Improving Uncertainty in Nondestructive Uranium Enrichment Analysis with Microcalorimeter Gamma Spectroscopy

Year
2024
Author(s)
Mark Croce - Los Alamos National Laboratory
Katrina Koehler - Los Alamos National Laboratory
Megan Booher - Los Alamos National Laboratory
Emily Stark Teti - Los Alamos National Laboratory
Jacob Ward - Los Alamos National Laboratory
Duc Vo - Los Alamos National Laboratory
David Mercer - Los Alamos National Laboratory
Matthew Carpenter - Los Alamos National Laboratory, Los Alamos
Katherine A Schreiber - Los Alamos National Laboratory
Rico Schoenemann - Los Alamos National Laboratory
Daniel Becker - National Institute of Standards and Technology, University of Colorado
Jacob Stuligross - National Institute of Standards and Technology, University of Colorado
Joel Ullom - National Institute of Standards and Technology, University of Colorado
Geon-Bo Kim - Lawrence Livermore National Laboratory
Nathan Hines - Lawrence Livermore National Laboratory
Abstract

Nondestructive analysis of uranium isotopic composition is a primary application of gamma spectroscopy for nuclear material accountancy and safeguards. With continued technology advancement in ultra-high-resolution microcalorimeter gamma spectrometers, these instruments are now being applied to a broader range of analyses including uranium enrichment. Improved energy resolution and comparable detection efficiency near 100 keV relative to high-purity germanium detectors allows current microcalorimeter gamma spectrometers to provide improved uncertainty in U-238/235/234 isotopic ratios using conventional response function analysis methods. Furthermore, direct gamma rays from 238U decay (rather than the decay products such as 234Th and 234mPa) are resolved in microcalorimeter spectra. This suggests the potential to provide a robust determination of uranium enrichment in freshly purified materials for which the 6-month equilibration between 238U and its decay products used for gamma spectrometry has not yet occurred, without knowledge of the separation date. An essential component of reducing overall uncertainty in nondestructive uranium isotopic composition analyses is improving knowledge of nuclear data such as gamma-ray emission probabilities for 238U, 235U, and 234U and daughters for which work is ongoing. Recent  developments are presented in the use of microcalorimeter gamma spectroscopy for uranium enrichment analysis, performance for enrichment standards, and progress towards improving uncertainty in routine measurements.