Ultra-High Energy Resolution Gamma Spectroscopy of Fission Products from Freshly Irradiated Material

Year
2024
Author(s)
K.A. Schreiber - Los Alamos National Laboratory
D.G. McNeel - Los Alamos National Laboratory
M. Keller - National Institute of Standards and Technology
M.P. Croce - Los Alamos National Laboratory
M.H. Carpenter - Los Alamos National Laboratory
R.U. Schönemann - Los Alamos National Laboratory
S. Dede - Los Alamos National Laboratory
S.E. Kossman - Los Alamos National Laboratory
E.S. Teti - Los Alamos National Laboratory
D.T. Becker - University of Colorado, National Institute of Standards and Technology
J.D. Gard - University of Colorado
J.A.B. Mates - National Institute of Standards and Technology
D.J. Mercer - Los Alamos National Laboratory
P.E. Magnelind - Los Alamos National Laboratory
N.J. Ortiz - University of Colorado
D.R. Schmidt - National Institute of Standards and Technology
D. Swetz - National Institute of Standards and Technology
J.N. Ullom - University of Colorado, Boulder, National Institute of Standards and Technology
B. Archambault - Pacific Northwest National Laboratory
L. Arrigo - Pacific Northwest National Laboratory
C. Harabagiu - Pacific Northwest National Laboratory
S. Herman - Pacific Northwest National Laboratory
N. Uhnak - Pacific Northwest National Laboratory
E. Warzecha - Pacific Northwest National Laboratory
B. Pierson - Pacific Northwest National Laboratory
Abstract

Irradiated uranium produces a variety of fission products. Many are very short lived, have small branching ratios, and have closely spaced gamma-ray energies. High energy resolution gammaray measurements enabled by microcalorimetry are desirable for a better understanding of the fission product yield. Microcalorimeters are highly sensitive gamma ray detectors, which operate at temperatures below 0.01 Kelvin and obtain energy spectra with energy resolution an order of magnitude greater than conventional high purity germanium detectors. A gamma ray peak at 100 keV measured by a microcalorimeter gamma-ray detector can have a full-width half maximum of 60 eV or less. We have employed microcalorimeter gamma-ray spectrometers developed by our collaboration to study fission products separated from freshly-irradiated uranium, measured as soon as a week after irradiation. SOFIA (Spectrometer Optimized for Facility Integrated Applications), with 256 gamma-ray microcalorimeter pixels, was used to obtain several spectra taken after irradiation. The High Efficiency and Resolution Microcalorimeter Spectrometer, 700 pixels (HERMES-700) has been developed to obtain high statistics gamma-ray spectra with very high energy resolution, and was also used to obtain spectra on a similar sample. HERMES-700 will have the largest microcalorimeter array of any gamma ray detector developed by our collaboration. Our measurements demonstrate the successful application of gamma-ray microcalorimeter detectors in the characterization of recently irradiated material. The use of ultra-high energy resolution gamma spectroscopy for these samples is impactful for the understanding of reactor physics, nuclear security, and safeguards.