Samarium isotope compositions of uranium ore concentrates: A novel nuclear forensic signature

Quinn R Shollenberger; Lars E Borg; Erick C Ramon; Michael A Sharp; Gregory A Brennecka

doi:10.1016/j.talanta.2020.121431

Samarium isotope compositions of uranium ore concentrates: A novel nuclear forensic signature

Talanta. 2021 Jan 1:221:121431. doi: 10.1016/j.talanta.2020.121431. Epub 2020 Jul 31.

Authors

Quinn R Shollenberger¹, Lars E Borg², Erick C Ramon², Michael A Sharp², Gregory A Brennecka³

Affiliations

¹ Institut für Planetologie, University of Münster, Wilhelm-Klemm-Straße 10, 48149, Münster, Germany; Nuclear & Chemical Sciences Division, Lawrence Livermore National Laboratory, 7000 East Avenue L-231, Livermore, CA, 94550, USA. Electronic address: qshollenberger@ucla.edu.
² Nuclear & Chemical Sciences Division, Lawrence Livermore National Laboratory, 7000 East Avenue L-231, Livermore, CA, 94550, USA.
³ Institut für Planetologie, University of Münster, Wilhelm-Klemm-Straße 10, 48149, Münster, Germany; Nuclear & Chemical Sciences Division, Lawrence Livermore National Laboratory, 7000 East Avenue L-231, Livermore, CA, 94550, USA.

PMID: 33076062
DOI: 10.1016/j.talanta.2020.121431

Abstract

Uranium ore is mined and milled to produce uranium ore concentrate (UOC), a regulated product of the nuclear fuel cycle. Diversion of UOC from the fuel cycle into possible weapons production is a key concern in global nonproliferation efforts. As such, the ability to trace the origin of seized nuclear materials is imperative to law enforcement efforts. Although isotopic signatures of UOCs have proven fruitful to pinpoint sample provenance, new isotopic signatures are needed because most existing isotopic signatures are not indicative of the original ore body from which the U is derived. In this work, we developed a new method to separate samarium (Sm) from a U-rich sample matrix and report the first Sm isotope compositions of 32 UOCs derived from a variety of worldwide uranium mines. Relative to terrestrial standards, approximately half the UOCs have resolved and anticorrelated ¹⁴⁹Sm-¹⁵⁰Sm isotope compositions, consistent with the capture of thermal neutrons by ¹⁴⁹Sm in the ore body. The UOCs with anomalous Sm isotope compositions tend to derive from older (~>1.5Ga) and higher-grade ore bodies, although other factors, such as the presence of neutron moderators like water, also play a role. Nonetheless, the Sm isotope compositions of UOCs directly reflects the neutron fluence over the history of the original ore body and can be used to discern different geologic conditions associated with that ore body. As such, this work demonstrates the potential use of Sm isotopes as a novel nuclear forensics signature for origin assessment of UOCs.

Keywords: Nuclear forensics; Origin assessment; Samarium isotopes; Thermal neutron capture; Uranium ore concentrate.