Trace-Actinide Measurements in Natural Ore and Depleted Uranium Material using Accelerator Mass Spectrometry*

Detection of trace levels of ²³⁶U provides a key identification signature of uranium ore material as well as clear indication of anthropogenic contamination from reprocessing activities or weapons fallout. Although commercial mass spectrometry methods can detect high levels of contamination, only Accelerator Mass Spectrometry is sensitive enough to measure natural concentrations of ²³⁶U/U, which span from 10^-14 to 10^-10. At the University of Notre Dame’s Nuclear Science Laboratory, we have improved our detection efficiency by a factor of five, primarily through the construction of a compact ionization chamber, and have successfully demonstrated capabilities down to the 10^-10 level, with projections of the current system limit as low as 6x10^-12. Additional isotopic signatures and their sensitivities for ²³³U (10^-11), which could provide indication of irradiation from fast neutrons, as well as ²³¹Pa (10^-10), and ²³⁰Th (10^-9), decay products of ²³⁵U and ²³⁴U respectively, have also been demonstrated. Details highlighting system requirements, measurement technique, improvements to the detection system, and measurement results will be presented.