Advances in Nuclear Forensics: GSA 2014 Technical Session

The lunar basalts in my doctoral research were almost four billion years old, plus or minus a couple hundred million years. The rocks I study now were created on July 16th, 1945, at 05:29:45 AM (Mountain War Time). It’s a strange thing to know so precisely. But how can I pinpoint the exact second of creation? Because these rocks are trinitite, the glassy result of a sandy New Mexico desert experiencing the first atomic bomb blast.

Two views of a common green glass variety of trinitite. Image from the Simonetti Lab at Notre Dame.

The first nuclear bomb test, codenamed Trinity, was performed at the White Sands Proving Grounds (near Alamogordo, New Mexico). The device, Gadget, was an implosion-type design with a plutonium (Pu-239) core. The heat resulting from the 18 kiloton explosion melted the desert sand surface out to distances of 400 meters from ground zero. trinitite_thin_section The surface sand melted to form a glassy layer (1-2 cm) on top of incipiently melted desert sand together, these form trinitite (alternatively, Alamogordo glass). This post-detonation material is a valuable tool in nuclear forensics research. Trinitite incorporated pieces of Gadget and the blast tower, and one of our goals is to identify and characterize the distribution and composition of individual components through geochemical and radionuclide analysis. At right, a vertical cross-section of trinitite is shown in thin section.

The analysis of postdetonation material (like trinitite) is one arm of the nuclear forensics field. An effective nuclear forensic analysis requires technical information and relevant databases, and specialized skills and expertise to generate, analyze, and interpret the data. This analysis combined with law enforcement and intelligence data can provide valuable information on the provenance of such materials, and processing history so as to improve source attribution. Identifying the source(s) of stolen or illicitly trafficked nuclear materials will therefore prevent, or make more difficult, terrorist acts that would use material from these same sources. Moreover, effective forensic analysis of postdetonation materials in the unlikely event of a nuclear terrorist attack is also expected to deter individuals or groups involved, and provides incentives to countries to enhance their security and safeguards relative to their nuclear materials and facilities.

The microscopic and macroscopic appearance, as well as the elemental and isotopic composition of nuclear materials, i.e. its ‘signature’ reflects its entire history. The term ‘signature’ is used to describe material characteristics that may be used to link nuclear samples to people, places, and processes, much as a written signature can be used to link a document to a particular person. Forensic methods employed to establish signatures in nuclear materials typically combine physical and chemical (e.g. X-ray fluorescence, scanning electron microscopy, electron microprobe analysis, secondary ion mass spectrometry) characterization and radiometric measurements (e.g. alpha, beta and gamma spectroscopy). The methodologies and interpretation of forensic analyses are constantly being advanced and perfected.

gsa-logo_14CAt this year’s annual meeting of the Geological Society of America, the Notre Dame crew (Drs. Tony Simonetti, Sara Mana, and myself) are chairing a session to update the geoscience community on the latest developments of nuclear forensics. The cleverly-titled session, “Advances in Nuclear Forensics”, will emphasize analytical techniques, database development, and implications for our ability to identify and possibly prevent nuclear attacks and trafficking of illicit nuclear materials.

UPDATE (Aug 9, 2014): The session has been designated a poster session.

Note: A significant portion of this post was reused from our session proposal, which isn’t published by GSA.

Further Resources: