Achieving 1% Assay of Special Nuclear Materials in 2 Minutes with Microcalorimeter-Array Gamma-Ray Spectroscopy

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Boulder, Colorado
Project Term:
01/16/2023 - 01/15/2026

Technology Description:

The University of Colorado, Boulder (CU-Boulder), will advance high-resolution gamma-ray spectroscopy using cryogenic microcalorimeter arrays, which are an emerging tool for improved nuclear material accountancy. Microcalorimeter spectrometers measure gamma-ray energy much more precisely than other gamma-ray detectors, allowing them to resolve closely spaced gamma-ray lines such as those produced by plutonium isotopes near 100 keV, and detect lines that appear only weakly above background. Microcalorimeters are currently capable of reaching the CURIE program’s 1% uncertainty target but fall far short of its speed goal. CU-Boulder will produce individual microcalorimeter pixels that can achieve 200 counts per second count rates (20x faster than current devices), which will allow a system with 4,000 such detectors to make the required 1% measurement of plutonium isotopic content in 2 minutes. This capability can determine uranium (U) enrichment in high-assay low-enriched U, fissile material content throughout reprocessing and waste streams, high-accuracy plutonium (Pu) isotopic assays, and potentially key U/Pu isotope ratios in uranium/transuranic products.

Potential Impact:

By enabling the secure and economical recycling of the nation’s inventory of LWR UNF, CURIE will have the following impacts:


Support the deployment of advanced reactor (AR) technologies by providing safe and sustainable domestic fuel stocks. Improvements in monitoring capabilities could enable more precise controls of various reprocessing stages while ensuring increased security of materials of concern.


Substantially reduce the disposal impact of the nation’s inventory of LWR UNF, decrease uranium mining requirements, and support a comprehensive national strategy to store radioactive waste safely and securely.


Complement ARPA-E’s existing nuclear energy research portfolio, further ensuring the commercial viability of innovative new ARs, and enable an additional revenue stream via valuable radionuclides recovered from UNF for diverse applications.


ARPA-E Program Director:
Dr. Jenifer Shafer
Project Contact:
Dr. Daniel Becker
Press and General Inquiries Email:
Project Contact Email:


National Institute of Standards and Technology
Los Alamos National Laboratory
Idaho National Laboratory

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