Pushing the plastic envelope: using physical measurements of polymers to infer uranium enrichment histories
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nguyen-avng-phd-nse-2026-thesis.pdf
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6.34 MB
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d180a6c610c6915c6178a3e5613af0c1
Author(s)
Nguyen, Avery
Advisor(s)
Short, Michael P.
Date Issued
February 2026
Publisher
Massachusetts Institute of Technology
Abstract
How can an inspector be certain that a uranium enrichment facility has never been employed to produce weapons-usable fissile material? One proposed method entails the use of differential scanning calorimetry (DSC) to measure radiation-induced changes in the properties of the common material polytetrafluoroethylene (PTFE), searching for physical traces left by exposure to enriched uranium. Although previous work confirmed the sensitivity of PTFE to the relevant radiation environment, several challenges remain before the technique can realistically be implemented.
In this thesis, I address two key questions for the DSC-based method. First, are the changes observable in DSC unique to uranium exposure, and if not, how can an inspector increase their confidence that a given observation is attributable to enrichment activity? I embark on a critical review of the PTFE literature that suggests that while measurements cannot provide insight about a sample’s history in isolation, a well-developed sampling procedure may increase confidence in the provenance of a set of samples. I describe an example protocol that could be employed to minimize errors in confirming or denying exposure to highly enriched material. Additionally, I develop the use of supplementary characterization techniques, including small-angle x-ray scattering and electron paramagnetic resonance spectroscopy, which can be used to corroborate claims of radiation exposure.
Second, PTFE is an exceptionally radiation-sensitive material. What if no PTFE is available for retrospective measurement? I explore two alternate candidate materials for retrospective DSC, polychlorotrifluoroethylene (PCTFE) and fluorinated epoxy. My measurements show that although these materials are not as sensitive or precise as PTFE, they might be used in its absence to make slightly weaker claims about the absence of weapons-usable material. I also present additional methods for analyzing DSC data which can be used to extract the maximum amount of insight from individual measurements.
Based on these findings, I suggest that retrospective DSC of irradiated polymers is a potentially powerful verification tool, but not a path to be undertaken lightly. To make a credible accusation based on this method, an inspector should be prepared to invest significant resources. The method is not technically infeasible, however, and its extension into other materials represents a promising expansion of its possible applications.
MIT Department
Massachusetts Institute of Technology. Department of Nuclear Science and Engineering
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