was cast or formed. PROFILER software was used to generate concentration profiles. The second method involves calculating the number of damage sites caused self-irradiation during the ff-decay of uranium isotopes. The OrigenARP module in SCALE 6.1 and SRIM-2008 were used to model the effects of these decays and predict the number of damage sites in an ideal sample. Further research is suggested to test the feasibility of combining the two approaches for forensic exploitation.